Spring reverb circuit oscillation

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smilan

Well-known member
Joined
May 29, 2017
Messages
463
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

 
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
 
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.
 
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
 
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.
 
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.
 
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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