[caleb]

Merry Christmas to all you forum members.

I have two x 7B SST.

They ahve started to make a buzzing sound when they power up.

Only for a fraction of a second and then they are a quiet as can be.

Anyone here experienced anything similar and is it anything to be concerned about?

[avahifi]

The buzz could be that something is drawing too much current at turn on.  Is the buzz coming from the speakers, or from the amp cabinet itself?

The buzz also could be from a "dirty" power line.  Units with torroid transformers seem to be more unhappy with a dirty power line than ones with the old iron transformers.  A good power line filter can help this.

If both amps are on the same AC circuit, try isolating them.

Get back to me with the results of my suggestions.

Frank Van Alstine

[James Tanner]

Merry Christmas to all you forum members.

I have two x 7B SST.

They ahve started to make a buzzing sound when they power up.

Only for a fraction of a second and then they are a quiet as can be.

Anyone here experienced anything similar and is it anything to be concerned about?

Hi caleb,

The 'buzz' is normal - torroid transformers have large turn-on power requirements then once 'on' the power requirement is much less.

james

[avahifi]

I don't think "the buzz is normal" is a good response.  We use toroid transformers in almost all out products and there is no turn on buzz if they are properly used.  We do use inrush current protectors on the AC lines and design supplies that do not overtax the transformers at turn on so no "normal" buzz.  I doubt it is normal in these 7B SST units either, if they are properly designed and correctly functioning.

Frank Van Alstine

[ScottMayo]

I won't comment on design, because I'm not that smart, but my 6B-SST makes a thunbzzzssh noise for about a half second on power up. It always has. It is then dead quiet - 0db at 0m, I put my ear on it - thereafter.

I doubt this is a transformer misuse, but I'm not very worried even if it is. My warranty runs for many, many years yet, and Bryston's amp warranty has proven functional the one time I used it. If the tranny cooks someday, they'll replace it, no worries. The 6B is possibly the most worry free audio purchase I've ever made.

[James Tanner]

I don't think "the buzz is normal" is a good response.  We use toroid transformers in almost all out products and there is no turn on buzz if they are properly used.  We do use inrush current protectors on the AC lines and design supplies that do not overtax the transformers at turn on so no "normal" buzz.  I doubt it is normal in these 7B SST units either, if they are properly designed and correctly functioning.

Frank Van Alstine

We also use 'soft start' circuits in our larger amplifiers as well. In fact I will check with engineering tomorrow but I believe the 'buzz' on start up is actually the 'softstart circuit' rather than the transformer.

james

[bsmith15]

My 4B SST make a "Buzz" at turn on for just a brief moment.  Not really a buzz but more the sound of electricial components turning on.  It just lasts until the LED lights turn on and the unit powers up.  Dead quite after that.  Did it with the dealers demo unit, did it with a freinds 14b SST and does it with mine.  Had a similar "noise" (not the same though) at power up with a Rotel RB-1080 with massive transformers; so I am sure it is as James indicated.  No worries.

[James Tanner]

Hi bsmith,

Yes my intent with the  'buzz is normal' comment was to put 'caleb's concerns at ease.

james

[James Tanner]

Hi All,

OK checked with engineering and the 'soft start' circuit we use has capacitors that 'charge' at turn on. The in-rush current with torroids is much larger on turn on then when operating. The purpose of the softstart is to ramp up the power (current) gradually to avoid stressing fuses, circuit breakers and switches etc.

The 'thunbzzzssh' noise as someone better described it on turn-on is the sound of the softstart circuit ramping up in combination with the power transformer. Once the charge-up is complete the softstart circuit is no longer operational and is out of the circuit.

Hope this helps.


james

[caleb]

Hi All,

OK checked with engineering and the 'soft start' circuit we use has capacitors that 'charge' at turn on. The in-rush current with torroids is much larger on turn on then when operating. The purpose of the softstart is to ramp up the power (current) gradually to avoid stressing fuses, circuit breakers and switches etc.

The 'thunbzzzssh' noise as someone better described it on turn-on is the sound of the softstart circuit ramping up in combination with the power transformer. Once the charge-up i ...

Thanks James for this re-assurance - as I said when the unit is actually on you can hear a pin drop - they are so quiet.
Regards
CBW