pedalbuilder1234
New member
I finally tested my build. It works fully... but Dwell and Tone knobs are backwards (the way I assembled it). The mixer knobs are not. Now that I look closer at the schematic, the Dwell and Tone knobs are numbered pin 3 to ground. At first I could tell not enough signal was driving the springs but I didn't notice the treble cut. Then flipped the enclosure over and started turning the knobs down from max rotation. Guess I could label them Muffle and Treble Cut. Or unDwell and unTone. Other than that it sounds surprisingly good.
I used a 3.9 ohm resistor for R15. The thin heatsink got about the hottest I would allow, unfortunately. Something will have to be done before I go to 1.5 ohm for R15. Luckily there's space in that corner of the enclosure to put something bigger. I might have to buy a wide roll of either double sided thermal or Kapton tape to get the heat transferred out of the enclosure without shorting.
Bias on TP1 is at 5.08V and I haven't adjusted R13 for it yet. If I need to go up in resistance it's gonna be harder than going down. Later on I could also try changing the bipolar transistor and see if it affects TP1. Also I for reference I found the note I made when I originally measured the jfets. They all tested between 1.54V and 1.58V and about 3.2 mA. Seemed spot on to what the build document called for so that's why I soldered them straight in.
I used 470k resistors for the first mixer stage. Increasing the input impedance might not have been necessary but it doesn't seem to cause excessive noise or anything. I'm happy with it, the mixer knobs seem to operate well and they even go the correct direction you'd expect.
The LED resistor being 1k would have blinded me or burned out my LED. I like my indicator LEDs dim. 47K worked well but I could've gone higher.
Still not finished. Overall really glad I found this thread. The R15 value is critical, no way 1.5k would have even worked. I think someone mentioned backwards knobs and I should've listened but at least the thing works first try. Also for the record the test reverb tank is a Mod 4AB3C1B. I have a couple other tanks but it's my beater tank.
If I were to build another of these I'd leave out the improved mixer, solder extra extra long shaft pots on the component side, and use an enclosure with more vertical height.
I used a 3.9 ohm resistor for R15. The thin heatsink got about the hottest I would allow, unfortunately. Something will have to be done before I go to 1.5 ohm for R15. Luckily there's space in that corner of the enclosure to put something bigger. I might have to buy a wide roll of either double sided thermal or Kapton tape to get the heat transferred out of the enclosure without shorting.
Bias on TP1 is at 5.08V and I haven't adjusted R13 for it yet. If I need to go up in resistance it's gonna be harder than going down. Later on I could also try changing the bipolar transistor and see if it affects TP1. Also I for reference I found the note I made when I originally measured the jfets. They all tested between 1.54V and 1.58V and about 3.2 mA. Seemed spot on to what the build document called for so that's why I soldered them straight in.
I used 470k resistors for the first mixer stage. Increasing the input impedance might not have been necessary but it doesn't seem to cause excessive noise or anything. I'm happy with it, the mixer knobs seem to operate well and they even go the correct direction you'd expect.
The LED resistor being 1k would have blinded me or burned out my LED. I like my indicator LEDs dim. 47K worked well but I could've gone higher.
Still not finished. Overall really glad I found this thread. The R15 value is critical, no way 1.5k would have even worked. I think someone mentioned backwards knobs and I should've listened but at least the thing works first try. Also for the record the test reverb tank is a Mod 4AB3C1B. I have a couple other tanks but it's my beater tank.
If I were to build another of these I'd leave out the improved mixer, solder extra extra long shaft pots on the component side, and use an enclosure with more vertical height.