lowering the noise of an RNC

[canadiansteve]

Hi, I bought a pair of FMR RNC's because I needed some extra comps for "secondary" tracks... basically tracks that I do not want to put through the subgroups that my real good comps are strapped to... The thing is they are so noisy that I can barely stand them, but I do like the sound they get. Does anyone know of any PSU mods or anything like that for these units to lower their noise floor? Thanks, Steve

[peeder]

Are you sure the units are noisy? Compressors do raise the noise floor of an input signal. The RNC runs unbalanced and so the cables going in can pick up noise. Moreover, unbalanced outputs of preamps etc. I find to be very very noisy in comparison to their balanced equivalents in many cases. The RNC isn't very noisy on its own.

One thing I've done with an RNC is buy an Ebtech hum eliminator (~$60). It will unbalance the preamp outputs and lift the ground correctly without much loss of tone.

[canadiansteve]

Well, I just got off the phone with someone at FMR in Texas (I think), and they admitted that the RNC's weak point is that it has a high noise floor. I am using the comp out of a mix insert on my console, and I do not have any noise issues with any other pieces of gear. I will try a few more solutions and keep posting the results... but I was surprised to hear someone form FMR say "The RNC's are just sort of noisy"....

[Harvey Gerst]

That's weird; I think they quote something like -90dB, and the ones I've measured have been orders of magnitude lower than their spec. Now the RNP is noisy when you push it hard.

[zimv20]

if i add gain to the RNC output, it gets noisy pretty quickly. that aside, it's fine.

[Jim Williams]

You can try a different opamp. There's a AD OP275 at 8 nv/hz/sq dual in there, pop in a machined socket and try some quieter stuff. The new AD 8599 dual is a good place to start, 1 nv/hz/sq but is surface mount and requires a header, the National LM4562 is 2.3 nv/hz/sq and comes in a 8 pin dip from digi key.

Jim Williams
Audio Upgrades

[canadiansteve]

Thanks Jim, I will check into that. Initial research that I did pointed towards the PSU, but I am open to suggestions. Cheers, Steve.

[Jim Williams]

I believe there's a small TO-92 7815/7915 regulators in there. I did add a couple of 220 uf 25v Panasonic FM caps and some .1 uf mono ceramics on the power rails.

Jim Williams
Audio Upgrades

[mwikkid]

Originally Posted by Harvey Gerst

I think they quote something like -90dB, and the ones I've measured have been orders of magnitude lower than their spec.

Wouldn't "order of magnitude lower" here mean -900 dB or more?

[Harvey Gerst]

Originally Posted by mwikkid

Wouldn't "order of magnitude lower" here mean -900 dB or more?

1/10th the noise would be 10 dB quieter;1/100th the noise would be 20 dB quieter. The dB scale is logarithmic.

[Sounds Great]

Originally Posted by Harvey Gerst

10 times less noise would be 10 dB quieter;100 times less noise would be 20 dB quieter. The dB scale is logarithmic.

That sounds about right.


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I'm not such a big fan of the RNC, but noisyness is not something I would accuse them of. Sounds like something in your system might not be set up quite right.