The Amp Garage

I didn’t add the extra filter stage. Went with Robinettes minimal mods. I also undid the LNFB on the PI, 4.5k PI cathode bias and the 500 ohm v1 bias. Kept the 100k plate and tail resistors though. I don’t have my voltages. Next step is to measure this stuff. I’d like to ascertain what the PT is ca...

MJW Modified 5E3.gif There we go! I've omitted the VVR just for the sake of space. It only operates on the B+1 and B+2 voltage lines. One thing I do notice is just how little voltage dropping is going on. 1500 resistor and 8200 resistor, assuming I'm reading the values right. Any thoughts on this? ...

Despite believing that Jelle is 100% correct about these boards, I have decided to see if Brad and Lyle’s advice has any merit on this board. I cleaned around one of the terminals and the voltage dropped around 10 volts, and I suspect the most improvement is gained from cleaning the top of board an...

Congratulations! Isn't it great when a plan comes together?

Current features The VVR, PPIMV and triode/pentode switch were features on the original Bantam model. The idea behind them was the player could shift overdrive to pre- and/or power-amp with any of those controls. I'm also working on the schematic, but not sure I'm competent enough to include the VV...

Thanks Stephen, I'll see what I can do. Regarding the power scaling, that came installed when I ordered it. I had it on the original model, so I asked for it on this. I don't know too much about how it had been configured, but when you turn it down, you also have to pull the MV down to avoid fizzin...

Thanks Stephen I believe you are correct the original WEM was a LTPI, and the first Bantam I had was wired this one. But with this Tweed variant, the builder had indeed used a cathodyne PI, per the 5E3 circuit. So I didn't have to change this over. However the output stage uses EL84 tubes like the ...

Super Vacuum Tube

Stumbled across this interview with Roger Cox. Some really interesting perspective in this...

Welcome Mark. I am curious. As I understand it, the WEM Dominator had a LTPI, and when you say you "swapped out all the preamp changes for the Dumble schematic" did you also include the cathodyne PI? What about a schematic??? I'd be curious to see how it stacks up against the WEM Dominator and the T...

Whoops! I see a mistake in the VVR drawing! I forgot to add in the 1Meg pot! I though you were going for fixed bias. Is there any reason you need this to be adjustable? Probably not. I think I could just measure my current values and put resisters in instead. I think it was more for experimental pu...

Whoops! I see a mistake in the VVR drawing! I forgot to add in the 1Meg pot!

I though you were going for fixed bias. Is there any reason you need this to be adjustable?

What was your thinking with the power MOSFET for the B+ branch feeding your reverb and FX loop? To get the magic 30V on the cathode your "B+5" voltage should be in the order of 260V on the plate of the driver and 360V on "B+4". With these values, the 30V is all but certain. That MOSFET is a VVR for...

... You aren't likely to need the 68pf cap on the Master though. Good to know. Thanks. I'm out of the loop on any discussion on that one. I see most with the 68pF, one with 15pF, and some with none. I guess with bright switch in the loop, and a presence control later, it becomes pretty irrelevant? ...

After doing a bunch more suggested reading on the Loop, Stephen, I lifted your circuit from your 183 build. In the interest of not drilling too many more holes or installing parts that I think won't get used, I removed the the line/instrument switch as well as the jacks for the passive loop. I'm th...

What would you recommend as a starter amp? Would it be a better learning experience to start with a kit or with a full build? Only you can really answer that. We know of quite a few amps that make good/great pedal platforms but the caveat is how much time, money and energy you have to invest. We al...