Tweedle Dee Issue

[passfan]

Funny issue with the circuit which plays and sounds great by the way. Plugged into the guitar input with volume at a 1/4 and if I run the mic volume all the way up the signal drops out completely. Is this feeding back through the coupling caps and plate resistors and causing phase cancellation?

[Stevem]

Which model deluxe did you build from?
Is your 1 meg pot for the Mic input wired that right way?
Is it a reverse taper pot?

[passfan]

I built from the Tweedle Dee schematic provided by Charlie Wilson and posted in the dumble sections. 1 meg wired the same as the guitar input with standard 1 meg pots. Just wondering if anyone else has tried this and noticed wether or not it does it. There is a path as both pots feed the PI on one side and the wipers each feed a respective coupling cap each tied to their own 100 k plate resistor fed from a common B+ . You could , theoretically ?? , feed signal off the guitar input volume pot , to the mic input pot , through a coupling cap , two 100k resistors , another coupling cap and back to the input of the guitar volume pot again. Perhaps the coupling caps and resistors throw it out of phase just enough to cause cancellation when the mic volume is on full. I'm only running the guitar pot at a quarter volume. If I'm correct then this would happen to anyone that built the amp, hence the question

[Long Distance Call]

Does the same thing happen if you plug into the mic input and run the guitar volume all the way up?
Thanks, LDC

[Reeltarded]

The guitar hates your singing.

[67plexi]

What are your voltages and what transformers did you use.
My voltages are exact to the real layout.
Plus I used real 1959 OPT that made all the difference.
I have over 1200 hours of play time on it now.

[passfan]

So the consensus is that no one else's does that and mines special ?

[passfan]

LDC , it does the same thing with the guitar plugged in to the mic input and raising the instrument input.
Miles , nobody likes my singing but I am the consummate professional about it. I'm getting paid either way. Some people pay me to stop. 67plexi, so does yours do it or not ? Both are built from the same schematic , transformers have nothing to do with my issue.

[sluckey]

So the consensus is that no one else's does that and mines special ?

There has always been an interaction between the volume controls in that circuit. My 5E3 does it (although I don't remember the signal dropping out completely). This is part of the charm of this circuit.

Strictly from a technical standpoint, I personally think wiring the volume controls like this is a mistake. But it's a happy mistake for many people.

[67plexi]

Passfan, Photos might help it could be a leaky capacitor.
Transformers are important I built two and went through five sets on the second build was lucky to get one more 1959 OPT and used the same PT
as #1 400 hours later they sound the same. It took only 4 hours to build
the first one. Is yours 3 input if so try a 68k on the first channel see if that helps. I only use channel two it sounds best to me volume 2 tone 4
And pin 3 and 8 on V-1 should be 1.15 volts. I used a matched 12AY7 on V-1 just like my 1958 Deluxe amp. And using a 250 ohm bias resistor
you are at 95% bias you may wish to try 300-330 ohm to cool it down a bit.
Good luck I'm off to my mining claim's for the next few day's.
One more thought the Switchcraft input jacks are crap now I had to replace a few.

[passfan]

Slucky , yes I've experienced the interaction on a typical deluxe build though I can't remember ever turning one up to full on or what it did if I did it. It's the shared feed to the cathodyne that is providing the feedback for the other volume pot. I don't know how you would get around that.
67 plexi my iron is vintage Hammond off an L100 chassis. They seem to be getting along fine. It takes the PT a couple of hours to get warm. A leaky cap would leak DC which would give me a buzz. Caps pass AC signal , which would be what they are doing. I'm assuming your referring to the two .022 coupling caps. I'm not sure what you think another 33k will do on the input of the mic ; I wouldn't think it wouldnt have anything to do with how the two volume pots interact , with nothing plugged into the mic input it is shorted to ground and the triode is shunted. I am running 3 82ohm cathode resistors for 246ohms on the cathode. I love the sound of an octal tube being squeezed to shit, wouldn't trade it for the world.
The amp sounds excellent and runs great and hands down beats anything I've heard for chime , harmonics, and bloom , even my dumble builds. Makes sense that Alexander built it.