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
so you should explain those benefits in the context of ''full
symmetrical phono-pre'' which is much more expensive to make
because on need twice as many components than by single
ended phono-pre. If this is correct than...[snip]
It isn't. It does not take twice as many components. That is a popular myth.
What one may save on cables one will lose on the amp.
Its hard to put a value on that if performance and the best sound is your goal so I regard this as a bit of red herring. We simply did the balanced phono section because it sounds better.
I don't think there is room for 'belief' when it comes to the advantages of balanced operation. The benefits have been well-documented and understood for decades. IOW its not a matter of belief. Its a matter of knowledge. If someone tries running balanced and does not get superior results, there are some variables- chief amongst them in high end audio is the simple lack of understanding among many designers that there is actually a balanced standard.
Dover deed not comment on my question about possible benefit of the symmetrical connection.
Correct (I added that part); my intention was in correcting statements which did not seem factual:
Nandric - for all phono both balanced and unbalanced the arm earth ( 5th
pin ) should be a separate wire which you connect to preamp chassis.
In this case above, a balanced system does not employ the ground wire as its built-in to the XLR connection. It becomes a separate wire when the cartridge (which is a balanced source) is operated single-ended. You have to do something with the ground (the tone arm itself, which is shielding only) and so it gets connected to the chassis.
-and in the same post, above:
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 ).
The problem I had here is the tone arm ground should be tied to the shield of the interconnect and then to pin 1 of the XLRs. Its not common practice to leave the arm tube floating as is suggested in this quote.
I suspect that this was not what he mean to say, but that is what was written.
While the above discussions make me to feel like a mental midget, I am happy to report the problem turned out to be a bad rectifier tube in the power supply section of my Modwright SWP 9.0 SE phono stage.
The comments posted above will be great reference material should I ever turn to balanced connections in my analog front end.
^^ Actually except for the balanced thing, Dover and I were on the same page. I thought I had made that clear in my last post.
I do feel I should clarify some things in **your** post however :) (please note that I am not quarreling)
First, if an XLR appears on a preamp the expectation should be that it supports the AES file 48: the balanced line standard. However in practice you are correct in that buyer beware- in high end audio, the XLR connector is often there in appearance only.
I feel the term 'balanced' is the more common word but I like 'symmetrical' as that might be more descriptive when used to describe the preamp.
The reason to go balanced with a phono setup is not simply because the cartridge is a balanced source! There are two advantages- the one most people know about is the possibility of lower noise, particularly if the preamp is fully differential from input to output. Any noise imposed on the cable cannot get amplified. BTW, if a step up transformer is used, all transformers have the ability to operate balanced and even if the output is single-ended, the ability to reject noise in the cable is maintained.
The second benefit of balanced line is less understood by audiophiles, but was actually the intention of balanced line from its inception- and that is to reduce or eliminate any artifacts that come from the interconnect cable itself. For anyone that has been considering a large sum of money to buy an expensive single-ended phono cable this should be welcome news. The fact is that if the interconnect cable is built correctly (twisted pair within a shield, pin 1 of the XLRs being tied to the shield and no need for a separate ground wire) it will not need to be expensive and will compete easily with cables costing thousands of dollars.
IOW it will sound better.
Now you see debate in high end audio all the time about whether balanced is better or not! Some people say its only better if long lengths are employed. While it does excel at long lengths, even if its only 6 inches its still going to work better. But quite often the debate arises simply because the high end audio equipment used didn't support the balanced standard and as a consequently the result are variable!
That standard is there for a reason (which is to eliminate cable artifact).
I know this sounds a bit circular, but frankly I don't understand why a manufacturer would present an expensive product that does not do what it should. This is distressingly common in high end audio!
Here are the elements of balanced operation. If you follow these, the cable will have far less artifact and so will sound better:
1) pin 1 is ground, pins 2 and 3 carry the signal. 2) ground is ignored. It is for shielding only and at no point carries any signal current! 3) the cable will be a twisted pair within a shield. 4) the output of the balanced connection will drive a low impedance if possible, which will appear between pins 2 and 3.
In the case of a LOMC, point 4 is very easy, since many LOMCs are loaded at only 100 ohms. For this reason the interconnect cable should not impose any sonic artifact whatsoever.
FWIW, most high end audio manufacturers get messed up on 2) above. Quite often if they have a balanced product, they design it such that the output of pin 2 is with respect to ground and the output of pin 3 is with respect to ground. This is a mistake- the output of pin 2 should be with respect to pin 3!
@cleeds , Thanks for pointing that out. I have worked on a lot of broadcast gear over the years and have yet to see see any balanced phono sections and so conflated that to thinking that no-one had sorted out that phono cartridges are a balanced source. I do know for a fact though that our MP-1 was the first balanced line preamp ever offered in consumer audio and that its phono section was the first fully differential phono section ever made.
... FWIW, we were the first to recognize that the phono cartridge is an
inherently balanced source and began using it that way in 1988.
Ralph, you are mistaken. Broadcasters used balanced phono connections way back in the '60s and '70s, and maybe even earlier. Back then, LPs and 45s were common in radio studios, even where the station also used broadcast carts.
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).
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.
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 Dear Dover, Which method should be used to connect the XLR connectors? 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?
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 ).
Bass frequencies missing in action would suggest one channel may be out of phase. 5th wire on DIN connector should earth the arm and be connected to chassis earth on phono or pre. If the 2 signal channel cables have a floating shield ( as in twisted pair plus shield ) most phono cables connect the floating shield to the -ve side of the RCA ( if not using balanced connectors ). Personally I prefer to solder wires to the floating shield and keep them separate from the RCA. This means that you can connect the floating shield to the chassis. The problem with connecting the shield to the RCA is that it is dumping noise into your phono section directly.
When testing for continuity make sure you disconnect the cartridge. In some instances a meter can burn out coils in a MC cartridge.
Can also be a bad phono stage because you said bass is missing in action. That means your missing the RIAA EQ stage or the wires are out of phase since a lot of vinyl has the bass in mono.
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