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-   -   Replacing turntable RCA cable question (https://www.diyaudio.com/forums/analogue-source/284925-replacing-turntable-rca-cable-question.html)

ChrisM91 7th January 2016 12:11 PM

Replacing turntable RCA cable question
 
I have a Kenwood KD-3070 that I am replacing the RCA cable on. The turntable has a two prong 120V power cable.

The turntable connects to a standalone DIY phono preamp. The RCA jacks on this DIY phono preamp are isolated from the chassis. All the sleeves of the RCA jacks run back to the signal ground which in turn gets connected back to the chassis through a grounding lug.

Now when I replace the RCA cable on my turntable do I connect the shield at both ends of the cable? i.e. do I connect the sleeve at the turntable as well as to the sleeve connection of the male RCA jacks that hook up to my phono stage?

I would think yes. I am not certain if I will still need the turntable ground wire but I will include it just in case.

AndrewT 7th January 2016 12:26 PM

What comes out of the TT?

The output needs two channels and each channel must have both a signal flow and a signal return.

That equates to 4 signal wires, which is also what is on the back of the cartridge.

An RCA plug and socket uses the tip as the signal flow connection and uses the sleeve/barrel as the signal return connection. Those TWO signals must start at the source (the pins on the back of the cartridge) and go to the receiver (the TWO inputs on the mono phono pre-amp. There are no grounds. Both wires are signals.
These two signal wires are repeated for the other channel.

The "other" metalwork of the TT can have a separate earth connection. This requires a separate wire connection to a separate earth terminal on the receiver.

Do not mix up earthing with signal.

ChrisM91 7th January 2016 12:34 PM

The TT has an RCA cable that comes from it. The cable is made up of a shielded wire for the right channel and a shielded wire for the left channel, and also a ground wire currently.

I understand what you are saying. The RCA sleeve connections are grounded at the phono preamp. I will have to see if I need the ground wire running from the TT to the phono preamp.

AndrewT 7th January 2016 01:06 PM

The separate ground/earth wire must be taken separately to the receiver.
Do not mix it with the signal wires.

The screen around the signal flow wire is not a ground. It is the signal return wire.

russc 7th January 2016 06:37 PM

Andrew, thanks for clarifying that. There are a lot of people confused about the function and correct implementation of the separate ground wire on turntables. Therefore a turntable with wooden plinth and non-conductive tone-arm would have no need of this separate ground wire. I asked a similar question a few threads back as I used a balanced type cable for each channel (I had some spare, it is nice cable). At first look, the scheme of grounding the screen is not dissimilar to grounding a tone-arm tube for screening. In practice I have hum. I will ditch the separate ground wire and a) connect screen at RCA plug into phono pre-amp or b) use 1 core only plus screen for signal and return.

AndrewT 8th January 2016 08:24 AM

If there is mains into the TT and there are metal parts, then I think you should retain the separate Earth wire.

russc 8th January 2016 08:02 PM

I would say if a safety ground is required then it should go straight to the mains plug. My DIY turntable is low voltage using an "outboard" stepper motor. Once I have sorted the big hum problem, if I have any other noise issues I may experiment with earth wire to stepper motor and the metal box containing processor & driver. However, there are no sources of mains hum from the turntable, only what is picked up from surrounding equipment/wiring. It's tricky experimenting on actual turntable as it has DIY WTL tone arm (silicon fluid - you wouldn't want to spill). I will breadboard an old cartridge/cabling and find the quietest arrangement first then implement on actual turntable.


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