What'd I do wrong?

sandworms

So, I was doing some experimenting last night, comparing my current amp (xpa3) to a parasound hca 1000. I bridged the hca for the left channel and left my xpa on the right while listening to 2ch, well the parasound was humming loudly at low volume, which I have never had a hum with my xpa3. could there be an issue with the amp ( just got from flee bay ), or is this the way older amps pick up interference (ground loop). sorry for the beginner questions, but I still learning this hobby, slowly but surely

tonyb

In bridged mode, some may hum a bit more. Also some amps in bridged mode don't like anything under an 8 ohm load. Take it out of bridged mode and just use one channel if you want to compare the way your doing it.

reeltrouble1

good advice tony, whenever you have a system problem, simplify, no bridging, bi-amping and so on, hook the parasound up regular and see if there is hum, make sure it is hum not hiss, if you have hum it can be a ground loop, it can be a bad connect or there can be something amiss in the signal path, but keep it simple to begin with. If it still hums both channels or just one??

RT1

cnoat

+2 I run a 750a in bridged mode for my center.Not alot of hum but a noticeable "hiss" when you put your ear to it.

sandworms

definetly a hum, so I will try it not bridged first, see how it sounds. I'm hoping it's not an internal issue, just a connection issue. Thank you for the help guys, love this place!

TroyD

I'm reminded of the old story:

Patient: Hey, Doc, it hurts when I do *this*
Doc: Well, don't do that.

BDT

sandworms

I took it out of bridged mode and 80% of the hum went away,I didn't try the other channel yet, however it still has what I consider to be unacceptable low volume hum. tomorrow I'll try the other channel and a cheater and see if it goes away. I'm running RTi10's so not a difficult load.