Parasound A51 buzz/hum

thejck

I have recently picked up a used Parasound Halo A51 5 channel power amp from craigslist. I had turned it on to make sure that all the channels worked when I first bought it home. However after finally getting my theater room put together and hooking up the amp to all 5 speakers I think I might have a problem with the amp humming/buzzing.
I unplugged all the interconnects and speakers from the amp. There is a very soft hum coming from the amp when its on. When I plug in my speakers everything sounds fine except channel 5 that has its speaker terminals all the way at the bottom near the ac source . There is a definite buzz coming from just that one speaker. (i have swapped speakers to make sure its not the speaker)

I did a little research and am thinking its a couple of things.
1. the channel has something wrong with it and the amp needs to be serviced.
2. there is DC present in my AC current and since that channel is close to the AC its picking it up.

I took the amp down to my neighbors and it did the same thing there. I even plugged it into his panamax power conditioner with the same results.
Anyone have any thoughts on what might be going on?

Please help.

FTGV

thejck wrote: »

I did a little research and am thinking its a couple of things.
1. the channel has something wrong with it and the amp needs to be serviced.

That would be my guess if the problem always seems isolated to that channel.

2. there is DC present in my AC current and since that channel is close to the AC its picking it up.

Small amounts of DC can be present on the AC line which can cause transformers (mainly toroids)to emit a mechanical hum/buzz ,but it shouldn't be heard at the output.

TG Meat

Yeah, I have an A21 and it is dead silent when its turned on, if I listen to the unit itself. I do hear a little noise from the speakers, but not like you describe. You may consider packing it up and sending it to Parasound.

thejck

Ok here is a new twist. in the last 4-6 weeks most of my audio gear has been unplugged while I have been getting cabinets built stained and tv's installed. So i plugged in my hca 3500 amp the other night and listed to it using balanced audion input and I thought everything was fine. So today I switched the amp to unbalanced inputs from my receiver to test my surround sound settings and voila the same buzz is now in my speakers. I also had the hca-1500 amp hooked to my rear speakers and same buzz. The center channel was fine but its plugged directly into my receiver.

So i took both the amps out of the equation and ran all speakers cable to the receiver and the buzz is not there in any of them.. WHAT THE HECK IS GOING ON???

thejck

i took the a51 over to the Parasound Service center in the KC area. He checked it out and said that everything is just fine. Took it home and it is still humming out of channel 5 (still no inputs plugged in).
I have an hdmi cable from my cable box running from a different room into my theater room. When that is plugged into the integra dtc-9.8 and using the balanced outputs into the back of my amp all the channels have a buzz. the buzz goes away as soon as I unhook the hdmi cable. I presume this is the ground loop issue that I have read up about and should be fixable by a ground loop isolater on my coax line.
But my original problem still remains of the hum coming out of channel 5 when there is no inputs plugged in.
I took the amp to a place that sells parasound products and plugged it in there with no inputs and just my speakers plugged in. the hum is very very faint there. I have to put my ear right up against the speaker to hear it. So there might be a problem with the electricity in my house causing it.
I used a cheater plug on the amp and the hum does not go away on channel 5..
I am really desperate for any suggestions.

k0tuynh

The hum might come from video source, in this case, it's your cable. Try to unplug the Cable TV and see if the hum goes away. If it does, the cable tv ground loop isolator would do the trick
http://www.amazon.com/gp/product/B0017I3K9M/ref=oss_product
Hope this would help. Good luck bro

xandra

Had a similar prob with my Amp -- Local Cable company (Time Warner) installed a ground loop isolator - for free. That eliminated the buzz. So you might try your cable co. first.

NewHTguy

I have a Parasound 2250 and have the same problem, if you want to call it that. It concerned me at first, but since I cannot hear it from my sofa (8 feet away) even with everything quiet, I have pretty much forgotten about it.

Usually when you ask people they start suggesting ground loop problems etc, but the hum occurs even if it the amp is not connected to anything except the AC outlet. Parasound told me that they do not have any technical definition to determine if a hum is defective. So it seems to come down to whether or not it is sufficiently severe to interupt your enjoyment of the amp.

I know that nothing I said makes it go away, but at least you are not the only person with the issue.

HB27

I had the same issues with mine. I had to re-route all the IC cables, speaker wire, HDMI, power cords so they didn't touch or cross.
Since my HT cables weren't the quality of my 2 ch I was getting interference from the AC. One cable on mine wasn't shielded enough.
I was re-educated on proper and clean wiring and routing.
Just a thought about basics again.

NewHTguy

In my case, I tried the amp on a different outlet with no cables connected other than the power cord and the buzz was still there.

Marcinko7

http://www.bhphotovideo.com/c/product/365781-REG/Ebtech_HUM_X_Hum_X_Ground_Loop.html

Check link above. I saw this on a post at Outlawaudio.com a couple of years ago. Bought one and was thrilled. All hum was gone.

xandra

NewHTGuy: putting on a different outlet is not a full test for ground loop. (Mine still buzzed when I tried that.) Again - before spending bucks Try your cable provider. If they won't fix for free, Marcinko's idea sounds great (especially since he's already tested)...

NewHTguy

I appreciate the advice. Before I spend any money let me ask this. Could it be a ground loop if my the cable box and other electronics are not plugged in? I fully admit my ignorance in these matters.:o

cfrizz

Buy a 3 to 2 prong plug, put one end into the amp cord & plug the other into the wall/powerstrip. If the buzz/hum goes away, problem solved.

This is the fastest, cheapest way to start to solve this problem.

NewHTguy

Ok, thanks. I'll give it a try.

thejck

The hum coming out of channel 5 is not present when i try ch1-4. there has to be something wrong with the channel. Cannot be that its acceptable if its not present in the other channel.