Distort-o-matic XI Inductor Question

[soggybag]

This is the Distort-O-Matic XI from Stompboxology. I created a PCB and built it up. Sounds great but there's a lot of noise.

My layout is not so great and this is probably causing some trouble. I'm looking at the inductor and wondering if this could be a big cause of noise and if there is anything I can do to mitigate?

I had these boards made at PCBWay.com. They have a deal where 10 boards smaller than 100mm and 100mm are only $5. So this has been my prototyping system.

I pulled this inductor from an old crybaby. The pins didn't match the Eagle footprint so I mounted it to a small piece of perf-board. You can see it in the center of the box.

The tone control works great. It's got a wide range of treble and bass boost and cut. 

[Elijah-Baley]

Looking at the schematic I see two big polarized caps: a 10uF and a 6.8uF. Looking at the board I see an electrolytic and a tantalum, I guess, so probably those are the caps.
I hope I'm not telling you a something you know well, but didn't you use a 100uF/47uF electrolytic cap as filter? In case, trying it with a battery (externally) it could be less nosier.
Maybe you can try to see if if it's less noisy putting on the DC jack a 100uF filter, with the negative on ground, of course.

[soggybag]

I should have seen that. I just followed the circuit as it originally appears and there's no power filtering. I'll have to add that and check it again!

[antonis]

I've replaced inductor with a simulated one https://www.diystompboxes.com/smfforum/index.php?topic=122808.0 with absolutely no noise issue..

[soggybag]

Antonis! You're reading my mind! My next question was: is possible to replace the inductor. It's hard to fit on the board, I was also worried it might be adding noise.

[antonis]

I think you may use an extra board (like the one with the inductor)..
If you can fit somewhere the 470μF electro cap, there should be enough space for the rest items..

P.S.
BJT based gyrators need a fairly "quiet" power supply so a simple RC LPF with a 10nF - 100nF shunt cap should be suggested..

[soggybag]

You mean added a 100n and 10n caps on the power rail?

I'll give this a try on a smaller board. But I'm also going to redesign this PCB and order an updated version.

Did you build this? Mine sounds pretty good. I like the sounds. The tone control works well, I might adopt it for other projects.

I used some of those fake Si 1n34a diodes for clipping.

I'd like to replace Q1 with something easier to source like 2n5089 and dump that trim pot. I have some 2N5457 stashed but these are harder to get these days, and in this case the JFET isn't adding much to the sound here as far as I can tell.

[antonis]

You mean added a 100n and 10n caps on the power rail?

I mean to place a series resistor after RLED and an electro cap after series resistor (shunted to GND) and another cap (of any value between 10nF to 100nF) in parallel with electro cap..

I'd like to replace Q1 with something easier to source like 2n5089 and dump that trim pot.

It can be done but you'll have to re-design Q1 bias..
Of course, input impedance of a BJT in place of Q1 should be ridiculously low and you'll have to deal with bootstrap configurations so better let Q1 be a JFET..
(or use any MosFet handy..)