Paragon squeal is driving me mad!!

[KevTom23]

Hi all.
I've built the full size Paragon. I was lucky enough to be able to source genuine Panasonic MA856 and Toshiba 1s1588 diodes from European / UK suppliers, and I am absolutely blown away by how the pedal sounds. up to a point.
There's a squeal at the pedal's extreme settings that I can't get rid of, so looking for guidance.
The business diodes are socket mounted, as are resistors R3 (1k) and R17 (100k).
So far, I’ve swapped out the charge pump and both opamps for compatible versions, and shortened the diodes’ legs so that they sit flush berween the socket posts (I initially left them longer than they needed to be).
The squeal persists.
it’s only there when both sides are on and the pots are near maximum all round.
Boards are connected with trimmed header pins and none of the cables to the jacks or 9v are axcessively long. Jack sockets are open Neutrik jobbies.
Pots and 3PDTs are Alpha.
Any ideas on where to go next?

 

[KevTom23]

Should say that this is maybe my 20th build, bur my first KOT style. Not had this issue with anything else.

 

[Boba7]

With every pot maxed, the squeal is normal. I’ve had it with all my KOT builds.
Question is: will you ever use this setting?

 

[KevTom23]

Thank you
No, unlikely to ever use it with those settings, but had to ask

 

[Boba7]

The Bluesbreaker circuit isn't high gain, but I mean, two in series is quite a bit of gain, I think the squeal is to be expected.
Now did you try a buffered pedal (any Boss pedal) in front of it? Might cure the squeal

 

[KevTom23]

Not yet. Only used it to test either in isolation or in front of a Duocast to boost that (thise two are amazing stacked). I have a strobostomp tuner on by board which is buffered. I’ll try that.
Thank you

 

[KevTom23]

Resurrecting this one, sorry
A buffer in front if the paragon build works perfectly . But...
I’m trying all options to get rid of the squeal completely. It isn’t a budget build and it’s a tried and tested circuit. Great care was taken during the build process. Joints and components are all good and the cabling is as short as it can realistically be.
it’s not good enough as it is.
I changed my google search from “pedalpcb paragon squeal” to “kot squeal”, and found a post that recommended changing C4 and C15 from 10n to around 15n. Before I sucker that solder, do any experts here have a view on this?

 

[BurntFingers]

You could increase the value of the caps in the feedback loop parallel to the feedback resistor.

 

[zgrav]

as noted, the squeal when everything is dimed seems to be common in other KOT builds. it could be that the fix would be less desirable than the problem if it meant you changed something to limit the effective gain you were getting from one or more pots on the pedal. but it is easy to understand why anyone would want to be able to play a pedal with everything maxed out.

similarly, some pedals completely kill the sound when all the drive/gain/saturation settings are turned all the way down and that feels wrong if you think a pedal should always have some sound going through when everything is turned down.

 

[BurntFingers]

Putting something like a 150pf cap over r21 and r7 would help a great deal. You could solder this cap to the legs of the 220k already in place there.

 

[KevTom23]

Thanks all for taking the time to reply.
simplest potential fix seems to be the one suggested by BurntFingers. I’ll try that before changing anything else.

 

[KevTom23]

No joy with that method. Squeal is still there. I’ll try changing c4 and c15 and see if that works.

 

[KevTom23]

Oh, adjusting the trim pots changes the pitch of the squeal, if that provides any clues.

 

[KevTom23]

Can anyone from pedalpcb offer any solutions/workarounds?

 

[Armando21]

I used JRC4580DD dual op-amp chips. I can't find the where it says in the data sheet that the DD has some higher level of performance, but I remember reading it at some point. I can't be sure this is the issue but it may help. I read on reddit that people have tried the MAX1044 IC to replace the TC1044SCPA and it solved the squealing issue.

 

[KevTom23]

I put the dd’s in it and tried an alternative.
also tried an LT1054 in place of the tc1044scpa. No change. Squeal is still there.
I’ve yet to try changing c4 and c15 from 10n to 15n, tho. I bought a couple of boards so I might try socket mounting those next time.

 

[clarisso11]

Hi, have you had any success with that? I’ve been experiencing the same issue, keep asking myself if the original KoT has the same problem?

 

[KevTom23]

Hi. Yes and no….
I researched it to death and learned that a lot of clone KoT circuits do it. Some suppliers will even tell you that the squeal is normal when it’s maxed (FuzzDog in the UK, for example).
The only thing that worked for me was to either have a buffered pedal in front of the paragon, or build one between the paragon’s input jack and the board.
I have a Petersen Strobostomp tuner first in my chain, which has a selectable buffered bypass mode, so in the chain, the squeal is no longer an issue.

 

[clarisso11]

Very strange.. I always thought those diy clones are essentially the same circuit, just with the extra charge pump. I’ve actually built a FuzzDog Emperor without charge pump, so it should be the exact KoT circuit, but it squeals at high gain (buffer before in chain doesn’t help).
Either the original has the same issue and people just don’t write about it, or Analogman has figured out the secret!

 

[clarisso11]

Maybe someone who owns the original KoT could chip in? With yellow side boost and red overdrive, both sides on and all controls dimed, does it squeal?