jamesgorman2
New member
- Joined
- Oct 20, 2020
- Messages
- 1
tl;dr
most aftermarket op-amps won't work in an API 2500. They are likely to go into oscillation because modern API 2520 is lower gain than vintage-style op-amps and the feedback circuit is designed around this.
I have now replaced them with the JLM Vintage Twenty5Twenty Green and the unit is working
Known working op-amps:
API 2520
JLM Vintage Twenty5Twenty Green
--
The story:
Recently picked up a second hand mid 2010's 2500 and one of the op-amps died when I was doing a line test on it (as they do!). I'd seen a few people talking about replacing the op-amps with aftermarket ones so gave that a go with a spare gar2520 since I was hoping to not have to faff about ordering from API. As soon as I powered it up the needle pinned itself, a frequency analyser showed a ~50kHz spike and started to get hot fast. In case it was the particular op-amp I bought a pair of JLM25HV to test, but with the same result.
Since the only thing I could find on the internet about this problem was an old, unanswered post on the gar2520 thread here, I pinged Joe at JLM. He wasn't surprised and confirmed it was the op-amps going into oscillation (and explained about the difference between a modern API 2520 and vintage). He had a few clients who'd successfully run his V8, but had a new SMD based amp that was more likely to run well (and not die quickly!). He sent down both the new models (black and green). Black suffered the same fate, but the green ran straight up without any calibration.
Sound sample (original track and compressor in only, don't have the API amps to do an A/B), and some pictures of the op-amps fitted and the frequency spectrum to a test tone are here on google drive.
--
If anyone has any other op-amps known to work in most API 2500's I can add them above
most aftermarket op-amps won't work in an API 2500. They are likely to go into oscillation because modern API 2520 is lower gain than vintage-style op-amps and the feedback circuit is designed around this.
I have now replaced them with the JLM Vintage Twenty5Twenty Green and the unit is working
Known working op-amps:
API 2520
JLM Vintage Twenty5Twenty Green
--
The story:
Recently picked up a second hand mid 2010's 2500 and one of the op-amps died when I was doing a line test on it (as they do!). I'd seen a few people talking about replacing the op-amps with aftermarket ones so gave that a go with a spare gar2520 since I was hoping to not have to faff about ordering from API. As soon as I powered it up the needle pinned itself, a frequency analyser showed a ~50kHz spike and started to get hot fast. In case it was the particular op-amp I bought a pair of JLM25HV to test, but with the same result.
Since the only thing I could find on the internet about this problem was an old, unanswered post on the gar2520 thread here, I pinged Joe at JLM. He wasn't surprised and confirmed it was the op-amps going into oscillation (and explained about the difference between a modern API 2520 and vintage). He had a few clients who'd successfully run his V8, but had a new SMD based amp that was more likely to run well (and not die quickly!). He sent down both the new models (black and green). Black suffered the same fate, but the green ran straight up without any calibration.
Sound sample (original track and compressor in only, don't have the API amps to do an A/B), and some pictures of the op-amps fitted and the frequency spectrum to a test tone are here on google drive.
--
If anyone has any other op-amps known to work in most API 2500's I can add them above
