The Amp Garage

I built a 7591 Plexi that was going in a combo, but with the controls going the same direction as my others with the input on the left followed by the volumes, tone, and presence moving toward the right. So I needed to use a mirror image of the layout, basically put the turrets on the other side of ...

When you say "just the preamps", is this a preamp-only build?

I've built several plexi-style amps with a SS/tube rectifier switch in them. If your tube rectifier is a 5AR4, you probably won't hear much of a difference because there isn't much sag in it. I used a 5V4 in a couple of them and there is a definite difference between the SS and tube. I used a DPDT-c...

Or the "Trioderizer": http://www.radiomuseum.org/forum/the_trioderizer_a_solid_state_triode.html I know a couple of people who have played around with different troiderized jfets and mosfets (depletion mode) and they're supposed to sound very much like a real triode.... as long as they don't clip or...

...I am also wondering why there is very little use of drivers between the phase inverter and output pairs or quads in higher power versions using 6550s or similar. I admit freely to my amateur status and there are things I encounter that I don't comprehend. This is one of them. The use of "drivers...

darefugee wrote:Thanks for the tip. I think you mean the two 470k resistors tied to V2 pin 2 on the Plexi 6v6 schematic, right? I'll be sure to put them on the tube socket and to feed them with shielded wire from the volume controls.

Yes, those are the two I'm talking about.

P3 is simply a tie-off point that isolates the extra unused lead on the original 240V transformer. It isn't an electrical connection at all. Pretend anything that's connected to P3 doesn't exist. As for the cap and resistor (I think that's what RT1 is) on the mains, ignore them for the moment also. ...

We were all new to the game at some point. My JTM45 was my favorite amp for a long time. The only reason I sold it was because of medical bills. I'm hoping to build another one soon.

Matt

Just a note, the thing you circled as the "anode" is actually the getter flash and has nothing to do with the electrical function of the tube (other than keeping the vacuum solid). The anode is the big grey box in the center of the tube surrounding all of the other electrical goodies. If you get a c...

The only tip I'll give at the moment is to put the mixing resistors over directly on the V2 socket. I've built several plexi-style amps and every one that had the mixing resistors on the board picked up noise and a signal even when both volumes were turned down all of the way. With the mixing resist...

1. modified HO, my first build. 6EZ5 power tube, merlin's bootstrapped gain-stage/CF, jalapeno tone stack. _maybe_ can sub an SEL running a KT88 instead, but with the same mods. 2. Plexi6V6. Most flexible amp I've ever found especially when it has the plexi/ali switch _and_ variable NFB. Loves boost...

stephenl wrote:You can use them to supply the anodes in the LTPPI. This will add a little feedback in lieu of using feedback from the OT secondary. Pay attention to the phasing.

Quit giving me stuff to think about! Especially on christmas!

What's a banjo good for?



About 90 feet if you can get enough loft on it.

Just a +1 to what the other Matt said. The exact value isn't critical and having a fixed resistor to provide a solid grid-to-ground reference if a pot opens up is the important thing. My worry about a 100ishK vs 200ishK (or more) was not just for drive reasons, but also thinking a bit about tonal c...

I think you're overthinking it a little bit. A PPIMV is a variable grid leak , among other things (voltage divider for the signal). You want to aim for a 220k-ish grid leak value. That value is when the PPIMV is dimed and you effectively have 2 resistors in parallel. (pot resistive track || grid-lea...