Tweakers' Asylum

Schematic above (no text this post)

98.221.125.138

In Reply to: RE: Oscillation issue DQ LP1's "upgraded" op amps posted by jk on June 17, 2016 at 20:17:01

I didn't think of modifying the subject line when I posted the schematic. This post is just to let you know the schematic has been posted. John

Follow Ups:

How do you even know it's oscillating? - Cougar 20:48:49 06/17/16 (2)
Did you use a scope to see the oscillation or or ringing or does it feel really hot to the touch? Also brightness in the sound could be another sign of oscillation.
The reason I ask is that your question asking does an opamp get hot when oscillating.
So from I understand from your reply these exact opamp have been used in this exact circuit (crossover) without any problems? the only thing I see that I would change or try is changing the 47 ohm resistors. I would change them to 100 ohm to see if it stops the oscillation (that's if it's really oscillating). This would be quick, simple, and cheap to do.
Also, I have seen sockets cause opamps to oscillate due to the extra capacitance on the socket. Once the socket was removed, the opamp stopped oscillating. This was in a high speed circuit and "shouldn't" cause this in this circuit but you know how electronics go! anything can happen. Wouldn't hurt to try removing and see if that is the cause if all else fails.
Hope this helps!

Edits: 06/17/16
- RE: How do you even know it's oscillating? - jk 23:03:24 06/17/16 (1)
  I get a condition like feedback but the volume does not increase. Just goes distorted with a pulsating beat or literally oscillation.
  
  Since it does not literally feedback and get louder no fuses blow no speakers are damaged.the best way to describe it is an oscillating pulsating distortion.
  
  You asked a good question. I hope I'm interpreting this correctly. Since it is intermittent I do not have a scope handy. I wondered if a faulty opamps might get hot in hope of nailing down the culprit.
  - Make sure you got the ICs in the right way. - Michael Samra 19:38:09 06/18/16 (0)
    It is not hard to turn one around thinking you have it in right and I have seen this thru the years on many circuits that use OP amps..The LP1 is a fine crossover and I still have mine but it is very simple in nature and even if you get them in backwards,you will not blow the unit..It isn't unusual for different manufacturers to orient their ICs in a different way to make you think you are putting them in correctly..Look at them very carefully.If that doesn't do it,you may have to compensate for the new ICs with a cap change or two.
    
    "For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
    
    Edits: 06/18/16

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