Bryston amp, pop sound at power down.

Turn amp on and measure DC at speaker terminals. 

Also, disconnect inputs and see if problem persists

Of course, turn off your amp before playing with the inputs.  

Also, do you have a tube pre?

My 20 year old 4bST would send a quiet, dull thud sound to first the left speaker, then the right on shut-down, no matter what the preamp’s volume setting. I was told by my dealer and by Bryston’s James Tanner this is normal operation for that amp. I would not describe it as a “pop”.
I now have a 4b3, no more thuds on shutdown.
Send an email about it to James Tanner, he’s responded promptly to me in the past.
 

No tube preamp. I've tried the amp with two different solid state amplifiers and with no inputs at all and the pop still occurs. I noticed that it seems to be an equal pop on both left and right channels. 

I will perform the dc speaker terminal test tonight and report back

Thank you Erik.

I measured DC voltages at speaker terminals on the amp and both channnels measured .000VDC. This measurement was with a fairly decent fluke meter and had the volume set to zero on preamp and speakers disconnected. 

That's how to do it, correct?

bslon: I think my sound could be also described somewhere between a thud and pop. Interesting you had it on the older version as well. I'd be curious if anyone else who has the 4BSST2 has the issue. 

I will send an email to James tanner if I can locate the address on their website.

Thanks

I have 3 Bryston 7B ST's and all three give off a pop/crackle at power down, whether turned off at the pushbutton or due to loss of AC feed.  Since it is the same for all three, I guess it is normal.

While a bit disturbing, the sounds are not loud enough to endanger my speakers, and they no longer bother me as I am used to them.

I leave these amps on all the time, and so I hear the noises very rarely.

I own the 4BCubed for many years with Vandersteen Treo and Vandy Subs and it happens every time I power off.  My amp is on all the time unless I'm out of town for a week or more. My speakers sound great so I don't know of any damage that's caused by the pop that we both hear.

I had a Bryston pre and monos.  Exact same issue.  Even if I hit mute!  In the end it was the reason I sold them. Bryston was zero help.

Ok, so sounds like what I'm hearing is perfectly normal, which is what a technician at Bryston told me.  I will stop fretting!

Thank you all for your responses

It sounds like a cap discharging.  Should not be a normal thing or just a poor design.

My Symphonic Line tube pre-amp sends a loud pop through the speakers whenever I turn it off. I too was told that was normal when I first got it in 2012, and it continues doing it to this day with no issues.