Crowther hotcake squeal

[Dave]

So I'm after a bit of advice from the real experts over why this thing is squealing when the gain or presence is high. Looking at this circuit, am I right in saying that as gain is turned up, more resistance is placed between pin 2 of the IC and ground? If so, when the gain is high could it be that too much resistance is placed in between the ic pin and ground, this lowering the 220r resistor might help?
If I'm talking utter nonsense then tell me to shutup lol, its just that others seem to be having this problem too and its a shame because the pedal sounds so damn good!
Thanks for any help folks,
Dave

[Vince]

I offer no solution  I'm afraid. Just to say that I made two with the exact same squealing results. Both binned. Annoying as they sounded ok.

[Dave]

Hi Vince, did you build them verbatim to the layout? and what chip did you use? I got squealing with a Tl071, i wonder if it is chip specific?
Thanks
Dave

[Vince]

Hi Dave.

Yes, my builds were exact to the layout. I should of kept hold of them and tried different chips. I had squealing on the Purple Plexi too. That turned out to be a 'dodgy' chip so it may be worth trying a few different ones.

[otalgiafx]

Maybe try a LM741 in there dave to rule out the IC?  I'm guessing that its such a high impedence pedal that instability is expected (like silicon Fuzz Faces).

[Madferret]

Hi Dave, I built one of these a couple of weeks ago and I didn't have any problems with squealing. I know that may not help with your problem but the stock circuit is definitely good. I had the same problem as Vincent with a purple plexi and solved it by putting a small (100r I think) resistor in series with the gain pot, it turned out that due to the tolerances of the pots some just went too high and caused a whine. Check out the Lovepedal Purple Plexi layout comments for the correct resistor value. Hope this helps.

[Freppo]

Just wanted to chime in and let you know I have the same problem aswell... It squeals.
Will have a look at out the Lovepedal Purple Plexi layout comments. Thanks

[Dave]

Hi Chaps
Thanks for all the comments, some good suggestions. I havent checked out Madferrets suggestion yet but will do soon. I have found one fix, whilst doing some research I see that some versions of the pedal are buffered, so I tried putting a buffer before it and hey presto no squeal! The buffer i used was the one on the Vorg Warp sound which isnt very good and steals some of the high frequencies. Unfortunately I just sold my Klon buffer so cant test the theory with a high quality buffer but it may work without changing the sound too much.
Anyway, maybe thats something to try, let me know if you try it.
Thanks
Dave

[Freppo]

I tried with a buffer (Emma Reezafratzitz) in front, squeal gone!

[Dave]

Thats great, did you notice any change in tone? Aside from losing the screech...I think a really transparent buffer like the Klon would be ideal here.
Thanks
Dave

[jwroper]

I got the squeal too...will try squeezing a buffer in there with it, thanks for the tips all.

[alex.s]

I once modified Mark's layout to accommodate a TL072 as I thought I was out of 71s, might see if I can adapt it to implement a Klon buffer using the other side of the dual op amp... Looooong graveyard shift with work today, so I won't be short of time. Skills and patience, though, that's a whole different thing...! :)

[alex.s]

Just had a thought as I opened the Hotcake project and it suddenly dawned on me the whole thing runs on 8v2...!

How would that impair the functionality of the Klon buffer?

[alex.s]

Avoided going the dual op amp route and entertained myself by drawing a layout based on Mark's that includes a TS-style buffer. Might try to give this a go to see how it compares with the original.

Here's the layout should it be useful to anyone: