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Pass Labs Pearl Hum advise/help
Pass Labs Pearl Hum advise/help
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Old 27th May 2020, 01:59 AM   #1
creed2 is offline creed2  United States
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Default Pass Labs Pearl Hum advise/help

Pearl hum, I bought already built. Any advise where to try to reduce hum. First I thought it was Grado ref sonota 1, there known to hum so tried MI Soundsmith did same thing. Strange thing it changes when you bring tonearm towards spindle at beginning of record it's louder in right speaker. Go towards spindle hum fades louder to left speaker. Sounds like a non shielded cartridge having problems with motor but both cartridges do it. They have never done that on other preamps. It increases with volume. It's not bad at low volumes. Looks like ground mounted on Back for turntable ground is maybe not grounded in the best place will try that first. Are there some common places to look for hum, thanks for any direction.
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Old 27th May 2020, 05:17 PM   #2
Russellc is offline Russellc  United States
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Pass Labs Pearl Hum advise/help
How close is Pearl 2 located to other components? Mine hummed if power supply too close, or if another component, pre or power amp too close.

Russellc
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Old 27th May 2020, 07:52 PM   #3
McQuaide is offline McQuaide  United States
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Can you post a photo of the Pearl 2 internals? Checking continuity from TT chassis to Pearl 2 ground is a good idea.
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Old 27th May 2020, 08:39 PM   #4
creed2 is offline creed2  United States
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Sure it's a pearl 1 though. where do most people attach ground wire with that is connected to or mounted on back of case/box.
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Old 28th May 2020, 06:40 PM   #5
Russellc is offline Russellc  United States
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Pass Labs Pearl Hum advise/help
Quote:
Originally Posted by creed2 View Post
Sure it's a pearl 1 though. where do most people attach ground wire with that is connected to or mounted on back of case/box.
Dont have a Pearl 1, but a little unclear...are you saying there is a ground wire coming off the back of your Pearl? If so I guess original owners turntable didnt have a ground wire with interconnect so it goes to turntable?

If this is the case and you have a ground wire on your turntables interconnect, attach that ground to the ground that wire is attached to on your Pearl I guess. Normally there is a ground post on back of phono preamp. If no post on your Pearl, dont see why you cant add one. Sorry, just a little unclear on what you have there. Pics please.

Pics would help, lot of Pearl 1 owners here.

Russellc
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Last edited by Russellc; 28th May 2020 at 06:43 PM.
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Old 28th May 2020, 06:56 PM   #6
creed2 is offline creed2  United States
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Here are some pictures. Yes the ground that turntable RCA ground wire hooks to is what I question if it is good enough. You can see it mounted to the bottom of case with a little piece of electrical tape, this is how it came to me, thanks
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Old 28th May 2020, 07:16 PM   #7
jamayfie is offline jamayfie  United States
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Pass Labs Pearl Hum advise/help
The ground wire is soldered to the chassis bottom with the electrical tape just holding the wire in place. However, it is not star grounded. You could easily change to a star ground scheme by connecting all the RCA grounds to a single point, like the ground post or the chassis point. If you have leads with alligator clips, you could try this without soldering.

Grounding is maddeningly inconsistent for one user versus another, but the behavior you describe suggests a problem with the tonearm wiring, not the Pearl. The phono stage has no way of knowing whether the tonearm is close or far to the spindle. If you're getting a change in the left/right balance as the tonearm moves, it's probably the cartridge (which you tested) or the tonearm. I wonder if either the tonearm ground is detached, not making good contact, or the tonearm wiring is otherwise compromised.

Last edited by jamayfie; 28th May 2020 at 07:18 PM. Reason: fixed a typo
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Old 28th May 2020, 07:22 PM   #8
Russellc is offline Russellc  United States
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Pass Labs Pearl Hum advise/help
I suppose this thin wire goes to a post on back of chassis?
Or is this just grounding board to chassis? What does turntable interconnects ground wire attach to?
Russellc
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Last edited by Russellc; 28th May 2020 at 07:25 PM.
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Old 28th May 2020, 07:56 PM   #9
creed2 is offline creed2  United States
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When you say star ground do you mean disconnect all the white wires connected to back of RCA jacks for input and output and solder them together and then ground them to the chassis. Yes that thin wire is what is connected to jack on back of chassis that is in turn my tonearm ground connection.
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Old 28th May 2020, 08:19 PM   #10
jamayfie is offline jamayfie  United States
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Pass Labs Pearl Hum advise/help
Leave all the current grounds in place, but add additional wires connecting all the grounds to a single point. Easiest is to run a wire connecting each RCA ground tab to the ground post (adding four new connections).
 

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