THis is a dusie and I read the thread below about hum. I got my 7700 yesterday and simply swapped it for the 755. So I removed the 755 and hooked up the 7700 with same exact connections and NOW I HAVE HUM. No hum with 755. Hum with 7700.

I called Steve at outlaw. He suggested the usual things, those that are described in the manual and have been talked about here. Got started late last nite and gave up (tired). I don't understand why I should have a ground loop hum now when I didn't before, and everything is connected identically. Audio and speaker wires not running parallel or near the AC. Two dedicated 20 AMP new circuits wired in for my 755 setup worked well. Also a third that was already there in the living room.

And yes: I tested the circuits with on of those yellow testers, indicating proper connections, neutral, hot, ground etc. And yes I disconnected the dishnetwork power plug and coax feeds. Even disconnected the phone line from the dish receiver.

Very frustrating. I think I need to start from scratch and "re-build" the system.

Oh yes: Steve said that "differential amps" (of which the 7700 is one) are different from 755.
What does that mean? Thanks guys.

I'm having a similar issue with my new 7700. Prior to buying the 7700 I used five M200's with my 990 and there was no discernable noise or hum at any speaker at any volume setting. After installing the 7700 I heard 60 cycle hum that was easily heard 10 feet from the speaker. Interestingly the hum only appeared on the two surround channels and the center channel, the two mains were quiet - I'm not using the rear surrounds just yet. After rolling out my equipment rack to check my wiring again I noticed that the hum was reduced about 90% but still audible if you placed your ear close to the speaker which probably indicates some kind of wiring problem that was caused by moving the rack. I ran out of time to look into the problem further but will get back to it this weekend and report what, if anything, I find.

mike

If it is like my situation you may find the noise gradually disapating and going away after 20-30 minutes. Mine seems to be related to my Sat coax input, hopefully the weather will be good this weekend and I can check the grounding on the dish.

I had read about your experience with the hum diminishing prior to receiving my 7700 but after moving the rack the hum did not get any quieter over time.

This hum problem seems to be a frequent subject in the 7700/7500 discussions. I wonder what the problem is....

I have a 990/7500 setup...I have no hum at all in my system (its been up for about 3 weeks now)....dead silence. I use a DIRECTV H10 hi-def receiver; also have a rooftop OTA antenna conected to this receiver. My house is old (1925) with variations of modern wire, romex, "knob and tube"; all my gear is connected to a couple of surge protectors (reasonabally good ones) going into a couple of outlets, tied to 15A breaker. All receptacles are three prong, though. It's weird why this problem is affecting some users and not others.

Great help from tech support (Steve and Scott) today. Suggestion was made to troubleshoot, thinking of possible ground loop. So at outlaw suggestion I temporarily "lifted" the ground by inserting a "cheater". Hum went away. Dead quiet.
Now I know that I don't want to delete the ground pin, nor does outlaw want us to eliminate the safety accruing from ground. This was just a test, but what a simple test to do.

So it proved what I thought all along, that the amp was OK. After that I changed some things around. No hum. Dead quiet. Will check it again in AM after it has had a good snooze tonite. I expect it will be fine.

I still don't know why I had hum (ground loop) but as usual I'm quite happy with the product, the service, and support.

My $.02

Yep, in spite of the occasional wart, Outlaw's service is very good. Even though I give them the occasional ribbing, I frequently recommend their gear because of the support aspect.

Cheers,

**UPDATE**UPDATE**

So I thought the hum was gone. Not quite. This AM I turned on amp after being off 6 hours or so. Slight hum, no matter what else was disconnected, so long as unbalanced between 990-7700.

SO.......I got out some old mic cables (XLR(F)-XLR(M). And as I posted elsewhere: **VOILA** no hum !!!!

There is one variable and that is that the amp had been on for an hour or so. I'll leave it off awhile and if the balanced connectors do the trick that's it.

However there is one wrinkle: Been using an EQ between 990 and previous (755). It's an Alesis DEQ830, which you can use balanced or unbalanced.
So if I want to use it I'll make XLR-TRS adaptors for it.....or....if outlaws tell me it's OK to try (and I'm waiting for 9AM to talk to Scott) I'll prefer (for ease and cost) to go unbalanced if they tell me I can do that and have a XLR-XLR balanced in to carry whatever reduces hum. This will be tried later this AM.

Tune in again and I'll write the results.
One thing to remember if you have hum: it's not the amp. These are absolutely dead dead quiet.

To add to my previous post (no hum-990/7500)-I am using Outlaw balanced cables...