Recently Completed Stereomour - Hiss in Right Channel

[Doc B]

There is a pattern. The guys with high sensitivity speakers are hearing the hiss. Owners of lower sensitivity speakers don't seem to be noticing it. Noise issues are not all or none, it's more a matter of degree. So what we can say is that we will do what we can to find a chip with a consistently lower noise level. But if you have really sensitive speakers and you hear noise that bothers you, you may have to use the alternative approach we have offered here anyway. That is the one of trade offs - along with reduced bandwidth - that you have to deal with when you go to very sensitive speakers.

 

[Dr. Toobz]

I can confirm that the resistors don't sound noticeably worse or different than the 431's with my speakers, so the upside is that the alternative arrangement, when needed, still results in a wonderful-sounding amp.

 

[Montigne]

Dearest Bottlehead,

Success. Hiss=gone. There is slightly more ground buzz than before with the 431s, but it's only when I have my ear right next to the driver and is completely unnoticeable when listening. Thanks for all the help so far Paul.

-Chris

 

[Grainger49]

    .  .  .    only when I have my ear right next to the driver    .  .  .  .   

You would probably find this in multi-thousand dollar commercial products, tubed and solid state.

 

[ffivaz]

Hi,

I finally managed to get a new pair of 431s. Mine where noisy and read WS 431 on them. I replaced them with some FKA48 LM431 ACZ I found on the bay.

They are quiet as hell. My hiss is gone.

Thanks guys for finding the problem.

 

[borism]

A naive question out of curiosity. Do you have to take off the small board to change the 431s (if a consistently less noisy type becomes available) or can it be done with the board in place (and how)?

 

[ffivaz]

I had not too short pins, so I just cut the regulator out. Then with desoldering pump, I carefully removed the solder out of the holes, applying some heat. I finally was able to put the new regulator in and resolder it in place from the top, without removing the board. I was careful that the pins in the holes do not fall towards the socket and make some bad shorts.

BTW, I can send you some 431s. I received a handful. Just PM your address.

 

[Paul Birkeland]

I thought I'd let everybody know that we quarantined the WS-431's that we had in our inventory, and have switched over to a quieter part.

-PB

 

[Grainger49]

I thought I'd let everybody know that we quarantined the WS-431's that we had in our inventory, and have switched over to a quieter part.

-PB

Just what I would expect from Bottlehead. 

Awesome!  ! 

 

[bjorgens]

PB, PJ,
Can you share the vendor/ PN for the quieter part you mention above?

Am wondering if its worth experimenting with different 431s on my paramounts (in hopes that I might remove the 10000uF caps I have across -reg and Kreg.

bryan

 

[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.

 

[jrebman]

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.