[Mike-48]

My 4B3, bought new a little over 3 years ago, gives off a transformer buzz noticeable if you are close to it, within two or three feet. I don't hear it from my listening chair. The previous Bryston amp I owned -- a 14BST-- was silent. That makes me wonder about this one, what's going on? The amp is plugged into a Torus RM20 (which itself is silent), if that matters.

I like to eliminate all possible noise from my listening room. Is this transformer typical for the model, or is something to be gained by sending it back to Bryston for a look and listen?

Mike

P.S. Other than this mild concern, I think the amp is wonderful.

[RPM123]

Could be DC in your power line. That has been the experience in my home.

[Mike-48]

Would not the Torus unit provide isolation from the DC?

[RPM123]

Not unless the product literature states so. Otherwise, you will need to get a DC remover like a AV "humdinger",  PS audio "hum buster" or a Core Power "Deep=Core", if you want to hang on to your Torus. There are also several power conditioners from Puritan Audio Labs that remove DC and have received very favorable reviews from professional reviewers and consumers alike. I happen to own both a Deep=Core and a Puritan PC and they work great with no more hum, among other benefits!

[Mike-48]

OK, I unplugged a HumDinger (I have 3) from a sub and tried it on the 4B3. To the best of my ability to tell, the HumDinger didn't reduce this particular noise. That makes sense to me, as the main element of the RM20 is a large toroidal transformer, which should isolate the 4B3 from any DC offset on the AC line.

(Need I say I think the HumDinger is a useful device when the problem is DC offset? HumDingers are needed accessories to my two JL Audio subs and a Marsh amplifier.)

I tried to measure the noise to say something more objective. However, it is too quiet for my RadioShack SPL meter to measure. Since I can't hear it from a meter away, probably I should just accept it and not be shipping a heavy amplifier around. Two things elevated this to even a mild concern: (1) the absolute silence of a previous Bryston amplifier, and (2) too much time on my hands, due to pandemic-related isolation.

Thanks, @RPM123, for the suggestions. I always appreciate people taking the time!

And James, if you have anything to add, please do chime in.

[James Tanner]

A transformer (like the toroidal transformer in your Torus Power RM 20) will not pass DC since there is no direct electrical connection between the primary (input) winding and the secondary (output) winding. A transformer will pass low-frequency harmonics if they exist on the power line. The RM 20 behaves like a low-pass filter which allows the 60Hz sine wave from the power company to pass through while filtering out higher frequencies where noise, interference and distortion reside. The RM 20’s noise filtration begins at a frequency of 2kHz. If some or all of the harmonic distortion on the power line is below 2kHz the distortion can pass through to the connected components, including your 4B3 amplifier. The Torus Power RM 20 is immune to moderate levels of both DC and harmonic distortion as demonstrated by the fact that the RM 20 transformer itself is silent.

Electrical utilities are regulated and there are defined limits that apply to the harmonic distortion on the power they deliver. Contact your electrical utility and ask if they can measure the output of the transformer that serves your home to see if there is an excess of harmonic distortion on the line. If there is, the utility may be willing to replace the transformer.

[Mike-48]

Thanks, James. I'll contact the utility.
Does your reply imply that, absent something funny with the AC power, I should expect the same quiet from my 4B3 that I got from the 14BST?

[James Tanner]

Thanks, James. I'll contact the utility.
Does your reply imply that, absent something funny with the AC power, I should expect the same quiet from my 4B3 that I got from the 14BST?

Was the 4B always noisy or is this a later issue?

james

[Mike-48]

I'm not positive, but I think it always was noisy. (Again, not terribly noisy; but not silent like the other amp).

[James Tanner]

I'm not positive, but I think it always was noisy. (Again, not terribly noisy; but not silent like the other amp).

OK well monitor it and if it gets worse then please email me.

james

[dumanski]

You may want to take a flashlight,  sounds weird I know but what the heck were audiophiles...
Shine light top front of your amp notice if toroidal transformer is wrapped in silver or is black...or if your so inclined torx ten bit with power off remove top aluminum cover to see better. Transformers in silver will probably read eaglerise.
Black should read plitron. Plitron was in some very early 4b3 and primary in 4bsst  current in  my 7b3 ! My point being is I have had several 4b3 with silver eaglerise transformers that have measured slightly higher noise Than the black plitron transformer to make my point clear the solution was to install the plitron in place of the eaglerise the hum was gone... no effect on sound just something my curious sensation took me...
I sure the fine enthusiast at Bryston could verify your parts by your date code and serial numbers.
They have always provided pure excellence in any concerns in my experience !

[Speedskater]

Unless you live in a mixes use neighborhood, it's doubtful that any 'DC offset' is a power company problem.  These days most 'DC offset' problems harmonic distortions causing asymmetrical voltage. 

[ayang90]

So my 4B3 purchased Nov. 2017 is experiencing the same problem so you are not alone. I have to get pretty close to hear the low hum but it’s definitely there. Didn’t really notice it until a few months ago when I was rearranging my components. Didn’t hear anything when it was new but I can’t say exactly when it started. It doesn’t seem to impact sounds quality at all and I can’t hear it from my listening position so I’m just monitoring it to see if it gets worse. So far it hasn’t.

For what it’s worth I do have it plugged in to a PSAudio P20 regenerator and the hum is still there through that or direct to the wall.

Don’t know which transformer it has silver or black.

Thanks, Alan

[GrooveControl]

I know the square transformers were susceptible to transformer hum, especially the ones in the older 2B-LP, but I thought the toroidal transformers didn't have this problem?  I have several pieces with the toroidal transformers including a 3BSST and no mechanical hum.   I had an older 3B without toroidal and it had a bit of hum, but you couldn't hear it unless you were within a foot or so of the unit. I've never had humming transformers actually cause any output in the speakers.     

[drummermitchell]

I have to say all my SST-2 amps 28s and 7s no hum or buzz whatsoever.
They are on a 60a Torus(front) for 28s and a 7B-SST.
Surround amps are the 7 SST 2s on another Torus 20a (240v).
Obviously both are dedicated lines.
Also use a Environmental EP whole house surge protection at the panel entry(bubble within a bubble)protection.
Sides the above running a PJ,2xsb16 subs and Bryston digital dac and players ect.
Shhhhhhhhhhhhhh...dead quiet when up front at the front and back speakers.
I always check before and after and in between with movies music ect.
Me thinks maybe I should pay more attention to the wife as I do my audio........Just a second dear did you hear something I’ll be right back......I promise.

[Mike-48]

I think all audio gear should be mechanically silent. Any noise has got to lower the S/N ratio a little, at a time when better and better ones are being bandied about. However, unlike the fan noise of a Classé amp that I tried, the noise from the 4B3 is inaudible at my listening seat.

[john1970]

I have two Bryston 7B3 amps, mono versions of the 4B3 plugged into two Torus RM20 units each which plug into two dedicated 20 amp lines.  No noise from the amps and the system is dead silent.