14B-SST hum

JeffMO · « **on:** 24 Jan 2006, 01:12 pm »

I recently purchased a new 14B-SST amp. I noticed a low frequency hum coming from the amplifier itself. The hum exists with and without an input connected to the amp and whether using a balanced or unbalanced input.

There is a slight hiss (no hum) from the speakers but that is inaudible at my listening position and not a problem. I shut off all power in the house except for the amp circuit and there is still hum. I also connected the amp to different circuits via an extension cord with the same result. A different (non-Bryston) amplifer connected to the same outlet is dead quiet both with and without any source connected.

I sent the amp back to Bryston and was advised they will try a different set of transformers, however I was informed that the hum appeared to be within what Bryston considered normal (i.e., some are a bit louder and others a bit quieter depending upon the quality of AC at the outlet). I cannot say that the hum is "loud" but is audible (without any music playing) at my listening position (approx. 10 feet from amp/speakers) in an isolated and damped (i.e., very quiet) dedicated audio room.

If the amp is within "normal" noise parameters I presume that other owners of 14B-SST/7B-SST's have noticed this, as I assume not everyone has perfect or near perfect power in their home. So are your amps completely quiet and absolutely hum free or am I just being unreasonable in my expectations or too "sensitive" to the issue?

Phil A · « **Reply #1 on:** 24 Jan 2006, 03:31 pm »

I have a 14BSST and have not noticed any hum at all. It is plugged into its own circuit. You don't by chance have a cable box in your house?

JeffMO · « **Reply #2 on:** 24 Jan 2006, 04:53 pm »

Phil, I assume by cable box you mean cable television. I do not have cable but I do have Dish Network satellite television which is connected to a separate circuit in a different room from the amplifier. I turned off every other breaker in the house and the hum was still present so I am guessing that it is not something in my home which is causing the problem.

I'm glad that yours is quiet and wish mine was too.

I will be interested to hear from others. If I'm the only one with the problem then I wonder if it is normal.

Phil A · « **Reply #3 on:** 24 Jan 2006, 07:01 pm »

Jeff, you might want to try disconnecting the cable going to the Dish box and unplugging it just for the heck of it. Can't take very long. I've read many posts on different forums with people having ground loop problems. I also have most of the other (non-amplifier) components in my main system and bedroom system on the other side of the wall plugged into power line conditioners that not only are on different circuits, likely create parallel circuits. Assuming is not the amp (I sit about 11 ft. from my main speakers and have not noticed anything), the only other thing I can thnk up is perhaps separately grounding the circuits used on the audio system from the rest of the house. Keep us updated on the problem.

ctviggen · « **Reply #4 on:** 24 Jan 2006, 07:13 pm »

Assuming JeffMO is in the US, putting the audio equipment on a different ground than the rest of the house would violate the national electrical code (NEC), unless the second ground is properly connected to the first (house) ground. (By "ground", I mean a connection to a water pipe or a copper pipe/rod pounded into the earth.)

If he's moved the amp to multiple different circuits and without any inputs or outputs, the amp itself hums, there's not much to be done. You could try some type of AC filter unit, as perhaps the AC has DC on it. See:

http://www.psaudio.com/articles/hum.asp

Can you borrow an AC filter like a PS audio or even a Felicia? This would test the DC hum aspect.

JeffMO · « **Reply #5 on:** 24 Jan 2006, 07:16 pm »

Hopefully Bryston will find the problem and fix it but I am not very optimistic based upon my conversation with them yesterday. In any event, I have in effect tried what you suggested by turning off the breaker to the circuit feeding the Dish box, TV and another audio system which is located on another circuit and room separate from the amp. I am very confident it is not a ground loop but is simply internal noise from the amplifier (probably the transformer(s)). I might have to post on the audioasylum forum if I cannot receive any feedback from this forum.

James Tanner · « **Reply #6 on:** 24 Jan 2006, 07:47 pm »

Hi Jeff,

We are changing out the transformers on your 14B.
Hopefuly that will solve the problem for you.

james

JeffMO · « **Reply #7 on:** 24 Jan 2006, 09:02 pm »

Hi James,

I hope the new toroidal transformers cure the problem. In such a quiet listening room the hum was a bit of an annoyance to an otherwise great performing amplifier. I'm keeping my fingers crossed that the original transformers were perhaps just a little out of spec. My old amp is definitely not in the same league sonically as the 14B so I'm looking forward to getting the 14B back.

Mike-48 · « **Reply #8 on:** 30 Jan 2006, 03:46 am »

Jeff,

Sorry to hear you are having a mechanical hum problem with your amp. I have always heard (though I can't say for a fact) that such things *can* be caused by problems on the AC line. They can also be caused by bad (noisy) transformers. Humming transformers in audio gear are a pet peeve of mine. I am amazed at how many manufacturers make entire product lines that hum!

My listening room is also very quiet. The Bryston B14 SST is the quietest amp I have owned -- absolutely inaudible. It is quieter than the power conditioner I have now, quieter than the lamp on my desk, and quieter than the Adcom and Conrad-Johnson amps I owned previously. I am talking now about mechanical hum (though its electrical output is silent when it should be, too).

I've heard a few of these amps elsewhere, and they were all inaudible. Unless there is an AC problem at your house, I think it's quite likely Bryston will be able to fix the problem.

JeffMO · « **Reply #9 on:** 30 Jan 2006, 02:12 pm »

Hi Mike, thanks for the reply. Based upon your post and the lack of any other posts about mechanical noise I assume the hum I experienced is the result of a problem with my amp and not representative of other units. The reason I inquired was that the Bryston representative I spoke with told me that replacing the transformers might not solve the problem. I do not suspect it is my AC line as another amplifier connected to the same circuit is quiet, as are all of my other components and other audio/video devices in my home.

Hopefully the replacement transformer(s) fixed the problem and the amp will be quiet after I receive it back from the service department.