Is it possible to elminate my 60 hz hum?

Big Red Machine · « **on:** 10 Jan 2015, 03:13 pm »

I have tried quite a few things on my own to try and find the origin of a slight flutter, flutter, flutter coming from the tweeters. At this point it is either the amps or the preamp. It is not audible from my chair but the fact that it is there is making me angry.

If I disconnect inputs to the preamp the buzz is still there.

If I turn off the music server the buzz is still there with inputs connected.

If I add a cheater plug to the amps the buzz is way worse - sounds like a grounding issue.

For background the amps are balanced inputs only. The preamp has only psuedo balanced connections and the preamp itself is NOT grounded to the AC. It only has hot and neutral inputs connected off the IEC. So the balanced connectors have the shield and return tied together at each connector. Not sure this is relevant but mentioning it.

I am using balanced cables between the pre and amps right now. I don't recall that SE cables were less noisy with an adapter at the amp end. If it were the case I'd be there in the set-up.

If I move the amps to a different outlet on the same circuit the noise is the same.

If I move the entire front end power strip to a separate circuit, the noise is the same.

This tells me that the amps or preamp are causing the noise.

Any suggestions?

jtwrace · « **Reply #1 on:** 10 Jan 2015, 03:26 pm »

A list of equipment would make it easier to help. What preamp and what amp?

Davey · « **Reply #2 on:** 10 Jan 2015, 04:18 pm »

I'm not sure how you made the connection from "flutter, flutter, flutter" to a 60Hz issue, but the obvious thing to try (which you didn't mention) is to disconnect the preamp from the amps and see if the problem remains. That might tell you something.....maybe not.

I'm also unclear if this is a "power conditioning" issue or not. Maybe the power conditioning is causing the problem?
Power "conditioning" is such a nebulous topic.

Dave,

paul79 · « **Reply #3 on:** 10 Jan 2015, 04:30 pm »

You gotta find the component that is causing it.

Wayner · « **Reply #4 on:** 10 Jan 2015, 04:35 pm »

Quote from: Big Red Machine on 10 Jan 2015, 03:13 pm

I have tried quite a few things on my own to try and find the origin of a slight flutter, flutter, flutter coming from the tweeters. At this point it is either the amps or the preamp. It is not audible from my chair but the fact that it is there is making me angry.

If I disconnect inputs to the preamp the buzz is still there.

If I turn off the music server the buzz is still there with inputs connected.

If I add a cheater plug to the amps the buzz is way worse - sounds like a grounding issue.

For background the amps are balanced inputs only. The preamp has only psuedo balanced connections and the preamp itself is NOT grounded to the AC. It only has hot and neutral inputs connected off the IEC. So the balanced connectors have the shield and return tied together at each connector. Not sure this is relevant but mentioning it.

I am using balanced cables between the pre and amps right now. I don't recall that SE cables were less noisy with an adapter at the amp end. If it were the case I'd be there in the set-up.

If I move the amps to a different outlet on the same circuit the noise is the same.

If I move the entire front end power strip to a separate circuit, the noise is the same.

This tells me that the amps or preamp are causing the noise.

Any suggestions?

Big Red, I think this is a mistake to do. I would sever the ground and signal wire connection (at both ends) of your XLR interconnect. The amp(s) are grounded, so the shield of the XLR is grounded.......Now you have signal return (pin 3) and shield (pin 1) making a loop. IMO.

And really the proper term for pin 1 is "shield". It gathers all the nasty RF and other hash and gets it away, but you have mixed it in with the signal.........

Wayner

Big Red Machine · « **Reply #5 on:** 10 Jan 2015, 05:18 pm »

Quote from: Davey on 10 Jan 2015, 04:18 pm

I'm not sure how you made the connection from "flutter, flutter, flutter" to a 60Hz issue, but the obvious thing to try (which you didn't mention) is to disconnect the preamp from the amps and see if the problem remains. That might tell you something.....maybe not.

I'm also unclear if this is a "power conditioning" issue or not. Maybe the power conditioning is causing the problem?
Power "conditioning" is such a nebulous topic.

Dave,

Gotta have a load on the amps when you turn them on, correct? Otherwise you'll get a god-awful loud hum.

If I leave the pre OFF, the amp ON, I get the same noise.

Big Red Machine · « **Reply #6 on:** 10 Jan 2015, 05:20 pm »

Quote from: Wayner on 10 Jan 2015, 04:35 pm

Big Red, I think this is a mistake to do. I would sever the ground and signal wire connection (at both ends) of your XLR interconnect. The amp(s) are grounded, so the shield of the XLR is grounded.......Now you have signal return (pin 3) and shield (pin 1) making a loop. IMO.

And really the proper term for pin 1 is "shield". It gathers all the nasty RF and other hash and gets it away, but you have mixed it in with the signal.........

Wayner

The XLR to RCA adapters always tie return and shield together. Should I take one apart and disconnect the shield leg and try that? Otherwise I do not have an option but to clip a wire or try and desolder the shield connection inside the preamp.

What do you think?

Davey · « **Reply #7 on:** 10 Jan 2015, 05:42 pm »

Quote from: Big Red Machine on 10 Jan 2015, 05:18 pm

Gotta have a load on the amps when you turn them on, correct? Otherwise you'll get a god-awful loud hum.

If I leave the pre OFF, the amp ON, I get the same noise.

"Load" meaning speakers? I hope not. If you do, they're some pretty poor amplifiers.

If you mean the preamp "load," then disconnecting it will have no ill effects. But, (and I guess this is what you're referring to) you need to secure power from the amplifiers and let any residual charge in the reservoir capacitors dwindle before disconnecting your preamp interconnects. Then you can re-power your amplifiers with no inputs connected and evaluate.

The problem is most likely with the interface, and just turning the preamp off does not necessarily isolate the situation.

Dave.

Wayner · « **Reply #8 on:** 10 Jan 2015, 05:59 pm »

Do your amps have RCA jacks as well? If so, I would maybe forget the XLR route, because its not a clean connection (XLR to XLR), and just do some RCAs for the interconnects. If your preamp had XLR connectors, that would be a different story. I would not start cutting wires inside your preamp or amp.

I mean your setup works now except for some minor "bleed-thru" and I don't think you will get rid of that until you change the way you are sending signal to the amp.

What do you think?

*Scotty* · « **Reply #9 on:** 10 Jan 2015, 06:14 pm »

It should be noted that a large number of amplifiers will not tolerate be operated without a load present at the inputs of the amplifier. A no load condition at the input is an open door to RF and the amplifier can go into oscillation and DIE. I would never operate a power amplifier without a load present at the inputs for this reason. Shorting plugs should always be used in the inputs in the absence a conventional load such as a preamp.
Scotty

Davey · « **Reply #10 on:** 10 Jan 2015, 06:23 pm »

The preamp is not a "load" per-se, but a "source." You certainly can analyze it in the opposite direction (and that's valid) with one injecting signal into the other, and vice-versa. But darn it, let's not confuse the issue without cause.

Yes, it would be preferable to short the amplifier inputs, but any amplifier turned on without a source attached (and then experiencing problems) is either malfunctioning and/or very poorly engineered.

Dave.

Big Red Machine · « **Reply #11 on:** 10 Jan 2015, 06:30 pm »

Only XLR inpts on the amps Wayner.

Tried amps only with no connections and it was the same sound, slightly louder. Not much.

Tells me the amps are never going to be absolutely quiet.

No sense in going down the "power conditioning" trail as that's not going to fix this issue. It still sounds great, just knowing it was there bugged me. Will havta live with it for now.

jtwrace · « **Reply #12 on:** 10 Jan 2015, 06:52 pm »

Quote from: Big Red Machine on 10 Jan 2015, 06:30 pm

Only XLR inpts on the amps Wayner.

Tried amps only with no connections and it was the same sound, slightly louder. Not much.

Tells me the amps are never going to be absolutely quiet.

No sense in going down the "power conditioning" trail as that's not going to fix this issue. It still sounds great, just knowing it was there bugged me. Will havta live with it for now.

Yeah, after having a completely silent system (zero, nothing, nada, zilch at full volume with my ear to the tweeter) I could never have noise again. I never knew how much it bothered me until I had none.

*Scotty* · « **Reply #13 on:** 10 Jan 2015, 06:59 pm »

While the engineering of the amplifier can criticized, doing so after the amplifier has died is a waste time.
Assuming that the amplifier is "properly" engineered and can take this condition may come around and bite you in the ass depending on the vintage of the amplifier. No amplifier I have owned over the last 30 years could be operated without the inputs being shorted or terminated by a source or load.
Better to safe than sorry. If I had let the smoke out of the amplifier by failing to use shorting plugs my professor would have chewed my ass.
Scotty

paul79 · « **Reply #14 on:** 10 Jan 2015, 07:03 pm »

Sounds like there may be an issue with the amps. What all is on this circuit?

Davey · « **Reply #15 on:** 10 Jan 2015, 07:08 pm »

Quote from: *Scotty* on 10 Jan 2015, 06:59 pm

No amplifier I have owned over the last 30 years could be operated without the inputs being shorted or terminated by a source or load.

Wow.

Wayner · « **Reply #16 on:** 10 Jan 2015, 07:30 pm »

Quote from: Big Red Machine on 10 Jan 2015, 06:30 pm

Only XLR inpts on the amps Wayner.

Tried amps only with no connections and it was the same sound, slightly louder. Not much.

Tells me the amps are never going to be absolutely quiet.

No sense in going down the "power conditioning" trail as that's not going to fix this issue. It still sounds great, just knowing it was there bugged me. Will havta live with it for now.

OK, I got one last dumb thing....Do your amps have toroidal transformers? If so, the hum could be from DC voltage in the trannies. I'm not suppose to promote products here, so I'll promote a type of product called a DC filter used for cleaning DC out of and AC power source. DC can get into the lines via piss-poor step-down transformer rectifiers from other lesser built products in the home. They send their dirty, evil DC thru your home 120 volt wiring and with some products, can cause the toroidal transformer to hum....unless your are positive its coming out of your speakers.....

'ner

Phil A · « **Reply #17 on:** 10 Jan 2015, 07:42 pm »

Something like this might be useful to look at - http://www.avahifi.com/index.php?option=com_content&view=article&id=270:ava-humdinger&catid=41:special-functions&Itemid=256

kingdeezie · « **Reply #18 on:** 10 Jan 2015, 08:09 pm »

Quote from: Davey on 10 Jan 2015, 07:08 pm

Wow.

As far as I know, which is limited, any tube amplifier with an output transformer has to be hooked up to a load (dummy or speaker), or the transformer itself will be damaged.

I am sure some amp manufacturers can do something to the circuit to circumvent this issue, but my Manley Neo Classic 250s have to be hooked up to a load at all times, as per the manual.

I wouldn't consider them poorly designed, or not quality amplifiers, just the nature of the beast.

kingdeezie · « **Reply #19 on:** 10 Jan 2015, 08:10 pm »

BRM,

Did you try putting cheaters on the speaker servo amplifiers? Just a thought.