User manual

should be kept in mind as the Variac does not provide power to any part of the
amplifier other then the power section of the amplifier. The heaters for all the tubes,
including the power tubes, are all provided on an auxiliary basis. This means you do
not have to worry about under powered heater voltage on your tubes in the Dirty
Boy. The heater voltage on the 5U4 power tubes is also provided separately from the
Variac and allows the rectifiers to operate at the correct temperature.
3. Understanding How the Variac, Bias and Feedback Affect Your Sound. As noted
above, for safety of the power tubes, you would be better served using a slow ramp
up rather then an instant application of high voltage to the power tubes. The reason
for ramping up the power tubes rather then switching the amp on and off with power
applied to its high voltage section is that the bias is allowed time to catch up. The
Bias on the Dirty Boy is developed on the high voltage section. The power tube
rectifiers are considered a slow power supply. This creates a unique “behavior” from
the power supply. This behavior on the part of the power supply is also a contributing
feature to the Dirty Boy’s over all character and sound. The power amp section will
distort more when the power supply is running at lowered settings on the Variac.
Anything under 50% Variac power will exhibit a slower recharge time of the power
supply capacitors. The slower recharging of the power supply will create an effect that
sound like the amp is “catching its breath” so to speak. This is normal at drastically
low power settings. The replenishing of the power supply capacitors will be quicker
when the Variac is set higher or over 50%. The “breathing” effect is also partly
influenced by both the Feedback and Bias settings. You can experiment with this by
adjust the Variac, Feedback, guitar volume and Bias controls. The overall demands
on the amp when used at lower power levels will yield some very interesting and
unique results; the possibilities are very diverse.
3. Understanding the Dirty Boy’s Power Tube Based Distortion. The Dirty Boy
employs power tube based distortion. This statement holds true for many vintage
guitar amplifiers that are non-master volume. Most non master volume amplifiers
need to be turned up to full power in order to reach the threshold of the desired
overload sound or power tube distortion. The power tubes are distorting because the
power amps are exhausting the power supply of its ability to provide “gas” or power,
thus you get a distorted signal in the power tube. The only problem with this scenario
is the power section generates a tremendous amount of power and, therefore, a lot of
volume. The Dirty Boy is no exception since it was designed to be used as a live
amp or for recording with the amp powered up past the 50% Variac level for optimal
tone. The exception that the Dirty Boy can be adjusted to a lower power levels by
way of the adjustable Variac should not be confused with the concept that the sound
will be identical at the lower settings. There are a number of factors at play when the
Variac is adjusted. The first is the Bias; as the Variac is decreased so will the bias on
the power tubes or the Bias will become “cold”. This means the tubes are not going to
act on the input signal as easily and it may actually get cold enough to “cut off” the
power tubes. This is not a problem and can be very desirable. You will have to
experiment with this feature. If the Bias is set to fully COLD while the Variac is at a
power setting of over 50%, you will hear the amp go completely quiet. This is the fully
“cut off” state and your guitar signal will need to be of sufficient levels to over come
Dirty Boy User Manual