Spring reverb circuit oscillation

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smilan

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May 29, 2017
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Hi, I made a spring reverb circuit using this schematic:
rvb-f9.gif

I'm driving the reverb tank using this circuit:
rvb-f5a.gif

Everything sounds pretty good except when I'm hitting the reverb circuit too hard the recovery circuit starts to oscillate a high frequency that doesn't fade away until I'm disconnecting the power from the reverb circuit.
Any suggestions on how I can eliminate this problem?
Here's how it sounds:
https://youtu.be/O4Q4RRoKRwk

 

Audio1Man

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Nov 19, 2012
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Thousand Oaks CA, USA
I see a few things. No PS bypass. Why did you use U1B as the recovery amp while U1A is the drive amp?  The drive amp should be U1A & U1B. Layout cross coupling? You may need to add a small resistor to pin 5 of U1B to de que the circuit (stop ringing).
Duke
 

Bo Deadly

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Audio1Man said:
I see a few things. No PS bypass. Why did you use U1B as the recovery amp while U1A is the drive amp?  The drive amp should be U1A & U1B. Layout cross coupling? You may need to add a small resistor to pin 5 of U1B to de que the circuit (stop ringing).
Duke
The schem does say U1A & U1B for the drive amp. But if that's not the reality, yes, it should definitely be the same amp. And I agree a 1K in series with the input could fix it.
 

zamproject

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May 11, 2010
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hello

Audio1Man said:
I see a few things. No PS bypass. Why did you use U1B as the recovery amp while U1A is the drive amp?  The drive amp should be U1A & U1B. Layout cross coupling? You may need to add a small resistor to pin 5 of U1B to de que the circuit (stop ringing).
Duke

We can maybe suppose this is different schemo with IC for both amp labelled U1 ?

Now...what about the the wiring of the unused side of the recovery amp dual opamp ?
With all pin floating at unused opamp side you may have strange behaviour...which can interfere with used opamp side.

Best
Zam
 

smilan

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May 29, 2017
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331
Thank you all for your advice, I've grounded the unused side of the 5532 at the recovery amp, added 4*100nF bypass caps (which didn't solved the oscillation) and added a 1K resistor in series with the input of the recovery amp and now it sounds much better with no oscillation.
*U1B at the recovery amp is a different IC than  U1B at the drive amp.
 

Bo Deadly

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Note that if you're doing something on a breadboard, you can easily get weird results because of bad grounding, long wires and crappy jumper contacts. If you did the same thing on a proper PCB, the 1K might not be necessary.
 

Whoops

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Audio1Man said:
I see a few things. No PS bypass. Why did you use U1B as the recovery amp while U1A is the drive amp?  The drive amp should be U1A & U1B. Layout cross coupling? You may need to add a small resistor to pin 5 of U1B to de que the circuit (stop ringing).
Duke

maybe this helps...
This circuit is from Rod Elliot (ESP), he gives a nice explanation of the circuit over his website:

https://sound-au.com/articles/reverb.htm
 
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