Hang a scope on it.
Sometimes that fixes an instability, instead of displaying it.
Does the circuit have the appropriate decoupling for the new opamp?
Does the circuit avoid capacitively loading the new opamp beyond its stability limit?
Is the new opamp's input offset voltage and current going to cause output offsets larger than is desired?
These and other questions need asking and answering before any opamp substitution, they are not "rollable" in a naive sense.
Does the circuit avoid capacitively loading the new opamp beyond its stability limit?
Is the new opamp's input offset voltage and current going to cause output offsets larger than is desired?
These and other questions need asking and answering before any opamp substitution, they are not "rollable" in a naive sense.
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Hang the 'scope on the big amp's output, that won't have any effect on stability.Sometimes that fixes an instability, instead of displaying it.
Also if you use x10 setting on a scope probe it provides a much smaller load and it less likely to affect the circuit being probed (ie never use the x1 setting without a good reason).
I suspect you do not have an oscilloscope and have not checked to see whether the new op-amps are oscillating continuously or under some specific signal/time/temperature related condition and that is what is possibly destroying transistors in your power amplifiers. I would worry about your tweeters too.
The OP627 is an excellent op-amp and your pre-amp was designed and tested using this part, changing parts without understanding the consequences and testing for them is how you end up at this end of the street.
The OP627 is an excellent op-amp and your pre-amp was designed and tested using this part, changing parts without understanding the consequences and testing for them is how you end up at this end of the street.
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