About the
POWER AMPLIFIER SECTION
MATCHLESS amplifiers are cathode biased and operate mostly in a Class “A” mode. This
means that current flows continuously through the output tubes whether a signal is present
or not. Most amplifier designs employ the more popular “AB” or “AB1” biasing technique,
which although capable of producing more power for a given tube configuration and
transformer size, produces crossover distortion and more odd order harmonics. This is why
MATCHLESS amplifiers are described as having a smooth tone that won’t fatigue ears even
at a high volume.
The MATCHLESS design also does away with controlled or corrective negative
feedback, allowing the amplifier to run “open loop” or wide band. This is why your amplifiers
sound full and rich at low or high volume levels.
These are what we call “features of design” and very much a part of the distinctive
MATCHLESS tone.
There are four controls that enable the user to adjust the parameters of the power
amplifier section. The controls are the IMPEDANCE switch, the HI-LO power switch, the
CUT control and the MASTER VOLUME control. The impedance switch is used to correctly
match the speaker load to the amplifier, as mentioned earlier. This control (located at the rear
of the amplifier) should be set and left in the proper position before the amplifier is turned on.
“HI-LO” POWER SWITCH:
This switch is located at the rear of the amplifier and determines the overall output
power of the amplifier. In the “HI” position all four output tubes are functioning and the
amplifier is producing maximum power. C-30 amplifiers are conservatively rated at thirty
watts. In the “LO” position, two of the output tubes are turned off and power is reduced
approximately 50%. Cathode bias levels are adjusted for each power setting. This function is
very useful in recording studios or small clubs where less power may be preferable. The low
power setting also produces its own distinctive tone and should be explored fully.
“MASTER VOLUME”
The MASTER volume control function is activated by push-pull switches
attached to it. When the switch is pulled out, the master volume control circuit is
active. In the bypass mode (pushed in), the master volume control is completely out
of the signal path. The MASTER volume control adjusts the overall gain of the
output amplifier regardless of the Hi-Lo power setting and functions with channel
one and channel two. Normally this control would be set at its maximum (fully
clockwise) position or bypassed (switch pushed in). This allows the power amplifier to
run at full gain. This would be the normal configuration for a cleaner sound.
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