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Need help with DIN to RCA phono cable troubleshooting

Somehow, I am currently having an issue with an apparent ground problem with my DIN (female five pin straight connector) to RCA phono cable. The arm is a Dynavector 501 mounted on a custom plinth, supporting a Garrard 401 table.

There is a reduction in overall volume, bass frequencies are MIA, and this is all accompanied by a loud hum. I have tried doing a continuity test from a spare headshell to the ground cable, and RCA terminations. I can't tell where the ground was interrupted, I need guidance in how to test for proper continuity in relation to signal and ground leads. Also, I don't know where the shielding should be connected, so a thorough explanation will be needed.

 Thanks for any help that can be given.
 Regards,
 Dan
islandmandan
atmasphere's avatar
atmasphere
7,068 posts
 

Should the ground wire from pin 5 in the Din5 connector

be split in two such that each can be soldered to the pin 1 on the

XLR connectors? Or should only the (floating) shield of both

channels be connected to the pin 1 on the XLR connectors?

The ground of the DIN goes to pin 1 of both XLRs.
@nandric , This:
Nandric - for all phono both balanced and unbalanced the arm earth ( 5th pin ) should be a separate wire which you connect to preamp chassis. This simply grounds the arm itself and has nothing to do with the cartridge signal.

Floating shields on the signal cables should only be connected to earth at one end.
In the RCA's at the preamp end I connect the floating shield ( assuming a twisted pair plus shield construction ) to the chassis by cutting the connection to the RCA and soldering a tail for connection to the preamp chassis. This reduces the opportunity for noise collected by the shield to enter the phono signal in a single ended system.
In this arrangement you end up with 3 earth leads to connect to the preamp chassis - tonearm earth/ground plus left and right channel floating shield earth/ground.

XLR's have a separate -ve signal and earth/ground in a balanced system. Therefore you only need to ensure the shield is connected to the earth/ground pin which is already separated from the -ve signal. The tonearm end is left floating ( not connected ).
-is mostly incorrect!

The tone arm is in fact the ground (which is the ground wire in a single-ended system). So the arm wand provides a grounded shield to the cartridge wires within. This continues through the DIN connection and splits to the shields of the left and right channels. At the XLR connection it ties to pin 1 which is ground). In this way the shield is constant from the cartridge to the input of the phono section.

Note that the ground is otherwise not part of the cartridge signal and should be ignored by the phono section in any event (otherwise Common Mode Rejection Ratio will suffer).

In a single-ended system it is advantageous to prevent the ground side of the RCA connection from being shorted to the phono preamp chassis (otherwise it is possible to introduce ground loops). So the only ground to be seen at the chassis should be the ground wire of the arm itself and not the minus outputs of the cartridge!
nandric's avatar
nandric
3,263 posts
 

My Gosh, I feel, so to speak, as involved in a dispute between

Stalin and Beria. Those two were the highest  authorities in the

''good old Sovjet Union''. However we also have our authorities

in this forum while I have some experience with communist regime.

According to this experience I should pretend to be deaf as well

as mute and wait for Dover's response.  

dover
1,165 posts
 
Atmasphere-

I dont agree with your comment that my solution above is incorrect.
Maybe you misunderstood what I wrote.
The tone arm is in fact the ground (which is the ground wire in a single-ended system). So the arm wand provides a grounded shield to the cartridge wires within.
Agree
This continues through the DIN connection and splits to the shields of the left and right channels.
I don’t think this is optimal in a signal ended system. The fifth pin grounds the arm. You run the risk that if someone connects the shield to the RCA at the preamp end then an earth loop is created.

My suggested solution outlined above is to separate the floating shields covering the signal cables and earth the floating shields on the signal cables separately at the preamp end ( assuming twisted pair plus shield signal cable construct ) to the preamp grounding post.

What I actually said was that in a cable that has a conventional twisted pair plus shield construct that I prefer to disconnect the floating shield from the RCA and connect the floating shield ( not the -ve signal from the cartridge ) to the preamp grounding post/chassis via drain wires.

If I read your post correctly you are grounding the floating signal shields at the sending end ( tonearm ) via the arm ground wire to the preamp chassis, whereas I ground the floating signal shields at the preamp end separately to the preamp grounding post. Since all three shields are floating and only connected at one end they cannot create an earth loop.

In my experience my arrangement has demonstrably lowered the noise floor.
In a single-ended system it is advantageous to prevent the ground side of the RCA connection from being shorted to the phono preamp chassis (otherwise it is possible to introduce ground loops). So the only ground to be seen at the chassis should be the ground wire of the arm itself and not the minus outputs of the cartridge!
In my post above I never suggested connecting the ground side of the RCA connection to the preamp chassis.

Again, what I actually said was that in a cable that has a conventional twisted pair plus shield construct that I prefer to disconnect the floating shield from the RCA and connect the floating shield ( not the -ve signal from the cartridge ) to the preamp chassis via drain wires. In my experience that arrangement has lowered the noise floor.

In summary the only difference between you and me is that in a single ended system you ground the floating signal shields to the DIN whereas I ground the floating signal shields at the preamp ( ground post ) end by separating the floating shield from the RCA and running drain wires ( leaving the DIN end floating.







nandric's avatar
nandric
3,263 posts
 

I agree with comrad Dover. Not because I fear for my life but

because he promissed to me some of this New Zealand's

''holy water'' which I certainly can use at my age.

Well I hope I will not add to further confusion but I made myself

some of those ''symmetrical single ended ICs''. Not political or

ideological but scientific explanation is as follow. The shield around

(two wire) which is connected to only one side of the RCA

connectors is the so called ''Faraday cage'' with electrical property

to protect the signal  from outside ''disturbances''. Some IC's

have marked arrows which suggest the direction for the connection

which should follow the source signal. This can't be done by a

phono-cable so we must connect the other way round: at pin 1

of the XLR connector. The strange looking expression ''symmetrical

single ended IC'' is the name for the cables with such shielding

provision. A name is not predicative qua linguistic nature but

has only the function of reference.

atmasphere's avatar
atmasphere
7,068 posts
 
I don’t think this is optimal in a signal ended system. The fifth pin grounds the arm. You run the risk that if someone connects the shield to the RCA at the preamp end then an earth loop is created.
You are correct, however the comment was made in response was to this:
Nandric - for all phono both balanced and unbalanced the arm earth ( 5th pin ) should be a separate wire which you connect to preamp chassis. This simply grounds the arm itself and has nothing to do with the cartridge signal.
Which in the case of balanced operation is false. In a balanced setup, the tone arm ground is pin 1 no if ands or buts. You might want to take a look at how the balanced standard operates- AES file 48 defines it.

(FWIW, we were the first to recognize that the phono cartridge is an inherently balanced source and began using it that way in 1988. If there was a ground loop problem I'm sure we would have run into it by now, but if you understand how balanced works- the ground is **ignored** by the input of the phono preamp. This could be done by an SUT, which would have its primary connected to pins 2 and 3 of the XLR which is the cartridge connection, and no connection whatsoever to pin 1, which is the tone arm ground.)
If I read your post correctly you are grounding the floating signal shields at the sending end ( tonearm ) via the arm ground wire to the preamp chassis, whereas I ground the floating signal shields at the preamp end separately to the preamp grounding post. Since all three shields are floating and only connected at one end they cannot create an earth loop.

No, I don't think you read it correctly. I think it also possible I did not understand your post either.

In a single-ended system the cartridge is **never** at any point grounded to the tone arm, its grounding wire or the chassis. If the (single ended, with RCA input connection) preamp is wired correctly (and many are not) the circuit ground will not be the same as the chassis ground (if it is, a ground loop occurs). Usually the circuit ground is referenced to the chassis by some means that prevents any significant ground loop current. So the signal "ground" (which is arbitrary as the source is balanced), which is really the 'minus' or inverting output of the cartridge, is tied only to the circuit ground and not the chassis. Meanwhile the tone arm ground is tied to chassis and not the circuit ground. No ground loop is possible.

Again, what I actually said was that in a cable that has a conventional twisted pair plus shield construct that I prefer to disconnect the floating shield from the RCA and connect the floating shield ( not the -ve signal from the cartridge ) to the preamp chassis via drain wires. In my experience that arrangement has lowered the noise floor.
If such a wiring situation were to exist, this would be the proper practice (if this is what you meant the first time 'round, IMO you stated it much better this time!). However this is unusual in a single-ended connection (although in this case it is easier to see how the cartridge is in fact a balanced source).
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