Samson Speaker MDR1248 User Guide

TWELVEꢀANDꢀSIXTEENꢀCHANNELꢀMIXER  
WITHꢀ24-bitꢀDSPꢀEFFECTSꢀ  
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Instrucciones de seguridad / Istruzioni di Sicurezza  
PRECAUCION: Para reducir el riesgo de incendios o descargas, no permita que este aparato quede expuesto a la lluvia o la humedad. Para reducir el riesgo de descarga  
eléctrica, nunca quite la tapa ni el chasis. Dentro del aparato no hay piezas susceptibles de ser reparadas por el usuario. Dirija cualquier reparación al servicio técnico oficial.  
El símbolo del relámpago dentro del triángulo equilátero pretende advertir al usuario de la presencia de “voltajes peligrososno aislados dentro de la carcasa del producto,  
que pueden ser de la magnitud suficiente como para constituir un riesgo de descarga eléctrica a las personas. El símbolo de exclamación dentro del triángulo equilátero  
quiere advertirle de la existencia de importantes instrucciones de manejo y mantenimiento (reparaciones) en los documentos que se adjuntan con este aparato.  
Instrucciones importantes de seguridad  
1.  
2.  
3.  
4.  
5.  
6.  
7.  
8.  
9.  
Lea todo este manual de instrucciones antes de comenzar a usar la unidad.  
Conserve estas instrucciones para cualquier consulta en el futuro.  
Cumpla con todo lo indicado en las precauciones de seguridad.  
Observe y siga todas las instrucciones del fabricante.  
Nunca utilice este aparato cerca del agua o en lugares húmedos.  
Limpie este aparato solo con un trapo suave y ligeramente humedecido.  
No bloquee ninguna de las aberturas de ventilación. Instale este aparato de acuerdo a las instrucciones del fabricante.  
No instale este aparato cerca de fuentes de calor como radiadores, calentadores, hornos u otros aparatos (incluyendo amplificadores) que produzcan calor.  
No anule el sistema de seguridad del enchufe de tipo polarizado o con toma de tierra. Un enchufe polarizado tiene dos bornes, uno más ancho que el otro. Uno con  
toma de tierra tiene dos bornes normales y un tercero para la conexión a tierra. El borne ancho o el tercero se incluyen como medida de seguridad. Cuando el enchufe  
no encaje en su salida de corriente, llame a un electricista para que le cambie su salida anticuada.  
10. Evite que el cable de corriente quede en una posición en la que pueda ser pisado o aplastado, especialmente en los enchufes, receptáculos y en el punto en el que  
salen de la unidad.  
11. Desconecte de la corriente este aparato durante las tormentas eléctricas o cuando no lo vaya a usar durante un periodo de tiempo largo.  
12. Dirija cualquier posible reparación solo al servicio técnico oficial. Deberá hacer que su aparato sea reparado cuando esté dañado de alguna forma, como si el cable de  
corriente o el enchufe están dañados, o si se han derramado líquidos o se ha introducido algún objeto dentro de la unidad, si esta ha quedado expuesta a la lluvia o la  
humedad, si no funciona normalmente o si ha caído al suelo.  
ATTENZIONE: per ridurre il rischio di incendio o di scariche elettriche, non esponete questo apparecchio a pioggia o umidità. Per ridurre il pericolo di scariche elettriche evitate  
di rimuoverne il coperchio o il pannello posteriore. Non esistono all'interno dell'apparecchio parti la cui regolazione è a cura dell'utente. Per eventuale assistenza, fate riferimento  
esclusivamente a personale qualificato. Il fulmine con la punta a freccia all'interno di un triangolo equilatero avvisa l'utente della presenza di "tensioni pericolose" non isolate  
all'interno dell'apparecchio, tali da costituire un possibile rischio di scariche elettriche dannose per le persone. Il punto esclamativo all'interno di un triangolo equilatero avvisa  
l'utente della presenza di importanti istruzioni di manutenzione (assistenza) nella documentazione che accompagna il prodotto.  
Importanti Istruzioni di Sicurezza  
1. Prima di usare l'apparecchio, vi preghiamo di leggerne per intero le istruzioni.  
2. Conservate tali istruzioni per una eventuale consultazione futura.  
3. Vi preghiamo di rispettare tutte le istruzioni di sicurezza.  
4. Seguite tutte le istruzioni del costruttore.  
5. Non usate questo apparecchio vicino ad acqua o umidità.  
6. Pulite l'apparecchio esclusivamente con un panno asciutto.  
7. Evitate di ostruire una qualsiasi delle aperture di ventilazione. Posizionatelo seguendo le istruzioni del costruttore.  
8. Non posizionatelo vicino a sorgenti di calore come radiatori, scambiatori di calore, forni o altri apparecchi (amplificatori compresi) in grado di generare calore.  
9. Non disattivate la protezione di sicurezza costituita dalla spina polarizzata o dotata di collegamento a terra. Una spina polarizzata è dotata di due spinotti, uno più  
piccolo ed uno più grande. Una spina dotata di collegamento a terra è dotata di due spinotti più un terzo spinotto di collegamento a terra. Questo terzo spinotto,  
eventualmente anche più grande, viene fornito per la vostra sicurezza. Se la spina fornita in dotazione non si adatta alla vostra presa, consultate un elettricista per la  
sostituzione della presa obsoleta.  
10. Proteggete il cavo di alimentazione in modo che non sia possibile camminarci sopra né piegarlo, con particolare attenzione alle prese, ai punti di collegamento e al punto  
in cui esce dall'apparecchio.  
11. Staccate l'apparecchio dalla alimentazione in caso di temporali o tempeste o se non lo usate per un lungo periodo.  
12. Per l'assistenza, fate riferimento esclusivamente a personale qualificato. È necessaria l'assistenza se l'apparecchio ha subito un qualsiasi tipo di danno, come danni al cavo  
o alla spina di alimentazione, nel caso in cui sia stato versato del liquido o siano caduti oggetti al suo interno, sia stato esposto a pioggia o umidità, non funzioni corretta-  
mente o sia stato fatto cadere.  
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Copyright 2006, Samson Technologies Corp.  
Printed September, 2006 v1.1  
Samson Technologies Corp.  
45 Gilpin Avenue  
Hauppauge, New York 11788-8816  
Phone: 1-800-3-SAMSON (1-800-372-6766)  
Fax: 631-784-2201  
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Table of Contents  
MDR1248 and MDR1688 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3  
Front Panel Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4  
Front and Rear Panel Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6  
Controls and Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 12  
MONO INPUT CHANNEL SECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7  
MDR1248 and MDR1688 Input and Output Connections . . . . . . . . .13 - 14  
Operating the MDR1248 and MDR1688 . . . . . . . . . . . . . . . . . . . . . . . . . . 15- 18  
BASIC OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15  
Operating the MDR1248 and MDR1688 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16  
USING THE DIGITAL EFFECTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16  
SENDING AN INDEPENDENT MIX TO THE MONITOR SPEAKERS . . . . . . . . 17  
USING THE CHANNEL INSERT JACKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17  
USING AN EXTERNAL EFFECT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18  
PLAYING BACK A CD USING 2T TO MIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18  
RECORDING A MIX FROM THE MDR1248 and MDR1688. . . . . . . . . . . . . . . 18  
MDR1248 and MDR1688 System Set-Ups . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19  
MDR1248 and MDR1688 LIVE SOUND SET-UP . . . . . . . . . . . . . . . . . . . . . . . . 19  
MDR1248 and MDR1688 RECORDING SET-UP . . . . . . . . . . . . . . . . . . . . . . . . 20  
MDR1248 and MDR1688 Wiring Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21  
MDR1248 and MDR1688 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22  
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Introduction  
Congratulations on your purchase of the Samson  
MDR1248 or MDR1688 mixer! The MDR1248 and  
MDR1688 are great sounding mixers with a lot of  
inputs, flexible routing and stunning on-board digi-  
tal effects. Connecting all your microphones and  
instruments is simple, with four mic/line inputs plus  
FOUR additional stereo channels on the MDR1248,  
and eight mic/line inputs plus four additional stereo  
channels on the MDR1688. There are also dedicated  
stereo effects returns for the onboard digital effects.  
And the effects! You can add one of the MDR's 256  
dazzling digital studio quality effects, which include  
Delays, Chorus, Flanging, and lush Reverbs to your  
vocals or instruments, using the onboard 24-bit  
Multi-Effects Processor.  
In these pages, you’ll find a detailed description of  
the features of the MDR1248 and MDR1688 mixers,  
as well as a description of their front and rear panels,  
step-by-step instructions for their setup and use, and  
full specifications. You’ll also find a warranty card  
enclosed—please don’t forget to fill it out and mail  
it in so that you can receive online technical support  
and so we can send you updated information about  
these and other Samson products in the future.  
With proper care and adequate air circulation, your  
MDR1248 or MDR1688 will operate trouble free for  
many years. We recommend you record your serial  
number in the space provided below for future refer-  
ence.  
The Mic/line inputs feature a 3-band equalizer with  
sweepable midrange control and there is a four  
band fixed equalizer on each of the stereo input  
channels. Each of the stereo and mono input chan-  
nels have two Aux sends, plus you can switch one  
from Pre to Post. The MDR1248 and MDR1688’s  
master section includes two stereo Aux returns and  
a 2-track Input and Output for playing back stereo  
devices and for recording your mix. Clean, clear  
sound reproduction with sweet equalization and  
signal flexible routing in a rugged enclosure, ensure  
reliable high quality sound from performance to  
performance. Optimized for recording, live sound  
reinforcement and commercial installations, the  
MDR1248 and MDR1688 are ideal mixer solutions,  
offering big sound in a compact package.  
Serial number: ____________________________  
Date of purchase: __________________________  
Should your unit ever require servicing, a Return  
Authorization number (RA) must be obtained before  
shipping your unit to Samson. Without this number,  
the unit will not be accepted. Please call Samson  
at 1-800-3SAMSON (1-800-372-6766) for a Return  
Authorization number prior to shipping your unit.  
Please retain the original packing materials and if  
possible, return the unit in the original carton and  
packing materials.  
If you purchased your Samson product outside the  
United States, please contact your local distributor  
for warranty information and service.  
tech.com) for complete information about our full  
product line.  
2
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MDR1248 and MDR1688 Features  
The Samson MDR1248 and MDR1688, twelve and  
mixing. For added flexibility, AUX 1 can be con-  
figured as a Pre or Post fader send.  
sixteen channel mixers are a comprehensive, all-in-  
one solution for live sound, recording, fixed instal-  
lation and post production applications. Here are  
some of its main features:  
High quality, low noise, discrete microphone  
pre-amplifiers with 48-Volt phantom power, pro-  
vide Maximum Dynamic Range and transparent  
audio.  
The mixers offer plenty of inputs with four Mic/  
Line plus four Stereo inputs for the MDR1248  
and eight Mic/Line plus four Stereo inputs for  
the MDR1688.  
Twelve segment LED Meter with VU ballistics dis-  
plays the main MIX output.  
Flexible design topology ideal for live sound,  
recording and post production.  
High quality 60mm faders on the mono and  
stereo inputs, plus the Main and Control Room/  
Headphone outputs.  
The MDR1248 and MDR1688 has a built-in, 24-  
bit DSP (Digital Signal Processor) Multi-effects  
Processor with 256 selectable presets offering  
dazzling studio quality effects including Reverb,  
Delay, Chorus and Flanging.  
Advanced circuit design using discrete compo-  
nents and high quality, low noise op-amps care-  
fully selected at each stage of the signal path.  
Quality build and rugged construction ensure  
reliable performance from venue to venue and  
session to session.  
2 Track Input and Output allows you to con-  
nect a CD, DAT, Cassette, Mini Disk or Computer  
Sound Card.  
Standard 19-inch rackmount kit included.  
Three-year extended warranty.  
Three-band channel equalizer with sweepable  
mids on the mono input channels, along with  
four band fixed equalizer on the stereo channels,  
provide precise and musical results in contour-  
ing the tone of any signal.  
Two Auxiliary Sends for built-in or external  
effects, on-stage monitor mix, or headphone  
3
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Front Panel Layout  
21  
37  
38  
39  
40  
41  
42  
43  
44  
45  
46  
47  
48  
49 50 51 52 53 54 55 56 57 58  
59  
4
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Front Panel Controls  
FRONT PANEL  
right line input for the stereo channels.  
1
MIC IN – Input connector for Low-Noise Microphone  
pre-amp.  
22 LEFT/MONO LINE - 1/4-inch phone input connec-  
tor for the Left Line input for the stereo channels or a  
mono input.  
2
3
LINE IN–Input connector for Line level inputs.  
INSERT – 1/4-inch TRS (TIP/RING/SLEEVE) connector  
providing send and receive channel patch point for  
outboard effects.  
23 ALT 3/4 OUTPUTS jacks – Balanced, 1/4-inch phone  
connectors carrying the signal from the ALT 3/4 bus.  
24 CONTROL ROOM OUTPUT– Left and Right Control  
Room output connectors for connecting a monitor  
system.  
4
5
6
7
GAIN – Used to set the input level of the mic pre and  
line input.  
LOW CUT – Bass roll off switch at 75Hz used to elimi-  
nate unwanted low end rumble and hum.  
25 MAIN MIX OUTPUT (1/4-inch) – Left and Right Main  
Mix balanced output 1/4-inch TRS connectors.  
HIGH FREQUENCY – Controls the high band of the  
Channel Equalizer, +/- 15 dB at 12KHz.  
26 MAIN MIX OUTPUT (XLR) – Left and Right Main Mix  
balanced output XLR connectors.  
MID CUT/BOOST – This control knob provides +/- 15  
dB of boost or cut at the frequency set on the MID  
SWEEP control on the mono input channels.  
27 AUX RETURN 1 – Left and right input jacks for con-  
necting to the outputs of external line level sources  
like those from effects processors.  
8
MID SWEEP – Control knob used to set the center  
28 AUX RETURN 2 – Left and right input jacks for con-  
necting to the outputs of external line level sources  
like those from effects processors.  
frequency of the mid band of the Channel Equalizer.  
9
LOW FREQUENCY – Controls the low band of the  
Channel Equalizer, +/- 15 dB at 80Hz.  
29 FOOTSWITCH JACK – 1/4-inch phone jack for con-  
necting a standard footswitch used to turn the inter-  
nal DSP effects on and off.  
10 AUX 1 – Auxiliary send that can be used with an  
external effects processor, or to create a cue or moni-  
tor mix.  
30 PHONES JACK – Connect stereo headphones here.  
11 PRE / POST switch – Used to configure Aux 1 signal  
31 AUX SEND 2 – Line level output from the Auxiliary 2  
routing from a Pre fader to a post fader send.  
bus.  
12 AUX 2/DSP – Post-fader auxiliary send that can be  
used with an external effects processor, or to create a  
cue or monitor mix, or to send a signal to the internal  
DSP.  
32 AUX SEND 1 – Line level output from the Auxiliary 1  
bus.  
33 2 TRACK OUTPUTS – Connect to the input of a DAT,  
Cassette, Mini Disk or Hard Disk Recording system.  
13 PAN – Controls the channel’s position between left  
and right in the stereo bus.  
34 2 TRACK INPUTS – Connect the output from a DAT,  
Cassette, Mini Disk or Hard Disk Recording system.  
14 3/4 MUTE LED – When illuminated, the display indi-  
cates that the input channel is assigned to the ALT3/4  
bus and is muted in the Left /Right Main Mix bus.  
35 2 TRK LEVEL – Control knob used to set the level of  
the source connected to the 2-track input.  
15 3/4 / MUTE switch – When engaged, the input chan-  
nel is assigned to the ALT3/4 bus and is muted in the  
Left / Right MAIN MIX bus.  
36 VARIATIONS – Control knob used to select one of the  
sixteen variations for each of the sixteen DSP effect  
programs.  
16 SOLO LED – When illuminated, the display indicates  
37 PROGRAMS – Control knob used to select one of the  
that the input channel is assigned to the SOLO bus.  
sixteen DSP effect programs.  
17 SOLO switch – When engaged, the input channel is  
38 DSP PEAK – LED indicator illuminates when the input  
signal to the internal DSP is reaching an overload  
level.  
assigned to the SOLO bus.  
18 PEAK – Red LED will illuminate indicating when the  
GAIN has been adjusted too high.  
39 DSP MUTE switch – Used to turn the internal DSP  
effects on and off.  
19 LEVEL – Audio taper fader provides smooth control  
of level changes.  
40 ALT 3/4 TO MIX – Routes the ALT 3/4 to the Left /  
Right MAIN MIX outputs. Use the ALT3/4 Level (55) to  
set the volume.  
20 +4 / -10 switch – Used to set the line input sensitiv-  
ity from –10dB when the switch is pressed in to +4dB  
when this switch is out.  
41 2 TRK TO MIX - Routes the Left / Right 2 track inputs  
to the Left / Right MAIN MIX outputs. Use the 2 TRK  
21 RIGHT LINE – 1/4-inch phone input connector for the  
5
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Front and Rear Panel Layout  
FRONT PANEL CONTROLS - continued  
LEVEL control (35) to set the volume.  
50 AUX RETURN 1 – Used to mix in the level of AUX  
Return 1.  
42 POWER LED – Indicates the MDR1248 or MDR1688 is  
powered up.  
51 AUX RETURN 2 – Used to mix in the level of AUX  
Return 2.  
43 PHANTOM LED – Indicates that the 48 Volt Phantom  
Power is on.  
52 AUX RETURN 2 TO AUX 1 - Switch used to route AUX  
RETURN 2 into the AUX 1 output so that effects can be  
heard in the monitor mix.  
44 MAIN MIX – Routes the Left / Right MAIN MIX bus to  
the CONTROL ROOM / PHONES outputs. Use the Left  
/ Right MAIN MIX Level faders (58) and PHONES level  
fader (59) to set the volume.  
53 AUX SEND 1 – Control knob used to set the master  
level of the AUX1 SEND.  
45 ALT 3/4 – Routes the ALT 3/4 bus to the CONTROL  
ROOM / PHONES outputs. Use the ALT3/4 Level (55)  
and PHONES level fader (59) to set the volume.  
54 AUX SEND 2 – Control knob used to set the master  
level of the AUX2 SEND.  
55 ALT 3/4 LEVEL – Control knob used to set the level of  
46 2 TRK IN – Routes the Left / Right 2 track input to the  
CONTROL ROOM / PHONES outputs. Use the 2 TRK  
LEVEL control (35) and PHONES level fader (59) to set  
the volume.  
the ALT 3/4 bus.  
56 SOLO LED – Indicates that one or more channels are  
assigned to the SOLO bus.  
57 SOLO MODE – Selects the SOLO mode from AFL (After  
Fader Level) when the switch is pressed in, and PFL  
(Pre Fader Level) when the switch is pressed out.  
47 OUTPUT METER - Twelve segment LED display with  
VU ballistics indicates main Mix level.  
48 LEVEL SET LED – When an input channel is in SOLO,  
this indicator will illuminate to show that the chan-  
nel’s input gain level is displayed on the Main Level  
Meter.  
58 MAIN LEVEL faders – Used to control the overall vol-  
ume of the Left and Right main Mix output  
59 CONTROL ROOM / PHONES fader – Adjusts the  
volume of the control room speakers and/or head-  
phones.  
49 BALANCE – Controls the channel’s position between  
left and right of the stereo inputs.  
l
o
REAR PANEL  
A
B
C
POWER – Switches on the MDR1248 and MDR1688’s main  
power.  
PHANTOM – Engages the 48-Volt Phantom power supply to  
microphone pre-amps.  
AC ADAPTOR INLET – Connect External AC power supply  
here.  
6
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Controls and Functions  
2 - LOW CUT FILTER - switch  
MONO INPUT CHANNEL SECTION  
The following section details each part of the MDR1248  
and MDR1688’s MONO INPUT CHANNELS including the  
GAIN control, LOW CUT switch, 3-BAND EQ, AUX sends,  
PEAK LED, PAN, SOLO, ALT 3/4 bus and LEVEL controls.  
The input channels one through four on the MDR1248  
and on through eight on the MDR1688 feature high  
quality, discrete transistor pre-amps providing transpar-  
ency and extended dynamic range.  
Each of the MDR1248 and MDR1688’s mono input chan-  
nels include a LOW CUT (or high pass) filter which rolls off  
the low frequencies from 75Hz and below at the rate of  
18dB per octave. The LOW CUT filter allows you to remove  
the lower frequencies that you sometime just don’t want  
to pick up. For example, when you are miking a high-hat  
you only want to capture the frequencies that the hi-hat is  
producing. Therefore, by using the LOW CUT filter, you can  
reduce the amount of pick-up from the low toms and bass  
drum that may leak into the hi-hat mic. You can use the  
same technique on other instruments like acoustic guitar,  
violin, piano and even on vocals. In live sound applica-  
tions, the LOW CUT filter is especially useful for removing  
stage rumble.  
1 - GAIN - control knob  
The MDR1248 and MDR1688’s pre-amp stage has a vari-  
able GAIN control with a range of 0 to 40dB on the MIC  
input and –15 to +25dB on the LINE input.  
3 - Channel Equalizer  
The MDR1248 and MDR1688 mic/line input channels  
incorporate a 3-band equalizer, with sweepable Mid-  
range, allowing you to adjust the high, mid-range, and  
low frequencies independently on each channel. The fre-  
quency centers, range of boost or cut, and equalizer type  
for each band are described in the following section.  
HF (HIGH FREQUENCY) 12kHz +/- 15dB Shelving type  
The channel’s HIGH frequency response is flat when the  
knob is in the “12:00position. Rotating the knob towards  
the right will boost the channel's high frequency response  
at 12 kHz by 15dB, and rotating it towards the left will cut  
the high frequency by 15dB.  
MF (MID FREQUENCY) CUT & BOOST  
The MID CUT & BOOST knob is used in conjunction with  
the MID FREQUENCY knob to create the tonal shape in  
the mid-range frequency when using the mono channel’s  
equalizers. You can adjust the frequency on the mid-range  
control with the FREQ knob, and use the MF CUT & BOOST  
to either boost or cut that frequency by plus or minus  
15dB. The channel’s MID frequency response is flat when  
the MF knob is in the “12:00position.  
FREQ (MID FREQUENCY) Variable 100Hz – 5K  
The MID FREQUENCY is a control enabling you enhanced  
capabilities in the tonal shaping of the input channel  
signal. Thanks to the MID FREQUENCY control, you have  
a variable mid-range equalizer, allowing you to pin point  
the exact frequency you want to boost or cut. The MID  
SWEEP has a “fixed Qof two octaves (the amount, or  
width, of frequencies around the center point that are  
effected by the MID CUT & BOOST control) and can be set  
in a range from 100Hz to 5Khz.  
ꢁꢁ  
ꢁꢀ  
ꢁꢉ  
LF (LOW FREQUENCY) 80Hz +/- 15dB shelving type  
The channel’s LOW frequency response is flat when the  
knob is in the “12:00position. Rotating the knob towards  
the right will boost the channel's low frequency response  
at 80 Hertz by 15dB, and rotating it towards the left will  
cut the frequency by 15dB.  
ꢁꢂ  
7
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Controls and Functions  
MONO INPUT CHANNEL SECTION - continued  
Auxiliary Busses ( 4 - 6 )  
a monitor send. When the PRE/POST switch is set to POST,  
the signal feeding AUX 1 is sent after the fader, so the  
channel Fader has an effect on that level, meaning the  
Aux level tracks up and down with the channel Fader. This  
is the normal setting for using AUX 1 as an effects send,  
since when you set the channel louder, you normally  
want the effect to get louder.  
NOTE: The channel’s effects signal is sent to the AUX 1  
bus from a location in the signal path after the VOLUME  
control.  
The MDR series include two auxiliary signal paths, or  
buses, that can be used to create independent mixes for  
sending to the internal or external effects processors, or  
to an external monitor system. The flow of these buses  
start by sending the signal from each individual channel,  
which is set with one of the auxiliary control knobs. Then,  
the mix of all the channels auxiliary level is ultimately sent  
to either an internal effects processors, or to an output  
jack to connect to an external effect or monitor system. To  
help you control your effects and monitor mixes, the MDR  
mixers have two auxiliary buses. Plus, for added flexabil-  
ity, AUX1 can be configured as a Pre or Post fader send.  
6 - AUX 2/DSP  
The channel’s AUX 2/DSP knob controls the amount of  
signal that is sent to the AUX 2 bus. The AUX 2 signal can  
be sent to an external effects device connected to the  
AUX 2 OUT jack located in the MASTER SECTION jack field.  
NOTE: The channel’s AUX 2 signal is sent to the AUX 2  
bus from a location in the signal path after the channel’s  
LEVEL control. This is commonly referred to as a POST  
FADER send. This means that the amount of signal that is  
sent to the AUX 2 bus will be affected not only by the set-  
ting of the AUX 2 knob control, but it will also be affected  
by the setting of the LEVEL control.  
PRE….? POST….? What’s That?  
In order to operate your mixer correctly, it is important  
to understand the concept of PRE and POST Fader Aux  
sends. An auxiliary bus that is set up as PRE Fader routes,  
or sends, the signal to its output from a point in the chan-  
nelscircuit that is electronically before the channel Fader.  
That means the channel Fader has no effect on the PRE  
aux level. A Pre Fader send is what you want to use for a  
monitor mix, so when the level is changed for the mix in  
the main PA speakers using the channel Fader, the level  
in the monitor set by the aux control knob remains the  
same. An auxiliary bus that is set up as POST Fader routes,  
or sends, the signal to its output from a point in the chan-  
nelscircuit that is electronically after the channel Fader.  
That means that the channel Fader also affects the level of  
a POST aux send. A POST Aux bus is what you want to use  
(almost always) for sending to an effects processor, either  
internal or external. When using the POST aux sends,  
(while turning the channel Fader up or down) the level of  
effects will track the channel level correctly.  
7 - PAN  
The MDR1248 and MDR1688’s PAN control is used to  
place or position the mono signal into the stereo main  
Left and Right MIX bus. You can create a stereo image  
by panning some input signals to the left and others to  
the right. The MDR1248 and MDR1688’s PAN control is a  
Power-Pan circuit, which includes a 3dB dip in the center  
position. This is desirable since there’s a 3dB increase in  
gain when the mono input signal is heard in both the Left  
and Right MIX bus.  
8 - 3/4 MUTE switch  
The Mono Input channels feature a 3/4 MUTE switch  
allowing you to easily turn that channel on or off. When  
3/4 MUTE LED is illuminated, the channel is off, converse-  
ly, when the backlight is off, the channel is on. The switch  
also has a second purpose. When the switch is pressed  
down, signal from the selected channels is sent to the  
3/4 Outputs. This lets you use 3/4 as a second stereo bus  
which can be mixed in with the main left and right mix  
bus or sent out the 3/4 outputs without being heard in  
the main Left and Right mix.  
4 - AUX 1  
The MDR1248 and MDR1688 have two auxiliary sends  
which can be used for sending signals to external effects  
devices or for creating a monitor mix. The AUX1 section  
is often used for a monitor mix in a live sound mixing, or  
for a headphone mix in a recording application. AUX 1  
can also be used as a Pre Fader effect send by setting the  
Pre/Post switch to the Post postion. Each input channel  
includes an AUX 1 send which controls the amount of that  
channel’s signal that is sent to the AUX bus.  
NOTE: If the AUX1Pre/Post switch is set to Pre, the Aux  
controls are "PRE-FADER SENDS" which means they are  
not affected by the FADER level settings of each channel.  
This allows you to create a mix for the monitors that is  
independent of the main LEFT and RIGHT MIX.  
9 – 3/4 MUTE LED  
The MDR1248 and MDR1688’s has a 3/4 Mute LED indica-  
tor allowing you to easily see if the channel is muted or  
assigned to the 3/4 mix bus. When 3/4 MUTE LED is illu-  
minated, the channel is off and assigned to the 3/4 bus,  
conversely, when the backlight is off, the channel is on  
and not assigned to the 3/4 mix bus.  
5 - PRE/POST - switch  
The PRE/POST switch is used to select the point that the  
AUX 1 bus uses to send the signal. When the PRE/POST  
switch is set to PRE, the signal feeding AUX 1 is sent  
before the fader, so the channel Fader has no effect on  
that level. This is the normal setting when using AUX 1 as  
10 - Solo switch  
The Mono Input channel’s Solo switch allows you to  
listen, or “soloa channel or group of channels in the  
headphones. When the SOLO switch is pressed down, the  
channel is assigned to the solo bus and can be heard  
8
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Controls and Functions  
in any optional headphones plugged in to the PHONES  
connector located in the front panel jack field. If the  
AFL/PFL MODE switch, located in the master section, is  
switched out, the signal is sent pre fader, so you can hear  
the signal regardless of the position of the channel vol-  
ume Fader. This allows you to listen to a channel by itself:  
(let's say) to see if an artist is out of tune, or to cue up a  
channel without having to play it through the main PA  
speakers. If the AFL/PFL MODE switch is switched in, the  
signal is sent post fader, the signal you hear is dependant  
on the position of the channel volume Fader. This allows  
you to hear if there is any distortion on a channel added  
by the level of the channel fader.  
it towards the left will cut the frequency by 15dB. The fre-  
quency centers, range of boost or cut, and equalizer type  
for each band are as follows:  
High: 12kHz +/- 15dB shelving type  
High Mid: 3kHz +/- 15dB peaking type  
Low Mid: 500Hz +/- 15dB peaking type  
Low: 80Hz +/- 15dB shelving type  
ꢀꢁ  
ꢀꢂ  
11- SOLO LED  
The MDR1248 and MDR1688’s Mono Input channels  
include a SOLO LED which, when illuminated, indicates  
that the signal is assigned to the SOLO bus.  
12 - PEAK LED  
The MDR1248 and MDR1688’s MIC/LINE pre-amp also  
includes a PEAK LED which, when illuminated, indicates  
that the signal is peaking or overloading. To reduce dis-  
tortion, lower the GAIN control to keep this LED from stay-  
ing on.  
13 - CHANNEL LEVEL  
The MDR1248 and MDR1688’s LEVEL control knobs are  
used to adjust the overall channel volume.  
ꢀꢃ  
STEREO INPUT CHANNEL SECTION  
The MDR1248 and MDR1688 feature stereo input chan-  
nels for connected stereo line level devices like keyboards  
and drum machines, as well as the outputs from effects  
processors and digital guitar modelers. The MDR1248 has  
four sets of stereo inputs which make up channels 5/6,  
7/8, 9/10 and 11/12, while the MDR1688 has four sets of  
stereo inputs which make up channels 9/10, 11/12, 13/14  
and 15/16. The Stereo input channels have a four-band  
fixed equalizer and AUX 1 and 2 sends and are laid out the  
same as the mono inputs. The following section details  
the stereo input controls:  
ꢀꢅ  
ꢀꢄ  
ꢀꢈ  
ꢆꢀ  
ꢆꢉ  
ꢆꢇ  
14- GAIN switch  
ꢆꢆ  
The MDR1248 and MDR1688’s pre-amp stage has a vari-  
able GAIN switch with a range of -10 to +4dB on the ste-  
reo LINE input.  
ꢆꢁ  
15 - LOW/LOW MID/HIGH MID/HIGH - Channel  
Equalizer  
ꢆꢂ  
The MDR1248 and MDR1688 Stereo input channels fea-  
ture a 4-band equalizer allowing you to adjust the high,  
mid, and low frequencies independently on each channel.  
The stereo channel equalizer is laid out like a mono input  
on the control panel input strip, but internally, the equal-  
izer is effecting a stereo signal path. The channel’s fre-  
quency response is flat when the knobs are in the “12:00”  
position. Rotating the knob towards the right will boost  
the corresponding frequency band by 15dB, and rotating  
9
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Controls and Functions  
Auxiliary Busses ( 16 - 18 )  
Right stereo mix field. You can create a stereo image by  
panning some input signals to the left and others to the  
right.  
The MDR series include two auxiliary signal paths, or  
buses, that can be used to create independent mixes for  
sending to the internal or external effects processors, or  
to an external monitor system. The signal flow from these  
buses start by sending the signal from each individual  
channel, which is set with one of the auxiliary control  
knobs. Then, the mix of all the channels auxiliary level is  
ultimately sent to either an internal effects processors or  
to an output jack to connect to an external effect or moni-  
tor system. To help you control your effects and monitor  
mixes, the MDR's have two auxiliary buses.  
20 - 3/4 MUTE switch  
The Stereo Input channels feature a 3/4 MUTE switch  
allowing you to easily turn that channel on or off. When  
3/4 MUTE LED is illuminated, the channel is off, con-  
versely, when the LED is off, the channel is on. The switch  
also has a second purpose. When the switch is pressed  
down, signal from the selected channels is sent to the  
3/4 Outputs. This lets you use 3/4 as a second stereo bus  
which can be mixed in with the main left and right mix  
bus or sent out the 3/4 outputs without being heard in  
the main Left and Right mix.  
In order to operate your mixer correctly it is important  
to understand the concept of PRE and POST fader sends.  
For more information on Pre and Post aux sends, see the  
previous section “Pre…?, Post?… What’s that?Located on  
page 8 of this manual.  
21 – 3/4 MUTE LED  
The MDR1248 and MDR1688’s has a 3/4 Mute LED indica-  
tor allowing you to easily see if the channel is muted or  
assigned to the 3/4 mix bus. When 3/4 MUTE LED is illu-  
minated, the channel is off and assigned to the 3/4 bus,  
conversely, when the LED is off, the channel is on and not  
assigned to the 3/4 mix bus.  
16 – AUX 1  
Each of the MDR1248 and MDR1688’s stereo input chan-  
nels include an AUX 1 send, which controls the amount of  
that channel’s signal that is sent to the AUX 1 Output. The  
AUX1 section is often used for a monitor mix in live sound  
mixing, or for a headphone mix in a recording applica-  
tion. AUX 1 can also be used as a Post Fader effect send  
by setting the Pre/Post switch to the Post postion. Each  
input channel includes an AUX 1 send which controls the  
amount of that channel’s signal that is sent to the AUX  
bus.  
22 - Solo switch  
The Stereo Input channel’s Solo switch allows you to  
listen, or “soloa channel or group of channels in the  
headphones. When the SOLO switch is pressed down, the  
channel is assigned to the solo bus and can be heard in  
any optional headphones plugged in to the PHONES con-  
nector located in the front panel jack field. If the AFL/PFL  
MODE switch, located in the master section, is switched  
out, the signal is sent pre fader, so you can hear the signal  
regardless of the position of the channel volume Fader.  
This allows you to listen to a channel by itself: (let's say)  
to see if an artist is out of tune, or to cue up a channel  
without having to play it through the main PA speakers. If  
the AFL/PFL MODE switch is switched in, the signal is sent  
post fader, the signal you hear is dependant on the posi-  
tion of the channel volume Fader. This allows you to hear  
if there is any distortion on a channel added by the level  
of the channel fader.  
17 - PRE/POST - switch  
The PRE/POST switch is used to select the point that the  
AUX 1 bus uses to send the signal. When the PRE/POST  
switch is set to PRE, the signal feeding AUX 1 is sent before  
the fader, so the channel Fader has no effect on that level.  
This is the normal setting when using AUX 1 as a monitor  
send. When the PRE/POST switch is set to POST, the signal  
feeding AUX 1 is sent after the channel fader, meaning the  
Aux level tracks up and down with the channel Fader. This  
is the normal setting for using Aux1 as an effects send,  
since when you set the channel louder, you normally want  
the effect to get louder.  
23- SOLO LED  
The MDR1248 and MDR1688’s Stereo Input channels  
include a SOLO LED which, when illuminated, indicates  
that the signal is assigned to the SOLO bus.  
18 – AUX 2 /DSP  
Each of the MDR1248 and MDR1688’s stereo input chan-  
nels include an AUX 2/DSP send, which controls the  
amount of that channel’s signal that is sent to the internal  
DSP and/or AUX 2 Output. The signal that feeds Aux 2 is  
sent after, or post, the channel Fader, so the channel Fader  
has an effect on the Aux 2 level. This is the normal setting  
for an effects send, since when you set the channel loud-  
er, you normally want the effect to get louder.  
24 – PEAK LED  
The MDR1248 and MDR1688’s MIC/LINE pre-amp also  
includes a PEAK LED which, when illuminated, indicates  
that the signal is peaking or overloading. To reduce dis-  
tortion, lower the GAIN control to keep this LED from stay-  
ing on.  
19 - BALANCE - Control  
The MDR1248 and MDR1688’s BALANCE control is used to  
place, or position, the stereo signal into the main Left and  
25- VOLUME - Fader Level Control  
The VOLUME Fader control adjusts the level of the stereo  
channel.  
10  
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Controls and Functions  
27 - AUX RET 1 control knob  
MASTER SECTION  
26 - 2 TRK LEVEL  
The 2TK LEVEL control knob is used to set the volume  
level of the source connected to the 2-track input. If you  
want to mix in a CD, tape or MP3 player with your input  
channels connected to the 2TK inputs, use the 2TK LEVEL  
to adjust the level.  
This adjusts the amount of signal that is sent from the AUX  
1 RET jacks to the MAIN bus.  
28 - AUX RET 2 control knob  
The AUX RETURN 2 adjusts the level of the signal present  
at the AUX 2 RET jacks. This signal is summed, or mixed in  
to the main L/R MIX bus.  
29 - AUX 2 RETURN TO AUX 1 switch  
This routes the signal that is present on the AUX 2 RETURN  
jacks to AUX 1 so that the effects can be heard in the  
monitor mix.  
ꢀꢁ  
ꢀꢂ  
30 - AUX 1 SEND control knob  
The master AUX SEND control is used to send the effect  
mix bus to an external effect device connected to the AUX  
SEND 2 jack.  
ꢅꢁ  
ꢅꢂ  
ꢅꢃ  
ꢀꢃ  
ꢀꢄ  
31 - AUX 2 SEND control knob  
The master EFX SEND control is used to send the effect  
mix bus to an external effect device connected to the AUX  
SEND 2 jack.  
ꢅꢄ  
32 - ALT 3/4 Level control knob  
ꢅꢆ  
ꢅꢇ  
Use this control knob to set the level of the mix created  
from the channels assigned to the 3/4 bus. The ALT 3/4  
level control will control the level of the signal being  
sent to the 3/4 Output jacks. When the Master ALT 3/4  
switch(43) is switched in, the ALT 3/4 level control will con-  
trol the level of the ALT 3/4 mix that is heard in the Main  
Left and Right mix. Remember, the ALT 3/4 TO MIX switch  
must be set to the on or down position in order to hear  
the 3/4 mix in the main Left and Right mix.  
ꢉꢆ  
ꢉꢈ  
ꢉꢁ  
ꢉꢇ  
ꢅꢀ  
ꢉꢂ  
ꢉꢀ  
ꢉꢅ  
ꢉꢉ  
ꢅꢉ  
ꢅꢅ  
ꢅꢈ  
33 - SOLO LED  
The LED will illuminate when any one or more channel's  
SOLO switch is engaged, indicating that there is a channel  
in solo.  
34 - LEVEL SET LED  
When a channel's SOLO switch is pressed, the LEVEL SET  
LED will illuminate and flash indicting that the channels  
input level is now being measured by the main VU meter.  
35 - MODE (AFL/PFL) switch  
You can change the mode of the SOLO bus from Pre fader  
listen to After, or Post fader listen using the MODE switch.  
When the switch is pressed in, the SOLO mode is set to  
AFL (After Fader Listen), so the channels signal is sent after  
or post fader. When the switch is pressed out, the SOLO  
mode is set to PFL (Pre Fader Listen), so the channels sig-  
nal is sent before or pre fader.  
ꢉꢃ  
Auxiliary Returns  
ꢉꢄ  
36 - PROGRAM control knob  
The MDR1248 and MDR1688 feature an internal 24-bit  
DSP with 256 presets. The presets are organized in sixteen  
Program banks, each with sixteen variations. The Program  
control knob used to select one of the sixteen DSP effect  
programs.  
The MDR1248 and MDR1688 have two stereo auxiliary  
returns, which can be accessed via the two pairs of 1/4-  
inch phone jacks located on the master section jack field.  
The auxiliary returns can be used to connect any stereo  
line level signal, but they are primarily used to connect  
the output of external effects processors.  
37 - VARIATION control knob  
The MDR1248 and MDR1688 feature an internal 24-bit  
11  
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Controls and Functions  
MASTER SECTION (continued)  
output and will be adjusted by the CR / PHONES control  
fader.  
DSP with 256 presets. The presets are organized in sixteen  
Program banks, each with sixteen variations. The Variation  
control knob is used to select one of the sixteen variations  
for each of the sixteen DSP effect Programs.  
45 - Phantom Power LED  
This LED illuminates indicating that the 48 volt phantom  
power is applied to the microphone pre-amps enabling  
use with condenser microphones. The +48V LED will light  
up when the Phantom Power switch (located on the rear  
panel) is switched to the ON position.  
38 - PEAK (DSP INPUT) LED  
LED indicator illuminates when the input signal to the  
internal DSP is reaching a clipping level.  
46 - POWER LED  
39 - DSP MUTE switch  
The Power LED lights up to indicate that the main POWER  
switch (located on the rear panel) is on.  
This switch is used to turn the internal DSP effects on and  
off. When the DSP MUTE switch is pressed in, the internal  
DSP effects are turned off and when the switch is pressed  
out, the DSP effects are on.  
47 - Output Level Meters  
The OUTPUT LEVEL METERS allows you to monitor the  
level of the signal which is being sent to the MAIN MIX  
jacks.  
2 TRACK INPUT AND OUTPUT  
The MDR1248 and MDR1688’s 2 Track section provides the  
connections for playback and recording for an external  
device such as a DAT, cassette recorder, CD or Mini Disk.  
48 - MAIN MIX - Fader Control  
The master MAIN controls are the overall volume controls  
for the left and right mix bus. These line level signals are  
output from the MAIN MIX jacks.  
Main Mix Assign Switches  
The next two switch functions are used to select addition-  
al sources that can be combined with the Main Left and  
Right mix and sent to the main Left and Right Outputs.  
49 - PHONES / CR  
The PHONES / CR control is used to set the level sent to the  
control room outputs, and also to the headphone jack.  
40 - ALT 4/3 TO MIX switch  
The ALT 3/4 TO MIX switch is used to assign the ALT 3/4  
mix bus to the MAIN mix bus. If you push the ALT 3/4 TO  
MIX button, all the channels with their ALT 3/4 switch  
pressed in will be routed to the left and right MAIN out-  
puts and the level will be controlled by the 3/4 LEVEL con-  
trol knob and MAIN LEVEL fader.  
NOTE: To avoid distortion, adjust the Main Level control so  
that the 0 indicator LED lights occasionally.  
41 - 2TK TO MIX switch  
The 2TR TO MIX switch is used to assign the 2TR input to  
the MAIN mix bus. If you push the 2TR TO MIX button, the  
signal present at the 2 TRACK IN will be routed to the left  
and right MAIN output and the level will be controlled by  
the 2TK LEVEL control knob and MAIN LEVEL fader.  
Control Room and Headphone Assign Switches  
The next three switch functions are used to select addi-  
tional sources that can be heard in the headphones and  
sent to the Left and Right Control Room Outputs.  
42 - MAIN MIX switch  
The MAIN MIX switch routes the Left / Right MAIN mix bus  
to the CONTROL ROOM / PHONES outputs. Use the Left /  
Right MAIN MIX Level faders (48) and PHONES level fader  
(49) to set the volume.  
43 - ALT 3/4 switch  
The ALT 3/4 switch routes the 3/4 mix bus to the CONTROL  
ROOM / PHONES outputs. Use the ALT 3/4 LEVEL control  
knob (32) and PHONES level fader (49) to set the volume.  
44 - 2 TK IN switch  
The 2TR IN switch is used to assign the 2TR input to the  
Control Room output. If you push down the 2TK IN button,  
signal will be routed into the left and right Control Room  
12  
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MDR1248 and MDR1688 Input and Output Connections  
equalizer, compressor, noise gate, reverb and other audio  
devices. For more information on the channel INSERT  
points, see the section, “Using the Channel Insert Jackson  
page 17 of this manual.  
MONO INPUT CHANNELS - MIC and LINE INPUTS  
Channels 1 through 4 on the MDR1248 and channels 1  
through 8 on the MDR1688 are mono inputs, each pro-  
viding a 1/4-inch connector for line level signals and an  
XLR connector for the MIC signals. Channels 5/6 through  
11/12 on the MDR1248 and channels 9/10 through 15/16  
on the MDR1688 are stereo inputs, providing a pair of 1/4-  
inch connectors for line level inputs. By using the GAIN  
control on the mono channels, you can connect a variety  
of signal sources from microphones to line level devices  
such as synthesizers, and drum machines. All the LINE  
and MIC inputs are balanced. The MIC inputs are compat-  
ible with microphones with output impedances of 50-  
600 Ohms and the LINE inputs are compatible with line  
level devices of 600 Ohms. Following below is a detailed  
description of the MDR1248 and MDR1688’s input and  
output connectors.  
Stereo Input Channels - Line Inputs  
You can connect the outputs from stereo devices such as  
synthesizers, drum machines, effects processors or any  
stereo line-level signal. The LINE inputs have a nominal  
operating level of -40dBV through - 10dBV. The 1/4-inch  
TRS phone jacks Connector pin-out are as follows; Sleeve:  
Ground, Tip: Hot (+), Ring: Cold (-)  
%
&
"
D- LEFT MONO  
The LEFT MONO jack is used to connect the left output of  
a stereo device to the Left input of the MDR’s stereo input  
channels or use the LEFT input when connecting a mono  
input signal to the Stereo Input channels.  
#
$
E - RIGHT  
The RIGHT jack is used to connect the Right output of a  
stereo device to the Right input of the MDR’s stereo input  
channels.  
NOTE: It is not possible to simultaneously use both the  
LINE and MIC inputs on the same channel. Use only one of  
the inputs for the appropriate source on each channel.  
A - Microphone Input - Mono Input Channels  
Use these inputs to connect Low Impedance micro-  
phones and low level signals from direct boxes. The MIC  
inputs have a nominal operating level of –50dBu through  
-20dBu. The MIC inputs also feature +48V phantom  
power, allowing you to use condenser microphones. The  
Phantom Power switch (located on the MDR1248 and  
MDR1688’s rear panel) enables phantom power on all  
the microphone inputs when set to the ON position. XLR  
Connector pin-out - Pin 1: Ground, Pin 2: Hot (+), Pin 3:  
Cold (-)  
MASTER SECTION INPUT AND OUTPUT JACKS  
The MDR1248 and MDR1688 features several input and  
output connectors allowing you to interface a variety of  
external devices. A stereo recording device, such as a cas-  
sette recorder, can be connected to the 2 Track jacks, and  
power amplifiers or powered monitors can be connected  
to the CONTROL ROOM and MAIN output jacks.  
*
B - Line Level Input - Mono Input Channels  
Use these inputs to connect synthesizers, drum machines,  
effects processors or any line-level signal. The LINE  
inputs have a nominal operating level of -40dBV through  
- 10dBV. TRS phone jacks Connector pin-out - Sleeve:  
Ground, Tip: Hot (+), Ring: Cold (-)  
'
(
)
F - ALT 3/4 LEFT/RIGHT OUTPUT  
The ALT 3/4 outputs are 1/4-inch balanced jacks carrying the  
signal from the 3/4 bus. You can assign a channel or a group  
of channels to the 3/4 bus using the MUTE 3/4 switch on the  
stereo and mono input channels. The 3/4 output connectors  
are labeled Left and Right since the 3/4 bus follows the chan-  
nelsPAN control allowing it to be used for a second stereo  
C - Insert Point Jack - Mono Input Channels  
The MDR1248 and MDR1688’s mono input channels fea-  
ture a 1/4-inch, TRS INSERT jack providing a patch point to  
connect an external processor. You can use these connec-  
tions to interface an external signal processor like an  
13  
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MDR1248 and MDR1688 Input and Output Connections  
mix. You can also pan the channels hard left and right to cre-  
ate two mono buses. Keep in mind that using the 3/4 switch  
mutes the channel from the main mix, so use the ALT 3/4 bus  
for a separate stereo, or two mono, zone mixes.  
L - AUX RETURN 2 LEFT/RIGHT  
The AUX RETURN 2 LEFT/RIGHT are stereo inputs that are  
generally used to connect the outputs of an effects proces-  
sor, but can also accept the signal from any line level source  
like a keyboard, recorder and even another mixer. The signal  
connected to the AUX RETURN 2 LEFT/RIGHT will feed the  
main LEFT/RIGHT MIX bus. The overall level is controlled by  
the AUX RET 2 knob located in the master section on the  
front panel. Use the LEFT/MONO input when connecting a  
mono input signal to the AUX RETURN.  
G - CONTROL ROOM LEFT/RIGHT OUTPUT  
The Control Room outputs are 1/4-inch balanced jacks used  
to connect a studio monitor system. The Control Room out-  
puts have the same output as the L/R MIX, however, the level  
can be adjusted independently from the main mix using the  
C ROOM/HEADPHONES control.  
M - AUX Send 2  
H - MAIN MIX LEFT/RIGHT 1/4-INCH OUTPUTS  
In a live sound application, the LEFT/ RIGHT MIX outputs are  
1/4-inch balanced jacks used to connect a power amplifier  
or powered speakers. In a recording application, the LEFT/  
RIGHT MIX outputs are used to connect to the inputs of a  
stereo device such as computer sound card, DAT, or cassette  
recorder.  
The signal present at the AUX 2 output is sent from the AUX  
2 bus, which is fed from all the AUX 2 sends on the input  
channels. The AUX 2 output can be used as the MONITOR  
MIX bus in a live sound situation by connecting the output to  
a power amp and monitor speaker.  
N – FOOTSWITCH - 1/4-inch jack  
With a footswitch connected to this jack, you can turn on  
and off the on-board digital effects by simply stepping on  
the footswitch.  
I - MAIN MIX LEFT/RIGHT XLR OUTPUTS  
In a live sound application, the LEFT/ RIGHT MIX outputs are  
connected to a power amplifier or powered speakers. In a  
recording application, the LEFT/ RIGHT MIX outputs are used  
to connect to the inputs of a stereo device such as computer  
sound card, DAT, or cassette recorder.  
0 - HEADPHONE OUTPUT  
You can connect a standard pair of stereo headphones to  
the PHONES jack and depending on the position of the 2T  
TO CR switch, you will hear either the 2-Track input or the  
MAIN mix.  
J - AUX RETURN 1 LEFT/RIGHT  
The AUX RETURN 1 LEFT/RIGHT are stereo inputs that are  
generally used to connect the outputs of an effects processor,  
but can also accept the signal from any line level source like  
a keyboard, recorder and even another mixer. The signal con-  
nected to the AUX RETURN 1 LEFT/RIGHT will feed the main  
/
+
-
1
2
P - 2TR INPUT  
The MDR1248 and MDR1688 features dual RCA connectors  
for the left and right 2-track input. You can use these inputs  
to connect a CD, Cassette, Mini Disk, DAT or the output from  
a computer sound card. To listen to the input connected to  
the 2T IN, be sure to check the position of the 2T To Mix and  
2T TO CR switches. For more information on using the 2 Track  
inputs, see the section “PLAYING BACK A CD USING 2T TO MIX ”  
on page 18 of this manual.  
,
.ꢀ  
0
LEFT/RIGHT MIX bus. The overall level is controlled by the  
AUX RET 1 knob located in the master section on the front  
panel. Use the LEFT/MONO input when connecting a mono  
input signal to the AUX RETURN.  
Q - 2TR OUTPUT  
If you want to record the mix from your MDR1248 and  
MDR1688, you can use the 2-track OUT connectors. The  
dual RCA connectors can be connected to a CD, Cassette,  
Mini Disk, DAT or even the input of a computer sound card  
for hard disk recording. For more information on using the 2  
Track outputs, see the section “RECORDING A MIX FROM THE  
MDR1248 and MDR1688 ” on page 18 of this manual.  
K - AUX Send 1  
The signal present at the AUX1 output is sent from the AUX1  
bus, which is fed from all the AUX 1 sends on the input chan-  
nels. The AUX 1 output can be used as the EFFECTS SEND  
bus in a live sound situation by connecting the output to an  
external effects device.  
14  
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Operating the MDR1248 and MDR1688  
NOTE: SETTING THE INPUT GAIN - When connecting a  
BASIC OPERATION  
microphone to channels 1 through 4 on the MDR1244 or  
1 through 8 on the MDR1688, it’s a good idea to start with  
the Gain Control turned all the way down. Set the input  
fader to the "0" position and slowly raise the GAIN control  
until you see the PEAK LED turn on. Now, back the GAIN  
control down so that the PEAK LED only lights for a short  
time during the loudest input the channel will see.  
The following section explains the basic operation of the  
MDR1248 and MDR1688:  
CONNECTING MICROPHONES AND INSTRUMENTS  
1. Before connecting mics or instruments, make sure that  
the power of all your system's components including  
the MDR1248 and MDR1688 is turned off. Also, make  
sure that the MAIN LEVEL and PHONES / CR controls are  
turned all the way down.  
Note. You can also press the channel's PFL switch and  
use the LEVEL SET function. When the PFL is switched  
on, you'll see the LEVEL SET LED is illuminated and the  
channel's input level will now be displayed on the Main  
VU meter.  
2. Connect the cables to your microphones and instru-  
ments, and insert the other end of the cable firmly into  
the appropriate input on the MDR1248 and MDR1688.  
3. Switch on the power of any peripheral devices, and  
then power up the MDR1248 and MDR1688.  
NOTE: It is important to remember the Golden Rule of  
audio … " LAST ON, FIRST OFF". Translated, this means  
that when turning on your system, you should always  
turn your power amplifiers or powered monitors on LAST,  
and when turning your system off, turn your power amps  
off FIRST. This helps avoid any loud pops caused by rush  
current at power up, or down, which can sometimes dam-  
age loudspeakers.  
4. Turn on your power amp or powered monitors and  
raise the level control to the manufacturers recom-  
mended operating level.  
5. Set the MAIN LEVEL control in the MDR1248 and  
MDR1688’s master section to the "0" position.  
6. While speaking into the mic (or playing the instru-  
ment), adjust the channel LEVEL control so that the  
"0" LED of the MAIN section VU level meter lights  
occasionally.  
7. You can shape the tone of each channel by adjusting  
the channel equalizer controls as desired.  
NOTE: You may need to adjust the channel LEVEL control  
to compensate for the slight changes in level after using  
the channel equalizer.  
15  
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Operating the MDR1248 and MDR1688  
4. Next, locate the AUX SEND 2 knob and turn it about to  
USING THE DIGITAL EFFECTS  
a little past “5or half way.  
The MDR1248 and MDR1688 mixers feature a built-in,  
high quality, 24-bit Multi Effect Processor, offering studio  
grade digital effects. The MDR’s Effect section features  
clean Delay, lush Reverbs and multi-effects like Chorus  
+ Delay, Chorus Flange or Chorus + Reverb. You can add  
a broad range of studio quality effects by simply dialing  
through the 256 presets.  
5. Now, use the AUX RETURN 2 control knob to adjust  
the effects return level. The AUX RETURN 2 control  
knob sets the overall level control for the DSP effects  
processor in the main Left and Right Mix.  
6. Now, you can check out different versions of the  
PROGRAM presets by using the VARIATIONS control  
knob. Each of the 16 effects PROGRAM banks has six-  
teen variations providing a total of 256 effects presets.  
7. If you want to hear the effects in the monitors, press  
the AUX RETURN 2 TO AUX1 switch and you will have  
the output of the internal effects routed to the AUX1  
output. For more information on setting up a monitor  
mix, see the following section.  
NOTE: If the DSP PEAK LED lights up and effect sound is  
distorted, even though the AUX RETURN 2 is turned down  
low, lower the AUX SEND 2 control knob and the AUX2/  
DSP controls of each channel.  
8. If you want to bypass the effects, you can turn off the  
effects processors output by using the DSP MUTE  
switch, or an optional footswitch connected to the  
FOOTSWITCH jack.  
The following details the operation of the internal DSP  
effects in the MRD1248 and MDR1688 Effects section:  
1. Connect a mic or instrument to the desired channel,  
adjust the level and equalizer to your liking and make  
sure the MAIN fader level is set so you can hear it in  
your speakers.  
2. Now select the desired effects program using the  
PROGRAM control knob located in the Effects sec-  
tion in the middle of the mixer’s Master section.  
Set the PROGRAM control knob to one of the 16  
effects. You can check the effects Program List below  
the PROGRAM knob to find the effect type per-  
fect for your performance. The first PROGRAM and  
VARIATION banks have been preset with common  
effects for live performance, and the following banks  
are set up in groups by the types of effects.  
3. Once you have selected the desired effects preset,  
raise the AUX 2 DSP control on the channels you wish  
to apply the digital effect to.  
16  
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Operating the MDR1248 and MDR1688  
SENDING AN INDEPENDENT MIX TO THE  
USING THE CHANNEL INSERT JACKS  
MONITOR SPEAKERS  
To further control your signal, channels 1-4 on the  
MDR1248 and 1-8 on the MDR1688 feature an inser-  
tion point, or “effects loop, on one 1/4-inch phone jack,  
INSERT SEND and RETURN. An insertion point is a patch-  
point that interrupts the signal, allowing you to bring that  
signal outside to be processed by another device. You  
can use these connections to interface an external signal  
processor like an equalizer, compressor, noise gate, reverb  
and other audio devices. A common application for the  
MDR1248 and MDR1688’s insert point is using a compres-  
sor.  
The MDR1248 and MDR1688’s AUX1 auxiliary send can be  
used to feed a separate set of amplifiers and loudspeakers  
for stage monitors. This lets you build one mono mix for  
the amplifiers and monitor speakers facing the musicians,  
and the other stereo mix for the amplifiers and speakers  
facing the audience.  
1. Connect the AUX1 output to your monitor's power  
amplifier or powered monitor.  
2. Press the input channelsAUX 1 PRE/POST switches  
in, to set AUX 1 up as a pre-fader bus.  
To send a signal to an external processor, use a standard  
1/4-inch “Yinsert cable to connect the MDR1248 and  
MDR1688 channel insert point. Connect the TRS (TIP /  
RING / SLEEVE) plug to the channel INSERT point, and  
then, connect the 1/4-inch (TIP / SLEEVE), INSERT SEND  
plug to the input of the external processor. The signal is  
sent back to the MDR1248 or MDR1688, using the 1/4-  
inch (TIP / SLEEVE), INSERT RETURN plug connected to the  
output of the external processor.  
3. Raise the AUX SEND 1 control knob, located in the  
Master section, up to a little past “5or halfway.  
4. Raise the AUX 1 controls for the channels that you  
wish to hear from the monitor speakers.  
The diagram below shows a typical application for using a  
compressor (in this example a Samson C com opti) in the  
MDR1248 or MDR1688’s insertion point.  
NOTE: When the AUX1 PRE/POST switch is pressed in and  
set to “PRE, the AUX 1 controls are "PRE-FADER SENDS"  
which means they are not affected by the level settings  
of each channel. This allows you to create a mix for the  
monitor system that is independent of the main LEFT and  
RIGHT MIX.  
5. If feedback occurs, turn down the AUX SEND 1 knob  
to lower the overall level sending to the monitor.  
Then check the AUX1 levels of the individual chan-  
nels to see if you need to turn one or more channels  
down. Then try to raise the AUX 1 SEND level again.  
NOTE: Adjusting the balance between the channel AUX1  
control knobs and the AUX SEND 1 is a tricky but neces-  
sary part of getting good levels in the monitor system. In  
general, try to keep the master AUX SEND 1 higher than  
the channel AUX1 levels to achieve a cleaner mix. In order  
to get the most gain from your monitor mix, use an exter-  
nal graphic equalizer (like a Samson S curve 131or D2500  
digital EQ with feedback control) to cut out any frequen-  
cies that cause feedback.  
Below, is a diagram showing the wire for the TRSYInsert  
cable.  
6. If you want to add effects from the internal effect  
processor, or the effects from an external proces-  
sor connected to the AUX RETURN 2 inputs, engage  
the AUX RETURN 2 TO AUX 1 switch, located in the  
Master section, by pressing it in.  
17  
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Operating the MDR1248 and MDR1688  
USING AN EXTERNAL EFFECT  
PLAYING BACK A CD USING 2T TO MIX  
If you prefer to use an external device for effects process-  
ing, you can easily connect the unit using the MDR1248  
and MDR1688 AUX 2 bus. Follow the simple steps below  
to interface your processor:  
The MDR1248 and MDR1688 has a dedicated input for  
playing back a stereo device such as a CD, Tape or Mini  
Disk. Below is a description of how you can play back  
a CD, Tape or MD using the MDR1248 and MDR1688’s 2  
TRACK INPUT.  
1. Connect the AUX 2 OUTPUT to the input of the  
external effect processor.  
1. Turn the MAIN level control all the way down.  
2. Press the 2TK TO MIX button down.  
2. Connect the outputs of the effect processor to  
the AUX 2 RETURN located on the MDR1248 and  
MDR1688’s master section.  
3. Adjust the MAIN LEVEL control in the master section  
to the "0" position.  
4. Start playback on the CD, Tape or MD player, and use  
the 2 TK LEVEL control to set the desired level.  
RECORDING A MIX FROM THE MDR1248 and  
MDR1688  
You can record the audio from the MDR1248 and  
MDR1688’s mixer section including the MIC, LINE, 2T IN  
and AUX inputs to a Cassette deck, MD, DAT or any other  
type of recorder using the 2T OUT outputs. Simply con-  
nect the MDR1248 and MDR1688’s 2 TRACK OUT to the  
input jacks of the recorder as shown in the diagram on  
the right and follow the steps below.  
3. Set the MAIN LEVEL control to the "0" position.  
4. Raise the AUX 2 knobs for the channels to which you  
want the external effect to be applied.  
5. Set the input level of the external effect so that the  
sound is not distorted and so that the effect’s input  
meter does not indicate a clipped signal.  
1. Adjust the MAIN LEVEL control in the master sec-  
tion to the "0" position.  
2. Set a clean signal using the recorder’s input level  
controls and meters.  
6. Use the AUX RETURN 2 control to adjust the level of  
the effects processed by the external effects device.  
3. Press RECORD.  
4. Play back using as described in the previous section  
"PLAYING BACK A CD USING 2T TO MIX".  
NOTE: To avoid feedback, be sure to keep the 2TK LEVEL  
control knob all the way down while recording with the  
2TK outputs.  
18  
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MDR1248 and MDR1688 System Set-Ups  
MDR1248 and MDR1688 LIVE SOUND SET-UP  
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MDR1248 and MDR1688 System Set-Ups  
MDR1248 and MDR1688 RECORDING SET-UP  
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MDR1248 and MDR1688 Wiring Guide  
CONNECTING THE MDR1248 and MDR1688  
The are several ways to interface the MDR1248 and MDR1688 to support a variety of applications. The MDR1248 and  
MDR1688 features balanced inputs and outputs, so connecting balanced and unbalanced signals is possible.  
Unbalanced 1/4” Connector  
Balanced TRS 1/4” Connector  
XLR Balanced Wiring Guide  
1/4-inch TRSY” Insert Cable Wiring Guide  
21  
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MDR1248 and MDR1688 Specifications  
Mono input channels  
Microphone input  
Frequency response  
Distortion  
Gain range  
SNR (Signal to Noise Ratio)  
Line input  
Frequency response  
Distortion (THD & N)  
Sensitivity range  
electronically balanced, discrete input configuration  
10Hz to 45kHz  
(THD & N) 0.005% at 4dBu, 1kHz  
0dB to +40dB (MIC)  
105dB  
electronically balanced  
10Hz to 45kHz  
0.005% at 4dBu, 1kHz  
-10dBu to +30dBu  
Stereo input Channels  
Line input  
Balanced  
Frequency response  
Distortion (THD & N)  
10Hz to 45kHz  
0.005% at +4dBu, 1kHz  
Impedances  
Microphone input  
Channel Insert return  
All other inputs  
Tape out  
3k Ohm  
2.5k Ohm  
14.8k Ohm or greater  
1k Ohm  
All other output  
120 Ohm  
Equalization  
Mono Channels  
Hi shelving  
Swept Mid bell  
Low shelving  
Low Cut filter  
Stereo Channels  
Hi shelving  
High Mid bell  
Low Mid bell  
Low shelving  
+/- 15dB @ 12kHz  
+/- 15dB @ 100 to 5kHz  
+/- 15dB @ 80Hz  
75Hz, 18dB/oct.  
+/- 15dB @12kHz  
+/- 15dB @ 3kHz  
+/- 15dB @ 500Hz  
+/- 15dB @80Hz  
Main Mix Section  
Noise (Bus noise)  
Max output  
Levels full down: -100dBr (ref.:+4dBu)  
Level set to 0 dB: -90dBr (ref.:+4dBu)  
+28dBu balanced XLR,  
+22dBu impedance balanced, 1/4" jacks  
3/4 Output Section  
Noise (Bus noise)  
Levels full down: -100dBr (ref.:+4dBu)  
Level set to 0 dB - 90dBr (ref.:+4dBu)  
+22dBu impedance balanced, 1/4" jacks  
Max output  
Control Room Output Section  
Noise (Bus noise)  
Levels full down: -100dBr (ref.:+4dBu)  
Level set to 0 dB - 90dBr (ref.:+4dBu)  
+22dBu impedance balanced, 1/4" jacks  
Max output  
Aux Section  
AUX Return gain range  
AUX Sends max out  
-∞ to +15dB  
+22dBu  
Power supply (AC/AC Adaptor)  
Power Consumption  
MDR1248  
15W  
32W  
39W  
MDR1688  
Main voltage  
USA/Canada 108 - 132V, 60Hz  
Europe 210 - 230V, 50Hz  
U.K./Australia 240V, 50Hz  
Physical  
Net weight  
MDR1248  
MDR1688  
9.79 lb. (4.45kg)  
12.87 lb. (5.85kg)  
Shipping weight  
MDR1248  
MDR1688  
13.86 lb. (6.30kg)  
18.92 lb. (8.60kg)  
Dimension (W D H)  
MDR1248  
MDR1688  
16x 12.3x 2.6(405mm x 313mm x 65mm)  
16x 16.7x 2.6(405mm x 425mm x 65mm)  
Specifications are subject to change without notice.  
22  
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Samson Technologies Corp.  
45 Gilpin Avenue  
Hauppauge, New York 11788-8816  
Phone: 1-800-3-SAMSON (1-800-372-6766)  
Fax: 631-784-2201  
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