Boneyard painfull but, ok with buffer

[juansolo]

I have no clue why this works (as it looks like there already is a buffer in the first stage of this circuit), but running a buffer on the input has removed the squeal from mine too. Though bear in mind mine was build with the Bonyard v1 recommended parts, it didn't squeal quite as much in the first place. Tried the klon buffer and settled on a JFET buffer purely as it was smaller still (though a little less transparent) and I didn't have much space left in my enclosure. Both work, the klon one would be preferable out of the two really.

[angrykoko]

I have no clue why this works (as it looks like there already is a buffer in the first stage of this circuit), but running a buffer on the input has removed the squeal from mine too. Though bear in mind mine was build with the Bonyard v1 recommended parts, it didn't squeal quite as much in the first place. Tried the klon buffer and settled on a JFET buffer purely as it was smaller still (though a little less transparent) and I didn't have much space left in my enclosure. Both work, the klon one would be preferable out of the two really.

Cool!

So you used the buffer you posed in this thread?  I think I have all those parts around even.

Did you by chance try my jumper trick with R1?  Would be nice to know if it works for anyone else.
I'm going to keep playing around with some shielding around R1 before I build the buffer; less parts in the end are less for me to screw up 

[juansolo]

Well I shoved an unstomped Klone on the front of it which is the same thing. I actually ended up using a simple JFET buffer. Mainly because I'm lazy and it was in a box of built boards But also because it was fractionally smaller and fit in the box easier.

The Klon buffer is more transparent though, so if you can make it fit, use that one.

Again, I still have no idea why this works... All sorts of weirdness happening today. Plugging two cherrybombs together causes the one down the line to drop a load of output, unless you crank the gain when it goes the other way and it's louder than the one on the front. I expect something is very wrong with one of them as it'd doing this when the other pedal isn't stomped!

I'll be taking over a 3rd cherry bomb to test shortly to see if we can narrow it down to one pedal then figure out what's wrong with it.

[mgwhit]

Does anyone think that having R4 (from the primary gain stage feedback loop) running parallel right next to R1 (input resistor) might be what's causing the out of control whine that's so heavily documented on this particular board?  I don't know jack about laying out boards (and i certainly don't want to dis Bean), but I've heard that parallel traces can influence each other and I can imagine how this could cause nasty feedback in this position.  Maybe angrykoko's jumper is sending the potential interference to ground, and that's what's stopping the feedback.  And maybe using an input buffer changes the impedance enough that R1 is less susceptible to picking up the interference.

I fear I'm just talking out of my butt and revealing my ignorance of electronics simultaneously, but I have bread boarded this circuit at full gain and it worked like a charm.  I feel like we might have a chance to fix something here, like what went on with the Creamy Dreamer specs on the Mud bunny last week.  Thoughts?

[angrykoko]

I think your on to something.

When I got home from work I used something with a smaller area than the alligator clip's tip to try to narrow it down a bit and found that I had to be between the 2 resistors for the best result but, would come back when I cranked the pedals volume.

So then I came up with this dumb contraption... It is the quietest of my tests YET.. I can even crank the volume on the pedal with no whine.

Dont laugh too much.. yeah it's scotch taped tinfoil with a pice of wire taped to it running to ground
But it's between the 2 resistors and it works!

[alanp]

Cheapest mu-metal you ever seen.

Glad to hear you got it going right! The old Trainwreck amps were supposed to be pigs in terms of high gain wire-wrangling.

[oldhousescott]

Good find! R1 isn't strictly necessary, you could remove it and jumper the pads for R1 and RPD that are closest to each other. Or you could just replace R1 with a jumper.

And I can attest to the Trainwreck being layout critical. Squeals like stuck pig if it isn't just so.

[pryde]

Wow. this looks promising for a logical fix to the whine. As said, mine is all but gone but certain pickups with hi-gain can still envoke some whistle. I'm watching this one

[angrykoko]

And the final version for tonight.
I put C5, R5 and High Gain pot back to the original 2.2uf, 47R & 1M values.. works like a charm!

I'll hit the store tomorrow and pickup something other than tinfoil so I can solder that wire to it then add some silicone to hold it in place.  

I'm all ears if there is a beter way to do that shield?



Cheers!

[juansolo]

Hey don't knock it if it works.

There certainly seems to be something on the new board that didn't afflict my old v1 Boneyard build. I'll try your shield at the weekend and disconnect my buffer if that sorts it. It won't be the first time I've ended up with comedy shielding in one of my builds...

[angrykoko]

Ok, the shield bugs me because it has to be glued in and it's extra wire/clutter.

How about one of these 2 ideas:
Note: both look like they will bypass RPD, you'd have to figure out a jumper for that if your using it.

1) stand R1 on end and solder the input wire directly to the end of R1 sticking up
In the pic below, de-solder the 2 in red (keep the one in green in place) stand R1 up on end.


2) Move R1 to foot switch.  Remove R1 and input wire.  Solder R1 to foot switch -> Solder input wire to R1 -> Solder other end of input wire to green pad above.

For #1, I remember when I was building my amp the guys on that forum told me to try to bring things in at right angles to each other to help eliminate noise... maybe that will work here?

Anyway, off to work

[madbean]

Does anyone think that having R4 (from the primary gain stage feedback loop) running parallel right next to R1 (input resistor) might be what's causing the out of control whine that's so heavily documented on this particular board?

This may very well be the problem here. R1 could be removed from the board and wired from the 3PDT. Alternatively, R4 could be removed and re-wired underneath the PCB. It seems that I made a poor design choice here. I can draw up a couple of diagrams for suggestions which might eliminate the problem.

[pryde]

So I was intrigued with the findings here and tried one of the potential fixes. I removed R4 and flipped it to the underside of the pcb.

Running 1M hi-gain pot with R5: 100R and C5: 1uf is DEAD quiet at full cranked high-gain. Before I has some whistle using a 500k pot at full blast.

I then put the R5 and C5 values back to stock 47R/2.2uf. The whistle/feedback returned with the high-gain pot at 10 o'clock 

So for me I am very happy with the R4 "fix" using 100R/1uf combo with the stock pots (100k/1M). The high-gain channel produces serious distortion, quietly and sound great. I love this pedal 

[madbean]

I'll collate all this info together and make an update to the doc noting the modified values, R4 fix. The current production board is slightly different than the prototype I did (which was 5 PCB mounted pots rather than four---a change I made to allow more configurations), and R4 was probably in a different position.

I appreciate all the info---you guys are getting to be some creative box builder problem solvers!!