Hughes Kettner Stereo Amplifier VS 250 User Manual

USER MANUAL  
Hughes & Kettner  
VS 250  
Stereo Tube Power Amplifier  
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Hughes & Kettner  
Stereo Tube Power Amplifier  
Congratulations!  
You have just acquired a highquality sound tool which combines the sonic superiority of  
vacuum tubes with the optimum usefulenss of a guitar rack. The VS 250 incorporates the  
sum of our experience with vacuum tubes. May you enjoy the new measure of expressiveness  
and creative freedom it affords.  
The following operating instructions delve into the special features and capabilities of the  
VS 250 in detail.  
The Hughes  
&
Kettner VS 250 is a twochannel tube power amplifier. As with all tube  
devices, there are a few things you should pay special attention to:  
For this reason a tube device needs a  
Tubes require a specific operating temperature.  
moment after power-up (depending on the operating environment about 20 seconds or SO)  
until it is completely ready for operation.  
Tubes are sensitive to being jostled or shaken when hot. After use, allow the unit to cool  
down for a few minutes before transporting it. Avoid subjecting it to strong vibrations while in  
operation.  
A tube amplifier should never be operated without a load (speaker) connected to it.  
Make sure that the vents in the front and back of the unit remain  
Tubes produce heat.  
unobstructed.  
CONTROLS  
The VS 250 has two independent channels, identical to each other. The controls for each  
channel are likewise identical; so what is said below about channel A also holds true for  
channel B.  
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FRONT  
Stand by  
There are two different levels of voltage controlling the tubes:  
1) the basic voltage intended to warm the tube to minimum operational temperature. This  
voltage is always applied to the tube whenever the power switch is in the on position.  
2) the operating voltage (plate voltage) which drives the tube. The operating voltage is turned  
off with the STANDBY switch.  
The green LED indicates the unit is in standby mode, the red LED above the STANDBY switch  
indicates normal playing mode.  
If you are using only one channel of the  
switch the other channel into standby mode.  
Volume  
VOLUME controls how much the input signal is amplified, thereby controlling the output  
volume of the channel. Due to the special LINE DRIVER circuitry in each channel’s input,  
VOLUME offers a very wide range of control which also accommodates devices with very low  
output levels (300 mV are perfectly adequate to drive the output stage; voltages up to 10 volts  
can be accepted without overloading the input).  
Presence  
With tube amplification, the higher frequencies (PRESENCE) are most effectively controlled at  
the power amp stage. This frequency range plays a major role in determining the character of  
the guitar sound and its ability to cut through.  
a
The intensity of the PRESENCE control depends to a great degree on the guitar sound itself:  
heavily overdriven sound with a great deal of overtone energy will respond to the PRESENCE  
control much more dramatically than will a clean sound with little overtone content.  
Over the last 30 years of tube amp tradition, two different types of PRESENCE control have  
established themselves as standard:  
the  
"
British” type, which only affects higher frequencies, and only boosts, and  
the “American” type, which affects a broader range of frequencies from high mids to  
harmonic overtones, and can either boost or cut.  
Since both PRESENCE philosophies make sense, and both allow for very different characters,  
particularly with overdriven sounds, the VS 250 offers both types.  
The signal is unaffected when the control is in the  
PRESENCE 1 is the “American” type.  
3-o'clock" position.  
"
in the fully counterclockwise position, the sound is  
PRESENCE 2 is the  
unaffected.  
"
British” type.  
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With the SELECT switch you can alternate between PRESENCE 1 and PRESENCE 2. The  
triangular-shaped LEDs indicate which presence control is currently active. On the back of  
the  
there is one l/4” jack per channel for connecting a footswitch to select between  
PRESENCE 1 and PRESENCE 2.  
Please note: The PRESENCE controls do not affect the tone as strongly in TRIODE mode than  
in PENTODE mode!  
Mains  
Mains is the power switch of the VS 250. When the unit is powered up, the red LED above  
It is good practice to switch each channel of the VS 250 to STANDBY  
this switch will be on.  
both before powering up and before switching off.  
BACK  
Power Cord J ack  
If you are on tour in  
This jack accepts the 110/120-volt power cord supplied with your unit.  
Europe, this jack will accept a 220/240-volt power cord. (See “Main Fuse” and “Voltage  
Selector” below.)  
Main Fuse  
For overseas use, change the fuse to match local voltage:  
220/240 Volts -AT 2 1/2 Amp  
110/120 Volts Slo-Blo5amp  
-
Voltage Selector  
USA 110/120 volts  
-
European continent and Great Britain  
-
220/240 volts  
Anode Fuse  
Operating voltage of the tubes, fused separately for each channel.  
Fuse rating: Slo-Blo 0.315 Amp or Slo-Blo 1/2 Amp  
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Pentode/Triode  
The first guitar tube amps from the 30’s and 40’s utilized TREIODE power amp tubes. Since  
triodes tend to emphasize even-order harmonics, these amps had a very typical sound with a  
warm even tone, even when overdriven. Great for sweet, warm, full, fat blues.  
To obtain higher power levels, tubes were developed in the 50’s with 5 electrodes  
(PENTODES), and these have since become standard in all tube amplifiers. PENTODES likewise  
Even-order harmonics are neutralized, odd-order  
have their own typical effect on the sound.  
harmonics stand out. This adds richness to the character of the sound, but also makes it  
rougher, with an “edge”, lending itself spectacularly to rock-oriented music.  
Each of the two channels of the VS 250 can be switched separately from PENTODE to  
TRIODE mode. The power in triode mode is reduced to 25 watts RMS per channel; the sound  
character changes as described above.  
Please remember: for technical reasons, the effect of the presence control will be much more  
noticeable in pentode mode than in triode mode, and will be more noticeable the more  
overdriven a guitar sound you use!  
Presence Select Footswitch  
Connect a commonly available on/off footswitch to this jack, and you can alternate between  
PRESENCE 1 and PRESENCE 2. If only one footswitch is connected, both channels will be  
switched simultaneously.  
Ventilation  
Heat generated by the tubes in the VS 250 is transferred to a heat exchanger, which is cooled  
in turn by an extremely low-noise fan.  
This design prevents excessive heat build-up in the  
housing, and ensures even cooling of the tubes. Please see to it that the ventilation slots on  
both the front and the back of the VS 250 are not blocked.  
Circuitry in the power amp stage constantly monitors the internal temperature. In the event of  
overheating(caused, for example, by blockage of the vents), the VS 250 will automatically  
shut down and thereby prevent any damage to itself.  
Inputs  
Each channel of the VS 250 has two parallel inputs. The LINE OUTS of a guitar preamp (or  
effect unit) are to be connected here, one to each channel. The purpose of the parallel inputs  
is. to allow for input bridging. You could, for example, connect a cable from the second,  
parallel input jack of one channel to another power amp; or from Channel A of the VS 250 to  
its own Channel B, thereby using the VS 250 as a 2x50-watt mono power amp.  
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Speaker Outputs  
Each channel of the  
250 has three speaker output jacks with different impedances: 4  
ohms, 8 ohms, and 16 ohms. Use the jack which corresponds to the impedance of the guitar  
loudspeaker cabinet which you are using. All three jacks may be used simultaneously.  
If you wish to connect two &ohm cabinets to one channel, please connect one of the cabinets  
If you wish to  
to the 4-ohm input, and connect the second cabinet to the first in parallel.  
connect two 16-ohm cabinets to one channel, please connect one of the cabinets to the 8-ohm  
input, and connect the second cabinet to the first in parallel.  
Technical Specifications  
Tubes, each channel:  
Driver stage: 1 x ECC 83 (or 12ax7 or 7025)  
1 x ECC 82 (or 12AU7  
Power stage: 4 x EL 84  
Output per channel:  
Pentode mode: 50 watts RMS  
Triode mode: 25 watts RMS  
Input sensitivity:  
300 mV to 10 volts  
Presence control per channel:  
PRESENCE 1  
PRESENCE 2  
:
4
dB  
@
4000 Hz, broadband  
:
+2 dB @ 6000 Hz, broadband  
Loudspeaker jacks per channel:  
16 ohms; all usable simultaneously  
4
/
8
/
Cooling:  
Temperaturecontrol-circuitry, heat exchanger, and Papst fan  
Thermal protection, automatic shut-off  
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