Attenuator build help

[voskarp]

Is that why it gets more midrange than treble/bass as it's turned down?

[martin manning]

I don't know, but the speculation by the author in the Marshall Forum thread is that maintaining the Zo seen by the speaker is important. I'd build the reactive stage (M2 version) and try adding your L-pad vs. another stage or two of fixed resistors.

[voskarp]

Finally built a test version of the reactive stage for my in cab-attenuator. It's the M1 version, but I will build a M2 rated for 12W when parts arrive. This one is for a 50W amplifier, but I used it with my Tweed Deluxe clone, and no part got more than slightly warm even though I dimed the Deluxe and had the l-pad almost at full for some time. The coils are in the mini-pedal enclosure. The treble bypass comes in handy when playing at "baby sleeping in the other room"-level, with the l-pad at almost full.

It really sounds so much better than the L-pad alone.

[martin manning]

Good progress, and thanks for the follow-up report!

[roberto]

the speculation by the author in the Marshall Forum thread is that maintaining the Zo seen by the speaker is important.

Thanks Martin, how can this be solved? I would like to implement something similar as gain/volume control.

[voskarp]

Finally finished my version of the M2 attenuator.

I replaced the rotary switch with a variable L-Pad for fine tuning the output. That numbs the sound a little bit, but if you just use it for fine tuning it's hardly noticeable.
Oh, and I skipped the treble bypass since even though I tried some variants I couldn't find a setup that made much difference, as far as I could hear.

The first stage makes the amp a bit more quiet, but not very much. When you kick in the second stage it goes much quieter, perfect for playing it cranked at home without disturbing the neighbours. And if you use the variable L-Pad you'll get it down to a whisper, or even dead quiet.

I made mine custom made for my Tweed Deluxe:

AttenuatorInAmp.jpeg

AttenuatorM2plusL-pad.jpeg

Coil.jpeg