Completely eliminating hum -- is it possible?

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edgarryan
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Completely eliminating hum -- is it possible?

Post by edgarryan » 21 Jun 2019 20:58

I know this is like beating a dead horse, but is it possible to totally eliminate hum? I've tried lots of configurations for grounding, but I can't get rid of it. At normal listening levels, I can barely hear it, but when I crank the volume up, it is really evident. I don't know if it's the power supply, the phono preamp, the switch box, or the cables, but there it is.

bhuston
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Re: Completely eliminating hum -- is it possible?

Post by bhuston » 21 Jun 2019 21:13

1. Do you have it when listening to other inputs (CD, tuner, etc)? 2. What do you mean by switch box? 3. Try reversing the power plug on the amp. 4. Is the preamp internal or external and if external grounded to the amplifier ground?. Also, if external, you should run the phono ground all the way to the amp ground, not just to the preamp. I get hum and noise if I don't do that.
There are some carts that do hum, I've heard them on different systems, with these it's just the nature of the beast. Somewhere in your system you do have a ground loop issue. Try eliminating one at a time to isolate it. First, start by disconnecting every input, select the aux or CD input and turn on the amp loud. If you hear hum then it's your amp, reverse the plug see if that helps. If not, you found your source. If no hum select the phono. If it hums there then it's in that loop somewhere. Good luck.

circularvibes
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Re: Completely eliminating hum -- is it possible?

Post by circularvibes » 21 Jun 2019 22:36

I do not know which equipment you are using, but I have had times when moving components around helped. Sometimes a transformer or power supply in one component will be in a place to affect another piece of gear.

lenjack
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Re: Completely eliminating hum -- is it possible?

Post by lenjack » 22 Jun 2019 03:49

List all your equipment. Otherwise, we have nothing to go on.

edgarryan
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Re: Completely eliminating hum -- is it possible?

Post by edgarryan » 22 Jun 2019 10:19

I was thinking of grounding all the components in the system. I do not hear hum when I listen to other sources. Almost all my components are DIY: a switch that lets me listen to different tonearms, a tube phono preamp made by a friend, a China-made hybrid tube preamp/DAC, and a Dared MP5 hybrid tube amp.

rewfew
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Re: Completely eliminating hum -- is it possible?

Post by rewfew » 22 Jun 2019 14:35

You might try an isolation transformer as outlined from a newsletter I saved.


Technique for Reducing Turntable Hum

I have been experimenting with different turntables and have discovered a simple way that greatly reduces 60 Hz hum. By using a small isolation transformer to drive both the turntable and the phono preamp, (preferably a Transcendent Sound Preamp), power line hum can be virtually eliminated. I used a 50 VA Triad N-68X and installed it in a small plastic box, along with a duplex outlet. Connect the internal shield to the power line ground. The transformer costs less than $20. That's all there is to it. If you don't want to build one, Hammond makes a 100VA unit, model 171A, that sells for around $85. There are others available as this is a common device. Don't drive anything else with the transformer. Don't bother with a so-called high-end isolation transformer. Save your money.

Alec124c41
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Re: Completely eliminating hum -- is it possible?

Post by Alec124c41 » 22 Jun 2019 15:27

Be careful with placement of components, and with the routing of cables. Having a cable too close to a power cord or to a transformer can introduce noise.

Cheers,
Alec

NewOldVinyl
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Re: Completely eliminating hum -- is it possible?

Post by NewOldVinyl » 22 Jun 2019 17:48

In my experience, no it is not possible to COMPLETELY eliminate hum or other noise on a phono input when you crank the gain to max and listen with no source playing. You’re dealing with a few millivolts of signal and amplifying it by a factor of nearly 1000x just to get it to Line Level. More if it’s a MC input.

Try this: Disconnect the TT from the preamp. Now crank the volume. Chances are you will hear some hiss and/or hum. It’s the nature of the beast.

All the previous suggestions are good and valid and might help. But in my experience you cannot COMPLETELY eliminate hum and noise on phono inputs.

Coffee Phil
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Re: Completely eliminating hum -- is it possible?

Post by Coffee Phil » 22 Jun 2019 18:07

Many years ago a candy bar which I like was pulled of the market. The reason was that they exceeded the limit for fly wings and rodent excrement. I was stunned! What limit? I don't want ANY mouse crap or fly parts in my candy bar! I have come to realize that no mouse crap where peanuts are stored is not possible. A safe spec. has to be established and the product has to be tested to that. Hum is similar. If you get it below the random noise, that is all that is required.

Since you are only bothered with hum with the record player I'm guessing that the interconnect between the player and phono stage is the issue. Here is my "little essay" on turntable grounding and connecting:

There are two methods of “grounding” turntables of which I am familiar.
The first and most common is to keep the audio cables for each channel isolated from the arm and turntable chassis. The arm is electrically connected to the turntable chassis and a “ground” wire is connected from the turntable chassis to the phono stage chassis.
The alternate method is to connect the signal return (cable shield) of one channel, usually left, to the arm and turntable chassis. The signal return then serves as the “ground” wire connecting the turntable chassis to the phono stage chassis.
Either method above works, but to do both is inviting a ground loop. Read hum.

I will add to the above that running an "earth ground" to the turntable or using a three wire power cord is also inviting a ground loop.

Phil
edgarryan wrote:
21 Jun 2019 20:58
I know this is like beating a dead horse, but is it possible to totally eliminate hum? I've tried lots of configurations for grounding, but I can't get rid of it. At normal listening levels, I can barely hear it, but when I crank the volume up, it is really evident. I don't know if it's the power supply, the phono preamp, the switch box, or the cables, but there it is.

lenjack
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Re: Completely eliminating hum -- is it possible?

Post by lenjack » 22 Jun 2019 19:44

NewOldVinyl wrote:
22 Jun 2019 17:48
In my experience, no it is not possible to COMPLETELY eliminate hum or other noise on a phono input when you crank the gain to max and listen with no source playing. You’re dealing with a few millivolts of signal and amplifying it by a factor of nearly 1000x just to get it to Line Level. More if it’s a MC input.

Try this: Disconnect the TT from the preamp. Now crank the volume. Chances are you will hear some hiss and/or hum. It’s the nature of the beast.

All the previous suggestions are good and valid and might help. But in my experience you cannot COMPLETELY eliminate hum and noise on phono inputs.
That's not hum. That's low level system noise. You could measure it as signal to noise ratio.

lenjack
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Re: Completely eliminating hum -- is it possible?

Post by lenjack » 22 Jun 2019 19:47

By the way, if your table has a 2 prong unpolarized power plug, try reversing it. Probably won't help, but easy enough to try.

NewOldVinyl
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Re: Completely eliminating hum -- is it possible?

Post by NewOldVinyl » 22 Jun 2019 20:25

lenjack wrote:
22 Jun 2019 19:44
NewOldVinyl wrote:
22 Jun 2019 17:48
In my experience, no it is not possible to COMPLETELY eliminate hum or other noise on a phono input when you crank the gain to max and listen with no source playing.

All the previous suggestions are good and valid and might help. But in my experience you cannot COMPLETELY eliminate hum and noise on phono inputs.
That's not hum. That's low level system noise. You could measure it as signal to noise ratio.
Allow me to rephrase with emphasis.

In my experience, no it is not possible to COMPLETELY eliminate hum and other noise on a phono input when you crank the gain to max and listen with no source playing.

I hope that’s clearer. ;)

I’m very aware of the distinction between hum and noise. :) To the best of my recollection in 55+ years of owning many different turntables and cartridges I’ve never completely eliminated either hum or noise.
Last edited by NewOldVinyl on 22 Jun 2019 20:41, edited 4 times in total.

lenjack
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Re: Completely eliminating hum -- is it possible?

Post by lenjack » 22 Jun 2019 20:35

OK, got it. I was concentrating too much on the hum aspect. My bad. #-o

NewOldVinyl
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Re: Completely eliminating hum -- is it possible?

Post by NewOldVinyl » 22 Jun 2019 20:43

lenjack wrote:
22 Jun 2019 20:35
OK, got it. I was concentrating too much on the hum aspect. My bad. #-o
If there’s a magic bullet that completely eliminates phono hum, I’ve yet to find it. Not saying it isn’t possible to do, just that I’ve never been successful. And believe me, I’m as OCD about this stuff as anyone. :)

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Re: Completely eliminating hum -- is it possible?

Post by Legrace » 22 Jun 2019 21:58

Hum has many fathers. My Dual 721 hummed like crazy when first connected. Replaced the stock RCA's with Furutech RCA's and cleaned the headshell contacts with 99% IPA. Totally eliminated that cause.

But as I said hum has many fathers. Got into tubes and suddenly hum is back like the prodigal son. :evil: Tried all the connect this way and that recommendations, no luck. Finally I read how a mix of 3 prong and 2 prong connectors is a common cause. I picked up some 3 prong to 2 prong adapters for a couple bucks each and put them on my amps and it totally killed the hum, thankfully.

So answer to your question is yes it is possible.

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