Hum and buzz fix advice needed

[HarryO]

I'm going to a friends house this weekend to help rearrange and set up his 2 channel system. He's running a couple of tube amps, SS pre, passive dividing networks on Altec 604Es bi-amping, It will used on the same METAL wire shelving rack with the PC, HDTV, and the ac is being split between 2 breakers on his service box.

Right now he has extremely loud hum and buzz through his system. Imagine that.

I'm trying to talk him into seperating his systems isolating his audio from his TV/pc system.

ONLY the 2 outlets for power supply to feed everything. Close to 14 componens to blend and isolate.

I'm taking a bunch of 2 prong plug adapters, IC cables, power strips, speaker wire over to re-do the whole works. It's a very serious hum and buzz.

Since I can't talk him out of the metal rack I was wondering if I could use some type of insulating cover over the cables and wires, rubber matting will be used to isolate the components from the metal shelving unit (make-do rack-entertainment center. One of the big chrome things).

I thought about some kind of rubber tubing or hose to keep the cables and wiring away from the metal rack.

Any thoughts?

Thanks,

Harry

[Erland]

Sounds like a real mess of cables!

My advise would be to make an attempt to locate the "humm and buzz" by unplugging all components, straighten out any "birds nest" of cables and plug in just one source, the pre and the tube amps. If the disturbance is still there, I would look at the tube amps. Tubes get old and may need to be replaced.

The disturbance may also be related to other items in the room, or electical components connected to the same circuit, so make sure before you start ripping the tube amp apart. I had a light dimmer that sent "rays" of disturbance through the room. I ended up buying Synergistic research speaker and signal cables with active shielding to get rid of the problem. (when looking back, a new digital dimmer would have been much cheaper, but we all need exuses[] )

If the system plays without disturbance when all the other stuff are gone, you probably have better arguments when trying to convince your friend. If he still insist on keeping it all hooked up like before, there are some reasonalby good "pads" out there that does not cost to much. Ask around and get some reccommended ones (I have no idea of what's on the US market) preferably without any fancy lights or cheap switches on. Some of these pads are equipped with pretty good shielding, and may be enought to seperate the different components the can affect each other. Make the best out of it, and try to seperate the different systems from each other by using seperate pads.

When thinking of it, I do not even remember how the std. US electrical socets are like, but if there is an option, try to turn the connection 180 deg. Believe it or not, but a simple thing as changing the phase on a component that creates disturbance, can make it quiet.

Rearding the metal rack and the cables:
If the cables are so badly insulated that they get afected by the rack, unplug them and throw them away. You may safe the life of your friend and his family!

[MatrixDweller]

It could be a ground loop causing the buzz on the amps. Does he have a sub too?

Cable TV can
be bad for ground loops so I would try unplugging the coax cable first. After
doing some proper cable management I'd try plugging in only one amp
first to see if the ground loop is coming from the amps. You shouldn't
use 2 prong plug adapters for other than testing purposes. If there
ever was a short in a component the case (and possibly metal rack)
might become 'Live' or 'Hot' and you may be visiting your friend in the
morgue.

Erland is right about the rubber matting you mentioned. The shelf shouldn't have any impact on the wires. I have heard that placing rubber under components, to stop vibration, helps with sound quality but it shouldn't be causing that kind of hum unless it's shaking the tubes considerably. I've heard that a solid piece of granite or marble or something else very heavy under an amp can help stop them from moving (vibrating). You could also use spikes for feet.

The AC would be split on the breaker to provide 230V just like the stove and dryer circuits. The breaker might not be as compact as, or looks different than, the others because it was added in after the house was built by a different electrician.

Here is a good article on Hum and Buzz:

Audioholics - Eliminating System Hum and Buzz

[HarryO]

Thanks for the advice. I'm pretty good at isolating the ground problems. I'm sure it's the problem. I've just gone through some of his components freshening them up. Since he set this stuff up on the metal rack the hum came about. I moved some cables in my hand away from the metal rack and the hum changed. The IC's aren't very old but of average quality at best. There's definitely something going on with the cables in relation to the hum. It's why I was asking about some kind of tubing used as shielding. I don't have any budget to straighten out his system. He's not going to spend a dime. I'm just furnishing materials I have laying around not being used.

There's definitely 10 lbs of crap stuffed in an 8 lb bag going on in the rack. Just trying to help a buddy get his system sounding better.

Harry

[LarryC]

I'm absolutely no authority on this, but the fact that the hum changes when you move the cables around in your hand makes me think that at least one of the interconnects has a faulty shield/ground (I'm assuming RCA pins and jacks). I suggest you take the cables that happens with, and unscrew the shells at both ends of each one and pull them back in order to look at the solder connections between the wires and the connections on the back end of the plug. My guess is that he has 2-conductor I/C's, namely a central wire (positive, soldered to the central pin) and a metal woven shield (negative, soldered to the RCA's collar connection). Look for breaks anywhere, but I'd bet on a break between the woven shield and the negative collar of one of your RCA plugs.

If he has 3-conductor I/C's, namely 2 internal central wires plus a woven metal shield, you still look at the solidity of soldering, but now at all three: a wire to the central pin; a wire to the shield/collar; and the woven shield, which is attached to the negative shield at one end only. Don't make the mistake of thinking that the woven shield should be attached at both ends in a 3-wire I/C. Whereas it must be attached at both ends in a 2-wire I/C.

Larry

[HarryO]

Ok,

All is done on the re-vamp. Problems solved.

1: Eliminated most of the hum by going to the two prong adapters on power cords.

2: Changed 2 power cords out to heavier hospital grade cords.

3: Re-routed all cables and wiring. It was a mess and all intertwined. All his IC cables and wiring were fine. None changed.

4: Seperated the power between the 2 outlets with an extension cord allowing multiple power sources and isolating audio from video and PC.

5:Insulated the metal rack that was grounding components together. Used an old truck bed liner cut into sections to fit the rack. It was the final step to eleminate the grounding problems.

This was just a case of eleminating all ground problems and seperating the PC and Video systems from the same wiring circuit.

Thanks for all the suggestions.

Harry

[MatrixDweller]

1: Eliminated most of the hum by going to the two prong adapters on power cords.

You know of course that using three prong adapters is really only advised for diagnostic purposes. Hopefully your friend never has a short on those components. The ground is there for safety reasons. It doesn't have to be a physical wire inside the case touching the chassis, it could be a blown component sending it's current to ground instead.

Another thing to consider is that your friend's wife, or your friend if it killed his wife or kid(s) instead, could sue you because you put the 3 prong adapters in place. I doubt you would face a manslaughter charge because you're not a certified electrician, but you could be in deep doo-doo if they knew you read our posts and didn't heed our advice.

[pauln]

Rack mounted gear can loop ground through the rack. Go to a music store and buy some "HumFrees"; these are non-conducting "U" shaped tabs with pre punched holes. They are designed to be clipped on the rack at the very point where the gear screws go through the rack, therby isolating the gear from electrical contact with the rack.

Or cut up a sheet of plastic and fabricate your own.

[LarryC]

The ground is there for safety reasons. It doesn't have to be a physical wire inside the case touching the chassis, it could be a blown component sending it's current to ground instead.

I solved a hum problem once involving a pair of 1970's-era monobloc amps by floating one power cord with a 2-prong adaptor, leaving the other 3-pin in place. Apparently keeping both amps on 3 pins created a ground loop.

Some of my older equipment is just 2-prong, most of my newer is 3, but only the older monobloc pair created the problem. The RCA plug/jack shields might be a common ground through the system, but probably can't protect against a massive short like a 3rd pin can.

If you still want separate grounds in the setup, it seems to me you could try removing selected 2-pin adaptors until the hum returns.