Noise reduction for NE571

[The Dark force of dance]

Y-ellow Peter 'n' y'all.
	My original CN2R noise reduction systems, the only real success story I've
ever had with electronics to date, used the N571. I have a stack of them
left if anyone wants to trade for something I can use these days. But I
have to say that as anything else these things are pretty lousy. They're
noise city as a VCA and the control section is pretty limited.

The CN2R MKII used the much better NE572 which cost 3 times as much but are
worth it. The MKIIs were even DBX compatible but even by that time, circa
1992,  the noise reduction market was beginning to fall off. Everything was
getting cleaner.

We did make a few retros that could be used to reduce noise in other things
such as el-cheapo guitar FX peddles etc, but I haven't found a need for an
NR since. All the prototypes lay idle at the moment as my one and only
analogue recorder that I retained is "in the shop." and has been there for
the better part of 12 months. I really should find out what happened to that.

But the MK II CN2Rs were very good even if I do say so myself.

The NE571 is suitable for NR because it inherently suppresses it's own
noise. But only in a complimentary system. As a DNR they would be lousy. As
just about anything else they're pretty awful. I designed a stereo enhancer
using them and it was pretty good but still, as much as I tried, it was a
bit on the noisy side.

What you could do with them is place them either side of a noisy process.
Or a process where the dynamic range was limited. You can do wonders with a
BBD if you place it just right. Makes them sound much better than they are.
It does work but the 571s are a bit finnicky to work with. They do strange
impedance things because they are essentially a transconductance op-amp
with a rectifier placed in front of it. You cannot control the attack and
decay of the control because there is only one node upon which to place a
cap. Unlike the 572 which has two nodes and you can even make the
attack/decay times variable.

But for a quick fix to a dynamics or noise problem they're probably the go
if you have some on hand.

Hope this helps.

Be absolutely Icebox.

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