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Pass Labs Pearl Hum advise/help
Pass Labs Pearl Hum advise/help
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Old 28th May 2020, 09:11 PM   #11
mhenschel is offline mhenschel  Canada
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Join Date: May 2019
I think the thin wire connects the (isolated?) ground post to the chassis.

I wonder if star grounding could be accomplished more simply and correctly by connecting each of the ground pads in the middle of each board (where the signal ground plane is connected to the power ground plane) to the ground post and confirming a good connection from the post to the chassis.
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Old 30th May 2020, 06:34 PM   #12
creed2 is offline creed2  United States
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Sorry don't know why I said disconnect, but are you saying add an additional wires to each of the white wires on the rca's, solder them together and ground all four white grounds to the chassis, I pretty much know that's what I need to do but just double checking just don't want to damage anything, I'm kind of new to this , thanks
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Old 30th May 2020, 06:57 PM   #13
mhenschel is offline mhenschel  Canada
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No.

At the centre of each Pearl board is a ground pad connection point. You can see it at the other end of the jumper from the 3300uf capacitor. That is where signal ground and power grounds connect. Those pads need to be connected to the ground post. I don't see these conductors in your photos.

Note that the grounds of the jacks connect to the signal ground on the boards via the white conductors of the twisted pair wires. Right?

Make good the connection from the ground post to the chassis and I think you have that part done as well as it could be.

Not sure about the wiring of the power supply... can't see much there. It might need remedial work too. Try the signal ground work and then take it from there.

Proviso: there are much more expert guys on diyaudio than I. Good resources.
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Old 31st May 2020, 12:38 AM   #14
jamayfie is offline jamayfie  United States
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Pass Labs Pearl Hum advise/help
The Pearl has a jumper connecting the ground planes, wired on the underside of the boards. This was the grounding scheme used in the Pearl manual. You can see a picture of what this looks like and a discussion of some grounding options in 6L6ís Pearl phono post:

Pearl (one) Build

There is a second discussion of grounding schemes here:

Pearl Grounding

I suggested you connect the RCA grounds (using the tabs on the side of the RCA jacks) to the ground post because you can test this without soldering using a set of leads with alligator clips (like these Alligator Test Leads - Multicolored (10 Pack) - PRT-12978 - SparkFun Electronics). That is a temporary method, but you see if it makes a difference. If it does, solder a wire in place of the leads.

If that doesnít work, you can unbolt the boards, desolder the ground jumper, and wire the board to the chassis ground.

All three methods have been successful.
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Old 7th June 2020, 04:11 PM   #15
creed2 is offline creed2  United States
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Haven't had time to add ground on rca's been very busy. I thought it may be table/arm combo with Grado Sonota ref 2 which I understand have hum issue, I was using on a Linn table which I heard grado and Linn sometime have hum. I pulled out an old Well Tempered table last night and still have hum so I know it is Pearl not table/arm/cartridge issue. I'm going to try to fix problem this week. Going to ground rca's first. I notice most people move power supply out board could this be an issue and need shielding or move it out board? Thanks for everyone's help. I really like this preamp it sounds better than a PS Audio GCPH with Parts Connextion mods that I had, which I was very surprised I want to keep pearl but hum has to go it is very obvious.
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Old 7th June 2020, 06:30 PM   #16
Russellc is offline Russellc  United States
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Pass Labs Pearl Hum advise/help
Quote:
Originally Posted by creed2 View Post
I notice most people move power supply out board could this be an issue and need shielding or move it out board?

Many find they get hum with power supply close by. I moved mine to floor on umbilical. Mine hummed unless moved 2-3 feet away or so.

Mine is Pearl 2 however. I keep forgetting you have Pearl 1.

Russellc
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Last edited by Russellc; 7th June 2020 at 06:32 PM.
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Old 8th June 2020, 01:37 AM   #17
mhenschel is offline mhenschel  Canada
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The principle obtains for 1 as well as 2 I think.

PS -- Post ## on page 4 was supposed to be post 33.
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Old 8th June 2020, 02:41 AM   #18
creed2 is offline creed2  United States
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Took Pearl out of main system. Connected pearl to receiver and speaker. I don't know what type of wire previous owner used to run from ground jack on back of pearl for tonearm/turntable ground but it does not conduct a signal to ground on chassis of pearl on my ohm meter. Even touching just wire with meter no signal. So I left that wire conected and ran a wire parallel to this wire. Turned on receiver and pearl still bad hum. Ran star ground off of input/output negative to chassis ground still hum. Then I noticed when I put my hand close to back of pearl close to RCA jack hum became very loud. Put my hand on chassis hum went way down. I can take my hand and make it get close and far from chassis and it sounds like a wah wah pedal. This is strange part with pearl turned off and receiver still on The pearl still hums and does wah wah pedal thing when I put my hand close to it even if pearl is turned off. Can someone tell me what is going on. I'm not a DIY guy but trying to learn any guidance would be appreciated, thanks Paul
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Old 8th June 2020, 02:44 AM   #19
creed2 is offline creed2  United States
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I did not connect pearl to receivers phono in jacks, I connected to DVD in. Just in case someone thinks I made this mistake.
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Old 8th June 2020, 03:05 AM   #20
creed2 is offline creed2  United States
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After pearl is turned off 30 or 40 seconds hum goes away with receiver still on so I was wrong about hum continuing after pearl is off.
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