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The Phonoclone and VSPS PCB Help Desk
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Old 11th June 2018, 01:22 AM   #4031
rjm is offline rjm  Japan
Richard Murdey
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Quote:
Originally Posted by S.G.D View Post
I don't think there is a pattern in terms how often the noise happens. I have had it happen as frequent as every 1~2 minutes to as long as every ~20 minutes.
As others have said, that's all suspiciously like wifi/cell tower/RF interference. Given your efforts, we can conclude it's not local to your residence at least, and that it nothing to do with shielding or RFI-proofing the phonoclone circuit itself. It gets into the signal by some other vector, somewhere between the cartridge and the phonoclone input IC1. I suspect coupling between the IN- and earth.

Quote:
My TT is Rega P3 with RB300. Tonearm cable has been replaced with Cardas shielded tonearm cable to RCA sockets, then I use VDH Integration interconnect cable to connect to PC4. I have tested the continuity and tonearm is grounded.
While you are being really helpful to supply all the needed info and I appreciate that there are several times I feel you could be more precise in your description. To say the tonearm is grounded is imprecise since I don't know with respect to what, or under what test circumstances, or how exactly that connection is routed.

I do wonder a little bit if the shielded tonearm and the modifications there could be causing trouble somehow.

With the turntable/arm/outputs disconnected from the rest of the system, the tonearm should be isolated from the RCA grounds of the TT. The tonearm connects to the ground lug of the phonoclone by external wire.

Quote:
Tonearm is currently grounded to the PSU chassis which is also directly connected to earth from AC socket. Tested COM on DBRB and no continuity between COM and [PSU] chassis.
COM should be electrically isolated from the PSU chassis, in terms of the phonoclone build. When connected to the system however, the connection would be made regardless through the shared earth buss bar of the power strip. PSU chassis goes to earth, the amplifier chassis goes to earth, and the amplifier circuit common goes to earth, and the amplifier circuit common is connected to the phonoclone circuit common through OUT-. All common 0V circuit reference potentials will connect to each other, and the idea is there is just one connection to earth made in the audio system signal chain.

Quote:
GND point on PC4 boards used to be where the tonearm was grounded, then I switched to the current configuration because I thought the noise was due to some kinds of interference.

Motor on P3 is not connected to RB300 and not grounded. Some people have had humming issues with P3 when the cartridge is moving closer to the spindle but I have never experience that. Also because I get the noise regardless the TT is ON or OFF so I never bother to troubleshoot that direction.
You should get more interference with the tonearm connected to earth of the PSU chassis than the phonoclone chassis/GND. The tonearm needs to be kept at the same potential as IN- to avoid interference, and the PSU earth is further away from that in terms of noise than phonoclone GND which is connected to IN- directly within the Phonoclone boards.

Let me ask one more thing: how is the noise apart from the 1s bursts, is it otherwise quiet and hum free? Does turning on the Rega motor made a noise in the speakers for example? Does disconnecting the tonearm ground wire made a big increase in noise?
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Last edited by rjm; 11th June 2018 at 01:26 AM.
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Old 11th June 2018, 06:05 AM   #4032
rjm is offline rjm  Japan
Richard Murdey
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ps your emerald boards are in the mail, no charge.
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