Arm cable RCAs into mic pre XLRs

[Jas0_0]

Hi all,

I've decided to replace my MM cartridge with an MC and replace my noisy phono pre with a clean, high impedance ribbon mic pre and do RIAA eq digitally.

The mic pre has balanced XLR inputs, while the arm cable currently has single ended RCAs and a ground wire. Ahead of converting the arm cable wiring to fully balanced, can I just use RCA-XLR converter plugs? If so, what do I do with the ground wire?

Thanks in advance,

James

 

[intaud]

I think the following should work. Connect the RCA sleeve wire to pin 1 on the XLR then jumper pin 3 to pin 1 on the XLR. By the way what mic preamp are you using and what are you using for the RIAA eq? I was thinking of trying something similar.

Thanks, Dave

 

[boXem]

Converters are usually not properly cabled.

Use microphone cable to build cables like this:

(image Hypex)

Other solutions, even if looking the same electrically, will catch noise.

If you are not into diy, we can make these cables for you, just PM me.

 

[RayDunzl]

Isn't the output of a 4 wire cartridge two differential channels?

Why not wire those to the hot and cold of the XLR?

 

[Jas0_0]

Thanks

I think the following should work. Connect the RCA sleeve wire to pin 1 on the XLR then jumper pin 3 to pin 1 on the XLR. By the way what mic preamp are you using and what are you using for the RIAA eq? I was thinking of trying something similar.

Thanks, Dave

View attachment 89892

Thanks Dave. I just bought a second hand AEA TRP mic pre and I’ll be sending that signal (via an RME AD/DA converter) to a Mac Mini running Audio Hijack and this audio units plugin: https://www.kvraudio.com/product/riaa-by-vacuumsound

 

[Jas0_0]

Converters are usually not properly cabled.

Use microphone cable to build cables like this:
View attachment 89949
(image Hypex)

Other solutions, even if looking the same electrically, will catch noise.

If you are not into diy, we can make these cables for you, just PM me.

Many thanks - my turntable arm cable currently has rca plugs on one end and a 5 pin DIN plug where it connects to the arm. How would I wire the DIN outputs to two XLR plugs?

Thanks for the offer of supplying a cable - could you also supply DIN to XLR?

 

[Jas0_0]

Isn't the output of a 4 wire cartridge two differential channels?

Why not wire those to the hot and cold of the XLR?

Thanks, my arm cable has a 5 pin DIN plug - how would this correlate with the cartridge wires?

Or should I get rid of the DIN and rewire the whole arm?

 

[Frank Dernie]

Hi all,

I've decided to replace my MM cartridge with an MC and replace my noisy phono pre with a clean, high impedance ribbon mic pre and do RIAA eq digitally.

The mic pre has balanced XLR inputs, while the arm cable currently has single ended RCAs and a ground wire. Ahead of converting the arm cable wiring to fully balanced, can I just use RCA-XLR converter plugs? If so, what do I do with the ground wire?

Thanks in advance,

James

How are you getting the input impedance correct for your cartridge?
If you haven't sorted that yet you could incorporate it into your cable.

 

[Jas0_0]

How are you getting the input impedance correct for your cartridge?
If you haven't sorted that yet you could incorporate it into your cable.

I have heard that one can solder an appropriate resistor across the pins of each channel’s XLR plug.

Though if there’s a neater way I’d be interested to know

 

[boXem]

How would I wire the DIN outputs to two XLR plugs?

I guess 4 pins for the 2 differential signals + 1 for ground, but I am not a turntables specialist at all.

Thanks for the offer of supplying a cable - could you also supply DIN to XLR?

Looks feasible, but I need to know the wiring.
I would use this: http://www.rean-connectors.com/en/products/din-cable-connectors/nys322

I have heard that one can solder an appropriate resistor across the pins of each channel’s XLR plug.

That's what I would do. These XLR connectors are big enough to hide a lot of stuff inside

 

[intaud]

I believe the MC cartridge has 4 wires for the left and right channels. Each channel needs to be connected to its own input on the preamp, so you would need two RCA to XLR cables.

The single ended input impedance of the TRP is about 16k ohms. The typical source impedance of a MC cartridge is around 100 ohms so using the 10x rule the ideal preamp input impedance would be around 1k ohm. You could try adding a 1k ohm resistor between pins 2 and 1 on the XLR to load the MC cartridge and help reduce the rise in response above 10kHz. You might want to look at what the cartridge manufacturer recommends for input impedance loading.

Let me know how the TRP works out, James. I've used it with ribbon mics and it was excellent.

Thanks, Dave

 

[sergeauckland]

For moving coil cartridges, the load needs to be some 10x the coil's impedance (actually mostly resistance) but it can happily be more. I used my TSD15 into 47k perfectly well. There's therefore no need to try and reduce the input impedance of the mic amp, unless one wants to play about and see how much (or little) difference it makes.

As your arm has a DIN connector at its base, the chances are that the arm wiring is balanced up to that point, and the unbalancing is done in the cable from the DIN to the RCA plugs. In which case, it's trivially easy to replace that cable with one going from DIN to two XLRs. As to what to do with the ground wire, that can best de determined by experiment. One could try attaching it to the metalwork of the mic amp, or to Pin 1 of one of the XLRs, or even to the turntable mains ground wire assuming it has one. Whichever results in lowest hum, or greatest convenience is the one to use.

S.

 

[Jas0_0]

For moving coil cartridges, the load needs to be some 10x the coil's impedance (actually mostly resistance) but it can happily be more. I used my TSD15 into 47k perfectly well. There's therefore no need to try and reduce the input impedance of the mic amp, unless one wants to play about and see how much (or little) difference it makes.

As your arm has a DIN connector at its base, the chances are that the arm wiring is balanced up to that point, and the unbalancing is done in the cable from the DIN to the RCA plugs. In which case, it's trivially easy to replace that cable with one going from DIN to two XLRs. As to what to do with the ground wire, that can best de determined by experiment. One could try attaching it to the metalwork of the mic amp, or to Pin 1 of one of the XLRs, or even to the turntable mains ground wire assuming it has one. Whichever results in lowest hum, or greatest convenience is the one to use.

S.

Thanks - really helpful. Will experiment with resistance and ground. Am I right in thinking a resistor (if needed) is soldered across pins 1 and 2 of each XLR?

I’m slightly confused by why there are 5 pins on the DIN. I’ve found diagrams showing the left two are left channel +/-, and the right two are right Channel +/-, then the one in the middle is a ground. Is this a different ground to the chassis ground I have that’s a completely separate cable? How should that DIN ground be wired to the XLRs (if at all)?

 

[RayDunzl]

I’m slightly confused by why there are 5 pins on the DIN. I’ve found diagrams showing the left two are left channel +/-, and the right two are right Channel +/-, then the one in the middle is a ground. Is this a different ground to the chassis ground I have that’s a completely separate cable? How should that DIN ground be wired to the XLRs (if at all)?

Assumptions, since I'm not a vinyl guy:

Two pairs of signal, and "ground".

A balanced/differential pair doesn't "need" ground.

My guess would be chassis ground, which would likely be Earth ground.

If you have a separate ground cable, then I'd start with just the two pairs of signal.

Put a meter between the 5th pin of the DIN and the ground cable and see if there is continuity.

 

[Martin]

Buy this and be done with it: https://www.turntablelab.com/produc...onearm-cable-5-pin-din-to-xlr-cc-5p-xlr-1-23m

Martin

 

[sergeauckland]

Thanks - really helpful. Will experiment with resistance and ground. Am I right in thinking a resistor (if needed) is soldered across pins 1 and 2 of each XLR?

I’m slightly confused by why there are 5 pins on the DIN. I’ve found diagrams showing the left two are left channel +/-, and the right two are right Channel +/-, then the one in the middle is a ground. Is this a different ground to the chassis ground I have that’s a completely separate cable? How should that DIN ground be wired to the XLRs (if at all)?

If you need a loading resistor, it should be between pins 2 and 3. Pin 1 is ground and pins 2 and 3 carry the signal.

As to the 5 pin DIN, the centre pin (pin 2) is the ground, and the other pins carry the signals. As to how your arm is wired, you'll have to test that with a continuity tester, as there's no standard for arm wiring. If I were wiring an arm to a DIN socket, I would put pins 1&4 to the left channel +-, and pins 5&3 -+ so the outer two pins are both +, but as I said, there's no standard and yours could be wired differently. By the way, if you use a continuity tester, remove the cartridge from the arm and buzz through from the cartridge leads to the DIN socket. The ground pin 2 may or may not be connected to the arm metalwork, or may be left unconnected, and the separate ground wire used to ground the arm metalwork or possibly both are connected. If the arm ground goes to the DIN pin 2, then you can use that instead of the separate wire, and connect it to the shield (pin 1) of one of the XLR cables, not to both, as that would set up a ground loop. If the receiving XLR has been correctly wired with Pin 1 going to the chassis, then that's the same as using an external wire.

Grounding arms and cartridges is a bit of a trial and error exercise as there's no standard, just use whatever means results in lowest hum. Just NEVER EVER remove any safety ground from the turntable itself.

I've taken this from Wikipedia

Pins on male connectors are numbered (from right to left, viewed from outside of the connector, with the five pins upwards, and facing them): 1–4–2–5–3. Holes on female connectors are also numbered 1-4-2-5-3, but from left to right (facing the holes).

Hope this helps.

S.

 

[Jas0_0]

If you need a loading resistor, it should be between pins 2 and 3. Pin 1 is ground and pins 2 and 3 carry the signal.

As to the 5 pin DIN, the centre pin (pin 2) is the ground, and the other pins carry the signals. As to how your arm is wired, you'll have to test that with a continuity tester, as there's no standard for arm wiring. If I were wiring an arm to a DIN socket, I would put pins 1&4 to the left channel +-, and pins 5&3 -+ so the outer two pins are both +, but as I said, there's no standard and yours could be wired differently. By the way, if you use a continuity tester, remove the cartridge from the arm and buzz through from the cartridge leads to the DIN socket. The ground pin 2 may or may not be connected to the arm metalwork, or may be left unconnected, and the separate ground wire used to ground the arm metalwork or possibly both are connected. If the arm ground goes to the DIN pin 2, then you can use that instead of the separate wire, and connect it to the shield (pin 1) of one of the XLR cables, not to both, as that would set up a ground loop. If the receiving XLR has been correctly wired with Pin 1 going to the chassis, then that's the same as using an external wire.

Grounding arms and cartridges is a bit of a trial and error exercise as there's no standard, just use whatever means results in lowest hum. Just NEVER EVER remove any safety ground from the turntable itself.

I've taken this from Wikipedia

Pins on male connectors are numbered (from right to left, viewed from outside of the connector, with the five pins upwards, and facing them): 1–4–2–5–3. Holes on female connectors are also numbered 1-4-2-5-3, but from left to right (facing the holes).

Hope this helps.

S.

This really helps a lot, thank you for the detailed reply.

 

[Jas0_0]

I'm leaning towards the DIY route as the ready made cables seem quite expensive to me.

Does anyone have a recommendation of what cable to use for this?

I was thinking a run of Van Damme XKE microphone cable to each XLR might be good.

Also am I right in thinking that because this will be balanced, the final cable can be longer than the usual 1.2m for arm cables without worry of too much RFI? Nothing too crazy - something like 1.5 to 2m. Would that work?

Thanks all for your help.

J

 

[sergeauckland]

Arm cable length is more limited by the need to keep capacitance low than rfi considerations. Moving Magnet cartridges are very sensitive to capacitance, and more than a metre or so of cable can make a significant difference. Moving coils are almost completely immune to capacitance in the cables due to their very low inductance, and with a balanced connection, rfi or hum pickup will be very much reduced, so don't worry too much about cable length. 1-2m is fine. Use decent screened mic cable but it'll need to be fairly thin as you'll have to get two lengths into the DIN plug. There's less choice available in balanced cables 2-3mm thick, but it's not critical. You may do better with a cable with two twisted pairs and one overall screen. At these impedances and lengths, crosstalk between the channels won't be significant, and anyway, will be far less than the cartridge's own crosstalk.

S

 

[Jas0_0]

Arm cable length is more limited by the need to keep capacitance low than rfi considerations. Moving Magnet cartridges are very sensitive to capacitance, and more than a metre or so of cable can make a significant difference. Moving coils are almost completely immune to capacitance in the cables due to their very low inductance, and with a balanced connection, rfi or hum pickup will be very much reduced, so don't worry too much about cable length. 1-2m is fine. Use decent screened mic cable but it'll need to be fairly thin as you'll have to get two lengths into the DIN plug. There's less choice available in balanced cables 2-3mm thick, but it's not critical. You may do better with a cable with two twisted pairs and one overall screen. At these impedances and lengths, crosstalk between the channels won't be significant, and anyway, will be far less than the cartridge's own crosstalk.

S

Thanks, for the latter option something like a single run of Van Damme star quad?