I am having an issue with my new 990. Each time I switch inputs or mute I get a thud through the system sounding similar to a tap on a microphone. Any ideas on how to trouble shoot this? I am using a 990 to an ATI 3005 using the balanced inputs. I also have bass management going from the 990 to the SMS-1 to the Sampson using balanced inputs.

There are a lot of things which can cause this problem, not the least of which might be DC on your outputs or a defective muting circuit (which is supposed to block transients like this). Unfortunately, there is nothing you can do about it at home - see a technician or contact Outlaw.

I had the same problem when I had the Model 7500 amp connected via balanced connections. I went back to the un-balanced connections and the thumb or tick went away.

Do you think they can fix this through a firmware update?

If it's a timing problem, probably yes. I doubt that is the case though.

What level of firmware are you currently at?

It came with 3.07 and I upgraded to 3.11. Like the new features but still have the thumping. After reading about a few users who switched back to unbalanced connections which solved the problem I am concerned that this is not a configuration problem, but one that is inherent with the 990 when using balanced connections.

Have you resolved the problem yet?
I had the same problem of thumping when muting or switching inputs when I upgraded to some modified Hafler amps. The problem was also there with a 2ch preamp. It turns out the the amps needed a capacitor input, shorting (muting) the dc input caused the problem. I'm using unbalanced RCA's.

MeanGene,

I am running my 990 with balanced connections to my 2200's and 7500 and I do not experience any thumping at all.
I can change inputs and mute and it is deaqd quiet.
I get the inital small click or pop when everything is first turned on but that's it.

No, I still have the problem and I just bought a $3000.00+ amp not to long ago. I will get a different pre/pro before I buy another amp.

I think I have found a work around. So far I have tried: another 990 (Thanks Outlaws), firmware updates, configuration changes, etc. I finally discovered that the Thumping was coming from the subs only and if I did not use the balanced LFE output from the 990, everything else worked very well. I now have an unbalanced connection from the 990 to the SMS1 and a balanced connection from the SMS1 to the Sampson SX 2800. I am also using balanced connections from the 990 to the ATI 3005's "Pure Balance" inputs. It is now very quiet with no Thumping during muting or switching between DSP modes or inputs. I tried a number of different cabling configurations and using the unbalanced LFE output of the 990 was the ticket.