RNC 1773 compressor - modifications - pics

Hi,

I did some simple mods on my RNC compressor

I changed the opamp to a burr brown opa2604
and the two that2155 to 2180LB for better distortion and dynamic range

I still have to do some listening tests with an untouched unit, if it really sounds better now...

I hoped this would eliminate the annoying the noisefloor of the rnc
... but ... no luck ...

I think this is really strange, because the ssl comp is also based on that21xx and standard opamps, but is is really quiet...

any ideas what to do ?? maybe chage some electrolytic caps to better qual. types ??


some pics:






cheers,
matthias

Looks like the unit is using 78LXX/79LXX Vregs. That could be bettered, allthough I don't think you'll get improved SN. Doesn't it originally use OP275s? That's one of the best sounding opamps to my ears and more often not switching to a BB or whatever made it sound worse. YMMV & all that jazz..

What is the U8 opamp?

U8 is a multiplexer or analog switch ic .. maxim max318

So there's only a dual opamp + two VCAs in the signalpath?

yes... !! and maybe some elcos ??

[quote author="matthias"]yes... !! and maybe some elcos ??[/quote]

Hey, I take offence to that! :wink:

Cheer,

elco
:shock:

I agree with Jaakko - the noise must originate from inadequate CV signal. If this unit is done with a low-grade D/A conveter - which it has to be at this price - there's a real chance that much of your noise comes from this.

But also the source impedance for the circuit that drives the control port in the VCA's has to be very low to work well. In "the clone" the 5534-circuit were added for this.

So maybe try buffering the control voltage to the VCA - possibly adding a low-cut filter (maybe around 1KHz) when you're at it.

Jakob E.