The Amp Garage

Hmmm, just tried the MV there and not sure I love it. Seem to be getting blocking distortion... from the preamp section as I try to dial in a nice breakup. This being a PA system, this could be a futile effort.

Thanks Steve for your input.

A

PS yes your drawing was very helpful

sluckey wrote: ↑Mon Oct 09, 2023 6:54 pm Any pre PI MV will allow you to crank up the preamp for front end overdrive. Then dial the volume down with the MV.

Does the 470k just before the PI look like a reasonable spot? Might you have any references from one of your builds for that style MV?

Thanks A

Ian, when you say "from the book" I am looking at Valve Wizard, is it the floating paraphase you are referencing? No. It's just a plain and simple paraphase inverter, exactly like the one at the top of this Wizard page... http://www.valvewizard.co.uk/paraphase.html Yup .. I guess I do not understan...

Sluckey... from a thread over on EL34.... "You have a paraphase inverter. It's not gonna like any of the post PI MVs. About all you can do is put a standard volume pot in front of the PI." On this amp I am working on, would an addition of a volume (Master) pot right in front of the PI allow for brea...

Hello -- Actually that PI circuit is classic "from the book" paraphase dual triode, just strangely rendered and therefore at first glance looks to be an oddly misused pentode. Best .. Ian Ian, when you say "from the book" I am looking at Valve Wizard, is it the floating paraphase you are referencing?

Can a paraphase inverter take the PPIMV setup?

Tom, great to see you back. How goes it? Anything on the bench.

Ange

2 un-used 6AU6 tubes. Maybe tremolo like the Silvertone and a one tube Reverb? Looking into it.

So I found a 5V4 in the stash, and it lit up. Then in go the other tubes since no shorts and adequate voltage and wham, its a guitar amp. Treble and Bass do have a nice response and the volume is substantial into a nice breakup. So just the addition of new caps and input & output jacks did the deed....

So this amp has 6AU6-A preamp tubes, and yes has the 6SN7GT in the PI. Since I do not find a schematic with the actual compliment of preamp tubes, I can look at creating a schematic. I am close to just giving it a try as I have added the input jack and speaker jack and soon will have the new power c...

Steve, how would you proceed with this pentode input? Is it worth having a listen as is? Put in an input jack, speaker jack, power caps..... have a listen. Can I set up the input per the usual with the 1M to ground?

A

yup - looks like the dropping R's got cooked, I pulled them and also getting ready to put 3 prong safety plug and rewire the on/off. The on/off is weird, when you pull it lights up the 6.3v light but the AC is not flowing and when it's off the AC is conducting??? Need to re-do all that with the safe...

Just saw this Tony, way cool and you shared some great tidbits of knowledge. The fixed bias over the cathode bias, now I am looking for more of how you implemented that. You should do some more vids with the Guitologist, great the way you guys were bouncing off each other and getting into stuff.

HI, Looking for the correct schematic for this McGohan amp. It varies somewhat from the M20B schematic that is readily available. The M20B has 6SC7 tubes (triodes) and one 6SQ7 in the preamp section, whereas the M20 has 6AU6-A tubes (pentodes). The PI and power and Rectifier tubes are otherwise the ...

OK done, should last a while longer. Sounds like an Epiphone.