I got a hold of a 2mm thick piece of aluminum and had my dad help me cut it to size with some sort of radius. I stuck some offset aluminum angles on the sides and mounted it in the box, then mapped out where the holes needed to be and drilled them out.
The circuit is a modified Fender 5E3 circuit with some values taken from the Roninette Simplified Tweedle Dee. I wasn't sure whether to post this in the Dumble or Fender section, so I closed my eyes and clicked, and landed here. Anyway...
I consolidated down from 4 inputs to 1 and added a cascaded gain option available via a 2-way slide switch. Right now I have a GZ34 rectifier, 2 6V6, a 12AX7 phase inverter, and I am still deciding whether I prefer the 12AY7 or 12AX7 preamp.
Last edited by professormudd on Sun Mar 06, 2022 7:21 pm, edited 1 time in total.
-Matt
It may very well be that the sole purpose of your life is only to serve as a warning to others.
With the second one, I went ahead with 2 inputs rather than a switch. I also went with 22ga stranded wire rather than the 20ga solid cloth lined and it was quite a bit easier to manage.
Both of them sound the same, neither makes more noise than the other and neither are very noisy. I really like the sounds I get out of these when I put them through most any cabinet, but believe it or not, my favorite right now is a 15" closed back bass cabinet with the horn attenuator turned all the way down. The amplifiers have very little clean headroom, which is one of the reasons I love them so much. I have actually been quite fond of playing some pretty hard rock through these.
They are also the only amps I have that seem to like this EHX Soul Food pedal I have had lying around.
Anyway, just wanted to update this post for posterity.
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Last edited by professormudd on Mon Mar 07, 2022 6:35 pm, edited 1 time in total.
-Matt
It may very well be that the sole purpose of your life is only to serve as a warning to others.
Welp, one of these things is dead silent, and the other (the second one with 2 inputs and yellow plate wires in the pics) hums quite a bit... Here is what I have learned and tried so far:
1. Hum was persistent without any guitars plugged in, changing with volume. I thought it might be related to the subtle difference in the input posistions so I re-did the input with a switch rather than 2 inputs.
2. Now hum is only when the "lead/cascade" channel is activated. Persistent without a guitar plugged in. Changes with volume. When set to bright, the amp can be cranked with only the slightest (perfectly acceptable) hiss.
3. With tone all the way down and "Normal" (lead) volume all the way down, I hear 60Hz that changes with bright volume. No audible hum when the bright volume is all the way down.
4. As I turn up the "Norma;" (lead) volume, it sounds like some 120Hz is being added into the mix.
5. Pulling V1 eliminates the hum.
6. Replaced both preamp tube sockets and re-wired to match the lead dress of the silent one.
7. Rolled various combos of 12AX7 tubes through both positions. Some are louder/noisier than others, but they all hummed.
8. Re-wired all filaments,
9. Replaced both V1 grid resistors.
10. Replaced all ground leads.
11. Pulled out the silly-scope to probe (throwing Hail Marys here):
11a. With only the bright volume up and Tone and Normal set to 0, I can sort of "see" the AC ripple when I probe V1 plate at pin 6, checking the plates at the PI, you can see the wave grow much more pronounced.
11b. Bringing up the normal volume and you can "see" the addition of the 120Hz changing the shape of the waveform.
I am running out of ideas here. I think the origin of the noise is somewhere around V1, but at this point I am not so sure. The layouts and lead dress between the two are as close to identical as I could make them, the components all seem to test well, solder connections have all been reflowed (many more than once).
Does anyone have any thoughts?
-Matt
It may very well be that the sole purpose of your life is only to serve as a warning to others.
Gave a go at using some shielded wire, but that did not make any difference at all.
Also removed the risers from under the board to test for changes when reposition the board. Nada.
Tried a different set of power tubes. No change.
Further modified grounding to give buss bar dedicate chassis ground point instead of the input jack. I a
Sure does get noisy when the tone is turned up. I think I might replace the tone and bright caps and the bright pot because why not?
I am also thinking about isolating the jacks from the chassis and running ground wires.
I noticed when I touch the chassis with my hand, the 60Hz is reduced very slightly. I can hear a very slight reduction in the volume, and on the scope I can see the very subtle reduction.
-Matt
It may very well be that the sole purpose of your life is only to serve as a warning to others.
Re-did the power supply ground buss. No change, but it is still better now in my opinion anyway.
While I was at it I connected the filament center tap to the positive side of the power tube cathode bypass cap as I heard that could quiet down some hum. This did not help. It might have made the hum worse, but I'm not 100% sure about that. So I reconnected it to the power supply ground.
Voltages in general were reading a little high, so I switched to the black (125 vac) primary on my power transformer. I had originally used the grey as it is intended for 115 vac, which is what came out of the wall in my old house. Here it is 125. Switching the power transformer primary did not help the hum.. Neither did swapping out the rectifier tube, which I decided to try since it was the last piece of glass I hadn't swapped.
So, I've ruled out more I guess.
The hum hunt continues.
-Matt
It may very well be that the sole purpose of your life is only to serve as a warning to others.
I stuck a CV4004 into V1 and the hum dropped significantly. It did not disappear, but it is a lot less obnoxious.
I think I found the source of the hum. I just don't know how to address it.
When I use the scope and probe the "bright" channel grid, I do not see any AC on the input side of the resistor, but I do see it on the pin-side of the resistor. When I clip my probe to the pin, the hum drops significantly. When I let the probe "rest" across the socket after having clipped to the grid pin, the hum vanishes entirely.
I believe there is AC getting in right there, but I do not know how to deal with it. No amount of re-positioning the wires seems to help. I have tried to adjust the tube pins to their least-noisy positions.
-Matt
It may very well be that the sole purpose of your life is only to serve as a warning to others.
