ASK AMP MAN
JeFF BoBer
CAN YOU TURN THAT THING DOWN?
Hi Jeff,
I have a Fender Twin Reverb. I really love
the tone of the amp with the volume set
to about 5 or 6, but at that point it’s just
too loud to play anywhere. How can I still
get that great tone at a useable volume?
Is there a safe way to do it? Is there a best
way to do it? I don’t want to use pedals.
Can you help?
Mike
Hi Mike,
Nice amp… nice loud amp. Ah, I remember
the day when you could actually rock out on
a Twin set on 7. Fortunately I still have my
hearing! While a Twin is certainly a benchmark of tone, getting a naturally overdriven
tone out of one in a small club environment
can be a challenge. Luckily, there are quite a
few options to accomplish this, some newer
and some old school. Fortunately, these
options are also reversible, so the full frontal
assault of your Twin is still available should
you need it for those bigger stages. Let’s
start with a couple of newer options.
You may first want to explore an external
attenuator, such as the Tube Amp Doctor
Silencer, the Dr. Z Airbrake, the THD Hot
Plate, or many other such devices. These can
be inserted between the output jack of the
amplifier and the speakers and function by
reducing the amount of signal level sent to
the speakers. There are many different units
available and they do function in different
ways—some with simple design, some more
complex. They also vary in size, so do a bit of
research and see which unit best serves your
application. To return to normal operation
here, simply remove the unit and plug the
speakers directly into the amplifier.
The next option would be to explore a
device know as the Yellow Jacket by THD
Electronics. These adaptors plug directly into
the output tube sockets of the amplifier and
allow the use of 6BQ5/EL84 output tubes.
These output tubes are capable of less power
output, and the voltage and current supplied to them through the adaptor is limited
accordingly so that the output of your amplifier is substantially reduced. Keep in mind
that using a different output tube will substantially change the tone signature of your
amplifier. This could open up a new sonic
palette for you, but if you’re married to the
tone of the current 6L6 output tubes in your
amp, it may not be a viable option. To return
to normal operation, should you choose this
method, you would simply remove the units
and reinstall the 6L6 tubes.
Okay, let’s visit a couple of old-school options,
the first of which will require a trip to your local
amp tech. Have your tech install a couple of
different half power switches, the first of which
would be a Pentode/(quasi)Triode switch. This
switch reconfigures the operation of the output
tubes by switching the screen grid resistor connection from the screen grid supply over to
the plate of the tube. This simulates the operation of a tube in triode mode and will reduce
the output of the amplifier by 40–50 percent.
There is a bit of a change in the tone and
feel of the amp, but to me it becomes a bit
smoother, which is not necessarily a bad thing.
He could also install a switch that would disconnect the cathode connection of either
the inside or outside pair of output tubes,
thereby electrically removing them from the
circuit. This will also reduce the output of the
amp by 40–50 percent. Some might argue
that this mismatches the primary/secondary
impedance of the output transformer, but this
method of power reduction has been used for
decades with no known adverse affects. The
above Pentode/Triode switch also theoretically
mismatches the impedances, but again this
method has been used for many years without
cause for alarm. To return to normal operation
here, simply place the switch(es) in their “
normal” mode and the amp is returned to stock.
If your amp is more of a vintage/collectable
model and you don’t wish to adulterate the
rear panel with switch holes, you could have
your tech simply hardwire the changes internally. This would not, however, allow you to
return the amp to its stock configuration with
the simple flick of a switch.
The last, quickest and possibly most cost
effective option I have for you would be to
simply disconnect one of the speakers. This
will also reduce the amount of clean output
power that the amp is capable of producing
due to the change in output impedance load,
which will rise from 4 to 8 ohms. The one thing
to keep in mind here is that while the constant output power of the amplifier has been
reduced, it still does seem capable of outputting substantial peaks on the attack of the
notes, so you might want to consider installing
a different 8-ohm speaker with a higher power
capability for use as the constantly connected
speaker. Just because the amplifier volume
control is set at 5 or 6 doesn’t mean that the
amplifier is outputting only 50 or 60 percent
of its output power. With most decent guitar/
pickup configurations, the amplifier has long
since reached its maximum available power at
those settings. The rest just tends to overdrive
the output stage more… which ain’t necessarily a bad thing either! Of course, to return
to normal operation here, simply reconnect
the second speaker. By the way, two different types of speakers in an amp most times
complement each other so the tone of the
amp may actually improve. I hope that helps
you tame the Twin.
Jeff Bober
Jeff Bober, Godfather of the low wattage amp
revolution, co-founded and was the principal
designer for Budda Amplification. He can be
reached at pgampman@gmail.com.
