Hello,
I’m new here and I’m looking for some ideas to eliminate noise on my turntable input. I have not begun attacking the problem in earnest so I guess I’m doing a bit of trolling first.
My system:
Neurochrome (Tom Christensen) DG 300B valve amplifier
Bob Brines MLTL M-10 A-10 Speakers
Schiit Gungnir DAC
Rega RP3 turntable with Rega Exact cartridge
Signal Transfer Company (Douglass Self) RIAA balanced phono preamp and power supply
Furman Power PST-8 strip and AC-215A conditioner.
The Problem:
The driver board on the 300B has only one input. It’s an amp, not an amp-preamp, so when I purchased the turntable I put another pair of XLR jack in the backplane and an Elna rotary switch. When the DAC is selected everything is quiet. When I switch to phono I get mild but noticeable hum. I don’t detect it much when an LP is playing because my hearing is not-so-good. I guess it kinda blends in.
I don’t want to assume it’s a ground loop and buy a gadget. I’d like to track it down to the root. One thing about the Rega RP3. It has a power brick and L&R RCA plugs. But no ground wire. Probably because it’s DC.
Any ideas where to start attacking this will be appreciated.
Kind regards,
Luke
I’m new here and I’m looking for some ideas to eliminate noise on my turntable input. I have not begun attacking the problem in earnest so I guess I’m doing a bit of trolling first.
My system:
Neurochrome (Tom Christensen) DG 300B valve amplifier
Bob Brines MLTL M-10 A-10 Speakers
Schiit Gungnir DAC
Rega RP3 turntable with Rega Exact cartridge
Signal Transfer Company (Douglass Self) RIAA balanced phono preamp and power supply
Furman Power PST-8 strip and AC-215A conditioner.
The Problem:
The driver board on the 300B has only one input. It’s an amp, not an amp-preamp, so when I purchased the turntable I put another pair of XLR jack in the backplane and an Elna rotary switch. When the DAC is selected everything is quiet. When I switch to phono I get mild but noticeable hum. I don’t detect it much when an LP is playing because my hearing is not-so-good. I guess it kinda blends in.
I don’t want to assume it’s a ground loop and buy a gadget. I’d like to track it down to the root. One thing about the Rega RP3. It has a power brick and L&R RCA plugs. But no ground wire. Probably because it’s DC.
Any ideas where to start attacking this will be appreciated.
Kind regards,
Luke
If you unplug the Rega power brick's AC cord (keeping the RCAs plugged in) does the hum change?
Is the hum more of a buzzing, or a lower pitch 60Hz?
How about if only one RCA is piugged in, does the hum go away in both channels then?
No change.
It occurred to me. If I have the noise when the turntable is unplugged that points to the phono pre-amp.
Possibly, if even just one channel being connected still has noise.
Is that a new RIAA unit, or older? Is there noise with the amplifier inputs shorted?
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I'm pretty sure it's a current design from Douglass Self. The circuit schematics show 2013
If there's a change he'd make it cuz he's very well regarded and published.
If there's a change he'd make it cuz he's very well regarded and published.
You have to short the preamp inputs for this.
The strange item for me is the Rega. Not having a ground wire is not a good sign. The tonearm tube has to be grounded and if a separate ground wire is missing, the ground is probably connected internally to one of the channel grounds. Not ideal.
Or it can indeed be a ground loop. Easy to investigate by lifting the preamp ground connection.
Ya not having a table ground wire raised some red flags.
I'll try what Everybody says NOT to do and lift the Mains ground wire.
I'll try what Everybody says NOT to do and lift the Mains ground wire.
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