Thank you once again for your help, Hugh! (Very useful step-by-step instructions ^^ !).

--------------------
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 Hugh Robjohns:

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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.

---

Another slightly cheaper yet high audio quality contender recently brought to my attention is from Orchid Electronics, based just up the road from me in Exeter:



http://www.orchid-electronics.co.uk/dual_isolator.htm

It's just £35 inc VAT & shipping, while a single channel version is also available from them for £20


Martin

--------------------
YewTreeMagic

A bit moot?

http://www.hall-elec.co.uk/7.html

I was having a bit of a clear out and came across June 2007 SoS with Hugh's review of the Hall BalunAmp.

The company still seems to be trading and the .pdf book of the box looks as tho' they have taken some of Hugh's comments on board.
The unit is also now at the much more attractive price of just under £68.00.

Dave.

I've not tried the Orchid transformer isolator, but judging by engineering and sound quality of the company's other units I'm sure it would be very good. A quick google revealed that the ART CB2 is, surprisingly, slightly cheaper than the Orchid box - even from Amazon of all places... and as the OP lives in America, I suspect the ART unit would be the more cost-effective solution in this case simply because of distribution/postage costs.

I had forgotten about the HED Balan box -- it is an interesting approach to the problem and does have some advantages in some situations, balanced by disadvantages in others. Probably not appropriate here, though.

hugh

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Technical Editor, Sound On Sound

I almost wish SOS had left this one alone. The damage done by opening the door to the idea of "magic" cables may be more than it's worth!

Quote Exalted Wombat:

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I almost wish SOS had left this one alone. The damage done by opening the door to the idea of "magic" cables may be more than it's worth!

---

More or less what I said about the "Vovox man". Should have shot him.

Dave.

Quote Exalted Wombat:

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I almost wish SOS had left this one alone. The damage done by opening the door to the idea of "magic" cables may be more than it's worth!

---

There's nothing 'magic' about the SOS Pseudo-balanced cable! It employs solid scientific principles its effectiveness in resolving ground loop hums in compatible systems is easily demonstrable in a reliable and repeatable fashion.

The reason we've made the cable available is simply because none of the usual cable makers seems to want to do it, and a lot of our SOS readers don't want to build their own.

The cable is built exclusively for SOS to our bespoke design, and is very good value considering the quality of cable, connectors and construction... and doubly so for subscribers who can buy at a very attractive price indeed! If you bought all the bits and pieces from Maplin to make your own you wouldn't get much change from a £20 note!

hugh

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Technical Editor, Sound On Sound

Quote ef37a:

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More or less what I said about the "Vovox man". Should have shot him.

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That would be unkind, Dave -- I can vouch for the fact that he's a very nice man!

hugh

--------------------
Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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There's nothing 'magic' about the SOS Pseudo-balanced cable! It employs solid scientific principles its effectiveness in resolving ground loop hums in compatible systems is easily demonstrable in a reliable and repeatable fashion.

---

"Your name is Russ, and I claim my £5....no that's wrong....I pay YOU £500...."

No, that's a bit too logical for Russ. But will newbies be able to tell real technospeak from Russ Andrews technobabble? Will accepting your nice sweetie lead to heroin and Brilliant Pebbles? My head hurts. :-)

Quote Hugh Robjohns:

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There's nothing 'magic' about the SOS Pseudo-balanced cable! It employs solid scientific principles ..

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I'm surprised no one else did it first. All those SoS articles about hum you'd think one cable maker would have provided the Hugh cable. Good on SoS. Long overdue. I hope SoS make a ton.

--------------------
17ft here! Too deep for non divers.

Quote St.Hamund the contrite:

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Quote Hugh Robjohns:

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There's nothing 'magic' about the SOS Pseudo-balanced cable! It employs solid scientific principles ..

---

I'm surprised no one else did it first. All those SoS articles about hum you'd think one cable maker would have provided the Hugh cable. Good on SoS. Long overdue. I hope SoS make a ton.

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Nah, see post #975860

Dave.

Enlighten me. - Joyless lee, I looked for post #975860. I'll bet it's bad news

--------------------
17ft here! Too deep for non divers.

Quote Martin Walker:
--------------------------------------------------------------------------------

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


--------------------------------------------------------------------------------



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! No not easy to find as the list is not numbered!

And I am Dave not Lee and quite happy thanks?

Quote Hugh Robjohns:

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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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Hi Hugh, was just wondering whether it's worth doing the full capacitor + resistor caboodle for patch cables that will be about 30cm long? (I'm trying to work out a neat way to connect my external preamp insert points [which are unbalanced] to my audio interface's balanced inputs!)

Hi mjfe2!

It's certainly worth doing the resistor caboodle, to break any ground loops, but to be honest I've never fitted the capacitors as well, and (touch wood) haven't have any RF interference as a result.

Of course, your mileage may vary, but with such short leads I'd be surprised if you didn't get away with it


Martin

--------------------
YewTreeMagic

Quote Martin Walker:

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Hi mjfe2!

It's certainly worth doing the resistor caboodle, to break any ground loops, but to be honest I've never fitted the capacitors as well, and (touch wood) haven't have any RF interference as a result.

Of course, your mileage may vary, but with such short leads I'd be surprised if you didn't get away with it


Martin

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Thanks, Martin! Would something like this be okay? http://www.ebay.co.uk/itm/360208771993?ssPageName=STRK:MEWAX:IT&_trksid=p3 984.m1423.l2649

They look rather big to fit into a TS connector but can I just remove the long spiky bits? (I really wish I could remember more electronics from school!)

When you connect with simple cables, is there an actual problem?

Just FYI:

CPC flyer just though the door shows a video ground loop isolator, £15.62+vat. Pt# SR0797107.

Might save someone's A sometime?

Dave.

There's one of these in my bits box, with a selection of adapters.
http://www.maplin.co.uk/ground-loop-isolator-33172

Pooh-pooh the audio quality if you wish! But it's often been a very useable quick-fix, particularly when people bring backing tracks along on a noisy laptop computer.

Quote Exalted Wombat:

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Pooh-pooh the audio quality if you wish!

---

I've not measured it, so I wouldn't pooh-pooh it out of hand... but I've heard reports that it's not the greatest in the LF distortion stakes. But as you say, it's cheap and cheerful and it can get you out of deep holes in an emergency.

I have tested the ART DTI which is more expensive but doesn't need the raft of adapters and that's very good.

http://www.soundonsound.com/sos/feb12/articles/art-dti.htm

The Orchid dual transformer isolator is another option that I'm told performs superbly well and I'm inclined to believe it.

http://www.orchid-electronics.co.uk/dual_isolator.htm

hugh

--------------------
Technical Editor, Sound On Sound

Quote Exalted Wombat:

---

There's one of these in my bits box, with a selection of adapters.
http://www.maplin.co.uk/ground-loop-isolator-33172

Pooh-pooh the audio quality if you wish! But it's often been a very useable quick-fix, particularly when people bring backing tracks along on a noisy laptop computer.

---

I actually "scoped" one of those a couple of years ago E.W. No noticeable distortion at about a volt rms down to 40Hz and osc' source Z was 600Ohms, load 10k. The frequency response was flat to 25Khz or so then started to rise slowly to a peak at about 60kHz. I dare say some juggling with a Zobel load could easily tame that.

Used on a neg 10 setup they are more than good enough IMHO.

Dave.

Quote Hugh Robjohns:

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Quote Exalted Wombat:

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Pooh-pooh the audio quality if you wish!

---

I've not measured it, so I wouldn't pooh-pooh it out of hand... but I've heard reports that it's not the greatest in the LF distortion stakes. But as you say, it's cheap and cheerful and it can get you out of deep holes in an emergency.

I have tested the ART DTI which is more expensive but doesn't need the raft of adapters and that's very good.

http://www.soundonsound.com/sos/feb12/articles/art-dti.htm

The Orchid dual transformer isolator is another option that I'm told performs superbly well and I'm inclined to believe it.

http://www.orchid-electronics.co.uk/dual_isolator.htm

hugh

---

We should run a test. No point in paying £50 if a third of that sounds much the same. We all own the adapters anyway.

Quote Exalted Wombat:

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.We should run a test.

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Easily done, but I'm reluctant to spend money on something I don't need or want just for ten minutes of testing! If you'd like to loan yours to me I'll happily test and return.

Quote:

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No point in paying £50 if a third of that sounds much the same. We all own the adapters anyway.

---

The ART DTI is under £40, but I take the point. Although for anyone that needs to buy a set of adapters to make the Skytonic thing as flexible the costs wouldn't be that far apart. Being in a metal box the ART version is inherently more robust and, since it doesn't require a bunch of adapters, probably more reliable, more convenient and quicker to patch in... I'd happily pay a small premium for that, but each to their own.

H

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Technical Editor, Sound On Sound

Maybe enough to just mention it exists, with confirmation that it's not as rubbish as might be imagined.

There's one big advantage. It's on the shelf at your local Maplins now. Next to a variety of adapters. And Maplins open on Sundays!

Quote mjfe2:

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Thanks, Martin! Would something like this be okay? http://www.ebay.co.uk/itm/360208771993?ssPageName=STRK:MEWAX:IT&_trksi d=p3984.m1423.l2649

They look rather big to fit into a TS connector but can I just remove the long spiky bits? (I really wish I could remember more electronics from school!)

---

Woo - only just noticed this!

Those are entirely unsuitable I'm afraid - first of all, a suitable value to break a ground loop is perhaps 50 to 100 ohms (not 100,000 ohms as you've got there) and second, tiny 0.25 watt types are perfectly adequate, so you don't need huge 2-watt wirewound types

These should do the job, and are just £1.84 for 50 including postage: http://www.sourcingmap.com/resistors-ohm-ohms-14w-250v-carbon-film-p-16134 7.html

Alternatively, Bitsbox do suitable 56 ohm resistors for just 4p each, although there's a modest £1.50 postage charge to add on: www.bitsbox.co.uk/resistors/cfr.html


Martin

--------------------
YewTreeMagic

Quote Martin Walker:

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Quote mjfe2:

---

Thanks, Martin! Would something like this be okay? http://www.ebay.co.uk/itm/360208771993?ssPageName=STRK:MEWAX:IT&_trksi d=p3984.m1423.l2649

They look rather big to fit into a TS connector but can I just remove the long spiky bits? (I really wish I could remember more electronics from school!)

---

Woo - only just noticed this!

Those are entirely unsuitable I'm afraid - first of all, a suitable value to break a ground loop is perhaps 50 to 100 ohms (not 100,000 ohms as you've got there) and second, tiny 0.25 watt types are perfectly adequate, so you don't need huge 2-watt wirewound types

These should do the job, and are just £1.84 for 50 including postage: http://www.sourcingmap.com/resistors-ohm-ohms-14w-250v-carbon-film-p-16134 7.html

Alternatively, Bitsbox do suitable 56 ohm resistors for just 4p each, although there's a modest £1.50 postage charge to add on: www.bitsbox.co.uk/resistors/cfr.html

Martin

---

Oops, I missed the 'k' that turned 100 into 100,000 ohms! Anyway, thanks for the links -- but can I just check, is it okay that these are made of carbon film because I remember Hugh saying be sure to get metal oxide resistors?

And when it comes to the actual DIY do I just solder the screen to one end of the resistor (does it matter which end?) and leave the other end alone?

Metal film has slightly better noise perfomance when DC is flowing through it but for AC operation it does not matter.

In any event 91Ohms produces a noise voltage somewhere below -130dBu..WE should be so lucky!

And BTW, thanks Martin for that link, the first people do a goodly range of the allyclad resistors so beloved of the DIY power soak builders.

Dave.

In this case it doesn't really matter -- the resistor isn't in the signal path. I generally use metal film because thats what I use in audio circuitry generally and there are loads of them in the box of bits.

Resistors are non-directional so it doesn't matter which way around you connect them.

hugh

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Technical Editor, Sound On Sound

Brilliant, thanks guys! I have to say, this is the only forum where one can get multiple definitive answers to a technical question within a couple of hours!

And re the resistors link I found these, which are even cheaper: http://www.ebay.co.uk/itm/160517016165?ssPageName=STRK:MEWAX:IT&_trksid=p3 984.m1423.l2649

Yes I generally use nothing but metal film resistors.

Regarding "polarity" I was reffering to "shot" noise as being better in metal film resistors. I have not gone all "Russ Andrews" on you Hugh!

Dave.

Quote mjfe2:

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Brilliant, thanks guys! I have to say, this is the only forum where one can get multiple definitive answers to a technical question within a couple of hours!

And re the resistors link I found these, which are even cheaper: http://www.ebay.co.uk/itm/160517016165?ssPageName=STRK:MEWAX:IT&_trksid=p3 984.m1423.l2649

---

We aim to please

And that link is incredible value - one hundred 100 ohm resistors for 0.99p and no postage charge

It will cost them at least 50p to put a stamp on your jiffy bag

Do let us know if this dealer is reliable


Martin

--------------------
YewTreeMagic

A possible clarification as to why some people may think you need big chunky resistors.

I once was in an ancient TV/Radio/Audio workshop where they had sort of semi-isolated supplies for each bench. All the test gear had to be 'earthed' to a curious neon bridge circuit, but at the same time they didn't want earth loops so they fitted resistors. However, under worst case conditions, The earth of one piece of kit could end up connected to the live of the equipment under test, while the earth of another was connected to the equipment's neutral, hence they used resistors that could withstand the full mains voltage continuously.

--------------------
It wasn't me!
(Well, actually, it probably was)

Can a TRS jack be used on the unbalanced side of a pseudo-balanced cable instead of a TS jack?

Quote mjfe2:

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Can a TRS jack be used on the unbalanced side of a pseudo-balanced cable instead of a TS jack?

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Assuming that you are only connecting the tip and sleeve then yes, most of the time, it will work. I say 'most of the time' because there are just a few sockets which have a contact which lines up with the insulation between the ring and sleeve of a TRS connector. As I have quite a bit of older gear which potentially has this problem I would personally go for TS connectors.

James.

--------------------
JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

Good point, James. The reason I asked though is because I'm using a Mackie Onyx 400f as an external preamp unit, using the (unbalanced) inserts as analogue outputs. However, if I let the signal flow continue past the insert point (using a TRS connector, or pulling out a TS connector a notch) it continues to the A/D stage of the Mackie and the LED metering then works for the preamps, which is nice. So I think I'll go for 2 x TRS with these pseudo-balanced cables!

+1

It can be done, obviously, but is likely to cause confusion (is this cable balanced or unbalanced?) and might not work reliably with some sockets as James says (unless you link the ring and sleeve terminals). The fact that there are three terminals also reduces the internal volume available for the ground-lift components making the job just that little bit harder still!

Hugh

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Technical Editor, Sound On Sound

Yes, treat TRS and TS as different animals.

I have an old WEM 15watter that will just not work with a TRS lead. Then there is pedal power switching to consider.

Dave.

Quote mjfe2:

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The reason I asked though is because I'm using a Mackie Onyx 400f as an external preamp unit, using the (unbalanced) inserts as analogue outputs.

---

Ah yes... special case and no alternative. You'll have to use TRS plugs for the mixer end and wire the tip and ring together to ensure the pass-through.

Just make sure you label the cable in some very clear and unambiguous way to avoid utter confusion later when you accidentally try to use the cable for a normal balanced connection!

hugh

--------------------
Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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Quote mjfe2:

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The reason I asked though is because I'm using a Mackie Onyx 400f as an external preamp unit, using the (unbalanced) inserts as analogue outputs.

---

Ah yes... special case and no alternative. You'll have to use TRS plugs for the mixer end and wire the tip and ring together to ensure the pass-through.

Just make sure you label the cable in some very clear and unambiguous way to avoid utter confusion later when you accidentally try to use the cable for a normal balanced connection!

hugh

---

But will I still benefit from the pseudo-balanced technology?!

Any news on shorter lengths Hugh?