BFPR Clone "just fishing"

[frankeg]

One more PI question please. I am not going to use/build the vibrato circuit and I was wondering if I could just parallel that tube? In other words, I'd have a parallel wired PI. I have paralleled pre-amp tubes before with nice results - a hair more gain and better signal to noise ratio, but never a PI. It looks doable but am I asking for trouble here?

[tubeswell]

One more PI question please. I am not going to use/build the vibrato circuit and I was wondering if I could just parallel that tube? In other words, I'd have a parallel wired PI. I have paralleled pre-amp tubes before with nice results - a hair more gain and better signal to noise ratio, but never a PI. It looks doable but am I asking for trouble here?

You mean paralleling the PI driver stage? Don't see any advantage tone-wise.

[frankeg]

Yea, I agree. After thinking about for a while it seems like a bad idea. I think I'll keep the vibrato and try to tweek it so it is richer/fuller. thanks

[tubeswell]

Hi frankeg

Here's the link to my BFPR-something schematic and soundbyte (so you can see the IRF820 source follower in the trem circuit) Using a source follower in this way is really handy, because it doesn't affect the signal and only helps to improve the smoothness of the trem, and doesn't use up any heater winding juice. I would recommend Merlin's ground scheme (which I implemented in this build using separate filter caps, hence the different coloured ground return circuits) for low low noise floor. JM2CW

http://music-electronics-forum.com/t20860/

[Bruce / Mission Amps]

I've heard good things about the OT upgrade and am leaning that way but I don't want to alter that PR mojo too much. I also like the idea of discrete caps - I trust them more. Thanks MWJB... I've followed peaveybandits build as well and will go with higher voltage to the PI but not sure if I want to mess with the PI bias mod - is any PI truly balanced? any thoughts there?

To keep more of the PR "mojo" use a good quality tweed Deluxe output tranny. The PI mod works well on the black face fixed bias Princeton circuit ... not quite as well on cathode biased power tube amps using the cathodyne type driver.

[frankeg]

To keep more of the PR "mojo" use a good quality tweed Deluxe output tranny. The PI mod works well on the black face fixed bias Princeton circuit ... not quite as well on cathode biased power tube amps using the cathodyne type driver.

Thanks Bruce! I just recieved my trannys from David Allen. I went with the beefier PT and the Deluxe style OT. I also carefully matched all the PI's components which MWJB recommended. I tried to go with separate power caps but in the interest of neatness I compromised and used a 32+32 uf can for the first two and separate board mounted spraque atoms for the preamp power. I left the vibrato circuit intact but changed the 1meg resistor to 470k as suggested. My board is finished and my wife said it looks like modern art...Nice...Perhaps "Geek Art" is more applicable... I'll post some pics when I can. Thanks to you and everyone else here who responded to my questions. I sincerely appreciate it. frank