Recently Completed Stereomour - Hiss in Right Channel

[Paul Birkeland]

Hello Bryan,

I'd look for Fairchild or ON Semiconductor TL-431 ACZ. 

-PB

[bjorgens]

thanks Paul !

is there any pre-install measurement I can make to determine if one part is potentially quieter than another, or is it simply a listening test only?
bryan

[Paul Birkeland]

Nah, smoke it and see!

[bjorgens]

[Paul Joppa]

To be clear - the TL431 and LM431 are supposedly the same and meet the same specifications. We seem to have acquired a batch that don't meet specifications (i.e. they are very noisy).

I think this may have happened in the past as well; I recall a time period where we suddenly had a number of noise problems with Foreplay upgrades. At the time we were not aware that the parts may be out of spec, but we found a modification which helped. Now I am wondering if we got another bad batch. (The mod is not applicable to the Paramour or Paramount.)

[borism]

A brief update. After stating in a post before that my WS 431s were quiet and reading Docs note that hiss comes in degrees I went back and realized that there was a soft noise from my speakers audible from within 2 feet.
 
Then Fabien reported that he had replaced his noisy WS 431s with some FKA48 LM431 ACZ (I believe Fairchild) to good effect and he graciously offered to send me some extras.

So, I accepted his offer and replaced the WS ones in my amp. The result was eye opening. The soft noise that I originally attributed to tube rush is completely gone. The speakers are dead quiet now.

Thank you Fabien.

[ffivaz]

I'm glad I could help.
Fabien

[johnsonad]

I wanted to add a little something to this.  I too received these WS marked 431's in my soft start kits.  I replaced them this morning with two different brands of LM431ACZ regulators.  Both are equally quiet with a slight difference in noise that they make but both are significantly quieter than the WS marked regulators.  Before I could here the noise in my listening chair and through the quiet passages of music.  Now I hear nothing at the listening position.  Thank you for the heads up on this.  I'm no longer chasing noise through my amps.

[Jim R.]

I just got a couple dozen fairchild lm431 aczs and will replace any of the ws ones I find in my amps. Thanks all for doing the detective work.

-- Jim

[DesignTaylor]

Also wanted to add a note here since I found this thread helpful in my search. I had a lot of background hiss (especially noticeable when I added some bullet tweeters) and after reading this I checked and sure enough, I had the WS marking on my 431s. The BH folks kindly sent me some replacements and I swapped them out (not super easy on an assembled unit for someone with my soldering capabilities).

The replacements cut the noise in half if not more. There is still some low hiss present but you need to be less than a foot or two from the driver to really head it.