I get a loud popping sound when I mute the 990, turn the volume from -75 to -76, when connecting to a dts/dolby source (skipping tracks on a DVD).
I have already tried connecting only 1 speaker to the 990 through only 1 channel of he bryston 3b or 4b with nothing else connected at all and just pressing mute on the 990 and the pop is still there. the 990 is connected to a belkin pf-60 ...so ac should be clean.
I have had the popping since I bought the 990 and have lived in 2 seperate houses with the exact same problem. any ideas would be greatly appreciated.
-thanks

I put an oscilloscope on the output of the 990 and noticed that there is a voltage spike when the volume is put all the way down or muted or locking on to dts or dolby digital.

When I tried out a 990 about 18 months ago I noticed similar behavior.

what kind of amp(s) did you try the 990 with?

I used it with my old Kenwood KM-X1 THX Ultra 100W x 6 channel amp.

At the time I was looking for a replacement of my Kenwood KM-C1 prepro that died. I eventually went with Integra Research RDC-7.1 as I was able to get Onkyo employee discount on it.

I liked the 990, but felt it was a bit unpolished because of little things like the popping noises. That and lack of coax digital inputs led me to get the RDC-7.1.

Although I'd have to say that you get more for your money on the 990 at (then) $1100 vs the RDC-7.1 at $2500 (which is what I paid for it). I wouldn't pay full price for the RDC...in fact, now that they've said they aren't coming out with any upgraded modules, I'd be downright pissed if I spent $5000 on it.

Do you use balanced or un-balanced cables between your amps and 990?

Looks like his Brystons have RCA/unbalanced connections only.

When I tried the 990 I was using RCA as well.

I had the popping noise when I used balanced cables but the popping went away when I switched back to un-balanced.

BllogingTGuy, I don't understand your reference to the 990 not having coax digital inputs. Mine has coax (plus optical and analogue) for every input on the back panel except tape and phono, which are analogue only. It's all discussed in the manual.

The 990 only has 2 coax SPDIF digital audio inputs.

This wasn't enough for me at the time with all the gear I had.

I'm guessing you didn't want to use coaxial-to-optical converters or didn't want to use optical from sources that offered both, right? (Edit: converter ...)

You are correct gonk. I'm not even sure I knew about coax to toslink converters at the time. And now that I know about them, lack of inputs isn't an issue.

Now all I'm lacking are HDMI inputs that accept multichannel lossless audio, but I think I can live without that for some time to come. Particularly since my future HD DVD transport of choice (Xbox 360 HD DVD drive) doesn't offer HDMI 1.3 output.

Although really, I'm waiting for Oppo to come out with an HD-DVD transport.

Ive tried both unbalanced and balanced outputs on the 990 and they both pop. my bryston 4B is balanced and the 2 3Bs are unbalanced.
I'm starting to think it might have something to do with the 990 not having a 3 prong plug on it and not having the same ground potential as the brystons.

Oh sorry, forgot to check the manual on the 4b.

went through many attempts at solving the problem...even called bryston.
I ended up buying a Denon 988 from a local store(with the intention of bringing it back within the 30 day period). there is absolutely no popping sound from the Denon(using the pre out from the denon connected to the brystons). I will return the Denon 988 and buy a Denon 3808CI once the Outlaw 990 is sold.
I find it a shame that the 990 didnt work with the Bryston because of the dc change at the ouput of the 990. Overall I find that the 990 was a great product and would have held on to it a while longer if not for the interaction with the bryston amps.
-thanks to everyone for the help.