Nasty sounding diode cut-off

[notneb]

Grr I know I can't be the only person to have this happen, so I know one of you gurus can help me out. It all started here: http://www.diystompboxes.com/smfforum/index.php?topic=108893.0
   This is what it's morphed into:
http://www.dropbox.com/s/qld5t6d9skdmpw4/classicoverdriveSchem.jpg?dl=0
http://www.dropbox.com/s/4wk9s85kcj1t35l/classicoverdriveBrd.jpg?dl=0 (tried to upload to forum from hard drive, kept getting error 7, go figure)
(yes, I realize I chopped the edge off my ground poly at the edges and disconnected the ground at three points... it's been fixed, more about that in another post)
   I originally experimented with this diode array because of the jagged decay I was getting with the LEDS. Now it's back. I built this and rebuilt it on my breadboard several times and it was gone. Now it's back. I'll try to post a sound file to further illustrate but it sounds to me like the diodes turning off as the signal fades out but it happens too early and it's VERY noticeable. Very abrupt and jagged sounding. It really sounded sweet on the breadboard and I was excited to get it in a box, but the way it sounds now I'm ready to chuck it and start over. I traced and re-traced the schematic and the layout diagram against the board so many times my head is spinning and I'm confident  it's all consistent. I'm kinda at a loss right now. Please help!

[midwayfair]

Serious answer -- you might have stopped noticing due to ear fatigue.  This usually happens in a really high register. In any case, more filtering is probably the only way to get rid of it.

[samhay]

Breadboards have quite high parasitic / stray capacitance, which may have been working in your favour by filtering some of the high frequency content you can now hear. You could try temporarily tacking a smallish (10s-100s pf) capacitor across (parallel to) the diodes to see if that helps.

[notneb]

I tried adding the cap and it had no effect on the noise.
Here's how it sounds. https://www.dropbox.com/s/s89bboqa6v5mee5/Bensoverdrive.mp3?dl=0
I had to record on phone so, um, not studio quality... but you'll get the point. It almost sounds like string buzz, but it's not.
And btw, I can't upload any files, pix or sound. I followed the links in "read this before you post" and I keep getting upload errors. Don't know what's up.

[Digital Larry]

One thing I noticed is that your op-amp drives the clipping diodes directly (ok, through a coupling cap) but there is no series resistance between the op-amp output and that clipping circuit.  It might be causing issues with excessive output current.  I think you could drop in a 470 ohm or 1k resistor in series and see if that helps.  It will also soften the edges of the clipping diode transfer curve somewhat (which you may not want, but pick your poison).  Now, "why" it worked OK on the breadboard but not on the PCB is not answered by my suggestion.

[notneb]

I don't remember why exactly I thought it was a good idea to omit that resister... 'cept that it made it louder..  but yeah, a 1k resister later, the buzzing is pretty much gone  It did tame the highs maybe a tad too much, though. Thanx for the input! I'll sleep better tonight!