A possible twist on the power attenuator?

[Marc]

This is a link for a stereo autoformer volume control like you'd use to control remote speakers. Since it's not an L-pad it's not strictly a resistive load. Would it be a candidate for an on amp a level control...? I am guessing it would not be a power soak since it's a transformer...

Marc

http://cgi.ebay.com/Stereo-in-wall-v...QQcmdZViewItem

[Steve Conner]

You're right that it won't soak any power, so the amp will be impedance mismatched when you turn the control down, which could hurt it. You could use it in combination with a big power resistor to do the soaking and ease the mismatch. The power rating is somewhat low, but since it's a stereo unit you could gang the channels.

Personally, I always got great results with a big (like 10" long) 16 ohm wirewound slide resistor I got off eBay for $20. I connected it like a giant volume control, with the amp output across the resistor, and the speaker between the wiper and the cold end of the amp output. It's not as fancy as a THD Hotplate or whatever, but I found it plenty good enough, and even used it with no speaker at all and a cheap Behringer DI box, to record bass parts.

I never bothered much with trying to get "Cranked tone" at low volumes, because of all that crap about Fletcher-Munson curves, speaker non-linearities, feedback, the adrenalin buzz of knowing you could get evicted, and the like. The sky is blue, grass is green, and electric guitar sounds better when it's loud. It's just a fact of life.

[Analog Assassin]

The sky is blue, grass is green, and electric guitar sounds better when it's loud. It's just a fact of life.

Amen, brother man.

[hasserl]

I've looked at these autoformer attenuators also, they are available from different mfgr's in mono at ratings up to 200 and even 300 watts. But these tend to be designed for the 70v outputs of pa type amps. So I don't know how this would match up to a typical 4 or 8 ohm output. I do believe they will maintain a consistent impedance throughout their volume adjustment range, but that impedance may not match to what the amp should see.

However, there is still hope for this idea. These same mfgr's also produce impedance transformers, to transform a typical 4 or 8 or 16 ohm output to 70v output. Why not run one of these transformers in series with the attenuator, between the amp's OT and the autoformer, this way the load should remain consistent and correct for the amp while attenuating the signal out to the speaker.

The only drawback I've seen to this is the cost, by the time you've purchased the 70v impedance matching tansformer, and the attenuating autoformer, and a good metal case to install them into, you've got quite a bundle tied up into it. You could easily build a resistive load such as Steve describes above for much less, add some capacitance and maybe a little inductance for tone shaping and you'll have a very nice and effective attenuator.