[Stephan1310]

Hi,
Just received 4B-SST2 amp with BP26/MPS2 to be used on my PMC OB1i speakers a week ago. Sound is excellent. However, on my right speaker I can hear a humming sound; it's not loud, not noticeable from my listening position, only when I put my ears close to the speaker. Meanwhile I have done a few experiments to detect the cause:
- only 4B-SST2 connected to speakers -> dead silent
- preamp connected to speakers with all other connections unplugged -> hum on right speaker
- reversing XLR interconnects on preamp side -> hum goes to left speaker
- after previous also reversing XLR interconnects on poweramp side -> hum moves back to right speaker
Hum level is not affected by what is connected to the preamp, source selection or volume level.

Although I can not really hear the hum when listening to music, I would like to get the issue sorted out since everything is brand new and I guess hum should not be there...

Any suggestions are welcome...

Besides that, Merry X-Mas and Happy New Year to all Bryston lovers out there!

Regards,
Stephan1310

[James Tanner]

Hi Stephan,

Have youi tried reversing the complete left and right cables or better still try a different set of XLR cables from the preamp to the power amp-just to eliminate a cable problem.

Also just for testing try a pair of RCA cables to the amplifier just to see if its a problem in the Balanced circuit.

It appears to be coming from the right side of the preamp but it could be a bad cable or the speaker itself may have a slight difference so even changing the complete left side of the system to feed the right side speaker and visa versa may trace down the problem. 

Low level hum is usually a ground loop or RF problem.

james

[Stephan1310]

Hello James,
First of all, a happy New Year! Thank you for your recommendations. I have followed your suggestions and solved the issue: the hum was related to a bad XLR interconnect. Now replaced it with a Harmonic Technology Pro Silway MkIII XLR interconnect. The system plays like a dream! Thanks and regards to all Bryston addicts out there

Stephan

[predrag]

James,

What could cause hum coming from my MPS2?
I suppose it is a noisy transformer.
It can be clearly heard at about two feet from the unit.
Do you have an idea how to solve this?

Oh, BTW I had a complaint from my neighbour for being too loud tonight.
Couldn´t help myself, 7B SST2 are so great!

Regards,

Predrag

[James Tanner]

James,

What could cause hum coming from my MPS2?
I suppose it is a noisy transformer.
It can be clearly heard at about two feet from the unit.
Do you have an idea how to solve this?

Oh, BTW I had a complaint from my neighbour for being too loud tonight.
Couldn´t help myself, 7B SST2 are so great!

Regards,

Predrag

Hi Predrag,

It could be a bad transformer (highly unlikely) or noise and distortion on the powerline. Also make sure you do not have florescent lights or adjustable dimmer lights on the same circuit as the preamp.

I would be interested in your comments on the SST vs the SST-2 squared?

james

[jethro]

Oh, BTW I had a complaint from my neighbour for being too loud tonight.
Couldn´t help myself, 7B SST2 are so great!

predrag,

Are you in an apartment or a house 

[predrag]

Hello Jethro,

I live in an appartment block unfortunately!