The Amp Garage

like this:

[img1473]http://music-electronics-forum.com/atta ... -tubes.jpg[/img]

Good point - I read the OP too quickly. You'd want to scale the B+ to the screens, not vary the screen R.

That would be a form of power scaling, although most PS circuits vary both plate and screen voltages.

your original plan looks good to me. R7 is in series with R8, so there won't be a load problem on that arm.

Kevin O'Connor does something similar with his Standard preamp design.

yes, what they said. Sorry for being late to reply.

(sorry I was too tired to read all the preceding replies). Consider a typical hot-rodded JCM800 gain stage, where gain is increased by using a larger plate resistor (220k-330k instead of 100k). Then consider the interstage attenuator (voltage divider or pot) that comes next. The resistance in that a...

I'd ask Kevin O'Connor (London Power) directly.


Note: you could also scale the PI with the LP SV2 kit.
Note 2: Kevin also sells a kit called VLK that will prevent the preamp voltages from increasing as you scale back the power section.

I use a version of the bootstrapped MV that Kevin sells as a kit (and explained in TUT4): http://www.londonpower.com/amp-mods/london-power-master-volume It works very well, except that it interferes with NFB and controls inserted in the NFB loop (e.g., Presence). So, like a PPIMV, this MV makes the ...

Are you sure it's not 'pick chirp'? I built an amp with a 4-stage preamp from Kevin O'Connor's TUT book (also used in the Rocca HG100) and was bothered by an overtone. It took me a while that it was from my heavy pick attack. Jake E Lee could get some mad pick chirping, likely on purpose. Check out ...

Just a few general comments and questions: - why do you want to avoid preamp distortion and have only power amp distortion? Don't be afraid of preamp distortion. - you definitely need more than one preamp gain stage to overdrive an output tube (in response to another one of your threads) - the easie...

cool! Sounds raw, in a good way.

they were used in the 10-watt Phaez Daisycutter kit amp:
https://www.youtube.com/watch?v=qumL2poI7dQ

Sounded good in that amp (I built one).

I might not understand what is being shown in the 'graphics' file. Shouldn't the unbypassed cathode gain stages have flatter gain across the frequency spectrum (and be different from the cathode-bypassed gain stages)?

I just built an 18-watt amp with 2204 preamp that has a bootstrapped MV (pre- PI) as well as a PPIMV. So I can use one, the other, or both to bring down the volume and get different levels of distortion.

Your ears are not deceiving you. The PPIMV gives more distortion because of the PI....[/img]