Attenator Pedal for Combo Amp?

[kylemyers33]

So I'm wanting to build an attentor pedal that basically lets you play at an overdriven tube amp sound but at a low volume. I have no output or master volume on my tube combo amp. How do I connect the circuit to the amp?

[patrickbrose]

I'm going to tread lightly on this since doing it wrong  can and will destroy the output transformer on you tube amp:
A true attenuator is a device that acts as a load on the output of your amp in a similar fashion as a speaker. Different attenuators do this in different ways, some use very large Resistors, others use speaker motors, others use Rheostats (which are really just variable resistors) Depending on the amp you are using, you need to use an attenuator that can handle roughly double your amps output power. For example: my little champ combo puts out 6-10 watts depending on which tube I use. I would want an attenuator that can handle at least 25 watts. Why? Well, as you turn up your amp into distortion, the amp becomes more efficient and actually produces more than the stated output power (a rating of 10 watts on an amp relates to clean output, not distorted). Here is where the concern is: if you burn up an attenuator (and believe me, it can happen), you can end up with a few situations. 1. The OT can short to ground and cook itself. 2. All of the output of the amp can be sent to the speaker (and at the least you will get  a very loud amp, worst, your speaker blows) 3. The OT shorts to itself and burns up.
So all that said, if you still want to use an attenuator you need to:
1. Get one rated for double your output power to be safe.
2. Connect it as the instructions say. Typically you plug your speaker out of your amp into the attenuator, then connect the attenuator to the speaker.
3. Using a standard volume pedal or pot will not work. They cannot handle the output power of a tube amp.
DIY'ing it is possible, but typically not a good idea unless you are going to making an attenuator under 25 watts. More than that, and the parts get tough to find and quite costly. Also keep in mind that an attenuator dissipates a large amount of heat. So heatsinks, venting etc. are needed to keep it cool.
One last thing, a heavily attenuated amp almost never sounds like a lower powered amp, just a really choked high power amp.
-P

[GermanCdn]

A possible suggestion if you don't want to go with the external attenuation might also be to look at the Marverick or Reignmaker series of speakers from Eminence, which allow you to control the overall output by varying the flux density of the speaker.  I've personally never tried it, and assume that you'd want a pretty close match, but it's cheaper than a good quality attenuator.

[sirbergersworth]

What amp and speaker/s are you using?

[kylemyers33]

Typically you plug your speaker out of your amp into the attenuator, then connect the attenuator to the speaker.

Where exactly is the speaker output?

[angrykoko]

patrickbrose is right on.

Check this out on Webers site: http://www.tedweber.com/atten.htm
It's not overly in depth but a nice starting point.

That said... I've priced how much to make an Dr.Z Airbrake (lite) and it's going to run me over $100.00 US  using mouser parts, not exactly inexpensive to build.

Koko

[patrickbrose]

Before we go any further, you need to tell us what type of amp you are using. Also note if it is a combo (amp and speaker in one, or a head and separate speaker cab)
-P

[kylemyers33]

Before we go any further, you need to tell us what type of amp you are using. Also note if it is a combo (amp and speaker in one, or a head and separate speaker cab)
-P

I am wanting to do this on my Vox AC30 Combo. Thanks!

[rjkanejr]

I'm no expert but since the ac30 has an effects loop can a volume box be used?  I have a fender hot rod deluxe and use one and hit works Greta.  the only issue with using one of these is that it works great as sort of a master volume and I can great pretty good tone from the preamp, but if your wanting to overdrive the power amp section like lots of the pros do, then you must use an attenuation between the out of the amp and speakers as others have said previously.  check out this link to see what I am talking about when I say volume box.  http://www.justinholton.com/hotrod/tooloud.html#volumebox  there is a dude that sells these on eBay  check it out here..http://omnisonicvolumebox.com/

[patrickbrose]

Ok, so that is a high power beast of an amp (even though it is rated at 30 watts, it is a pretty major amp). You are going to want to get a 100watt attenuator for that thing. Hot Plate and Weber both make some great ones:
http://www.thdelectronics.com/product_page_hotplate.html

http://www.tedweber.com/atten.htm

Read the Weber page thoroughly. Don't cheap out and get something less than 100watts (trust me on this). You will be looking at $175+ depending on the model that you choose. Be careful, an AC30 is a nice amp and it would be a shame, and cost quite a bit to fix a cooked OT. You also need to make sure that you get an attenuator that either matches the output impedance of your amp (I believe it is 16ohm, but you need to verify this, the manual should tell you), or get an attenuator that can match impedances.
-P

As for the effect loop volume box- don't buy one DIY it if you like. It is a pot and 2 jacks in a box. That's it. It goes in the effect loop ONLY.