EL Sunnbeam

C

comradehoser

Well-known member
Holy geez.

Most intense boxing ever.

Crowded layout, double layers putting component ends on top of ICs and barely enough 3pdt threads to hang the nut, that big honking dual gang pot pushing all the off-board levels up, a huge 220 cap, and that's before I decided I wanted to try to make everything including the TRS/XLR jack happen in a 125b. It ALMOST didn't happen by a millimeter and a half.

I had to cram the 9v and in jack way over, drill and file (only could find my rat tail so it was ragged and shittastique to say the least) a huge irregular hole, trim off parts of the 9v jack and TRS/XLR jack to fit, forgo jack and 3pdt washers, use incorrect screws (actually bolts) to fasten the XLR. Also had no idea what to do with the XLR side ground. Had to bend the hella big 220uf cap out of the way of the "3pdt and friends" board, as well as bend all of the caps on top to make the backplate fit on. Almost ran out of component legs to pull up. Oh yeah, you have to jumper the tabs for the XLR to the corresponding TRS tabs.

Tried to Erik S my wiring. Still l am the student and not the master.

The playing: does a dang good sunn beta, except for big pops from the 3pdt. Will go look at the pulldown resistor situation later. What's a sunn beta? I've built three, one from pcb guitar mania, two from Aion, so... I like them. Very powerful EQ. Up to noon on Drive pot is evocative (?) cleans. Makes your guitar sound surprisingly great and sparkletastic. After noon, filthy, filthy, beautiful distortion. And this circuit is LOUUUUUD. Can doom amply confirmed.

Also bonus: no oscillation issues as with both of my Aion builds. [Edit: as in, both my Aion builds had oscillation issues]

IMG_20250325_223037462.jpg
IMG_20250325_223044057.jpg IMG_20250325_222231855.jpg
 
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Nice! I built one of these last year as well (need to do a build report!) and my experience was identical to yours. Getting that daughter board in there was a huge pain in the ass and mine pops as well. It’s actually nice to hear some corroboration. IIRC the relevant resistor is hidden behind the daughter board so you can’t even check it without unboxing the whole damn thing.

I’m similarly happy with the (ungodly loud) sounds mine makes, though!
 
Unclear to me why the pops. PDR is 1M and in the right spot according the schematic, so.... ? Guess a continuity probe/jumper to ground is in order.

I wouldn't think the balanced out/XLR board would affect anything, but maybe? I don't feel like desoldering/resoldering all those dang pins.
 
Forgive my ignorance, but I assume the output pulldown would be 1M to ground, T'd into the board output to 3pdt line? or anywhere between board and output jack? Mirroring the input PDR, basically?
 
C1 on the DI breakout board appears to be backwards. (On the schematic)

1743017530119.png

Pin 7 (from the main effect) should be near 0 volts due to the bi-polar power supply. The right end of C1 will be pulled high by R1/VR.

This would apply reverse polarity to C1, which isn't spec'd as a non-polar cap.


I could be wrong, or this could be unrelated, but it's worth investigating.
 
I've just finished building mine, having a tricky time getting a decent amount of voume/distortion out of it. Drive pot is also giving me some grief, I really hate dual gang pots :( + diagnosing the pedal after it's built back into the enclosure is PAINFUL.

I bought 2x PCBs and have yet to house the 2nd one, so I'm hoping that goes a bit better than the first...
 
Did you put any insulation on the back of the pot? 99% of the time with dual gang pots this is the problem. Some cardboard or a thin guitar pick will do the trick
 
comradehoser said:
Holy geez.

Most intense boxing ever.

Crowded layout, double layers putting component ends on top of ICs and barely enough 3pdt threads to hang the nut, that big honking dual gang pot pushing all the off-board levels up, a huge 220 cap, and that's before I decided I wanted to try to make everything including the TRS/XLR jack happen in a 125b. It ALMOST didn't happen by a millimeter and a half.

I had to cram the 9v and in jack way over, drill and file (only could find my rat tail so it was ragged and shittastique to say the least) a huge irregular hole, trim off parts of the 9v jack and TRS/XLR jack to fit, forgo jack and 3pdt washers, use incorrect screws (actually bolts) to fasten the XLR. Also had no idea what to do with the XLR side ground. Had to bend the hella big 220uf cap out of the way of the "3pdt and friends" board, as well as bend all of the caps on top to make the backplate fit on. Almost ran out of component legs to pull up. Oh yeah, you have to jumper the tabs for the XLR to the corresponding TRS tabs.

Tried to Erik S my wiring. Still l am the student and not the master.

The playing: does a dang good sunn beta, except for big pops from the 3pdt. Will go look at the pulldown resistor situation later. What's a sunn beta? I've built three, one from pcb guitar mania, two from Aion, so... I like them. Very powerful EQ. Up to noon on Drive pot is evocative (?) cleans. Makes your guitar sound surprisingly great and sparkletastic. After noon, filthy, filthy, beautiful distortion. And this circuit is LOUUUUUD. Can doom amply confirmed.

Also bonus: no oscillation issues as with both of my Aion builds. [Edit: as in, both my Aion builds had oscillation issues]

View attachment 92981
View attachment 92982View attachment 92983
Click to expand...
Last year, Aion updated their Sunn Beta boards to fight those oscillation issues you are having. It looks like an easy addition to those with old boards. Is this what you were experiencing?

"In version 1.2, we added a trimmer called “Treble Limit”. This is a variable resistor in series with the
treble control that essentially reduces the upper range of the knob, and can be used to eliminate any
possibility for oscillation across any of the knob settings.

Start with the trimmer turned all the way up. Set the volume to zero and then turn treble and gain to
max. Slowly turn up the volume. If you hear any oscillation or feedback with these control settings, turn
the trimmer down until it goes away. If the trimmer is turned all the way up, it’s out of the circuit and the
treble knob is full-range."

xxx.png
 
tegendemuur said:
Last year, Aion updated their Sunn Beta boards to fight those oscillation issues you are having. It looks like an easy addition to those with old boards. Is this what you were experiencing?

"In version 1.2, we added a trimmer called “Treble Limit”. This is a variable resistor in series with the
treble control that essentially reduces the upper range of the knob, and can be used to eliminate any
possibility for oscillation across any of the knob settings.

Start with the trimmer turned all the way up. Set the volume to zero and then turn treble and gain to
max. Slowly turn up the volume. If you hear any oscillation or feedback with these control settings, turn
the trimmer down until it goes away. If the trimmer is turned all the way up, it’s out of the circuit and the
treble knob is full-range."

View attachment 102376
Click to expand...
Oh nice, thanks!! My fix for oscillation was to just skip the last step through the cmos, and I was really satisfied with how it sounded but this looks like a nicer solution!
 
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