Jump to content
  • 0
IGNORED

How does 4-wire connection of transducers "improve" audio?


iaval

Question

Hi,

I have been wondering - it's usually recommended to use two wires for the common negative and terminate the contact only at the end of headphone cable near the 3.5mm/6.35mm jack as it's said it should "improve" audio, in another words, reduce crosstalk. BTW, I'm not talking about "balanced" connection. 

Digging through NwAvGuy's blog revealed this paragraph:

 

Nearly all headphones use a 3 wire connection via a 3.5mm or 1/4" phone plug (and some use 3 wire cables). The shared ground degrades crosstalk performance in inverse proportion to the load impedance. Lower impedance loads draw more current creating more drop in the common ground connection which shows up in the opposite channel. Just 50 mOhm of resistance at the headphone jack degrades crosstalk over 30 dB when you drop from 600 ohms to 16 ohm headphones.

 

Okay, I can understand crosstalk degradation, as negative poles are mixed, and that it's a significant deal for low impedances (below 80Ohm), but why does it happen at the connector? 

2.5 metres of even good Mogami cable could result in over 200mOhm of resistance on the cable. Jack could add another 50 and PCB traces also 50. 

I did the 4-wire connection, because I assumed capacitance is somehow related to the crosstalk. If it's about Z or R difference on the positive and negative pole, then simply using thicker gauge for the negative should partly solve the problem (or simply use the shielding, provided the parameters are similar). 

Answers more inclined towards objectivism would be appreciated. 

 

Thanks

Link to comment

7 answers to this question

Recommended Posts

  • 0
On ‎12‎/‎18‎/‎2018 at 11:56 PM, iaval said:

anyone?

The greatest advantage for 4 wire would be achieved when using a headphone amplifier with dual mono topology , where the 0 volts (earth side) aren't connected together at the headphone jack.  In other words you would ideally also need to use a 4wire headphone jack too. My own DIY Class A HA is capable of this, but unfortunately my ATH M70X headphones use a 3 pin connector and I am loathe to try and convert them to using a suitable 4 wire cable due to the risk (small) of damage to the headphones.

 

(Yes, I have seen this article before )

The attached photo was taken before a DACT2 attenuator was fitted.

 

 This may also be of interest ?

http://www.amb.org/forum/benchmark-engineer-on-balanced-v-unbalanced-headphone-amps-t326.html#p2942

Class A HA-Will's PCBs before DACT 2.jpg

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

Link to comment
  • 0
4 hours ago, sandyk said:

The greatest advantage for 4 wire would be achieved when using a headphone amplifier with dual mono topology , where the 0 volts (earth side) aren't connected together at the headphone jack.

Okay, but that's not an answer to my question:

Quote

How does 4-wire connection of transducers "improve" audio?

 

On 12/13/2018 at 2:07 PM, iaval said:

 why does it happen at the connector? 

 

 

 

4 hours ago, sandyk said:

I am loathe to try and convert them to using a suitable 4 wire cable due to the risk (small) of damage to the headphones.

TRRS sockets that are some good aren't easy to find. Another option would be to permanently attach 4-wire cable. 

 

 

5 hours ago, sandyk said:

:)

 

On 12/13/2018 at 2:07 PM, iaval said:

BTW, I'm not talking about "balanced" connection. 

 

Here's my theory - since the negatives are shorted, then what makes a difference is not the overall cable resistance, but the resistance/capacitance difference between joint negatives and each of the positive

Link to comment
  • 0
1 hour ago, iaval said:

How does 4-wire connection of transducers "improve" audio?

 If you are unable to work that out from what I posted, including a photo which may shed further light on what I have said (without me stuffing around taking measurements) , then you shouldn't be asking questions requiring an Objective slant .

I have provided the hints, and I have left it up to you to " join the dots" ,which  include a further improvement in measured channel separation at 20kHZ with dual mono construction.

You may also be able to see in the photo that the 0 volt lines from both external transformers

only come together at the input to both PSU voltage regulator PCBs.

 In the Preamp version you should also see that I have gone to some trouble to roughly equalise the resistances of the 0 volt references by using an additional 0 volts wire to the more distant channel in this layout. You will also notice the use of a thicker white lead for the -VE rail supply of the more distant PCB.

 Incidentally, both the Class A HA and Class A Preamp are fully DC coupled, with the 0 volts ( earth side ) of each input also switched through to reduce the crap getting in from unselected inputs in the Preamp. This gives a worthwhile further improvement in S/N as seen on a CRO at max. sensitivity preceded by a Low Noise 10 x battery powered Preamp 

 

 

 I only posted the Elias Gwynn link as a matter of further interest for some members.

 

Current Class A Preamp 2017.jpg

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

Link to comment
  • 0

The ear usually hears time differences between the left and right ears, rather than volumes caused by a small junction of m ohms. If the time differences were that bad, then four core HP cables would have been around a lot sooner.

 

IMHO, the common wire between two channels is fine, I don't hear much drift or channel swapping, moving images.  To truly have a four wire system, it would have to go right back to the source, which is possible but a bit of an ask.

AS Profile Equipment List        Say NO to MQA

Link to comment
  • 0
37 minutes ago, sandyk said:

If you are unable to work that out from what I posted, including a photo which may shed further light on what I have said (without me stuffing around taking measurements).

You posted a photo without further description, how should I have guessed your intent? 

 

39 minutes ago, sandyk said:

then you shouldn't be asking questions requiring an Objective slant .

Objective answer would be definite, ie. "this is measured at the connector, because ..." and would not require

41 minutes ago, sandyk said:

hints

 

 

 

41 minutes ago, sandyk said:

I have left it up to you to " join the dots" ,which  include a further improvement in measured channel separation at 20kHZ with dual mono construction.

This is exactly the case where a graph of channel separation would be beneficial. 

Separation is also linked to impedance. If there's an improvement in channel separation at 20kHz, it would be useful to know how much it was improved and what was the tested load. 

Link to comment
  • 0

 

Quote

This is exactly the case where a graph of channel separation would be beneficial.  

Separation is also linked to impedance. If there's an improvement in channel separation at 20kHz, it would be useful to know how much it was improved and what was the tested load. 

 

If you want measurements with your replies, I suggest that you ask your questions in another forum. This is an Audiophile Forum, NOT Hydrogen Audio !

 Nevertheless, I have attached a measurement made by another DIY Audio member (Jeremy from Melbourne Au.) of what my very close front end balancing (as per the attached link) did when tried in a different amplifier design from Silicon Chip magazine .

 https://www.diyaudio.com/forums/solid-state/133018-current-mirror-discussion-15.html

Front End Balancing.jpg

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

Link to comment

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



×
×
  • Create New...