Quick Boneyard Question

[oldhousescott]

If touching the volume pot lugs calms it down, I would be tempted to try putting 100pF across lugs 1 and 3 of the volume pot.

[mgwhit]

Yeah, I keep going back to that bit about touching the volume pot killing the whine, but not sure what it could mean.  I'll be interested to see if that cap helps.

The board looks good -- thanks for posting.  For a second I thought that 47K to the left of the op amp IC was a 470K, but I think it's just the light (and my terrible color vision).  Probably wouldn't hurt to double check though.

[pryde]

Still no luck. Here is what I have tried:

1. 100pf cap on lugs 1 and 3 of vol, made no difference
2. 1M resistor on lugs 1 and 3 of high gain pot to cut it to 500k, still whines badly
3. put a 1k resistor on input lug to ground on 3pdt switch. Killed the whine completely but the pedal sounded way crappy/muffled.

Really bummed. I love the sound of this pedal in higher gains but the whine/squeel makes it unusable.
Not sure what to do next??? Has anyone built this pedal per the build doc and not had this issue? If so, then I got to have a bad component or something?

Thanks for any additional help.

[mgwhit]

If you can wait a few days, I'll get my components off the breadboard and actually populate my fabbed board.  I'd just like to take it over to the rehearsal space this weekend and try it with humbuckers through a bigger amp before I commit to solder.

[pryde]

Thanks mgwhit and all others. I look forward to what you come up with on this. I found a thread here that descibes exactly what is happening with my build:
http://www.madbeanpedals.com/forum/index.php?topic=2886.0

It looks like the only solution is to run a buffered pedal infront of the boneyard?

[shawnee]

Reducing the gain of this beast helped mine quite a bit. In my humble opinion, there is no need for this much gain. At some point, you are just adding noise and not really increasing gain all that much passed a certain point. I reduced the gain on mine by using a 100 ohm resistor for R5 and a 1uF cap for C5. (You could even go 220 ohms with a 470n cap but that will reduce the gain maybe too much. With the 500K pot it still may rock enough though). I used a 50KB for the crunch pot and a 250KB for the high gain pot further reducing noise (and gain). I can still get singing sustain with the gain on the 250K pot at about the 2:00 position. It is plenty for me to play 80's rock and it keeps the noise to a minimum.

I noticed when I built mine and it was unboxed that the noise almost disappeared when I would touch the output wire (just on the insulation, not even bare wire). I used shielded wire on the input and output and it is really quiet but mine is lower gain than the stoclk build. I am not sure if we had the same problem but mine seemed almost unusable stock. The 100 ohm, 1uF change may help a lot.

[pryde]

Shawnee,

THanks for the suggestion. I tried your tweaks and the squeal is all but gone! Here it is as stands:

R5 100R
C5 1uf
High gain pot: 500k with 470k resistor (yielding about 240k pot)
Crunch pot: took it down to 50k.

This works great! THe high gain at full blast still has alot of spongy-saggy marshall gain. I will keep my eyes peeled for mgwhit's findings but this is sounding pretty damn great. THANK YOU. I will post a build report soon.

[shawnee]

Awesome news! Glad I was able to help Pryde.  If you like the way it sounds now, increase the voltage to +/-12v and it sounds even more amp like. If you are still using a TC1044, it can take a 12v input.

I am not even remotely close to being able to tell you what madbean, old house scott, mgwhit, and several other can so their advice is golden. I spent months tweaking this circuit (with Scott's help) so what I know is from them and a lot of breadboarding.

[mgwhit]

Apologies, pryde, but I'm not going to able able to build this one until I get back from vacation in a week.  Too busy prepping and finishing up work tasks this week, and if I pack my soldering iron I might be sleeping on the balcony.  I really wanna see what happens, so I'll get on it as soon as I get back.

[pryde]

No problem mgwhit. THanks again for all your help. I actaully took the high gain pot back up to 500k (from 250k) and there is still no squeal with using R5 100R and C5 1uf combo. It is really sounding super nice.

Good luck with your build please share your findings when finished!

[madbean]

Good to see you were able to work this out. Please feel free to post your changes in the Mods section, too, as it may benefit others.

Thanks to shawnee and mgwhit for their helpfulness

[k.rock!]

Well, I just finished putting together another boneyard. The first one I built a while back had the squeal issue but it was very very minimal so the fix Brian suggested of placing a cap between some pins on the charge pump worked fine for me.

Now, I have a huge squeal problem just like it has been posted a few times. I didn't realize I got the MAX1044CPA from SB instead of the SCPA...So my question is, would the fix posted here work on a MAX1044CPA as well? Anybody has any experience fixing the squeal with a CPA?

Thanks dudes..

-Kaleb

[pryde]

Not sure about the CPA vs SCPA with these mods.

Maybe you could do all the changes suggested and see if iy works with your current chip. If not, the only thing left would be to swap in a SCPA.

R5: 100R
C5: 1uf
Crunch: 50k
High gain: 500k

Also, did you use sheilded wire for all input/outputs?

[k.rock!]

OK, so this is what I found. I only changed R5 to 100ohms and C5 to 1u and the squeal is completely out. I didn't get any on the crunch mode all the way up. Then I switched over to high gain and I was only getting squeal on the last quarter.

Interesting enough, I turn up the amp, switch to crunch and play for a little bit, switch back to high gain...no squeal!...even all the way up. I'm using stock everything else and the MAX CPA.

Only thing I need help from you guys, I'm getting a pop when I engage/disengage the boost. I'm thinking of adding a cap somewhere to maybe filter out some of the current peak? Or a resistor to ground to bleed it out somewhere? Any suggestions?

-Kaleb

[mgwhit]

I finally moved mine from the breadboard to the circuitboard.  I had lowered the gain a bit using the R5=100R/C5=1uF mod while I had it on the breadboard just because I preferred the gain range(s) like that, so I kept it that way when I moved it to the PCB.

No whine at all, but it is a lot noisier (hum?) at the extreme end of the High Gain pot on the PCB (going through my test rig) than it was on the breadboard.  I didn't bother with shielded wire, but I may reconsider (at least on the input) if it's still that intense after I box it.

Edit: I just gave it another spin cranked with the high gain dimed, and the noise wasn't nearly as bad as I remembered from this morning.  Can't hardly wait to box this...but I have to since I've decided to order a different enclosure for it.