HOT NEWS!

For anyone that needs to connect equipment with unbalanced line level outputs to balanced line level inputs, with the specific aim of avoiding ground loops, the infamous, unique and utterly bespoke 'SOS specification' pseudo-balanced cable design is now available in ready-made form.

Hugh Robjohns and Martin Walker have been describing the DIY construction of this cable to SOS forum users for years as a very effective way of solving the perennial ground loop problem when connecting unbalanced devices like synthesisers and outboard equipment.

Made exclusively for SOS by Pirahna, using quality cable and Neutrik connectors, this extremely useful problem-solving cable is available from the SOS shop at the extremely reasonable price of £16.99.

The pseudo-balanced cable is 3 metres long, with an unbalanced quarter-inch TS plug at one end and a 3-pin male XLR at the other:

http://www.soundonsound.com/shop/Product.php?ProdID=424

We may well make unbalanced TS to balanced TRS if there is sufficient demand, so please let us know!

hugh


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Technical Editor, Sound On Sound

Aren't you going to make special edition ones available too, personally hand-soldered by Hugh Robjohns?

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~~~ A weasel hath not such a deal of spleen as you are tossed with! www.feline1.co.uk ~~~

Does this feature the resistor and the capacitor as described here? I made a few of those myself, but they were a bit of faf.

I'd be interested in some TS-TRS ones in blue cable.

I'm amazed it's taken this long for such a product to appear - my studio features loads of these cables connecting unbalanced synth outputs to balanced mixer inputs, and they have cured all my hum and digital background nasties


Martin

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YewTreeMagic

I would be interested in TS-TRS cables as well. Any change to have shorter ones? (Like 1 meter)

Quote Martin Walker:

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I'm amazed it's taken this long for such a product to appear - my studio features loads of these cables connecting unbalanced synth outputs to balanced mixer inputs, and they have cured all my hum and digital background nasties


Martin

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Well I am not in the slightest part amazed Martin! We are soooo slow to innovate/market in this country. Look at how long the Art boxes have monopolized the mid price hum cutter market even tho' we have our very own OEP making excellent transformers*. It is only quite recently that a lone company Orchid has come to the fore (goo'orn SoS, give 'em a free 1/2 page ad' one month!).

In my own small way some 5 yrs ago (when I had SOME energy left!) I sent some ideas off to a few companies.None were interested and most did not even respond.

But then why special cables? It would add peanuts to the cost of a £400 synth e.g. to provide a TRS jack and a Z balanced output. These are simple matters that I think SoS reviewers could be a tad more aggressive about?

*And a box using Sowters could rival any imported Radials!
Dave.

This is awesome... for those of you on the other side of the pond. Seems these nifty, inventive cables are not available in the US. Well, hope you all enjoy! Can't wait for what's next from SOS.

Kind regards,


Living Room Rocker

Quote Seccione:

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I would be interested in TS-TRS cables as well. Any change to have shorter ones? (Like 1 meter)

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There's no problem in creating short TS-TRS cables, other than the cost of having them made and stocking them. So we need to establish demand before commiting to a big outlay.

Do you really think 1m would be a useful length? How would you plan to use a cable that short?

Hugh

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Technical Editor, Sound On Sound

Quote Living Room Rocker:

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Seems these nifty, inventive cables are not available in the US.

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I don't think there is any fundamental reason why they shouldn't be available to our US colleagues, and can only guess that it is an issue with the cost of shipping.

At the moment the people I need to discuss this with are at the Frankfurt Mussikmesse show, but as soon as they get back I'll raise it with them and report back here on the situation.

Hugh

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Technical Editor, Sound On Sound

Can I point out that the term "pseudo-balanced" is also used to describe a wiring technique that I would rather be called "shielded return" in which the outer screen does not make DC connection at one end of the cable but the signal "return" is carried by the cold conductor. There may or may not be an RF tie down capacitor, usually not. These are not of course in any sense "balanced" cables.

The SoS offering should I believe more properly be called "Impedance balanced"?

Dave.

Only if it has a build out resistor built into it to match the output Z of the source would it be impedance balanced.
Then you have to stock a 47 ohm one, and a 100 ohm one, and a 1K one for that POS keyboard.....

Not quite sure what the right name is, but 'impedance balanced' is taken and has a very specific meaning.

Regards, Dan.

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Audiophiles use phono leads because they are unbalanced people!

Quote dmills:

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Only if it has a build out resistor built into it to match the output Z of the source would it be impedance balanced.
Then you have to stock a 47 ohm one, and a 100 ohm one, and a 1K one for that POS keyboard.....

Not quite sure what the right name is, but 'impedance balanced' is taken and has a very specific meaning.

Regards, Dan.

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Hi Dan. I was under the impression that the SoS cable HAD a build out resistor of an arbitrary 100Ohms? Schematic perhaps?

"Quasi"-impedance balanced then?.....We can call them "Quibs" to further confuse the non-catered for noobs!

Dave.

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#They did not listen, they are not listening still...Perhaps they never will?#

Edited by ef37a (23/03/12 07:29 AM)

Quote ef37a:

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The SoS offering should I believe more properly be called "Impedance balanced"?

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No, they are not providing any form of impedance balance -- how could they when there is no way of knowing what the output impedance of the unblanced source device might be?

They could be described as a 'shielded return' cable, but the shield is tied down to maintain effective RF shielding.

I choose to call them 'pseudo-balanced' because they only work with a balanced input and they offer the freedom from ground loops that is a welcome property of a proper balanced input.

hugh

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Technical Editor, Sound On Sound

Quote ef37a:

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I was under the impression that the SoS cable HAD a build out resistor of an arbitrary 100Ohms? Schematic perhaps?

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Dunno where you got that idea from. I've certainly never mentioned that. I'm not going to publish a schematic here, but I've described the construction (and several variations on the theme) countless times on these forums, as well as in the magazine.

Quote:

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"Quasi"-impedance balanced then?.....We can call them "Quibs" to further confuse the non-catered for noobs!

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As Dan states, there is no impedance balancing going on. That's not what this cable is about. It is purely and simply about avoiding ground loops.

An 'impedance balanced' interface is a 'balanced' interface -- the interference rejecting properties of the 'balanced' interface rely 100% on it having matched and balanced impednaces to ground on both legs. An interface can't be 'balanced' unless it has balanced impedances!

The reason some people refer to it as 'impedance balanced' is actually to highlight the fact that only one leg carries an active audio signal and that is is therefore unsymmetrical, as opposed to the more traditional forms of balanced interface which involve symmetrical (equal and opposite) audio signals on both legs.

The term 'pseudo' means "not actually but having the appearance of; pretended; false or spurious; sham".

This cable 'has the appearance' of being balanced because it uses a 'balanced' cable and a 'balanced' connector at one end.. but it is not balanced, so it is 'false, spurious and a sham' of a claim!

Hence, it seems to be an entirely, etymologically and technically accurate phrase to use!

hugh

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Technical Editor, Sound On Sound

Sorry Hugh.
Got the wrong end of the stick (cable!) there.

So, it is a "braid breaker" with an RF bonding cap? Gotcha!

Dave.

'Braid breakers' are usually designed for use in unbalanced interfaces... this will only work with a balanced input...

Do we change ends now?

hugh

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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'Braid breakers' are usually designed for use in unbalanced interfaces... this will only work with a balanced input...

Do we change ends now?

hugh

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Sorry?

Dave.

Pardon?

H

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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Quote Seccione:

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I would be interested in TS-TRS cables as well. Any change to have shorter ones? (Like 1 meter)

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There's no problem in creating short TS-TRS cables, other than the cost of having them made and stocking them. So we need to establish demand before commiting to a big outlay.

Do you really think 1m would be a useful length? How would you plan to use a cable that short?

Hugh

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I guess my use case is somewhat marginal; my noisy synths (unbalanced) are wired to patch bay, from where I route them to mixer or processor (balanced). Those synths and patchbays reside in the same rack, I'd like to keep them cables short for purely practical reasons.
-
How about 1,5m?

Fair enough. I'll mention the requirement to the team...

hugh

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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an unbalanced quarter-inch TS plug at one end and a 3-pin male XLR at the other

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The Shop Description might state this (even tho' it can just about be deduced from the pic).

And don't forget: if you buy 1000m of the stuff then you qualify for the Hugh Rosary.



This is a highly sought after item and only available from good retailers like LIDL.

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Samplecraze
Stretch That Note

Personally I chant at least ten Hugh Maries a day using this rosary, and it really does make a difference in this mad, mad world


Martin

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YewTreeMagic

Did you find that things 'sounded' better when using the HR?

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Samplecraze
Stretch That Note

Yes, the highs are marginally cleaner, while the bass end sounds a tad warmer IMO.


Martin

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YewTreeMagic

Quote Martin Walker:

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Yes, the highs are marginally cleaner, while the bass end sounds a tad warmer IMO.

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Seriously? How do you explain a cable distorting the signal in this way?

Quote Exalted Wombat:

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Quote Martin Walker:

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Yes, the highs are marginally cleaner, while the bass end sounds a tad warmer IMO.

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Seriously? How do you explain a cable distorting the signal in this way?

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Oh dear! Here we go again!

Hugh, when that guy showed up with that Vovox wire you should have shot him. Just shot him and kept shtumn!

Dave.

I think it's something to do with the sunny weather... they're not normally this mad! Really they're not!

hugh

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Technical Editor, Sound On Sound

Quote Exalted Wombat:

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Quote Martin Walker:

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Yes, the highs are marginally cleaner, while the bass end sounds a tad warmer IMO.

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Seriously? How do you explain a cable distorting the signal in this way?

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The Rosary is responsible for some LF smearing (but in a nice HD way) and the top end is only treated at the air band. Explaining how the Rosary and subsequent 'Hughness' works requires both deep quantum physics and some lateral thinking.

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Samplecraze
Stretch That Note

...and it's also a mandatory requirement to have 'faith' that it will work, as with all religious talismans


Martin

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YewTreeMagic

Indeed.

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Samplecraze
Stretch That Note

What are the special isolating components?

Quote Dishpan:

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What are the special isolating components?

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None of us really know. The Rosary does its own thing and seems to work in all situations and under any circumstances.

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Samplecraze
Stretch That Note

Quote Dishpan:

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What are the special isolating components?

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Buy a wire and have a look!

Dave.

Quote Dishpan:

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What are the special isolating components?

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There's no secret -- I've described the cable construction in the magazine and in these forums often enough. The isolating components are a capacitor and a resistor.

hugh

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Technical Editor, Sound On Sound

But I got the impression from a post you made above that these cables don't have the resistor???

Quote Dishpan:

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But I got the impression from a post you made above that these cables don't have the resistor???

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This might help.

http://www.performing-musician.com/pm/feb08/articles/technotes.htm

Dave.

I've noticed some low level noise when recording the audio from my Motif L/R outputs to my M-Audio Omni I/O Stereo Aux in (connected via a "Y insert cable" - T/S coming out of each of the mono outputs, T/R/S going into the Stereo return).

The hum is most noticeable/annoying at the tail end of amplified/compressed notes. I'm not sure what exactly the noise is - ground loop hum? ... amplified noise floor? ... 60 Hz noise?

I was wondering - is my situation at all relevant/analogous to the "avoiding ground loops" construction of the bespoke SOS cables? On a superficial level the cables seem somewhat similar (T/S at one end, T/R/S at the other), but of course there's no resistor in my insert cable.

Thanks for any thoughts - I read the link in Performing Musician by Hugh, I see it was Part 2, I plan on reading part 1 to try and fully understand the ground loop concept -

Thanks!

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Alexis -Cubase 6.5.0/SX3.1.1.944, XP SP2, 4GB RAM (1GB not accessible, but used just to balance the computer so it doesn't tip over); Delta 66 in Omni i/O Studio; Motif8; UAD-1

Quote Dishpan:

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But I got the impression from a post you made above that these cables don't have the resistor???

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There are several possible ways you could use a resistor. The SOS pseudo-balanced cable doesn't use a 'build-out' resistor to create an impedance balanced interface in the way Dave assumed it did... because that would be impossible.

But it does use a resistor to mitigate a ground loop path.

hugh

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Technical Editor, Sound On Sound

Quote alexis:

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I'm not sure what exactly the noise is - ground loop hum? ... amplified noise floor? ...

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Compression will always make a background noise problem worse... but with unbalanced feeds involved this is quite possibly a ground loop problem.

Quote:

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I was wondering - is my situation at all relevant/analogous to the "avoiding ground loops" construction of the bespoke SOS cables?

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No, because the SOS pseudp-balanced cable avoids the ground loop problem by making use of the differential nature of a balanced input... and you are not using a balanced input for your keyboard.

In your situation the first thing to do is make sure the keyboard and the interface are plugged into adjacent mains power outlets. That minimises the chances of a ground loop forming inthe first place. If that doesn't cure the problem then it could be electromagnetically induced hum from mains cables into the unbalanced audio cables, so make sure they are kept well apart.

If you still have a problem then it is reasonable to assume it is a ground loop problem -- and the best way of dealing with it would be to use a dual-channel line isolation box, such as the ART Cleanbox2.

You should run unbalanced TS-TS leads from the keyboard to the box, and then your existing insert cable from the box outputs to the interface. The Cleanbox2's transformers will provide complete galvanic isolation between the keyboard and interface grounds, and thus prevent any ground loop hum. The ART box costs about £40 in the UK, so it's not going to break the bank.

hugh

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Technical Editor, Sound On Sound