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Hum in speakers

hbird20

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Apr 7, 2022
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This is like a shot in the dark. Alright first of all I have a Music Hall MMF 5.1 Turntable with a Clearaudio Maestro cartridge. Next is a Rotel RC-1580 control amp. Then the Jolida JD9 tube phono stage. All going into the Creek Audio Evolution 50 power amp. Oh I forgot the APC G5 filter/surge protector which was recently added a week ago. All the components are plugged into it as they should be. Mind you when I turn the gain up half way or less with no music playing I get the hum. I'm ashamed of myself for not being able to trouble shoot this down. I know all about stereo gear, what's good and what's not, but that is the extent of it. I know this will be a process of elimination but don't know where to start. And what needs to be grounded to what? The turntable to the control amp? One of the pairs of input cables has a ground wire? Never have seen that. Where is that supposed to be grounded to? Any help would be great.
 

DVDdoug

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I assume it's not there when you unplug the turntable from the preamp?

The turntable manual says:
Attach the small ground wire to the thumbscrew connection. Connect the other end of the interconnect cable to the MM (moving magnet) phono input on your receiver or pre-amplifier in the same fashion.
Your preamp probably doesn't have a ground thumbscrew, but try touching it to the ground on one of the RCA connectors, or maybe try touching it to an "available" screw holding the preamp chassis together, if there is one. If that works you can rig-up some kind of semi-permanent attachment.

It doesn't say what that ground is... I'm guessing chassis ground which is usually also power-earth ground so I'm not sure if it's really doing anything. It could be a shield for the tonearm which might not otherwise be grounded, and in that case it will help if that's where the hum is coming from.

But it's probably not that simple... Phono preamps are high-gain so any hum gets amplified.

Is the turntable near, or on top of, anything with a transformer? There's a coil in the phono cartridge and if electromagnetic hum gets-into the cartridge, you're doomed! ;) Unless you move the turntable.

Mind you when I turn the gain up half way or less with no music playing I get the hum.
How loud is the music at that volume/gain setting? You're always going to get some hum & hiss and if you turn it up enough you're probably going to hear it.

...I don't miss records! Digital is so much simpler and better! And cheaper! :p
 

chad2

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So rule of thumb is always ground closest to the source. For example preamp to amp, ground to preamp. Also never chain everything on the same ground so NEVER ground the source to preamp to amp. You could also open your amp shell and make sure that your amp has a good ground connection, check power cord terminal surface is bare metal, circuit card grounding post has bare metal to the chassis. You can usually identify the grounding post for the circuit card because it will be metal as the other ones are plastic USUALLY. While you are in there you can also check all connections to make sure they are all seated properly and check for corrosion on the connector pins. This is only a start.
 
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hbird20

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Ok the turntable is on top of all the components sitting on a 1/4 in. piece of glass. below that is the control amp. Then the phono stage which sits on top of the Rotel CD player all separated by 8 or so inches. Each component sits on a piece of glass as I said. The turntable has a grounding thumb turn screw, so does the control amp as does the phono stage. I don't know maybe the tubes in the phono stage are causing the hum. I know that any amp is going to produce a hiss or hum I just never noticed it before until the other day. I have decent 12AX7 Gold Lion custom tubes @ 50.00 bucks each. Maybe I should try running the turntable directly into the control amp phono input and bypass the outboard phono stage. Should I ground the turntable to the control amp thumb screw which is closest to the turntable? I'll check all the cables to make sure they all tight. Why would the outboard phono stage have a grounding terminal? By the way I have decent cables I think. Not the crap that usually comes with the components. I will try and get this ironed out somehow. Thank you both for your time and info. I will be back either way!
 
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