[SoundGame]

I've been curious about signal-to-noise ratios (SNR) of Bryston amplifiers lately, since I'm facing a low-level hiss from the tweeters of my speakers (6ohm / 87 dB sensitivity) when connected to my 4B-SST2 amp alone - no preamp nor source connected.  I've been told by Bryston that this is normal; however, it's got me thinking whether a higher SNR could have possibly elimated all noise whatsoever - regardless of speaker sensitivity and distance from the speaker.
 
Bryston rates all their SST2 amps as having a minimum SNR of 113 db, when used at the lower 23db gain setting.  One other well established Canadian amplifier manufacturer (located in the Toronto, ON vicinity) who's also known for consevative rating of its components is Anthem of Paradigm fame.  Anthem rates it's MCA and Statement amps as having a 120db SNR and a friend of mine attests to his amps "absolute" quiet demeanor. 
 
My question is how is such a low SNR achieved and what might be the compromise in the design, if anything? 
What would it take to get the Bryston SST2 amps to achieve a 120db+ SNR across the model line?
Is this something that Bryston has considered for the next evolution in the amplifiers?
What are the compromises or the cost offsets of obtaining such a high SNR?
 
The reason I ask this is though this may be nit-picking.  The low-level hiss on my speakers that can be detected from 4 to 6 inches away is the only shortcoming I have perceived with this very high-quality amplifier.
 
 

[lanchile]

Did you take "all" the sources out to check if it is coming from sources? I asked this because I had the same problem and it was my sat-dish receiver that was causing this noise. if I take all the sources out and turn on my amp I do not hear nothing even at full power!

PS: and my amp S/N is 106db!

[Sasha]

What you hear depends on your tweeter sensitivity as well.

[SoundGame]

Did you take "all" the sources out to check if it is coming from sources? I asked this because I had the same problem and it was my sat-dish receiver that was causing this noise. if I take all the sources out and turn on my amp I do not hear nothing even at full power!

Yup - all the sources and the preamp disconnected.  So ONLY the speaker cables (Kimber 4PR) and the OEM Power Cord connected to the amp.  When I power on, as soon as I hear the soft-start click on and the lights go green, the low-level hiss is there - only heard when you line up your ear with the tweeter and listen from 4 o 6 inches away.  I spoke to Bryston directly and they said this is the inherent sound of the electrical current through the amp and considered normal.  I was going to drop it but it comes up when others with different equipment speak about how "absolute" quiet their amps are.
 
I've attached an impendence/frequency chart for my speaker.  It is rated only up to 20,000 Hz

[lanchile]

Yup - all the sources and the preamp disconnected.  So ONLY the speaker cables (Kimber 4PR) and the OEM Power Cord connected to the amp.  When I power on, as soon as I hear the soft-start click on and the lights go green, the low-level hiss is there - only heard when you line up your ear with the tweeter and listen from 4 o 6 inches away.  I spoke to Bryston directly and they said this is the inherent sound of the electrical current through the amp and considered normal.  I was going to drop it but it comes up when others with different equipment speak about how "absolute" quiet their amps are.

Well, it can be with "how" sensitivity are those tweeters. My speakers are 89db SPL.
also it can be noise in your power line, move amp to another outlet or get a ac filter like monster cable has.
Those epos els3 use 1" aluminum-dome and are very "sharp". can you try with another speakers?

[SoundGame]

 

Well, it can be with "how" sensitivity are those tweeters. My speakers are 89db SPL.
also it can be noise in your power line, move amp to another outlet or get a ac filter like monster cable has.

Sorry - here is a frequency response diagram for my speaker.  It appears there is an little bit of a upward blip in the uppermost frequencies - perhaps this is why I can hear it?  But looking at it closer - the blip is between 18,000 and 20,000 Hz, the threshold for hearing - so I would think if this was the culprit it would be harder for me to detect.
 

[Sasha]

The noise you hear is way below 20kHz, that blip (most likely tweeter resonance) is not the cause of white noise you hear.

[SHV]

"But looking at it closer - the blip is between 18,000 and 20,000 Hz, the threshold for hearing "
********
Humans begin to loose high frequency hearing, at varying rates,  after age 8 years.  IMO, it would be the very rare adult that could hear anything close to 18 kHz.  Perhaps a willing and cooperative canine would be a better subject for testing reproduction of high frequency by speakers. :>).

Steve

[SoundGame]

"But looking at it closer - the blip is between 18,000 and 20,000 Hz, the threshold for hearing "
********
Humans begin to loose high frequency hearing, at varying rates,  after age 8 years.  IMO, it would be the very rare adult that could hear anything close to 18 kHz.  Perhaps a willing and cooperative canine would be a better subject for testing reproduction of high frequency by speakers. :>).

Steve

Actually, quite of number of muscians and musically trained individuals hear into or near the 20kHz levels, possibly why they do so well at such a profession.
My understanding is that, apart from hearing loss due to damage, hearing does not begin to significantly diminish until you reach your mid-to-late teens.  Again, just being able to hear a 20Hz signal does not mean you will hear it loudly - there are sensitivities to the db as well as the frequency. 
 
So we've established that this is not a super-sonic / ultra-sonic hiss I'm detecting but rather an audible hiss.

[Mag]

My Sony player allows me to filter out 20 khz freq.. I can indeed hear freq. above 20 khz, IMO it has a subtle halographic effect on music in my room, which is why I have it engaged.

Other audiophiles might perceive these freq. as sounding harsh, digital artifacts or with metal tweeters. Prefering instead to filter out or choose speakers that roll off high freq..

[SoundGame]

My Sony player allows me to filter out 20 khz freq.. I can indeed hear freq. above 20 khz, IMO it has a subtle halographic effect on music in my room, which is why I have it engaged.

Other audiophiles might perceive these freq. as sounding harsh, digital artifacts or with metal tweeters. Prefering instead to filter out or choose speakers that roll off high freq..

Mag - you may be hearing the secondary harmonics / reflections of the 20kHz frequencies.  In other words, you may not be able to hear to 20kHz (sorry to cut you down to size...LOL) but the reflections of these frequencies within your room will change their frequency - scattering them and taking them down a notch as they lose energy - you may be able to hear this i.e the room / environment effects of the 20kHz frequencies.  In addition, the Sony filter is probably not filtering out exactly and only the 20kHz frequencies and above but perhaps causing a sligh roll-off from say 16kHz to 20kHz and then everything beyond.  But this is off topic for the thread.
 
What I'm hoping to hear is something on the 120 db signal to noise ratio and/or why at 113db, I still hear hiss.

[lanchile]

Mag - you may be hearing the secondary harmonics / reflections of the 20kHz frequencies.  In other words, you may not be able to hear to 20kHz (sorry to cut you down to size...LOL) but the reflections of these frequencies within your room will change their frequency - scattering them and taking them down a notch as they lose energy - you may be able to hear this i.e the room / environment effects of the 20kHz frequencies.  In addition, the Sony filter is probably not filtering out exactly and only the 20kHz frequencies and above but perhaps causing a sligh roll-off from say 16kHz to 20kHz and then everything beyond.  But this is off topic for the thread.
 
What I'm hoping to hear is something on the 120 db signal to noise ratio and/or why at 113db, I still hear hiss.

Can you try different speakers? just too see if you still can hear it.

[Teyry]

   I had an Anthem MCA-20 back in 2002/2003. It was almost dead silent, probably the quietest amp through my Dunlavy SC-IV's. I have also owned a Classe CA-200, Pass Labs X150 and Emotiva XPA-1 monoblocks. I had also home auditioned a Bryston 4B-ST around 2001 at the same time that I owned the Classe and the Pass Labs. I found that I could have lived with either. They were all a pleasure to listen to. I should nothe that I had a BPT balanced power conditioner at the time I owned the Anthem which possibly could have added to the silence.
   I am hoping to start rebuilding my music system early next year. My top considerations for amps are Bryston and the Aesthetix Atlas, but I will have to audition them both. I was also considering an Anthem system but after seeing the insides on a youtube video of the cheap clip on connectors it kind of turned me off. The Bryston looks better topless and you have to love the 20 year warranty.
   

[Diamond Dog]

Can you try different speakers? just too see if you still can hear it.

Excellent point. When I was researching speakers over the last while, one thing that came up was that with the speakers I was considering, the builders had put a lot of effort into improving the dynamics of the speaker by lowering their noise floor in comparison to earlier efforts. Having now installed those new speakers, I can certainly attest to the fact that they are much quieter than the speakers they replaced. I could readily hear the hiss emanating from the tweeters of the old speakers from a few inches away but the new ones are eerily quiet. As the speakers are the only thing which has changed in the system, well...you can see where I'm going with this.

D.D.

[*Scotty*]

D.D. What old speakers did your new speakers replace?
Scotty

[Diamond Dog]

D.D. What old speakers did your new speakers replace?
Scotty

PMC FB1i's. I saw them sitting in my dealer's showroom today - it was a weird feeling...

D.D.

[neekomax]

Excellent point. When I was researching speakers over the last while, one thing that came up was that with the speakers I was considering, the builders had put a lot of effort into improving the dynamics of the speaker by lowering their noise floor in comparison to earlier efforts. Having now installed those new speakers, I can certainly attest to the fact that they are much quieter than the speakers they replaced. I could readily hear the hiss emanating from the tweeters of the old speakers from a few inches away but the new ones are eerily quiet. As the speakers are the only thing which has changed in the system, well...you can see where I'm going with this.

D.D.

D.D., I am having the exact same experience with the brand new Soundfield Audio Monitors that I just hooked up for the first time this evening. I had a hiss/hum from my old Def Tech floorstanders. Since they have active bass, I figured it was a power/ground loop thing. But the new monitors are dead quiet, also have active bass, and are hooked up to same exact components in the same way with the same power strips, etc.

They are less sensitive, but your post makes me think that the new Kef UniQ drivers might just be very quiet.

[*Scotty*]

D.D. I was hoping for information on the new loudspeakers as well as the old ones.
Scotty

[Diamond Dog]

D.D. I was hoping for information on the new loudspeakers as well as the old ones.
Scotty

Sorry, Scotty - multi-tasking  . New ones are PMC FACT.8's.

http://www.fact-speakers.com/products/fact8/default.aspx

D.D.

[mike678]

I run into something like this on  jobs from time to time...there was a low level hiss on a system (below -100db noise rating) along with a bit of harshness. It turned out to be, in equal parts, the exotic interconnects and speaker leads picking up noise. In the IC's case, the unshielded wires were picking up all sorts of crap that the amp had to deal with, and in the speaker wire's case, picking up RF that was interacting with things in the amplifier's feedback loop.

When I replaced both sets of cables with good pro stuff, the hiss vanished, along with the harshness.

Also, amplifiers, and preamplifiers, noise ratings are usually given with the inputs shorted, or loaded. If the amp is NOT connected to anything it is just possible that it is picking up ambient noise from its inputs.  This seems to be more of a problem with wide-band amplifiers.

-113db, if actually achieved, should be well-nigh inaudible except to those of unusual hearing, or speakers with very uptilted top ends.