Shouldn't a Phono Stage Be Like a DAC? Why so expensive?

[svart-hvitt]

A nuancing contribution to the phono topology discussion: Phono stage XLR in and out or only in?

https://www.originlive.com/key-information-overview/balanced-configuration-xlr-fitting.html

 

[March Audio]

Whilst the above is correct that is is not madatory to use xlr and you can input a coaxial core plus screen phono type lead into a differential input (it will still provide benefit), it wont be as effective in terms of noise rejection.

You still need screened twisted pair cable to minimise noise.

 

[svart-hvitt]

The debate centered on whether the cartridge itself was inherently balanced (I was in the 'yes' camp):

https://www.head-fi.org/threads/what-a-long-strange-trip-its-been-robert-hunter.784471/page-108

I just read through the Schiit responses. While he has a point about noise added by balanced circuitry he doesn't really explain why this is relevant for phono gear only (he probably thinks MC signals are so weak that any noise added by design is bad and should be avoided).

It's normal for phono single-end input proponenents to put much emphasis on this part of the noise picture while they later on do not come up with measurements or recommend exotic cables and the like.

To me it seems like a balanced design with good specifications is a safe choice.

Why a producer of audio gear doesn't tolerate this fact based evaluation tells you something about the producer's curiosity and openness for fact based critique.

 

[March Audio]

Properly designed differential isnt noisy. The benefit it gives in terms of noise rejection, cmr, is not debateable. Any professional low noise instrumentation design will use diff. Audio is no different and why audio designers think they have to do something different is very odd.

I havent read the thread you link to and I am not really inclined to as it will probably piss me off

Scroll down to the video on in amp noise.

http://www.analog.com/en/products/amplifiers/instrumentation-amplifiers.html#

 

[DonH56]

Differential also cancels even-order harmonics resulting in lower THD and higher SFDR.

 

[watchnerd]

A nuancing contribution to the phono topology discussion: Phono stage XLR in and out or only in?

https://www.originlive.com/key-information-overview/balanced-configuration-xlr-fitting.html

I don't get it...doesn't the XLR config have better CNR than balanced-over-RCA?

 

[March Audio]

I don't get it...doesn't the XLR config have better CNR than balanced-over-RCA?

Yes it will, however if the input is differential you will still get some noise rejection benefit, just not as good as when the cabling is twisted screened pair as opposed to coaxial.

 

[svart-hvitt]

When we're into the connector debate (XLR, mini XLR, RCA) for balanced audio, it may be worth mentioning that there is even another option: RJ45.

http://www.studiohub.com/PDF/completeliterature.pdf

Interestingly, the brand new unbalanced to balanced converter from Sonifex has this option:

http://www.sonifex.co.uk/cmulr1/index.shtml

It would be quite nice to see if measurements favor one connector over the other*. Remember, XLR is from an ancient time where we tolerated more noise, while today's big data centers rely on RJ45 . Because Ethernet cables and RJ45 are mass produced to tight specifications - while specs are non-existing or lax in audio - one shouldn't rule out that RJ45 is the better (and cheaper, more flexible and user-friendly) connector choice.

And there's more: Mass produced low-cost Ethernet cables with tight specs, which means for example it's always 110 Ohm, are excellent for analog signals. In other words: If you wanted the best cables for your stereo, you should use Ethernet cables throughout with RJ45 connectors**. This isn't going to happen anytime soon in hifi or even pro circles, so this is more of a DIY issue.


*The only places I've seen connector measurements are here:

https://www.gore.com/sites/g/files/ypyipe116/files/2017-01/Designing Ethernet Interconnect for High-Speed Data Transmission - White Paper - Military - 111816.pdf

and here:

http://www.neutrik.com/zoolu-website/media/download/15427/Test+Report+-+etherCON+NE8MX6


**I also thought this AES note may be of interest for those who consider Ethernet cables instead of AES-EBU cables (see page 19):

https://tech.ebu.ch/docs/tech/tech3250.pdf

 

[watchnerd]

Yes it will, however if the input is differential you will still get some noise rejection benefit, just not as good as when the cabling is twisted screened pair as opposed to coaxial.

That's what I thought, especially on long runs.

 

[March Audio]

When we're into the connector debate (XLR, mini XLR, RCA) for balanced audio, it may be worth mentioning that there is even another option: RJ45.

http://www.studiohub.com/PDF/completeliterature.pdf

Interestingly, the brand new unbalanced to balanced converter from Sonifex has this option:

http://www.sonifex.co.uk/cmulr1/index.shtml

It would be quite nice to see if measurements favor one connector over the other*. Remember, XLR is from an ancient time where we tolerated more noise, while today's big data centers rely on RJ45 . Because Ethernet cables and RJ45 are mass produced to tight specifications - while specs are non-existing or lax in audio - one shouldn't rule out that RJ45 is the better (and cheaper, more flexible and user-friendly) connector choice.

And there's more: Mass produced low-cost Ethernet cables with tight specs, which means for example it's always 110 Ohm, are excellent for analog signals. In other words: If you wanted the best cables for your stereo, you should use Ethernet cables throughout with RJ45 connectors**. This isn't going to happen anytime soon in hifi or even pro circles, so this is more of a DIY issue.


*The only places I've seen connector measurements are here:

https://www.gore.com/sites/g/files/ypyipe116/files/2017-01/Designing Ethernet Interconnect for High-Speed Data Transmission - White Paper - Military - 111816.pdf

and here:

http://www.neutrik.com/zoolu-website/media/download/15427/Test+Report+-+etherCON+NE8MX6


**I also thought this AES note may be of interest for those who consider Ethernet cables instead of AES-EBU cables (see page 19):

https://tech.ebu.ch/docs/tech/tech3250.pdf

Rj45 will be of no benefit in this application over xlr, well apart from physical size perhaps.

What you are trying to acheive is that the high and low leg wiring is identicle. The wires are twisted to ensure that any noise that gets coupled into them is the same. This gets cancelled out by the differential input.

You could use many types of connector so long as they have 3 pins. Also there is already a huge array of perfectly suitable audio screened twisted pair cable available. No need to try and reinvent the wheel with ethernet cable. The 110 ohms characteristic impedance is not relevant at audio frequencies.

 

[svart-hvitt]

Rj45 will be of no benefit in this application over xlr.

What you are trying to acheive is that the high and low leg wiring is identicle. The wires are twisted to ensure that any noise that gets coupled into them is the same. This gets cancelled out by the diffetential input.

You could use manyvtypes of connector so long as they have 3 pins.

Did you read the Gore note?

My point is: An unbroken link is better than a chain which needs an extending, connecting device. So the question is if certain connectors have better specs than other connectors.

This question may be of little relevance in audio because connector integrity makes a difference only below hearing threshold. However, without measurements I can only speculate if XLR and RJ45 (or the expensive Amphenol variant) have the exact same signal integrity properties.

 

[March Audio]

No I didnt read the gore note, just skimmed to see what it covered. There was no need. Its talking about high frequency transmission lines not audio. Its not relevant. Audio frequencies dont have the problems of RF transmission.

Why are you so concerned about xlrs? Used on every microphone .

What do you think the problem is?

 

[DonH56]

As far as audio goes it's hard to imagine any difference between standard mic or AES XLR cables and Ethernet cable. IME the mic cable probably has larger wire (less loss) and is not as well shielded (braided) as some Ethernet cable (foil) but it really doesn't matter... Both are shielded twisted pairs. You can be cheap XLR cable or XLR cable targeting high-level signals that might not be as good but that is a special case. I have also seen bad Ethernet cables but that is rarer; more often the cheaper Ethernet cables have smaller conductors rather than really poor shielding and poor impedance matching (the latter does not matter for analog audio, natch).

 

[svart-hvitt]

No I didnt. No need.

Whynare you so concerned about xlrs? Used on every microphone .

What do you think the problem is?

I didn't ask if there's a problem about XLR. I asked if there are connectors out there that measure better than XLR.

If RJ45 measures the same or better than XLR, why not use it? Especially in DIY circles.

 

[dallasjustice]

I phono stage could be nothing more than a decent solid state mic pre/AtoD and digital filter. Total cost can be a few hundred bucks. I've done it before. It sounds okay for a record player.

 

[March Audio]

I didn't ask if there's a problem about XLR. I asked if there are connectors out there that measure better than XLR.

If RJ45 measures the same or better than XLR, why not use it? Especially in DIY circles.

Measure better in what way?

Its got to measure better in a relevant way.

Sounds like you are looking for a problem to solve that isnt there.

 

[DonH56]

Better for audio? Hardly... RJ45 is much more closely spaced so more likely to cause crosstalk. Both have positive retention but both rely on compression and friction/stiction for good contact. RJ45 is more likely to break due to the plastic capture clip (usually, unless you pay for metal housings, rare). Off-the-cuff I see no advantage to RJ45. And XLR is a bog-standard audio connector; I have a fairly large bag of patch cables, and I may have one RJ45 for my notebook in case I need it, but have never needed one for analog audio.

 

[RayDunzl]

Used on every microphone .

Not on my USB UMIK-1

(doesn't count, I know)

*remembers trying to sort unlabeled snakes from the soundboard to the stage - all XLR - with five minutes to showtime... The guy with the other van got lost (he claimed).

 

[March Audio]

I phono stage could be nothing more than a decent solid state mic pre/AtoD and digital filter. Total cost can be a few hundred bucks. I've done it before. It sounds okay for a record player.

Indeed, a mic pre would be fine. Followed by riaa. Just dont turn on the 48 v

 

[svart-hvitt]

Better for audio? Hardly... RJ45 is much more closely spaced so more likely to cause crosstalk. Both have positive retention but both rely on compression and friction/stiction for good contact. RJ45 is more likely to break due to the plastic capture clip (usually, unless you pay for metal housings, rare). Off-the-cuff I see no advantage to RJ45. And XLR is a bog-standard audio connector; I have a fairly large bag of patch cables, and I may have one RJ45 for my notebook in case I need it, but have never needed one for analog audio.

"As long as your circuits are balanced, there is almost no left/right crosstalk inside the cable. Tests conducted by Radio Systems measured greater than 102 dB of separation between pairs at 20 to 20kHz in a 200’ run of cable using a quality balanced input circuit (85dB of common mode rejection). Even with an only fair quality balanced input circuit (50 dB of CMRR), separation was still greater than 90dB".

Source: Studiohub