Attenuators WAS Variacs : Was Re: Amp Rectifiers

["G." <gigs@xxxxxxxxxxxxxxx>]

<quote>
Date: Mon,  5 Apr 2004 18:09:54 -0400 (EDT)
From: party_man1@xxxxxxxxxx
Subject: Variacs : Was Re: Amp Rectifiers

Hurricane sez ;
8<
This is a super advantage to maintaining your " signature sound " in any
size room . This is important if you have a rig ( tube amp )that's high
powered like a Fender Bassman or any tube amp with 50 watts or more . What
sounded great in a large hall with lots of people and noise will blow the
patrons out of the small coffee shop when you let that puppy get to the
sound you desire . The vairac serves to compensate for the size differential
of one room from another .

This regulation of input voltage to your amp  is a cool thing as it lowers
the voltage and giving you a " safe " way of getting that sound of "
crunchville at lower power levels . There have been comments made of this
being an " unsafe " thing to do and it can be if you don't realize how to
use one properly . The biggest mistake I have seen that has caused problems
is when some one turns up the "  rheostat " that controls the input voltage
to your  amp and fries something like the tubes and or a x-former ouch !
8<
Its a matter of choice I suppose . Like the old saying " There's more than
one way to skin a cat " applies here & " Look before you leap into a variac
" is also a cool  thing to know . But to protect my @$$ , YMMV :)

Sincerely :
HR
</quote>

  If you like the tone you're getting from your amp but have to crank it up
to get there, another solution is to get an attenuator, also called "power
soak", and "power brake".  These are plugged into the speaker output of your
power amp and provide an appropriate load (you need to make sure you have it
set to the correct impedance). You can use these to bring down the volume
without affecting the tone, the extra signal is simply converted into heat.

I own a Tom Scholz Power Soak which has served me very well when I had a
100Watt Soldano (because John Popper used them! :) ), and later on a more
traditional Fender Super 60. It certainly eased things between me and my
neighbours.   Even with the 100Watt class AB Soldano runnig at full power ,
it never really warmed up my Power Soak even slightly,  so I'm not sure how
hot other units get.

The way it works is you plug the power amp's speaker lead into the
attenuator which you dial to the correct impedance (4, 8 or 16 ohm - check
your manual, or the back of the amp, speakers or cab) and from there into
the speaker.
Its important that you only do this when the amp is turned off and unplugged
from the mains because the amp will fry itself if it doesn't have a load (be
it speaker or attenuator) while its powered up in any way shape or form.

Also it is advisable to have very solid connections that take effort to
disconnect, this is important because if your amp is on and the speaker
cable to the attenuator (or to the speaker for that matter) is disconnected,
your amp will blow.    There are connectors designed for this purpose, when
I bought my Power Soak the shop sold me 1/4" locking connectors which take a
fair amount of effort to unlock and disconnect - hard wire these into your
attenuator and amplifier and it'll be safe as houses - remembering amps
generally use either basic 1/4" jacks with no added protection, or simple
slip on connectors to the speakers.  Once the attenuator is connected you
can plug and unplug speakers/cabs/devices to the attenuator without any risk
to the amp head.

Attenuators have a dial which you can set anywhere you like to bring the
volume down to the level that suits the venue and your needs.  Turned up
full, everything is as it would be without the attenuator, it doesn't affect
the tone what so ever.    But you can also have all that tone and distortion
at very quiet volumes safe for shedding in your bedroom, and everything in
between.

I haven't tried these, but THD have their range of Hot Plates on offer, each
model is wired for a specific impedance so you have to be clear about what
you need for your amp before putting your money down.
http://www.thdelectronics.com/products/hotplate.htm
The cool thing about the THDs is they now come with an additional line out
with an independant volume control which lets you dial your speaker volume
to taste using one dial AND have a safe line out signal to the PA as well.

Marshall sell their own PB100 Power Brake. I haven't tried these either.
According to the local Rock Shop (NZ chain of music stores) staff they are
just as transparent and versatile as my Tom Scholz unit.
http://www.marshallamps.com/images/products/powerbrake/powerbrake.html
(Don't believe the hype about others being unsafe, its a clear case of FUD)
  I also found a link to a page on amptone's sight with Marshall's SE100
Power Brake with "Speaker Emulation"
http://www.amptone.com/marshallse100.htm
Might be useful if you wanted to use your amp head into a PA. This unit
isn't on Marshall's site, so it may be discontinued, and also it only has
attenuation pads, no dial which would limit its usefulness.
  I don't know this, but its possible the SE100's speaker emulation may work
like the Behringer Ultra-G GI-100,
http://www.behringer.com/GI100/index.cfm?lang=ENG
  where it simply knocks off the upper frequencies - which does work, but
its good to know how they do it, and suggests you could probably get just as
convincing results by bringing down the treble EQ on the mixing desk.  And
of course if you have a safe line signal coming from your attenuator, you
could buy a Ultra-G GI100 and use it's emulation.   Please don't take my
word for it.  Do try before you buy, make sure you like what you hear before
spending a cent if you can avoid it.

There are some trick things you can do with attenuators:
* The few models I've seen to date have two speaker outputs, so it can be
used as a splitter to feed a second cab from your amp if your amp only has
one speaker output.
* You don't need a speaker plugged into the attenuator as the attenuator
provides a load to the amp, this is useful if you have a seperate head and
would like to use it in a variety of settings.
* When you dial the attenuator to its lowest setting it is safe to use with
headphones and sound equipment - IE it lets you plug your amp head into a
PA, headphone or anything else that can accept line level signals. The main
thing here is just make sure that dial isn't moved until everything is
turned off and unplugged otherwise you'll fry whatever its plugged into.
  This is where THD's line out with independant volume control starts
looking very attractive - theres no risk of ever doing damage, and you have
more flexibility in your setup.  THD's only draw back is you can't change
the impedance of the unit for different amps, that said most amp's I've
played through have 8 Ohm speakers, so it may not be a big concern.

With proper caution, an attenuator opens a lot of options and makes your amp
combo or amp head that much more versatile, which in my book is always a
good thing.  And it doesn't sound like an attenuator is any more risk to
your amp than a variac http://www.variac.com/

- -- G.