M-150
Monoblock Power Amplifier
Owner’s Manual
Rogue Audio, Inc.
3 Marian Lane
Brodheadsville, PA 18322
Issue date: 10/27/03
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INTRODUCTION
Congratulations on your purchase decision! We at Rogue Audio truly believe that
our amplifiers provide the “smartest” value in high-end audio. If you have never
owned a vacuum tube amplifier you will be thrilled by the silky-smooth sound
and incredible detail that only a tube amplifier can provide. And with the M150
Monoblock amplifier, you can be sure that you are getting the very best in tube
amplification. We at Rogue Audio are extremely proud of our products and want
you to enjoy them to their fullest potential. So please, take the time to read
through this short manual so that you can be confident that you have set up your
amplifier properly.
UNPACKING THE M150 POWER AMPLIFIER
Tools required: none
WARNING - This amplifier uses voltages that could cause injury or
death. Never open the amplifier while it is plugged in, and always wait
at least one hour after turning the unit off to unplug and open the unit.
Lethal voltages can remain in the electronics after the unit is
unplugged.
The M150 amplifier has been painstakingly inspected for cosmetic flaws during
and after assembly. In order not to damage the cosmetic appearance of your
amplifier it is important that you follow the unpacking instructions carefully.
1. Carefully lift the amplifier out of the box, and remove the foam pads and
plastic bag.
2. Remove the banding holding the tube cage in place. Lift off the tube cage and
remove the foam pad holing the tubes in place. This foam pad is required
during shipment to prevent damage to the output tubes.
3. Remove the shipping pallet from the bottom of the amp. The pallet serves two
purposes. First, and foremost it acts to tie down the mechanically isolated
transformer platform. Secondly, it provides strength to the main chassis. Both
of these are critical to ensure that no damage occurs in transit.
4. Save the packing materials. The packing materials and box have been
carefully designed to protect your valuable equipment during shipping so you
don’t want to throw them away.
5. Using a glove or a clean dry cloth, straighten any tubes that may have tilted
during shipment. Ensure that all of the tubes are fully seated in their ceramic
sockets.
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CONNECTING M150 TO YOUR SYSTEM
Connecting M150 to the Loudspeakers:
The rear panel has binding posts for both 4 and 8 ohm loudspeakers as shown in
Figure 1. In general, if your speakers are rated at less than 6 ohms, use the 4 ohm
taps and use the 8 ohm taps if they are 6 ohms or greater.
CAUTION – Do not operate the amplifier unless it is connected to a
loudspeaker.
Connecting M150 to the preamplifier:
There are two types of input connections on the rear panel of M150:
1) Fully balanced XLR type input.
2) RCA input
The input connections can be made using either the XLR or RCA input,
depending on your system setup.
Note that if you have a variable output CD player you can drive the M150 with it
directly.
Main Fuse
4 Ohm Tap
8 Ohm Tap
Ultra Linear/
Triode Switch
Power In
XLR Input
RCA Input
Ground Lift
Switch
Figure 1. Rear panel layout
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Connecting M150 to the power outlet:
Connect the IEC send of the detachable power cord provided to the amplifier, and
plug the opposite end into corresponding outlet. It is recommended that both
M150’s and your preamp are plugged into the same wall outlet if possible
(perhaps using a power outlet strip). This is to avoid creating a ground loop.
Amplifier Location:
The M150 is an open tube design and depends on natural convection flow patterns
for proper cooling. To ensure proper cooling, the unit should be located in a
position so that the airflow is not impeded. Since there are vents on the bottom of
the unit, it should always rest on a firm surface to ensure adequate spacing
between the resting surface and bottom of the unit. In addition, the unit should
not be placed in an enclosed shelf, and should have a minimum of 6 inches of free
space above it.
OPERATION OF THE AMPLIFIER
After all proper connections have been made, you are now ready to turn the M150
amplifier on. The power on/off switch is on the front of the amp. Some
preamplifiers and sources can generate dangerous transients that can damage
loudspeakers. To avoid letting dangerous transients reach your loudspeakers turn
your system on in the following order:
1) Turn on all sources (CD, tuner, etc.) that you will be using.
2) Turn on the preamplifier.
3) Wait until preamp has stabilized.
4) Power up M150 amplifier
5) Select listening source and play music
When powering down your system turn the amplifier off first.
Note – Important! After turning off the amplifier, wait at least one minute to turn
it back on. Do not turn it on then off and then on again in quick succession.
Doing this will not allow the power supply to discharge between on/off cycling
and may result in transient noises.
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Triode/Ultralinear switch:
This switch is located on the back panel of the amp. See Figure 1. The output
transformer of a tube amplifier acts as the electrical interface between the very
different impedances of the loudspeaker and the tube circuitry. There are three
fundamental ways that the output transformer can be connected to the tube circuit.
1) Tetrode or Pentode connection – In this configuration, the highest power level
is achieved but at the expense of significantly higher distortion levels.
Practically speaking, this mode of operation is sonically inferior and has been
disregarded in the M150 design.
2) Triode connection – With this configuration, the lowest level of distortion is
achieved but at the expense of output power. In the case of the M150, its
power level in triode is high enough that it will likely provide plenty of power
for almost any speaker load.
3) Ultralinear operation – With this configuration, power levels near those of
tetrode mode are achieved with low distortion levels that approach those of
triode operation. For loudspeakers that demand very high levels of power,
ultralinear should provide excellent sound and plenty of power.
The triode/ultralinear switch allows the user to operate M150 in either of the two
modes. In general, the sonic differences are subtle but for a given loudspeaker one
mode is likely to sound better than the other. There is a complex relationship
between the output transformer and the crossover network so try both and see
which one works best in your system. This switch can be operated while the
amplifier is playing but you will hear a small relay noise through the loudspeaker.
SETTING THE TUBE BIAS
Tools required: bias tool (provided with amplifier)
The output tubes (the big ones) need to be “biased’ with a grid voltage that
controls the flow of electrical current through the tube. Tube biasing on the M150
amplifier has been designed to be both simple and effective. On some amplifiers
biasing is done for two or more tubes simultaneously. With this method, the total
current flowing through the group of tubes may be correct, but the current flow
through any individual tube may vary significantly from the optimal value. With
the M150 amplifier the bias is set individually for each tube so that the correct
operating point is assured. An added benefit to this approach is that, should a
tube fail prematurely, the single tube can be replaced without having to purchase a
matched set. Use the following procedure to set the tube bias:
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WARNING – There are dangerous and potentially lethal voltages inside this
amplifier. Do not touch any part of the amplifier other than as described
below. If you are uncertain about any of these instructions, please contact
your dealer and have them bias the amplifier for you.
Figure 2. Removable hatchplate
1) Allow the amplifier to warm up for at least 30 minutes.
2) Turn the preamplifier volume completely off so that no signal is entering the
amplifier
3) Loosen the 4 captive screws on the top hatch cover.
4) Remove the hatch cover. The bias tool is snap attached to the inside of the
cover.
5) Locate the toggle switches and associated small potentiometers (they are blue
and have a small screw in the top). There is a set of four in each amplifier.
Note the biasing meter.
6) Make sure that all of the toggle switches are pointed away from the meter (run
position). Begin with any switch, moving the switch into the “set” position.
You will see that the meter will rise up to show that the tube’s current is now
flowing through the meter.
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7) Using the bias tool, slowly turn the screw on the potentiometer that is adjacent
to the switch until the bias meter reads ~ 40 miliamps (mA). Turn the screw
clockwise to lower the bias and counterclockwise to raise the bias. Note that
there are two ends on the bias tool. Using the end with the recessed
screwdriver will greatly facilitate this operation.
KT88 (4)
12AX7 (1)
Output Tubes
Input Tube
12AU7 (2)
Driver Tubes
Potentiometers
Switches
Meter
Figure 3. Bias switches and potentiometers
8) Flip the switch back into the “run” position thus disengaging the tube from the
meter circuit.
9) Repeat the above steps for each of the tubes in both channels.
As it is a quick operation, the tube bias should be checked on a regular basis.
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TROUBLESHOOTING
Speaker Hum – If hum can be heard from more than a few inches from the
loudspeaker, there is probably a ground loop. If there is still hum, flip the
grounded/ungrounded switch on the rear panel to ungrounded. If this fails to cure
the hum, call customer service at Rogue Audio for further advice.
Tube will not bias – If the meter provides a reading but the tube will not bias, the
tube is probably bad. If no meter reading can be attained, check the fuse (1/4
Amp fast blow). If the fuse is bad, replace the fuse and then set the bias. If the
bias will not maintain itself and the fuse blows again, the tube should be
replaced.
Bias Meter reading is too high – Check that you do not have two of the bias
switches turned on.
Output sounds distorted - Check the bias on the output tubes to ensure that the
tubes are operating properly.
OWNER AND WARRANTY REGISTRATION FORM
Included with this manual is an Owner and Warranty Registration Form. Please
take a minute to fill out this card and return it to Rogue Audio. This card must be
returned within 30 days of purchase to validate the warranty.
FUSE VALUES
Main fuse located on rear panel (1) – 5 Amp slow blow
Tube Fuses (4) – 2/10 Amp slow blow
Power Supply Fuse on PCB (1) – ¾ Amp slow blow
SPECIFICATIONS
output power
frequency response
THD
150 WPC
5Hz – 50 kHz ± 1dB
< 0.1% typ, < 1% at rated power
1.0 V RMS
input sensitivity
dimensions
14 ½” W x 19” D x 7” H
55 pounds (25 Kg)
60 lbs (27 Kg)
weight
shipping weight
power requirements
115/230V - 50/60Hz
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LIMITED WARRANTY
Warranty Period
This product has been manufactured under the highest standards of quality and workmanship. Rogue Audio
Inc. (hereinafter “Rogue Audio”) warrants this product against defects in material or workmanship as
follows:
With the exception of vacuum tubes, Rogue Audio warrants to the original purchaser of this product all
parts of this product against defects in material and workmanship for a period of three years from the date of
retail purchase. Rogue Audio warrants the vacuum tubes for a period of six months from the date of retail
purchase. Any defective parts will be replaced free of charge, excluding shipping and handling.
Proof of purchase in the form of a bill of sale or recited invoice which indicates that the product is within
the warranty period must be presented to obtain warranty service. Rogue Audio suggests that the purchaser
retain the dealer’s bill of sale as evidence of the date of retail purchase.
What’s Not Covered
This warranty does not cover cosmetic damage or any damage that results from product misuse, product
abuse, installation error, connection to an improper voltage supply, accident, improper maintenance,
alterations, modifications not authorized in writing by Rogue Audio, lightening, power surges, or acts of God.
Use of any other than Rogue Audio factory parts may void this warranty.
This warranty does not cover the cost of parts and labor which would be otherwise provided without charge
under this warranty, obtained from any source other than Rogue Audio.
This warranty applies only to consumer use of this product and does not cover any product that is used in
any trade or business, or in an industrial or commercial application.
This warranty applies only to the original purchaser of this product when purchased from an
Authorized Rogue Audio dealer.
This warranty is valid only in the United States.
YOUR RIGHTS
ROGUE AUDIO LIMITS ITS OBLIGATIONS UNDER ANY IMPLIED WARRANTIES UNDER STATE
LAWS TO A PERIOD NOT TO EXCEED THE WARRANTY PERIOD. SOME STATES DO NOT
ALLOW LIMITATIONS ON HOW LONG AN IMPLIED WARRANTY LASTS, AND SOME STATES
DO NOT ALLOW THE EXCLUSION OR LIMITATION OF INCIDENTAL OR CONSEQUENTIAL
DAMAGES, SO THE ABOVE LIMITATIONS OR EXCLUSIONS MAY NOT APPLY TO YOU. THIS
WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS, AND YOU MAY HAVE OTHER
RIGHTS WHICH MAY VARY FROM STATE TO STATE.
To Obtain Service
To obtain service, you must contact Rogue Audio and obtain a return authorization number. The product
must be delivered to Rogue Audio in its original packaging prepaid at the following address:
Rogue Audio Inc.
3 Marian Lane
Brodheadsville, PA 18322
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