Valve Jr. mega-mod - VVR, NFB, input filter, effects loop, Baxandall-James

[bluefoxicy]

I've got a dead V1 VJ combo (...... yeah I know) and I'm thinking of re-fitting it with a new board and some new knobs. Trying not to add tubes; this should fit in a VJr V1 head, so here goes:

 

[*]Variable Voltage Regulator - The VVR mod, scale power down.

[*]Pentode/Triode Switch - Linearity decrease, power output decrease.

[*]Negative Feedback - Using 2 switches, standard variable NFB and resonance NFB circuits.

[*]Baxandall-James Tone Stack - Source follower on an IRF820 to get the tone stack close to the current source. Drop in after the volume pot but before the grid on the second triode.

[*]Effects loop - I'm not going with a JFET or MOSFET driven reverb tank; effects loop will let me hook up an Accutronics Type 4 or Type 9 with 2 tubes, in an external box.

[*]Input filter - DC input filter, a cap to remove DC offset and give -3dB cut-off below 16Hz right at the input.

 

That's 4 more knobs, 3 SPST switches, 1 DPDT switch (effects loop bypass).

 

Anyone have any other suggestions? I think this will make a rather complete little amp, and the effects loop will let me build an effects box with a trem and reverb and whatever else.

 

I thought about adding a parallel preamp switch (greater linearity), or using a tone stack loop (effects loop, use external tone stack), or a tone stack bypass in favor of an effects loop. I also considered adding a second tube for preamp overdrive, but figure I can just use the effects loop to change Volume to Gain and build an external second stage preamp box if I want that. So a few possible mods I figured weren't worth it.

 

This actually looks like a pretty complete amp to me, aside from having a tube-driven reverb (I refuse to use a MOSFET for reverb because the tube sound will have a distinct influence in that circuit). Any further suggestions are appreciated.

[m-theory]

Most often, simple is better, imo. Why don't you just plug in and play? It looks to me as though you're WAY overthinking what is ultimately a very simple, basic, decent sounding amp.

[bluefoxicy]

Well currently there's not even a board in that chassis, and the one that was in there had a fault in the power supply somewhere and ate itself... :s

 

I'd really like some reverb; I hate the sound of digital reverb (I've tried, most are just digital delay!), and want spring reverb (which sounds extremely nice). That's a bit over the top for a simple amp, hence the effects loop. I can build an effects box separate from the amp for all that.

 

The other stuff is all just stuff I'd like to add in while I'm building the thing anyway. Tone stack and VVR are the big ones; but I do like the NFB I added to the other amp (yeah I had 2 VJs).

[bluefoxicy]

I will ask, in that VVR is that really a MOSFET? The diagram looks like a JFET.