Hum issues - don't think there's any hope but....

I'm re-arranging my office due to the lucky acquisition of some new furniture. The paint is done, new shelving for CDs and LPs in place, desk in place and assembled, "new" stereo stand populated. Still fleshing out the closets and junk.

I'm getting hum and it's driving me crazy and I don't think there's anything I can do about it but replace my receiver.

My receiver is a circa 2000 Onkyo Integra DTR-7. It's been serving me well but has major issues, not just hum. One of the front stereo amp channels is dead, so I have an external amp connected to the L/R stereo mains. My sub is a passive Optimus sub with an old 1993 ProLogic receiver (Phillips FR-930) as the amp.

The hum comes on when I turn on the receiver/preamp. I am 99% sure it's been happening for a long time, but since I had a conventional setup before I didn't mind it much. Now in my new office I've set up a "nearfield" array. The volume I listen at is much lower, which means the noise floor is much louder and the hum is not only noticeable, it's intolerable. Most noticeable in the sub, but also happens in the mains.

Hum volume goes up and down on the sub amp with the volume knob. When I select a source other than the preamp on the FR-930 there's zero hum. I've replaced the cable from the pre to the sub amp. I've installed an EbTech Hum Eliminator between the components. Neither change made any difference.

The hum happens in the rears as well so it's completely internal to the receiver/preamp. My main home theater receiver is an Onkyo that hums through the sub output (not ground loop hum - known problem with that model) so I think I'm just hosed.

And yes, when it's done I'll post in the "Show your rooms" thread. The before and after are going to be astonishing.

 

Sounds like it is time for some new amplification. If stereo, I bought a NAD 320BEE off Ebay for a paltry $200 to use as a spare. It is an impressive little box.

 

I would bet it's ground related. Turn your plug 180 so you reverse the positive and negative. You might need a universal adapter (three to two) if your plug has a wider prong for the positive or if the plug is a three prong, going to two can eliminate this noise sometimes.

 

Well one would think that if it were ground related the EbTech boxes would have solved that. That's what they do. Great little boxes. I originally got them for an old separates home theater 5.1 system that started humming like the dickens when I got a new fridge. They completely eliminate ground loop hum.

However, this is not a pure separates system like that. It's a hybrid. I'm using the internal amps in the receiver for the rears and external amps for the front L/R and the sub.

I wonder though if I lift the ground on the receiver/preamp only as you suggest that would do the trick. The ground fault, if it is in place, would have to be completely internal to the DTR-7 since I'm getting 60 cycle hum from the rears which are using the internal amps. If the ground fault is inside the receiver/preamp, then doing a ground lift between that and my amp would accomplish nothing, right? The hum is already introduced and is part of the signal. Furthermore it would have to be somewhere between the pre-amp and the power-amp sections inside the receiver since my needledrops are clean and hum free.

Well, I have something to try before I give up on this receiver. Thanks!

 

Don't know if this will be of any help to you, but it worked for me:

I had an annoying hum in my bi-amped system that was driving me crazy. Process of elimination identified my bass amplifier as the culprit. I found the technical recommendations/solutions too complicated or costly to put into effect.

One on-line article I read said, among other things, to try plugging in the offending devise in a totally separate outlet from everything else in one's system. When I plugged the bass amplifier's power cord into a heavy duty extension cord and ran it to the kitchen or bathroom, the hum disappeared. But when I ran it to two other outlets in the same room and one in the next room, the hum was still there. Finally, I determined that one outlet in the same room, next to the front door, about 20 feet away from the sound system, produced no hum. So I routed the extension as unobtrusively as possible to where I can leave it coiled up behind a couch, and when I want to turn on the system, I pull the extension out, route it under a throw rug in front of the door and plug it in. No hum... for the last 3 years.

 

Whenever I've had a hum/buzz problem that wouldn't go away no matter what, it's almost always been a capacitor that's gone bad. Fortunately for me I have a really great tech that can track these things down and replace capacitors and other parts as necessary. Perhaps your unit needs service?

 

Just want to point out that removing a ground prong or using a ground-lift adapter is not legal.

 

The problem you describe sounds like a bad filter capacitor in the power supply. Your two options are to have a tech look at it, or simply replace the receiver.

 

I strongly suspect that is exactly what is happening here.

I noticed this morning, when I first turned on the receiver there was very little hum, I thought "Hey that's not so bad I can live with that". Then after playing a record when I went to put the next title on the hum seemed much louder and very annoying. I suspect that if the hum gets worse when the system warms up, it's some capacitor or something gone bad inside. The fact that one of my front channels is dead (telltale blowing wind sound of a bad capacitor) doesn't give me much confidence in the rest of the internals. Next time I turn it on from a cold state I'll listen for the hum. Interestingly enough the hum only seems to affect the pre-amp output stage. I'm running my computer as a tape deck for my needle drops and they have been and remain perfect.

Not worth my money to get repaired. The DTR-7 was a very good receiver in its day in 2000, but it's not really anything special. It certainly didn't go to waste - this thing was used and enjoyed for years and I used the phono stage and everything. Pre-HDMI receivers with 5.1 inputs are a dime a dozen, even the very high end ones. Heck, I may even go separates. A pre-HDMI pre-pro with 5.1 inputs is not going to run me too much, and I already have four channels of amplification here. Another AudioSource AMP 102 will only run me a couple hundred bucks. I'm not an "audiophile", just a music lover - I know it's kind of nuts for me to write that while contemplating separates ;-), but on this page it should be understood.

I just hope the next one doesn't have issues like this. At least this may mean I can get the old ProLogic receiver out of the mix.

 

I replaced my new-for-2000 Onkyo Integra DTR-7 with a new-for-2003 Sony STR-DA4ES that I got from Craigslist for $175. (slightly high price for this piece, but it was from the original owner in mint condition - seriously not a scratch on it).

Hum issues gone. The sub output to the AudioSource amp does hum, but the Ebtech Hum Eliminator box completely handles it. So happy. The Sony ES receiver has possibly the worst most convoluted setup/UI that I've ever encountered other than ITunes. It is truly impressive in its difficulty and counterintuitive nature. However, the book helped and I'm mostly set up. The remote control is a bewildering mess that will go right back in the box as soon as the much simpler basic Sony receiver remote that I ordered from ebay shows up.

Listening to "A Night At The Opera" in DTS 96/24 in 4.1 as I type this. Sound is more or less what I was used to already, but without the hum (these $1000+ home theater receivers tend to be fairly solid for both music and movies, at least for a non-audiophile like me). It's very nice to not have my old prologic receiver powering the sub any more. Much cleaner looking system. Also I think the receiver powering the speakers over my pool table is busted so one of these cast-offs will go there now.

 

This smells more like an old amp then ground problem. Borrow a re infer from some and test. No hum. That's your answer

 

Old Rotel amp to newer Rotel amp
Hum to no hum
That's what happened to me.