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.
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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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.
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.
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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.
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.
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.
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
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.
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.
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 6L6’s 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 doesn’t work, you can unbolt the boards, desolder the ground jumper, and wire the board to the chassis ground.
All three methods have been successful.
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 doesn’t work, you can unbolt the boards, desolder the ground jumper, and wire the board to the chassis ground.
All three methods have been successful.
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.
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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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