Balanced Interconnects without a screen

Michael

New member
Balanced cables theoretically cancel interference, so why are they mainly screened? Years ago when using a Decca cartridge which had a metal protective Can, I was advised by the Garrott Brothers (internationally renown for repairing and improving cartridges) to remove the Can. The cartridge was then certainly more vulnerable but the improvement in clarity and speed was startling. The Can evidently induced eddy currents which in turn distorted the signal, and is presumably why top level cartridges avoid metal bodies. Recently I suspected that the screening of interconnects might have the same effect with induced eddy currents in the screen, so commissioned an Australian cable manufacturer (Robertson Audio Cables) to make me a balanced interconnect (4 meters in length from pre to power) without any screening. He was initially reluctant, as he thought I'd be wasting my money, but agreed when I said that I was prepared to take the risk. There's no hum or interference, the result is a staggering improvement in clarity, speed etc. The first word that sprang to mind was that I was "flabbergasted" by the extent of this improvement. Is this what is meant by Hysteresis? I previously noticed this term mentioned in the context of the speaker connections on March Audio amps.
I'm interested in Allen's comments and if anyone else has been brave enough to use unscreened interconnects?
 
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Alan March

Founder of March Audio
Staff member
Hi @Michael

I'm afraid this is a bad idea. I will try and find time over the weekend to provide a detailed technical explanation and some measurements to demonstrate.

Alan
 
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Holmz

New member
Balanced cables theoretically cancel interference, so why are they mainly screened? Years ago when using a Decca cartridge which had a metal protective Can, I was advised by the Garrott Brothers (internationally renown for repairing and improving cartridges) to remove the Can. The cartridge was then certainly more vulnerable but the improvement in clarity and speed was startling.

What speed?


If the can on the cartridge was Nickel or steel it it different than some other material.

The Can evidently induced eddy currents which in turn distorted the signal, and is presumably why top level cartridges avoid metal bodies.
It would more get the currents induced in the can.
But the can is not inducing currents in the wires.
It would be reactively responding to the fields, and not actively causing currents.

Recently I suspected that the screening of interconnects might have the same effect with induced eddy currents in the screen, so commissioned an Australian cable manufacturer (Robertson Audio Cables) to make me a balanced interconnect (4 meters in length from pre to power) without any screening. He was initially reluctant, as he thought I'd be wasting my money, but agreed when I said that I was prepared to take the risk. There's no hum or interference, the result is a staggering improvement in clarity, speed etc. The first word that sprang to mind was that I was "flabbergasted" by the extent of this improvement. Is this what is meant by Hysteresis? I previously noticed this term mentioned in the context of the speaker connections on March Audio amps.
I'm interested in Allen's comments

and if anyone else has been brave enough to use unscreened interconnects?

Back in the day, we used no shield may times in test equipment.
About all one should see is somewhat lower capacitance, and XLRs already have good CMRR.

Personally I would avoid using the term “brave”, which is a value judgement term.
 

Alan March

Founder of March Audio
Staff member
Hi @Michael

Eddy currents won't be an issue in a twisted pair balanced cable. By removing the screen you have now exposed the signal conductors to a higher level of electromagnetic and electrostatic noise.

It's not just the cable that cancels the interference. This is also a function of the input amplifier. See my post here which talks about Common Mode Rejection CMR.

The physical construction of the cable (twisting conductors) assists CMR by making common mode noise as similar as possible on both conductors but also minimises the electromagnetic pick up.

Input amplifier CMR reduces dramatically with increasing frequency, so also want to minimise what noise the cable "picks up".


The shield is there for a very good reason. Without it you *will* be picking up more noise.

I will post some plots later to demonstrate. Any "improvement" in sound you are hearing is, Im afraid, more likely to be simply the result of conducting the comparison in sighted uncontrolled (biased) conditions.

Alan
 

Michael

New member
Thanks for your reply Allan. It’s good to learn the technicalities, and I’m very aware of your experience and knowledge which manifests itself in your superb amplifiers. I’m sure I’ve thanked you, and I’m planning to buy a pair of your speakers because of the reduction in distortion they offer.

I bought your P452 initially as a temporary replacement for my Audio Research Valve power amp which did a fairly realistic impression of Mt Vesuvius, while saving to buy a new ARC amp. However, having now tried a new valve amp I rapidly concluded that I prefer your Purifi version which has vastly superior qualities in all respects. At one tenth of the price!

At the risk of making this post rather lengthy, I feel that I must justify the comments I made in my original post of this thread. It’s not a slight improvement I hear with these cables, it is indeed substantial.

I’ve been a professional classical (i.e. non amplified) musician all my life, have spent decades as a solo woodwind (flute) player in several professional orchestras and been soloist, chamber musician, have made many recordings, etc etc (see my website: www.michaelscottflute.com)
It’s on record (pardon the pun) that a professional musician (while a student) needs to do 10, 000 hours of practice before being ready to face the public. At 3 hours a day, that’s about 10 years of practice - listening all the while and aiming for absolute perfection. My equivalent now to a normal 9 - 5 working day would be: morning, 3 hour orchestra rehearsal; afternoon: either another 3 hour orchestral rehearsal or rehearsal for something else; evening: concert performance. Often seven days a week.

This has been my life for over 40 years, with practice and teaching in any available spare time. All the while Listening to myself and those around me.

I might have to play a high note with a frequency of 1760 Hz (high “A”). But if I play 1759 Hz then I’m out of tune, and anyway that pitch needs to change in a different context. A split second later (literally) I’m part of a different chord, all the while Listening acutely to my colleagues of whom there may be 100 in a Symphony Orchestra. There can be no time lag between those 100 members on stage - zero, not even a millisecond or those wonderful recordings that audiophiles enjoy would be disasters.

The point I’m going to some pains to make here is that we use and have better, vastly more sensitive ears than most. We “Listen”, with a capital L. If I’m comparing Audio (Hi-Fi) then it’s with the real thing and not with a different amplifier / speaker / etc.

Sorry to labour the point, but I want to be taken seriously when I say that this balanced cable without screening sounds so much better than a screened one that I said I was “flabbergasted” by the improvements. The cables were otherwise the same as the standard screened version which I was previously using, being high purity silver, made by Robertson Audio Cables (Brisbane). I wrote to Warwick Robertson telling him what I thought and he took it upon himself to make an identical cable to try for himself. He was similarly surprised and impressed, indicating that he would like to include this configuration in his business. He even asked my permission, which I said of course was not necessary, as I know I’m not the first person to try it.

Surely the ear is the final arbiter? As I said at the beginning here, I have the utmost respect for your expertise Allen, but how do we reconcile the difference between the theory and empirical results?
 

Holmz

New member
I wrote to Warwick Robertson telling him what I thought and he took it upon himself to make an identical cable to try for himself. He was similarly surprised and impressed, indicating that he would like to include this configuration in his business. He even asked my permission, which I said of course was not necessary, as I know I’m not the first person to try it.

… but how do we reconcile the difference between the theory and empirical results?
Personally I would ask him to measure it.


Pin 1 is usually the shield, pin 2 the +signal, and pin 3 the - signal.

There is some capacitance between the pin 2 and pin 1, or pin 3 and pin 1.

That would be the only thing that I can conjure up to cause a measurable difference, but the output impedance of the preamp would need to be low.
It could also be impedance in terms of inductance.

Hopefully Warwick is able to measure them.
 

Holmz

New member
The only person I'd trust with measurements is Allen. What I'd really like is for someone else to try this, maybe even contact Warwick @ RAC (https://robertsonaudiocables.com.au/) under the pretext of a possible purchase and ask his opinion?

  1. I am not inclined to misrepresent myself as a prospective customer.
  2. If the fellow makes cables then he is probably as interested as they get in the subject. So if Warwick has the equipment, then I see no reason not to trust his input. The site did look like a typical magical cable website.
What sort of preamp are you running?
- a passive pre should definitely react to an impedance change from a cable.
 

Alan March

Founder of March Audio
Staff member
Hi @Michael

I just took some measurements to show the impact of not screening an audio cable.

I set-up an RME ADI2 DAC / ADC in loopback so it is measuring its own output. I set a test signal at 1kHz at -60dB Full scale.

I laid the cable on top of a source of interference, a switch mode power supply.

20220722_121833.jpg

The result, some very low level noise at 30 and 60kHz

RME loopback 8.jpg

I then stripped the screen from the cable.

20220722_121944.jpg

The result is significant pick up of mains frequency noise plus its harmonics stretching beyond 3kHz, and increased high frequency noise.

RME loopback 7.jpg

So even with balanced cables, the screen is essential.
 

Alan March

Founder of March Audio
Staff member
Surely the ear is the final arbiter? As I said at the beginning here, I have the utmost respect for your expertise Allen, but how do we reconcile the difference between the theory and empirical results?
Well yes, Im not going to argue with you if you are confident you can hear a positive difference. However there are a number of thing that need to be considered.

Firstly, its conceivable that the additional noise pick up you will now be suffering in your system is causing a spray of spurious signals that also intermodulate with the desired music signal. This will be a low level effect, but it could be causing a euphonic effect which you enjoy. Thats fine, but bear in mind its not accurate. Overall I think this is unlikely.

Secondly, the effect of bias. None of us are immune to this. We expect or hope to hear a difference, therefore we do. You have primed yourself to hear a difference. By performing the comparison sighted, knowing which cable is in use, from a scientific point of view you have invalidated the experiment.

The video below is a lecture given by Floyd Tool who performed a lot of research into the correlation between objective measurements and subjective human opinions regarding speaker sound quality. Its a superb lecture from a wider perspective and well worth an hour of your time, but I will also link to the section that specifically covers bias.



Bit about bias.


Finally there could something going on in your system that we haven't accounted for causing a difference in sound. Without examining your system in detail its impossible for me to be sure.
 
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Michael

New member
Thanks for your input above Alan, I appreciate the trouble you've taken here. I can certainly see the effect of that interference. However, I hear nothing audible in the way of interference, the sound being as crystal clear as when I first installed your amplifier. There’s no euphonic effect nor bias, the improvements do not need A / B switching for comparison - it’s just so obvious. Perhaps my location in the upper Blue Mountains is an advantage. The best description of the improved clarity of sound would be identical to what I heard, and wrote, about the quality of your P452 in my system - taking it even further in the same direction. There's no imagination at work in what I hear, or rather, what I don't hear - its as if there's been a removal of fog which I didn't even know was there. My first comment to Warwick of RAC was that it was as if a window had not simply been cleaned but removed altogether. I hear more detail that I know is real - for example, in loud orchestral tuttis I can hear the delicate sound of a triangle, the attack of hammers on a glockenspiel, the upper partials & wonderful shimmer of cymbals and orchestral tam-tam (big gong 80 inches in diameter) which I know to be real. Thinking about the most obvious effect of removing the screen seems to be the clarity of low level signals which manifests itself as increased clarity of transients and absence of blurring. Have you tried listening to an un-screened cable? I feel sure that you would also not only hear but see the difference if comparing the trace of a dynamic (not steady state) complex audio signal fading into silence. There would surely be visibly more low level detail / information.
Next time you’re in Sydney, if you’d like to take a trip to the scenic Blue Mountains (90 minutes drive) you’re most welcome to visit - I’ll offer lunch - and hear for yourself!

Meanwhile, to reinforce my comments about my hearing, and of other orchestral musicians (each & every one of whom have put in a minimum 10,000 hours of hard practice & study before even being ready to audition), I’ve attached photos of the Concert Hall of the Sydney Opera House - my workplace (plus others similar) for about 40 years. "A picture is worth a thousand words". I was at the opening 49 years ago and with colleagues suffered from the terrible acoustics ever since then. Now the Concert Hall has just been remodeled and the result is a stunning acoustic transformation! I was invited to the “Resurrection” last week. Interesting to note that this time, fine tuning was accomplished with the guidance of the musicians themselves, during two weeks of final rehearsals before the opening, by manipulating the various adjustable acoustic reflectors. No musicians were involved 49 years ago.

 

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Alan March

Founder of March Audio
Staff member
Thanks for your input above Alan, I appreciate the trouble you've taken here. I can certainly see the effect of that interference. However, I hear nothing audible in the way of interference, the sound being as crystal clear as when I first installed your amplifier. There’s no euphonic effect nor bias, the improvements do not need A / B switching for comparison - it’s just so obvious. Perhaps my location in the upper Blue Mountains is an advantage. The best description of the improved clarity of sound would be identical to what I heard, and wrote, about the quality of your P452 in my system - taking it even further in the same direction. There's no imagination at work in what I hear, or rather, what I don't hear - its as if there's been a removal of fog which I didn't even know was there. My first comment to Warwick of RAC was that it was as if a window had not simply been cleaned but removed altogether. I hear more detail that I know is real - for example, in loud orchestral tuttis I can hear the delicate sound of a triangle, the attack of hammers on a glockenspiel, the upper partials & wonderful shimmer of cymbals and orchestral tam-tam (big gong 80 inches in diameter) which I know to be real. Thinking about the most obvious effect of removing the screen seems to be the clarity of low level signals which manifests itself as increased clarity of transients and absence of blurring. Have you tried listening to an un-screened cable? I feel sure that you would also not only hear but see the difference if comparing the trace of a dynamic (not steady state) complex audio signal fading into silence. There would surely be visibly more low level detail / information.
Next time you’re in Sydney, if you’d like to take a trip to the scenic Blue Mountains (90 minutes drive) you’re most welcome to visit - I’ll offer lunch - and hear for yourself!

Meanwhile, to reinforce my comments about my hearing, and of other orchestral musicians (each & every one of whom have put in a minimum 10,000 hours of hard practice & study before even being ready to audition), I’ve attached photos of the Concert Hall of the Sydney Opera House - my workplace (plus others similar) for about 40 years. "A picture is worth a thousand words". I was at the opening 49 years ago and with colleagues suffered from the terrible acoustics ever since then. Now the Concert Hall has just been remodeled and the result is a stunning acoustic transformation! I was invited to the “Resurrection” last week. Interesting to note that this time, fine tuning was accomplished with the guidance of the musicians themselves, during two weeks of final rehearsals before the opening, by manipulating the various adjustable acoustic reflectors. No musicians were involved 49 years ago.

Hi @Michael

There is of course the possibility that something unrelated to the cable screening is causing the difference you are hearing. It's not possible to comment further without examining and measuring the system.

I will make and post some recordings using a screened and non screened cable. Wexwill see if you or other members can hear the difference.

I actually will be in Sydney in September. I am presenting at the Sydney Audio Club on the 11th, a technical talk and show casing our amps and Sointuva speaker.

It would be great to see you there.

Cheers

Alan
 

Michael

New member
Hi @Michael

There is of course the possibility that something unrelated to the cable screening is causing the difference you are hearing. It's not possible to comment further without examining and measuring the system.

I will make and post some recordings using a screened and non screened cable. Wexwill see if you or other members can hear the difference.

I actually will be in Sydney in September. I am presenting at the Sydney Audio Club on the 11th, a technical talk and show casing our amps and Sointuva speaker.

It would be great to see you there.

Cheers

Alan
I'll come to the Audio Club meeting Alan, as I'm also very interested in your Sointuva speakers. I've attended their meetings in the past but a long time ago.
Being Pedantic - it's not a "difference" that I hear, but a significant improvement! The inspiration came from my previous experience with the Decca cartridge in the attached photo, shown alongside its screening can. Using the cartridge "naked" gave a vast improvement in clarity, detail etc, same as I've been describing with the cables, but there was a significant hum which turned out to be caused by the direct drive turntable motor. To solve the hum problem & still benefit from removal of the can - I instead screened the turntable motor by placing and earthing a modified Pizza tray between motor and platter - as shown in the other photo with platter removed. The screen in your example could perhaps be placed around the switching power supply rather than around the cable, so as to benefit from the improvement in that cable?
By the way please look out for an email from me with comments sent to me that I should probably not post here for public viewing.
I look forward to meeting you in September!
 

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Alan March

Founder of March Audio
Staff member
I'll come to the Audio Club meeting Alan, as I'm also very interested in your Sointuva speakers. I've attended their meetings in the past but a long time ago.
Being Pedantic - it's not a "difference" that I hear, but a significant improvement! The inspiration came from my previous experience with the Decca cartridge in the attached photo, shown alongside its screening can. Using the cartridge "naked" gave a vast improvement in clarity, detail etc, same as I've been describing with the cables, but there was a significant hum which turned out to be caused by the direct drive turntable motor. To solve the hum problem & still benefit from removal of the can - I instead screened the turntable motor by placing and earthing a modified Pizza tray between motor and platter - as shown in the other photo with platter removed. The screen in your example could perhaps be placed around the switching power supply rather than around the cable, so as to benefit from the improvement in that cable?
By the way please look out for an email from me with comments sent to me that I should probably not post here for public viewing.
I look forward to meeting you in September!
Hi @Michael

I'm really looking forward to meeting you at the Sydney Audio Club session.

We can discuss further there 😀

Cheers

Alan
 
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