Here's another data point. When I have the Pearl 3 plugged into Korg B1 and nothing plugged into Pearl 3, I can increase the loudness of the hum by waiving my hand over the open RIAA. If I touch the chassis of the Pearl 3, the Korg, or the Aleph Jzm, the hum gets a little quieter.
Maybe I'm emitting EMI?
Maybe I'm emitting EMI?
If I touch the chassis with my finger hum goes away and what's left is just the white noise, which is tolerable. If I connect the two chassis together with a conductor, zero change. If I get my finger anywhere near (withing a couple inches) C10 and C11 on either board, the hum drastically increases.
I was very careful to sand off ever bolt point on the chassis so the entire chassis is connected conductivity, so I don't think that's it.
So odd. I'm thinking of resoldering the output RCAs to board with heavier gage wire. I used thin Mogami thinking signal wire can be thin.
I was very careful to sand off ever bolt point on the chassis so the entire chassis is connected conductivity, so I don't think that's it.
So odd. I'm thinking of resoldering the output RCAs to board with heavier gage wire. I used thin Mogami thinking signal wire can be thin.
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As 6L6 says, shielding the Pearl 3 well from EMI matters. It picks up the 60Hz buzz from my recessed ceiling lights quite admirably. Grinding off the anodizing of the top and bottom chassis covers and side rails and scoring the bare aluminum with a file to ensure continuity might seem a drag but it does reduce the buzz.
I used a dremel tool with flap sander. Every place a bolt goes, I sanded off all the anodizing or paint. I think it's something else, but I'm willing to go back and scratch everything up further. All continuity checks were good using DMM. If I touch any part of the chassis, or ground, the hum stops. Points to a ground problem. Get my finger, or a wire near C10 and C11, hum gets massively loudee.
If no one has other ideas, I'll disassemble and scratch it all up with a sharp edge.
Could installing the RIAA LEDs backwards caused any damage? I wouldn't think so, but I gotta ask cause that was an error I made.
If no one has other ideas, I'll disassemble and scratch it all up with a sharp edge.
Could installing the RIAA LEDs backwards caused any damage? I wouldn't think so, but I gotta ask cause that was an error I made.
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Did you connect the turntable ground to the Pearl 3 chassis ground?
Yes, when the turntable was hooked up via RCA in, so was the ground line to the post on RIAA. The hum remains even when turntable is disconnected. I hooked up a CD player in place of Pearl 3 to rule out other components. Dead silent all the way up to max volume on the Korg B1 into Aleph Jzm. It's clearly coming from Pearl 3. Only question is what's the cause.
Do I need to ground the standoffs? It looked like they just go to fiberglass. Guess that can't hurt.
I thought perhaps the Mogami W2381 is too thin for proper shielding? I doubt it, but figured it's worth asking the hive of minds. I'll make note that for the input wires, if I just tap the wire with my finger, I hear the "thump" of my finger hitting the wire in the speakers, which is crazy sensitive.
I turned off all lights in house to also rule out LED dimmer buzz. I'm in the process of scratching the chassis up more, although I'm not very hopeful that's going to make a difference, but perhaps I missed a spot with the dremel.
One chassis down, one to go.
Do I need to ground the standoffs? It looked like they just go to fiberglass. Guess that can't hurt.
I thought perhaps the Mogami W2381 is too thin for proper shielding? I doubt it, but figured it's worth asking the hive of minds. I'll make note that for the input wires, if I just tap the wire with my finger, I hear the "thump" of my finger hitting the wire in the speakers, which is crazy sensitive.
I turned off all lights in house to also rule out LED dimmer buzz. I'm in the process of scratching the chassis up more, although I'm not very hopeful that's going to make a difference, but perhaps I missed a spot with the dremel.
One chassis down, one to go.
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from the cheap seats...
I'd spend a bit more time trying to figure out the source of the interference. Perfecting the enclosure shield might be unproductive if something internal (the circuit itself) is the cause.
also...
it is stated that the ground lift bridge in the power supply is intended to break ground loops and provide a path to safety earth. yet the grounding scheme seems to wire across the "break". I haven't understood how that works.
Is that defeat of the bridge a factor in this noise issue?
I'd spend a bit more time trying to figure out the source of the interference. Perfecting the enclosure shield might be unproductive if something internal (the circuit itself) is the cause.
also...
it is stated that the ground lift bridge in the power supply is intended to break ground loops and provide a path to safety earth. yet the grounding scheme seems to wire across the "break". I haven't understood how that works.
Is that defeat of the bridge a factor in this noise issue?
A question I have is why are we concerned about the RCA panel mount not touching the chassis, only to basically connect them to the chassis through the chassis via the ground on the board. With the ground post disconnected from the "ground to chassis" for both boards, there's no continuity from ground post on RCA to chassis. The moment I hook up the ground post to the boards, there is of course continuity between RCA grounds and the ground post. We go to the trouble of keeping the RCA panel mounts from not "shorting to ground", only to intentionally short them to ground through the PCB ground. I don't understand that. Crude drawing below describes the words above.
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Ok, well I've confirmed that my chassis grounding is not the issue. I spent 3 hours totally disassembling the chassis and scratched up every contact point to the extreme. I replaced the blown LED's and wired them up properly.
I hooked it back up with no input into the Pearl 3, but output connected to Korg B1, into Aleph Jzm, and I get the same hum and white noise. Then, I put the tops on both chassis (I had the chassis tops off previously for troubleshooting). With the top plates securely on the PSU chassis and RIAA chassis, the ground hum is gone! The white noise still is present, so I'm chalking that up to EMI from external sources I can't control. I can live with the white noise at max volume. I suspect it's likely the RIAA is amplifying the radio and other EMI bombarding us at all times. Call it the "background radiation", but I don't think I can get rid of that without perhaps wrapping both chassis entirely in aluminum foil. I'm going to call this a win, even though I probably will still have issues with the cheap Pioneer PL-600 turntable once a new belt arrives. I did order a new belt, but it won't be here until I'm long gone and back in WA state, so it'll be up to "me ma" to get it playing records again. In the mean time I'll look into a good used higher end turntable for her. Open to suggestions there now that I have the Pearl 3 likely functioning.
Why the top plate has to be on to eliminate ground hum is beyond me, but it did the trick. I probably should have tried that 3 hours ago before embarking on the "Scratch Campaign". I suspect that would have eliminated it then, but we'll never know. Is 60hz on AC lines actively creating EMI at that frequency? That's my only explanation why putting the top plate on would eliminate the hum and lines up with why I didn't have to touch anything, just get close to the boards to create loud ground hum. Someone who is knowledgeable with EMI can likely explain it. It's all speculation on my end.
I hooked it back up with no input into the Pearl 3, but output connected to Korg B1, into Aleph Jzm, and I get the same hum and white noise. Then, I put the tops on both chassis (I had the chassis tops off previously for troubleshooting). With the top plates securely on the PSU chassis and RIAA chassis, the ground hum is gone! The white noise still is present, so I'm chalking that up to EMI from external sources I can't control. I can live with the white noise at max volume. I suspect it's likely the RIAA is amplifying the radio and other EMI bombarding us at all times. Call it the "background radiation", but I don't think I can get rid of that without perhaps wrapping both chassis entirely in aluminum foil. I'm going to call this a win, even though I probably will still have issues with the cheap Pioneer PL-600 turntable once a new belt arrives. I did order a new belt, but it won't be here until I'm long gone and back in WA state, so it'll be up to "me ma" to get it playing records again. In the mean time I'll look into a good used higher end turntable for her. Open to suggestions there now that I have the Pearl 3 likely functioning.
Why the top plate has to be on to eliminate ground hum is beyond me, but it did the trick. I probably should have tried that 3 hours ago before embarking on the "Scratch Campaign". I suspect that would have eliminated it then, but we'll never know. Is 60hz on AC lines actively creating EMI at that frequency? That's my only explanation why putting the top plate on would eliminate the hum and lines up with why I didn't have to touch anything, just get close to the boards to create loud ground hum. Someone who is knowledgeable with EMI can likely explain it. It's all speculation on my end.
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Told you so ;-)
Well, TBH I have been there and learned the hard way looking very stupid sending my unit to a friend, so I am not clever at all on all this LOL
Glad you are sorted, that's the most important bit.
White noise with RIAA amps when cranking pot to max is something frequent due to a lot of things and the high gains, but usualy you either don't listen at max volume or if you do so you are likely to have the music covering the noise by a large factor... or really a massive problem in your gain chain. Or inded something really polluting around.
Oh, and just something important: I assumed you have loaded your RIAA amp inputs, either by plugging the TT outputs with a cartridge of course, or with dummy loads. If the inputs are just "open", it can lead to quite some oddities re noise... they need load.
Enjoy your LPs!
Claude
Well, TBH I have been there and learned the hard way looking very stupid sending my unit to a friend, so I am not clever at all on all this LOL
Glad you are sorted, that's the most important bit.
White noise with RIAA amps when cranking pot to max is something frequent due to a lot of things and the high gains, but usualy you either don't listen at max volume or if you do so you are likely to have the music covering the noise by a large factor... or really a massive problem in your gain chain. Or inded something really polluting around.
Oh, and just something important: I assumed you have loaded your RIAA amp inputs, either by plugging the TT outputs with a cartridge of course, or with dummy loads. If the inputs are just "open", it can lead to quite some oddities re noise... they need load.
Enjoy your LPs!
Claude
The inputs were open, so RF noise is the likely culprit. I suppose I could short the inputs now and see what effect that has on the white noise.
I'm happy now with the current state. I suspect if I increased R27 resistance further to lower the current, the EMI white noise would be much less. I still don't fully understand why putting the top plate on eliminated the ground hum, but it did the trick. There's got to be some EMI created by AC 60Hz floating around.
If I had a functioning turntable to hook it up to, I don't think I'd notice the white noise at all. Max volume is something I would likely never actually go to. It was just a means to get to the extreme and troubleshoot the noise source.
Thank you for your input @ClaudeG. I have lots to learn and this was a great learning experience. For folks following along, the "scratch" method using the edge of a small flat head screwdriver worked great. I'd say it was even easier than using the Dremel tool sanding flapper "bit" for grounding and certainly was much easier clean up. Sanding with the Dremel made a lot of paint, anodizing, and aluminum dust.
I'm happy now with the current state. I suspect if I increased R27 resistance further to lower the current, the EMI white noise would be much less. I still don't fully understand why putting the top plate on eliminated the ground hum, but it did the trick. There's got to be some EMI created by AC 60Hz floating around.
If I had a functioning turntable to hook it up to, I don't think I'd notice the white noise at all. Max volume is something I would likely never actually go to. It was just a means to get to the extreme and troubleshoot the noise source.
Thank you for your input @ClaudeG. I have lots to learn and this was a great learning experience. For folks following along, the "scratch" method using the edge of a small flat head screwdriver worked great. I'd say it was even easier than using the Dremel tool sanding flapper "bit" for grounding and certainly was much easier clean up. Sanding with the Dremel made a lot of paint, anodizing, and aluminum dust.
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You are welcome.
Top lid means no somplete Farraday cage... RIAA = tons of gain with high sensitivity to small signals "flying" around etc.
You could just load the inputs to make sure your white noise is partialy gone or at least acceptable re level, BUT TBH I wouldn't change anything before plugging a real TT to assess really the music / noise ratio... it sounds all promising now TBH, no need to change resistors or else before assessing that IMHO.
Now you need a functioning TT 🙂
Top lid means no somplete Farraday cage... RIAA = tons of gain with high sensitivity to small signals "flying" around etc.
You could just load the inputs to make sure your white noise is partialy gone or at least acceptable re level, BUT TBH I wouldn't change anything before plugging a real TT to assess really the music / noise ratio... it sounds all promising now TBH, no need to change resistors or else before assessing that IMHO.
Now you need a functioning TT 🙂
So I decided to put the P3 on hold last night so to attack it with a fresh mind. Relocated the 2 chassis and vois la! Pretty dang quiet! 
thanks to all who made this project available and to those whose kind support helps us 
build these wonderful kits!
thanks to all who made this project available and to those whose kind support helps us build these wonderful kits!
There is 1 remaining issue, my RIAA unit's LED's worked briefly and then blew. I metered the voltage and the LED's are getting 20 volts?
It's been said multiple times but bears repeating, we are dealing with signals in the millivolt category. Any path for noise to enter, through signal cables, airbourne, and thru the power line is critical to be properly shielded, units to be located away from strong EMI fields, and grounded!