Lm1894n

[Kipper4]

I have no idea why I bought two of these.
Apparently a dynamic noise reduction chip.
Can anyone remember because I can't for the life of me.
Is there any use for them in stomps?


Another day another componant'!!!!!!!!

[Mark Hammer]

Those are single-ended noise reduction chips that do what the Burwen noise filter did.  Think of it as a sort of auto-wah in the service of eliminating hiss.

[Kipper4]

Intriguing Mark.
Auto wah you say

[PRR]

I didn't know you could actually buy these. At least when new you had to buy-into the DNR logo.

> do what the Burwen noise filter did

Yes; and the HH Scott filter before Richard, and several others.

IMHO what NS's "DNR" was *really* supposed to be was an alternative to using Dolby decoding on Dolby and non-Dolby sources. I've used Dolby single-ended to cut hiss on bad sources. And while no-Dolby playback of Dolbyized tapes in the car is interesting, almost "any" dynamic filter would be more natural.

http://www.ti.com/product/lm1894

For a guitar-hiss reduction scheme, you probably need a buffer in front. You sure want the sensitivity pot. You do not want the 19KHz filter. The suggested attack/release values are probably suitable for clean de-hissing. Use 0.0047uFd (5nFd) or even 10nFd caps in place of their 0.0033uFd caps for a more brutal low-pass in quiet sections.

[PRR]

For even more brutal low-pass, see section 5.7 here:
http://www.ti.com/lit/an/snoa673c/snoa673c.pdf

LM1894n internal details:
http://www.ti.com/lit/an/snoa670c/snoa670c.pdf

[Kipper4]

Thanks Paul
These might just come in handy one day.