SM PRO AUDIO OC8 noise

[joakimkarlthomas]

I bought a OC8 second hand a while ago. It's an 8 channel optical compressor by sm pro audio. It works all right, but it has a  noise and I would be really happy if I could fix this. I have it connected to the inserts on my console. Below is a link to how the noise sounds. First you will hear noise from the console and speakers and after a few seconds the extra noise when I turn this compressor on. I've tried all my other compressors (drawmer and dbx) and none of them have the same problem.

I was thinking of changing the power transformer. Could this help?

https://soundcloud.com/joakim-johansson-13/oc8-noise/s-MKLf0

 

[scott2000]

I'm always suspect of power supply caps when dealing with hum that hasn't been ground or interference related.

I don't know.  That hum before the unit is turned on is enough for me to want to investigate other areas in the room... That's all coming from the speakers???

 

[joakimkarlthomas]

The volume is much higher than I would have when working. The console is a Tascam m3500, known for beeing badly grounded and noisy. But I dont have this problem with any other of my outboard, like with the OC8. I recently bought a power conditioner to where all gear is connected. It helped a lot, lowered the overall noise with 15-20 db. Thinking of making a star ground mod on the console, but not right now.

 

[RuudNL]

A bit offtopic but: are you aware that the SM OC8 inverts the polarity of the audio signal? 
(Not a very nice design!)

 

[scott2000]

I'm not really giving too much thought into this as I know this could be a rabbit hole of what it could be ... I know cables and their connections can cause all kinds of problems. Not sure about the inserts and how you are wiring everything but, special care needs to be given to the type of input and output stages . It's never a good idea to assume that tying the ring to sleeve is necessary for example...

 

[RuudNL]

I find it strange that you experience a noise problem.
I used to have an OC8 myself and although it was a pretty crappy compressor, I never had a noise problem with it!

 

[joakimkarlthomas]

I changed the power transformer to a new one. It solved the problem. Thanks.

 

[scott2000]

That's great!

Good to know about the transformer!