Author Topic: Input signal clipping, need to clean it up...  (Read 472 times)

Rob Strand

Re: Input signal clipping, need to clean it up...
« Reply #20 on: April 03, 2021, 02:35:05 AM »
Quote
If you short Drain and Source on Q3, does the clipping go away? If not, it's not Q3.
Without trying that Q3 short test you are pretty much wasting your time.   If the JFET in the circuit really is a J113 (it might not be) it should work find without clipping.

I'm of course assuming the clipping problem is in Effects mode and not Bypassed mode.
The internet:  answers without the need for understanding.

iainpunk

Re: Input signal clipping, need to clean it up...
« Reply #21 on: April 03, 2021, 11:28:25 AM »
i recommend you grab an audio probe and check where the distortion starts, i honestly doubt its that first transistor.
cheers
i just want to re-state this:
i honestly doubt its that first transistor.
maybe check with an audio probe where in the circuit the distortion ACTUALLY starts

cheers, Iain
« Last Edit: April 03, 2021, 11:29:59 AM by iainpunk »
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antonis

Re: Input signal clipping, need to clean it up...
« Reply #22 on: April 03, 2021, 02:58:10 PM »
i honestly doubt its that first transistor.

Could you plz keep your opinion to yourself, Iain..??

P.S.
Late night with aged tsipouro here.. :icon_wink:
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

Vesperado

Re: Input signal clipping, need to clean it up...
« Reply #23 on: April 03, 2021, 03:06:34 PM »
Appreciate the feedback, gents.

Next time I get into the FX68 I will bypass Q3 and raise the Vbias to see what happens. The audio probe is a good suggestion. I agree, I do not think Q5 is culprit here, although I suspected it at the beginning.

The pedal is useable now, yet at any rate it wouldn't hurt to get a non-clipping signal at headroom...and preferable, no doubt.

Vesperado

Re: Input signal clipping, need to clean it up...
« Reply #24 on: April 03, 2021, 03:30:53 PM »
And while I'm in there I might replace the stock TL062, or cut the trace and lower the Vbias with a trimmer there. It is the only other place I can think of...

Vesperado

Re: Input signal clipping, need to clean it up...
« Reply #25 on: April 04, 2021, 11:29:41 PM »
Replaced the TL062 on the FX68, which removed the clipping. I have Vbias now set to 7.6V and Q5 at 7V. Good headroom, nice chime :)

Before disturbing the transistor on the 460 I will replace the ICs first. Probably all it needs...