Slight hiss appeared

Posted by: Stephen packer on 18 February 2018

I've noticed a (very) slight hiss appear from my speakers.   It's only really noticeable when I'm within (about) 1m of the speakers and is from the tweeter.  Changing the volume of the preamp makes no difference to the hiss, neither does the mute button.  Note that once music is playing I'm not aware of the hiss (excepting in completely silent passages.)

My system has a 282 (2xHiCap DR) feeding into a Snaxo 242 (Supercap) and then a pair of 200s into SBLs. 

If I switch the Supercap off the hiss stops, if I switch the HiCaps off it doesn't and given the mute button/volume lack of influence mentioned above, I think I can forget the preamp as the source of the hiss (note I have not switched the NAPSC off in this 'test')?

The Snaxo242 is about 4 months old, the Supercap is (about) 11 years old and is (over)due a service- I had planned to have this done when I'm on holiday in the summer (and when the hifi would be unused).

Could a Supercap being overdue a service cause this sort of noise?  Am I risking it developing a bigger fault if I don't get the PSU serviced pronto?

Posted on: 18 February 2018 by badlands

Sounds completely normal to me, all Naim amps I have owned or have heard exhibit what you describe.

Posted on: 18 February 2018 by Stephen packer

Hmm.  I *think* it's only recently developed.  It could be that I've only recently noticed it and now I can't help but keep listening for it!

Posted on: 18 February 2018 by Timo

A slight hiss coming from my PMC tweeter as well...

Posted on: 18 February 2018 by Huge

It's normal.

There's always a small level of noise at the input of any power-amp, which then gets amplified by the gain of the amp; an active crossover increases this.  Turning off the SuperCap removes the noise contribution from the active crossover circuit.  The higher the sensitivity of the speakers, the more noticeable it is.

Posted on: 18 February 2018 by joerand
Stephen packer posted:

I've noticed a (very) slight hiss appear from my speakers.   It's only really noticeable when I'm within (about) 1m of the speakers .....  I've only recently noticed it and now I can't help but keep listening for it!

I think the responses above are all reasonable and unless your normal listening position is "within (about) 1m of the speakers" your time would be better spent enjoying the music rather than attempting to detect inherent speaker hiss from a more distant seat. Like deep space, inky blackness can be a function of distance.

Posted on: 18 February 2018 by Richard Dane

Sounds normal to me.

As an aside, are you using SNAIC4s or active leads between the SNAXO and your NAP200s?  If SNAIC4s then I strongly recommend you switch to active leads (DIN4-DIN4 version of the DIN-XLR lead used with the bigger amps) as the SNAICs can push the SNAXO towards instability.

Posted on: 19 February 2018 by Stephen packer

Thanks for the feedback everyone.  It seems that it's the normal worrying about something I don't need to!  I guess I can drag out the service of the Supercap for another four months (during which I try to convince myself that I really need it DRd while it's serviced...)

The connections between the SNAXO and NAP200s are active leads so that's one less thing for me to worry about.  Thanks again.