madbeanpedals::forum

Hello,
I just put together a fabbed boneyard (new version) and used all stock values including a TC1044SCPA as specified in the build doc. The only sub is 82n in C7 as I am out of 68n right now.

When testing the circuit (unboxed) everything works fine except I get the dreaded high pitch squeel on either channel with the gain pots at 25% or greater.

Is this because it is not boxed-up yet? I plan on using sheilded wire when boxing but want to address the oscillation if possible before boxing it. Did anyone else get bad squeel when testing the pcb before boxing? Did it go away afterward?

Thanks for your insight

I breadboarded this circuit today (with only the high gain pot).  The only subs I made were 470pF's for C1 and C4 and a 1n for C13.  I get no squeal at all with the Gain totally maxed out, although it's pretty noisy with no enclosure.  This is (still) a fairly bright circuit and I kept the Tone at around noon while I was messing with it tonight.

Does rolling off your tone knob affect the squeal at all?  I would recommend trying higher values at C1, C4 and maybe C9.  Good luck!

The squeal is still present with the tone knob turned either way. The squeal/whine sound is effected when turning the tone knob but is never goes away.

With the gain on either channel up past 9-10 o'clock the high pitch comes in but is not present when actually playing/strumming. As soon as you stop playing it is screaming like a banshee.

All controls work great and the pedal sounds really awesome otherwise. Not sure if I should just start boxing it up or does this need to be addressed beforehand?

Thanks for any help

There's a notorious whine issue with some charge pumps in this circuit, but I think the TC1044SCPA is supposed to be immune to it.  I suppose you've found all the other threads about this -- if you haven't, search for "boneyard" and "whine" and you'll see what I'm talking about.  Earlier I was assuming that that probably wasn't your problem since you specifically said you were using the TC1044SCPA, but I can't help but wonder if you might have a bad one.  Do you have another charge pump IC you can try?  Maybe someone else who has had the same problem can chime in and help you better.

And for the record, I wouldn't box it yet except as a last resort.  It's not the end of the world to unbox, but it's not particularly fun either.

I just popped in a new charge pump (tc1044scpa) with the same results? Not sure what to do next. Gonna pick up tomorrow on this. must go to sleep...

Okay, so let's assume it's not the charge pump whine (since you're using the correct version and you've tested two of them).  My best guess is that you're either generating way too much gain or not cutting enough treble, and that there is a bad component value or a bad solder joint somewhere in one of your op-amp negative feedback loops.

To help us along, please post the voltages on each pin of your IC1 and IC2 and well-lit, in-focus, high-resolution photos of both sides of the board.

I think krock had the same problem.  I forget what his fix was.  You could pm him or you might be able to find the post if you search with his user name.

Josh

OK. back at it. I triple checked all values,  no solder bridges. changed both chips IC1 and IC2 with no results.


Here is something I found. When I just touch the volume pot on the lugs the pedal is dead quiet and works/sounds great. The Vol is a 10kA pot with 10k resistor soldered to lugs 1 and 3. Makes me think it may just be an un-boxed grounding issue? Just touching it (with a little firm pressure) kills the squeal at full gain.

THoughts? I can take some voltages and post pics still if necessary.

Thanks for your help.

It should go away once boxed. If not, reducing the value of the high gain pot as mentioned in the build doc should eliminate it.

All right I will box it up and hope all is well. Not sure about the gain pot though as it does the squeal on both channels (100kb and 1MA pots). I will report back. tHanks for all the help so far.

Not to hijack the thread, but I have the same issue.  Here's the weird part: No whine when the hi-gain pot is in the circuit at any level.  When the low-gain pot is in circuit, I get whine when it is over 1/2 rotation.  I am using a 50kB for low-gain and a 500kA for hi-gain pots.  I am using a MAX1044 charge pump. 

I originally had a TC1044SCPA, but then I would get the whine on the high gain pot.

DAMN...

Spent all night boxing it up and it still squeals/whines the same. I used sheilded wire on all pcb and jack inputs and outputs. Not sure about voltages but the LF347 has alot of 0's ? Got the same reading with 2 different chips?

TC1044SCPA:

1. 9.24
2. 5.58
3. 0
4. 3.45
5. 8.8
6. 4.62
7. 4.33
8. 9.24

LF347:

1. 0
2. 0
3. 0
4. 9.24
5. 0
6. 0
7. 0
8. 0
9. 0
10. 0
11. 8.8
12. 0
13. 0
14. 0

You didn't show it, but your voltages on TC1044SCPA pins 4-5 and LF347 pin 11 should be negative.  I'm assuming you just missed it because you weren't expecting it, but please go back and check.  If those pins are really negative then, all of your voltages look correct.  The 0's on LF347 are just because the Boneyard uses the +9V and -9V power rails and doesn't have to use a ~4.5V reference voltage (typically labeled VB in other circuits).

I'd still like to see the board, though.

Hey dude!

Here's the thread that Josh was mentioning: http://www.madbeanpedals.com/forum/index.php?topic=2290.0

This is what worked for me:

"In my case, I used a 150pF across pins 1 and 8 (I just stuffed it into the socket) and it took care of if. Now, I'm not sure if we have the same problem in common though. The frequency whine I had was very subtle and it wasn't very loud."

I know there has been more people with the same issue but as far as I'm concerned, everyone has solved it one way or another...Just try searching for "boneyard" "squeal" "whine" "plexi" keywords like that and you'll find a few threads discussing the matter...

Hope I could be of better help. Let me know if I can help with anything :)

Good luck!

-Kaleb

Yes the pin readings are negative that you pointed out. I tried a 100pf cap across pins 1 and 8 on the charge pump with no change at all.

Also, I have read all the posts I could find on the boneyard whine issue. Here is a pic of the populated board. Maybe i missed something but I think all is good?

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.

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.

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.

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.

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?

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.

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.

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.

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.

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!

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 :)

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

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?

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

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.