What's happening in this plate circuit?

[imaradiostar]

I'm sorry I didn't say anything sooner.

Using Merlin's load line calc the 12dw7 showed a net decrease in gain. I still think a pentode is the way to go if you want to stick with a three bottle musicmaster with a lossy fender tone stack. Even a marshall style stack with a silicon source follower will make a big difference in gain and usable volume. The Fender tone stack, however pretty, is throwing away all kinds of gain to give you that nice mid scoop. The ghia control does that with less loss if mid scoop is your poison.

You'll likely find the traynor circuit (treble bass) a better fit- perhaps overly interactive but many excellent sounds to be had. I currently have a prototype on my bench that has only one 12ax7, an LND150 cathodyne inverter and a pair of 6v6's. It sounds pretty darn good. I'm of the opinion the transformer PI is likely to sound even better.

give it a go- can't hurt, right?

jamie

[octal]

The other thing you could do is to change the PI xmer to one with a higher step up ratio... now that you've got a driver section (the 12au7) with a lower Ra, it should be able to handle a transformer with a "steeper" ratio if you will.

Nathan

[Groover]

Hey Jamie, could you put up or provide links to a) the Ghia tone control, I've been curious about that one, and b) the Traynor tone control you are talking about. (If they are illustrated in Merlin's book you can just give me the illustration #.)

If I can wire the tremolo bias-style like a BF Princeton and get it to work with the xformer PI I will then have an extra triode, and I thought I would like to try using it as a cathode-follower before the tone stack.

Also maybe now that I have the "right" Rk on V1b I may try the 12ax7 again. (I ran out of tweaking time last week before my weekend trip, so I kind of stopped experiments mid-stream)

My other idea is to return the VC to quasi-stock, and build a cathode-biased Princeton non-rev in one of these: Allen Amplification - Mini Chassis Project