SOUND ON SOUND

[Mike Shand]

I have long puzzled over the clean box II. On the top the sockets are clearly marked input and output, but on the bottom there is a schematic, which appears to indicate that one pair is wired as TRS balanced while the other is wired as TS unbalanced. However, there is no indication which sockets are which!!

The situation is further confused by Paul White’s 2005! Review which states

“ Both the inputs and outputs are unbalanced, but are wired to accommodate balanced or unbalanced connections on TRS jacks. ”

So curiosity finally got the better of me, and I took one apart. To my surprise I discovered that all 4 sockets are wired with tip and ring across the respective transformer winding, while the sleeves on each side are joined together. I.e. the two input sleeves are joined and the two output sleeves are joined. There are also a sprinkling of resistors, whose purpose I could not fathom.

So it looks to me that all sockets are balanced, and the schematic indicates what happens if you plug in a TRS or a TS respectively. I.e. for TS it (obviously) connects ring to sleeve, resulting in an unbalanced configuration.

So nothing earth-shattering, but at least my curiosity is now satisfied, and despite the Input and output labelling, it makes no difference which is which, as I had always supposed!

Mike

[ef37a]

You are as bad as some of the reviewers! You take things apart but don't give us pictures1

Heh! Thanks anyway Mike. I could hazard a guess that the resistors are either 'tie down' devices for where there is a DC leakage voltage present or they might be loading/damping Rs?

Dave.

[Hugh Robjohns]

... on the bottom there is a schematic, which appears to indicate that one pair is wired as TRS balanced while the other is wired as TS unbalanced. However, there is no indication which sockets are which!!

Both pairs are wired the same; the schematic is just showing a typical application! I agree it's not the most helpful of schematics!

I discovered that all 4 sockets are wired with tip and ring across the respective transformer winding, while the sleeves on each side are joined together

Yes, this ensures that both inputs and outputs can accommodate balanced or unbalanced connections equally well. But there is no continuity of ground across input/output.

There are also a sprinkling of resistors, whose purpose I could not fathom.

They are there to ensure the transformer has a defined load to control any wayward HF resonances.

...and despite the Input and output labelling, it makes no difference which is which, as I had always supposed!

I wouldn't be quite so certain about that. It may be that the loading resistors are symmetrical on each side of the transformer, which would support bidirectional use... but more likely that they are not... in which case you may well find it has a slightly different frequency response when used in the reverse direction (depending on the source and destination impedances)!

[Mike Shand]

I wouldn't be quite so certain about that. It may be that the loading resistors are symmetrical on each side of the transformer, which would support bidirectional use... but more likely that they are not... in which case you may well find it has a slightly different frequency response when used in the reverse direction (depending on the source and destination impedances)!

Good point. Thanks Hugh.

[twotoedsloth]

Hello All,

I've been intending to purchase an Art CleanBox for what has to be years now. Now is as good a time as any, though I don't have an immediate need for it.

Do I want the: CleanBox, CleanBox II or the Cleanbox Pro?

Many thanks,

Peter

[Hugh Robjohns]

The original Cleanbox is obsolete, and the Cleanbox Pro is an active bidirectional interface for consumer gear and not comparable at all.

So the real question is ART Cleanbox2 or ART DTI. (There are other manufacturers of line isolation transformer boxes, too). Here's the DTI:

https://www.soundonsound.com/reviews/art-dti

AFAIK the internals are identical in the CB2 and DTI... but whereas the CB2 just has quarter-inch sockets for the inputs and outputs, the DTI has XLRs, 1/4inch sockets and rca-phonos, on each side, all wired together, which enhances its usefulness considerably IMHO. See my review above.

I have 1x CB2, and 5x DTIs, and a T8 which is an 8-channel DTI (as well as a couple of other similar units from other suppliers)... That probably neatly reveals which I value most highly...:-)

[twotoedsloth]

Hello again,

I already have an Orchid Electronics Dual Transformer Isolator:

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

Is there any point in buying the DTI or Cleanbox?

I'm trying to assemble a "tool kit", though this is taking years, I think it's worth doing.

Many thanks,

Peter

[Mike Stranks]

Hello again,

I already have an Orchid Electronics Dual Transformer Isolator:

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

Is there any point in buying the DTI or Cleanbox?

I'm trying to assemble a "tool kit", though this is taking years, I think it's worth doing.

Many thanks,

Peter

The advantage of the DTI is that it also acts as a connector adapter. I found I used it just as much for that as for its isolation facility.

It's function apart from that is identical to the Orchid box you already have.

[shufflebeat]

I'm trying to assemble a "tool kit", though this is taking years, I think it's worth doing.

It will never end.

[twotoedsloth]

Hello again,

Sorry to bother you again, but will the ART DTI also function as a splitter? IE plug 1/4" in and output in 1/4" and XLR (and RCA) at the same time?

Many thanks,

Peter

[shufflebeat]

I think not, I'm pretty sure I tried this and meant to find out why it wouldn't but I suspect it was something to do with the balanced/unbalanced mechanism.

Might have to get that toolkit out.

[Hugh Robjohns]

....will the ART DTI also function as a splitter? IE plug 1/4" in and output in 1/4" and XLR (and RCA) at the same time?

Yes, it can serve as a splitter, and from either the input side, or the output side, or both. I often use it in that role myself -- it's one of its flexible strengths.

BUT, the split destinations must be the same format -- ie, balanced or unbalanced. If you mix formats everything will end up unbalanced, and you might find yo have ground loop problems too.

[shufflebeat]

Ok, this is not how I remember things, although that itself is not always reliable. I'll check tomorrow and most likely confirm what Hugh is saying.

To clarify, Hugh, if I were to feed phono L/R into the input I should be able to take balanced signals out if both XLR and TRS Jack on the output. Is that the scenario?

[ef37a]

... on the bottom there is a schematic, which appears to indicate that one pair is wired as TRS balanced while the other is wired as TS unbalanced. However, there is no indication which sockets are which!!

Both pairs are wired the same; the schematic is just showing a typical application! I agree it's not the most helpful of schematics!

I discovered that all 4 sockets are wired with tip and ring across the respective transformer winding, while the sleeves on each side are joined together

Yes, this ensures that both inputs and outputs can accommodate balanced or unbalanced connections equally well. But there is no continuity of ground across input/output.

There are also a sprinkling of resistors, whose purpose I could not fathom.

They are there to ensure the transformer has a defined load to control any wayward HF resonances.

...and despite the Input and output labelling, it makes no difference which is which, as I had always supposed!

I wouldn't be quite so certain about that. It may be that the loading resistors are symmetrical on each side of the transformer, which would support bidirectional use... but more likely that they are not... in which case you may well find it has a slightly different frequency response when used in the reverse direction (depending on the source and destination impedances)!

I have found a schematic (not block diagram) for the CB2 and there is Zobel CR network across the output. Therefore using it 'the wrong way' is likely to throw the response all over the shop depending upon source and sink impedances as you say Hugh.

Dave.

[Hugh Robjohns]

To clarify, Hugh, if I were to feed phono L/R into the input I should be able to take balanced signals out if both XLR and TRS Jack on the output. Is that the scenario?

Yes, that's perfectly fine. It's just a simple parallel split. Requires reasonably high input impedances on the two balanced destinations, of course, but that's not usually a problem if you're feeding line inputs.