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Pangloss
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After playing around with a few transformers....
      #897262 - 25/02/11 09:10 PM
Well...

I have spent a couple of weeks playing around with a few different transformer models with a view to making some much needed isolation between my recorder I/Fs and my (unbalanced desk) and here are a few useful conclusions I have drawn which I thought I might share with you.

Firstly, the xformers I tried were:

Behringer Hum destroyer with very small, cheap transformer (600:600)
Jensen JT-11 output style transformer (600:600)
Oxford Electronics A218 mini input style transformer (600:600)
Oxford A262 input style transformer (600:600 or 600:2400)
A straight piece of coax wire

I recorded the same track (with a variety of sources) through each and normalized the results, which I compared.

Now then, my plan was to situate the isolation boxes at the patch bay, rather than at the desk input. The advice I have read (e.g. on the Jensen website) is that in this case the best transformer type is an output type transformer. This is because capacitance of any downstream cable can destroy the top end of the signal if an input transformer is used. You will notice that only one of the transformers I had to try was an output transformer.

The first thing I realized was that the input type transformers weren't (in my case) any worse than the output type transformers in this role. In fact, at low signal levels (so as not to cause saturation) the Jensen, OEP262 and straight wire did not sound different enough to make a difference (I did not null, simply listened).

Secondly, remarkably, at consumer signal levels the Behringer was not half bad. If I was hooking up bits of unbalanced -10dB kit I wouldn’t have any concerns about using them, providing the levels were not too hot.

Saturating the transformers, obviously produced different results. In many cases there was no outright “best”sound as this depended entirely upon the instrument being recorded.

The Behringer obviously saturated easier. In addition to compressing the signal it also played with the top end a bit, making the signal wooly on some sources. HOWEVER – it had a great effect on kick drum, snare and toms. To the extent that I actually used it as an insert on some drum channels on the last mix I did.

The OEP A218 seemed to produce the same level of biggening on hot sources but WITHOUT harming the frequencies in the same way (not even compared to the straight wire). In fact, it sounded GREAT on vocals. I used it as an insert on lead vocals on the same track mentioned above and it was an instant Neve-a-sizer when the (balanced level) signal was nice and hot. I am going to mount one of these in a box for exactly this purpose. I recommend it as a very cheap way to get chubby but clear vocal sounds.

Lastly, the Jensen and OEP262 were both very good and the A262 was pretty much impossible to saturate. I was surprised at how similar they sounded, given their completely different constructions.

I have had a lot of fun with this and can see that a collection of transformers can actually be a great creative toolkit.

Fun fun fun.

Alec

--------------------
'These are my principles and if you don't like them...well, I have others' (Groucho Marx) www.ownlittleworld.net/tunes.html


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grab



Joined: 08/07/07
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Re: After playing around with a few transformers.... new [Re: Pangloss]
      #897281 - 25/02/11 10:59 PM
Cool - sounds fun! How much were those transformers each?


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Pangloss
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Re: After playing around with a few transformers.... new [Re: grab]
      #897292 - 25/02/11 11:38 PM
Hi there,

I got the A218 from RS for about 11 quid plus VAT. I mounted mine in a mild steel box and got away without mu metal cans but if you are using an aluminium box or just want to be safe the can is about 7 quid. I think I will get cans for all of mine.

It works out about the same price for two of those as for a Behringer 2 channel box.

I got the Jensens off the bay second hand in a lot of 12.

I don't know if OEP still sell the A218 minis but you can get them on RS. OEP were recommended to me by a forumee here and I can second that they are very helpful indeed if you contact them direct.

--------------------
'These are my principles and if you don't like them...well, I have others' (Groucho Marx) www.ownlittleworld.net/tunes.html


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ef37a



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Re: After playing around with a few transformers.... new [Re: Pangloss]
      #897296 - 26/02/11 12:01 AM
These;

http://www.maplin.co.uk/ground-loop-isolator-33172 are actually pretty good in a neg tennish situation and can actually be found for 1/2 that price on the web.

I would be intersted to see how they stack up against your other collection Pan'
Dave.


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Pangloss
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Re: After playing around with a few transformers.... new [Re: ef37a]
      #897299 - 26/02/11 12:21 AM
I'm camping outside Maplin now.

Thanks for the OEP pointer BTW. Very nice people.

--------------------
'These are my principles and if you don't like them...well, I have others' (Groucho Marx) www.ownlittleworld.net/tunes.html


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nathanscribe



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Re: After playing around with a few transformers.... new [Re: Pangloss]
      #897456 - 26/02/11 09:26 PM
So are we talking about just a transormer in a box, with a jack at either side? No other omponents?

What were you actually plugging into these? I'm prrsuming a line level output with fairly typical impedance..?

What inputs were these going into on your mixer - again, I'm presuming unbalanced line?

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Pangloss
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Re: After playing around with a few transformers.... new [Re: nathanscribe]
      #897474 - 26/02/11 10:52 PM
Hi - a couple of different situations actually.

The intended use for these iso boxes (which I used after my testing for one mix) is placed between my (balanced) Soundscape DA interfaces (output impedance about 50ohms, I think) and my (unbalanced) Soundcraft Series 2400 desk which has line input impedance of about 10kohms and runs at +4dBu levels.

However, the simple test I ran went from my Soundscape DA interface, through the transformers and back (recorded) into Soundscape via the balanced 25kohm inputs. Again the interfaces run at +4dBu levels.

As you say, they were simply trannies in a box. If I find the time I might try a few more models.

--------------------
'These are my principles and if you don't like them...well, I have others' (Groucho Marx) www.ownlittleworld.net/tunes.html


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nathanscribe



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Re: After playing around with a few transformers.... new [Re: Pangloss]
      #897577 - 27/02/11 04:39 PM
Righto, cheers for that. Something to look into I think!

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Martin WalkerModerator
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Re: After playing around with a few transformers.... new [Re: Pangloss]
      #897773 - 28/02/11 02:19 PM
Quote Pangloss:

Saturating the transformers, obviously produced different results. In many cases there was no outright “best”sound as this depended entirely upon the instrument being recorded.

The Behringer obviously saturated easier. In addition to compressing the signal it also played with the top end a bit, making the signal wooly on some sources. HOWEVER – it had a great effect on kick drum, snare and toms. To the extent that I actually used it as an insert on some drum channels on the last mix I did.

The OEP A218 seemed to produce the same level of biggening on hot sources but WITHOUT harming the frequencies in the same way (not even compared to the straight wire). In fact, it sounded GREAT on vocals. I used it as an insert on lead vocals on the same track mentioned above and it was an instant Neve-a-sizer when the (balanced level) signal was nice and hot. I am going to mount one of these in a box for exactly this purpose. I recommend it as a very cheap way to get chubby but clear vocal sounds.

Lastly, the Jensen and OEP262 were both very good and the A262 was pretty much impossible to saturate. I was surprised at how similar they sounded, given their completely different constructions.




Hi Alec!

We most definitely need audio examples




Martin

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


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ef37a



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Re: After playing around with a few transformers.... new [Re: Martin Walker]
      #897836 - 28/02/11 04:25 PM
Quote Martin Walker:

Quote Pangloss:

Saturating the transformers, obviously produced different results. In many cases there was no outright “best”sound as this depended entirely upon the instrument being recorded.

The Behringer obviously saturated easier. In addition to compressing the signal it also played with the top end a bit, making the signal wooly on some sources. HOWEVER – it had a great effect on kick drum, snare and toms. To the extent that I actually used it as an insert on some drum channels on the last mix I did.

The OEP A218 seemed to produce the same level of biggening on hot sources but WITHOUT harming the frequencies in the same way (not even compared to the straight wire). In fact, it sounded GREAT on vocals. I used it as an insert on lead vocals on the same track mentioned above and it was an instant Neve-a-sizer when the (balanced level) signal was nice and hot. I am going to mount one of these in a box for exactly this purpose. I recommend it as a very cheap way to get chubby but clear vocal sounds.

Lastly, the Jensen and OEP262 were both very good and the A262 was pretty much impossible to saturate. I was surprised at how similar they sounded, given their completely different constructions.




Hi Alec!

We most definitely need audio examples




Martin




.wavs mind you, none of this MP3 *hit!
And two more traffs are on their way mate.
Dave.


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Pangloss
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Re: After playing around with a few transformers.... new [Re: ef37a]
      #897922 - 28/02/11 09:45 PM
Martin, Dave,

I may have some time on Thursday morning to create a few wavs using some of my own material.

--------------------
'These are my principles and if you don't like them...well, I have others' (Groucho Marx) www.ownlittleworld.net/tunes.html


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Pangloss
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Re: After playing around with a few transformers.... new [Re: Pangloss]
      #897923 - 28/02/11 09:48 PM
Dave, you are a very kind man. I owe you a pint if you find yourself in London.

--------------------
'These are my principles and if you don't like them...well, I have others' (Groucho Marx) www.ownlittleworld.net/tunes.html


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Martin WalkerModerator
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Re: After playing around with a few transformers.... new [Re: Pangloss]
      #898140 - 01/03/11 04:42 PM
Make sure you don’t get him saturated, or you might need a new transformer

(I’m only winding you up )


Martin

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Folderol



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Re: After playing around with a few transformers.... new [Re: Pangloss]
      #898164 - 01/03/11 06:03 PM
Gah!
I respond with great reluctance having thought we used all these up in that 'other' thread

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nathanscribe



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Re: After playing around with a few transformers.... new [Re: Pangloss]
      #910449 - 25/04/11 04:57 PM
I'm resurrecting this to ask a quick question:

If I was to DIY an isolator for hum removal what would be the practical difference between a 600:600 and a 10k:10k transformer? I've seen isolators with both specs, and not a good explanation of why.

My sources are synths and similar, I run them to patchbays, and they're connected to my mixer, which is then routed back to patchbays and then to a firewire interface. I'm not yet sure exactly where the best place for isolation would be, but I suspect the nearer the mixer the better.

My first guess would be 10k:10k, but please correct me if I'm wrong.

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ef37a



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Re: After playing around with a few transformers.... new [Re: nathanscribe]
      #910467 - 25/04/11 08:20 PM
Yup!
Wrong!
For a general purpose isolator box you need "600" Ohm types.

10+10k transformers are usually used at inputs to unbalance a balanced line and they have a high winding resistance of around 2-3k total. This hardly matters at an input which should have an Zin greater than 10k (but there will of course be some loss, always is power loss with traffs). The transformer will also present much the same impedance to the line as the input alone and thus not load it unduly but put such a transformer at the SOURCE of a signal and you greatly worsen the output Z of the line probably causing HF loss with any reasonable length of cable.

600R traffs have winding resistances of typically 30Ohms and thus add very little loss in the line. They also tend to be somewhat cheaper to make and thus sell for any given level of performance. They are not however suitable for input duty.

So, put 600R 1:1 jobs on outputs to balance the signals and if you are feeding balanced inputs fine. If the inputs are not balanced this often does not cause much trouble for short runs, less than 15mtrs say, but where a problem does arise buy the best 10k "bridging" transformers you can afford and keep the unbalanced "higher Z" feed from the traff as short as possible.

And horses for courses. Traffs for electric guitars, synths,tape signals, FX pedals and other sources of less than splendid fidelity or at neg 10 levels probably won't benefit from 100quid Lundahls!

Dave.


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nathanscribe



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Re: After playing around with a few transformers.... new [Re: ef37a]
      #910487 - 25/04/11 09:52 PM
Thanks Dave. The sources will almost entirely be unbalanced, and the patchbay routed to the interface and mixer is balanced (but currently patched with unbalanced cabling... which I intend to remedy when I can as I'm getting a touch of hum when patching into the mixer from there). So at the moment I'm not sure whether I'll be using isolation nearer the inputs or outputs. My reason for guesstimating a bridging type was because of that uncertainty. However, sticking a 600 Ohm box at the output of a synth that is causing ground loops makes sense and is something I'll take on board.

I've just grabbed a cheap ART cleanbox ii, which I've seen various recommendations for - and I believe that's a 10k 1:1. Better using that on the inputs, I take it?

Also, Canford seem to be doing a deal on some OEP Z300 at the moment. I fancied grabbing a couple and seeing what I could do.

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ef37a



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Re: After playing around with a few transformers.... new [Re: nathanscribe]
      #910517 - 26/04/11 05:47 AM
Yup.
You're right!

From the specification the Art CB ll must use 10+10k transformers since they quote an insertion loss of 5.5dB when loaded with 10k. That would imply a 3dB roll off starting at about 20kHz for 1000pf of cable and typical balanced mic cable is about 100pf/mtr(that's a back of the e'lope guess!) so it would be wise to put the box close to the input not the source and not to exceed 5mtrs or so of cable.

Having a mixture of balanced and unbalanced sources in a system can be a nightmare but since virtually all mixers, even the very cheapest Berry types have balanced line ins it is very cheap and easy to "balance" sources such as synths, soundcard outs etc by wiring in a 120Ohm resistor in the earth side and making such sources impedance balanced. The downside is no earth loop break but the advantage is no signal degradation which must obtain with all but perhaps the very best transformers.

Of course you don't need to impedance balance if you use a 600R traff.

Dave.


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Hugh RobjohnsAdministrator
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Re: After playing around with a few transformers.... new [Re: Pangloss]
      #910557 - 26/04/11 09:41 AM
If all your inputs are balanced (mixer and interface), and you want to run the patchbay balanced, then there is an easier and cheaper solution which I would strongly recommend: make up some new cables for your synths to operate as 'pseudo balanced'.

This approach almost always negates any problems with ground loop hums, doesn't degrade the sound as transformers can, is cheaper than buying a box load of transformers, and only requires a little light-duty cable construction and a few cheap electrical components.

The idea is to make use of the differential aspect of a balanced input to detect the unbalanced source signal without referencing it to the local ground -- and hence avoid ground loops.

All you need to do is wire up a TRS-TS jack lead using balanced cable. The TRS end (which connects to the balanced patch bay) is wired up in the usual way (but leave the screen off for the moment). The TS end connects to the unbalanced synth, and this is wired up with the hot wire to the tip and the cold wire to the sleeve. The cable screen connects to the sleeve, too.

In the balanced connector, you have two three choices. You could just trim back the screen, insulate it and leave it disconnected. This avoids re-connecting the ground loop and works perfectly well in 95% of cases.

However, in theory at least, the screen now acts as an aerial to dump nasty RF stuff into the source's ground! A better solution is to connect it to the balanced connector's ground pin via a 100 ohm resistor. This will present a high enough impedance to render any ground loop currents ineffectual but maintain the screen integreity reasonably well.

The best solution is to wire a 0.1uF capacitor across the resistor to provide a very low impedance path for Radio frquencies, and thus optimise the RF screening.

This arrangement is not an impedance balanced system -- so the normal ability of a true balanced circuit to reject electromagnetic interference doesn't apply here, despite using a 'balanced input'. But with near-line level signals that's rarely an issue anyway. The important thing is that this configuration does benefit from ground loop hum immunity because of the differential input's freedom from ground referencing, and that's usually the greater evil when working with ubalanced synths and the like.

The other advantage of this configuration is that you can now patch your unbalanced synths (or other outboard) without causing grounding problems across the entire system, and all the hums that go with it!

You can find suitable resistors and capacitors at Maplins in the UK (or any electronic supply outlet), and typical Maplins components would be the M100R resistor and N43CJ 0.1uF ceramic disc capacitor. These are small enough to be built into the TS plug given a little care. Make sure the cable screen is sufficiently insulated to prevent accidental contact with the sleeve or plug body. Some heatshrink insulation works well.

Hope that helps

hugh

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

Edited by Hugh Robjohns (27/04/11 03:28 PM)


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nathanscribe



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Re: After playing around with a few transformers.... new [Re: Hugh Robjohns]
      #910584 - 26/04/11 11:25 AM
Thanks again chaps.

Quote Hugh Robjohns:

Hope that helps




It does indeed - in fact you recommended this to me in another thread about ground loops. It's on my list of things to try, I just need to wait for pay day to get some TRS jacks and a reel of cable..!

I'm presuming that to take advantage of this method I'd still need to run my patchbay-mixer connections balanced.

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zenguitarModerator
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Re: After playing around with a few transformers.... new [Re: Hugh Robjohns]
      #910619 - 26/04/11 01:16 PM
Quote Hugh Robjohns:

If all your inputs are balanced (mixer and interface), and you want to run the patchbay balanced, then there is an easier and cheaper solution which I would strongly recommend: make up some new cables for your synths to operate as 'pseudo balanced'.

This approach almost always negates any problems with ground loop hums, doesn't degrade the sound as transformers can, is cheaper than buying a box load of transformers, and only requires a little light-duty cable construction and a few cheap electrical components.

The idea is to make use of the differential aspect of a balanced input to detect the unbalanced source signal without referencing it to the local ground -- and hence avoid ground loops.

All you need to do is wire up a TRS-TS jack lead using balanced cable. The TRS end (which connects to the balanced patch bay) is wired up in the usual way. The TS end connects to the unbalanced synth, and this is wired up with the hot wire to the tip and the cold wire to the sleeve.

The cable screen connects to the sleeve, but via a 100 ohm resistor, wired with a 0.1uF capacitor across it in parallel.

The 100 ohm resistor is there to raise the impedance of the screen connection for audio frequencies, minimising the chances of suffering ground loop hums, while the capcitor maintains a very low impedance for RF frequencies to maintain good RF screening protection.

This arrangement is not an impedance balanced system -- so the normal ability of a true balanced circuit to reject electromagnetic interference doesn't apply here, despite using a 'balanced input'. But with near-line level signals that's rarely an issue anyway. The important thing is that this configuration does benefit from ground loop hum immunity because of the differential input's freedom from ground referencing, and that's usually the greater evil when working with ubalanced synths and the like.

The other advantage of this configuration is that you can now patch your unbalanced synths (or other outboard) without causing grounding problems across the entire system, and all the hums that go with it!

You can find suitable resistors and capacitors at Maplins in the UK (or any electronic supply outlet), and typical Maplins components would be the M100R resistor and N43CJ 0.1uF ceramic disc capacitor. These are small enough to be built into the TS plug given a little care. Make sure the cable screen is sufficiently insulated to prevent accidental contact with the sleeve or plug body. Some heatshrink insulation works well.

Hope that helps

hugh




That might make a useful piece for the Q&A pages in the magazine, with a nice diagram and picture too.

Andy

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ef37a



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Re: After playing around with a few transformers.... new [Re: Hugh Robjohns]
      #910621 - 26/04/11 01:25 PM
Nice one Hugh!

You could of course put a shedload of such gizmos in a tin as jack-jack "problem solvers".

Dave.


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Hugh RobjohnsAdministrator
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Re: After playing around with a few transformers.... new [Re: nathanscribe]
      #910624 - 26/04/11 01:31 PM
Quote nathanscribe:

I'm presuming that to take advantage of this method I'd still need to run my patchbay-mixer connections balanced.




Yes, it only works with balanced inputs, and any cabling or routing between your source and the balanced inputs have to be balanced too.

Hugh

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Martin WalkerModerator
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Re: After playing around with a few transformers.... new [Re: Pangloss]
      #910922 - 27/04/11 06:44 PM
Soldering up some pseudo-balanced cables for all my keyboards made a HUGE difference to my background noise levels a few years ago

Highly recommended if you’ve got synths/keyboards with unbalanced outputs and a mixing desk with balanced inputs


Martin

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ketracel



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Re: After playing around with a few transformers.... new [Re: Pangloss]
      #1108792 - 20/06/14 11:46 PM
Fantastic thread for resolving the interference side of things.

What are the variations in addressing the issue of level?

Consider unbalanced synth outputs are usually -10dBv running into mixer inputs which are balanced +4dBu. In this case there is a massive 12dB loss of signal. Sure, significant amounts of gain can be applied on the mixer, also with additional noise mind you is there a cleaner, efficient or optimal solution, can transformers also help here?


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ef37a



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Re: After playing around with a few transformers.... new [Re: ketracel]
      #1108814 - 21/06/14 08:10 AM
Quote ketracel:

Fantastic thread for resolving the interference side of things.

What are the variations in addressing the issue of level?

Consider unbalanced synth outputs are usually -10dBv running into mixer inputs which are balanced +4dBu. In this case there is a massive 12dB loss of signal. Sure, significant amounts of gain can be applied on the mixer, also with additional noise mind you is there a cleaner, efficient or optimal solution, can transformers also help here?




I would not consider 12dB to be a "massive" loss nor making it up "significant"! The line inputs on even a cheap mixer should be capable of this without adding noticeable noise. Indeed, any noise that does intrude is likely to come from the synth!

Yes, decent transformers might be a good idea to balance the signal and give galvanic, possibly earth free operation but unless you go for a step up ratio you will always incur a small voltage loss. But be wary of a step up past 1:2 (~ +6dB) because just this ratio, with a 10k line input Z, will load the synth by 2.5k any lower and the output amplifiers might start to protest. The TL07 series are very poor at driving loads much below this for example.

Note I said "good" transformers? The products from OEP/Walter at about £10 each (600R:600R) are actually a bit too good for synths! I would not go for exotics.

Dave.


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nathanscribe



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Re: After playing around with a few transformers.... new [Re: ef37a]
      #1108832 - 21/06/14 09:20 AM
FWIW, I have an Orchid Electronics isolator that was an absolute bargain at 35 quid shipped - absolutely no trouble at all with the sound quality, there's plenty of bottom end coming through (which is something I've had problems with from the ART Cleanbox), and a peek inside revealed transformers of about that calibre. That's no criticism, I'm very happy with it.

The only thing I've got against these budget units is they all distort from my 909 clone and Moog LP outputs. I'm guessing those chaps are just a little hotter than most

By way of pondering, would it be possible to rig up a box with a switchable step up/down/1:1 operation..?

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ef37a



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Re: After playing around with a few transformers.... new [Re: nathanscribe]
      #1108855 - 21/06/14 11:05 AM
Quote nathanscribe:

FWIW, I have an Orchid Electronics isolator that was an absolute bargain at 35 quid shipped - absolutely no trouble at all with the sound quality, there's plenty of bottom end coming through (which is something I've had problems with from the ART Cleanbox), and a peek inside revealed transformers of about that calibre. That's no criticism, I'm very happy with it.

The only thing I've got against these budget units is they all distort from my 909 clone and Moog LP outputs. I'm guessing those chaps are just a little hotter than most

By way of pondering, would it be possible to rig up a box with a switchable step up/down/1:1 operation..?




I can't find a proper specc' for the Orchid box (shame Orchid!) but the Cleanbox 2 is rated for 0.05%thd at +24dBu at 100Hz and that is pretty good and I doubt the Orchid is any less? In any event the Orchid is available with XLR connectors? Be a bit daft to fit "pro" connectors to a device that cannot handle pro levels? And, AFAIK Orchid lekks are NOT daft!
I suspect the distorting devices are to blame in some way.

Re switchable ratios? By the time you have bought a suitable switch (head hurts! Can you do it with a bog-s DPDT?) and faffed about you might as well make two boxes IMHO! In any case there would always be the danger of a 6dB hike in level. At the worst possible moment of course!

A MUCH more flexible arrangement would be to go active and use an LM4562 or similar.

Dave.


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Folderol



Joined: 15/11/08
Posts: 3570
Loc: Rochester, UK
Re: After playing around with a few transformers.... new [Re: Pangloss]
      #1108904 - 21/06/14 05:11 PM
Another wrinkle to this.

A few weeks ago, I was browsing Canford Audio (as you do) and noticed they were selling off OEP 10k input transformers at £7 each as stock clearance, so at that price I decided to grab a pair for experimenting (today they still have two left).

OEP kindly provide reference schematics for using these in current mode as an active unit with a TL071. I tried out a slight variation and was astonished at the performance! In fact I thought I must have made a mistake in the wiring, and double and triple checked that I was indeed getting total isolation from my sig gen.

For instance, after the usual sine wave checks, I tried bunging in a 100Hz square wave at +20dBu, and my jaw hit the floor as I saw a near perfect square wave on the 'scope

A lower amplitude square wave at 10kHz (I didn't want to be too unkind to the unit) showed just a bit of ringing, but increasing the neg. feedback cap killed that, with only a moderate (quite acceptable) rounding of the front edge.

I haven't had the chance to do any serious distortion checks, but simple A/B listening doesn't reveal anything.

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


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nathanscribe



Joined: 19/01/07
Posts: 818
Loc: Yorkshire, by 'eck.
Re: After playing around with a few transformers.... new [Re: ef37a]
      #1108950 - 22/06/14 09:24 AM
Quote ef37a:

I can't find a proper specc' for the Orchid box (shame Orchid!) but the Cleanbox 2 is rated for 0.05%thd at +24dBu at 100Hz and that is pretty good and I doubt the Orchid is any less? In any event the Orchid is available with XLR connectors? Be a bit daft to fit "pro" connectors to a device that cannot handle pro levels? And, AFAIK Orchid lekks are NOT daft!
I suspect the distorting devices are to blame in some way.




The Orchid uses a VTX 101-1604, which is 600:600 - haven't seen distortion specs to compare though. Like I say, it's noticeably better than the ART, whatever the quoted figures. I also know that the Moog and 909 kick put out enough welly in the sub-100Hz range to cause nastiness - even the Radial JDI I had could be tickled into nervousness around the edges by certain bass patches - I don't know why, or even what kind of distortion exactly was happening, but my ears tell me 'tis the case


Quote:

you might as well make two boxes IMHO!




Fair enough! Just pondering.

--------------------
my nerdy synth tech blog


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ketracel



Joined: 14/10/07
Posts: 4
Re: After playing around with a few transformers.... new [Re: ef37a]
      #1108980 - 22/06/14 01:40 PM
Quote ef37a:

Quote ketracel:

Fantastic thread for resolving the interference side of things.

What are the variations in addressing the issue of level?

Consider unbalanced synth outputs are usually -10dBv running into mixer inputs which are balanced +4dBu. In this case there is a massive 12dB loss of signal. Sure, significant amounts of gain can be applied on the mixer, also with additional noise mind you is there a cleaner, efficient or optimal solution, can transformers also help here?




I would not consider 12dB to be a "massive" loss nor making it up "significant"! The line inputs on even a cheap mixer should be capable of this without adding noticeable noise. Indeed, any noise that does intrude is likely to come from the synth!

Yes, decent transformers might be a good idea to balance the signal and give galvanic, possibly earth free operation but unless you go for a step up ratio you will always incur a small voltage loss. But be wary of a step up past 1:2 (~ +6dB) because just this ratio, with a 10k line input Z, will load the synth by 2.5k any lower and the output amplifiers might start to protest. The TL07 series are very poor at driving loads much below this for example.

Note I said "good" transformers? The products from OEP/Walter at about £10 each (600R:600R) are actually a bit too good for synths! I would not go for exotics.

Dave.




Hi Dave,

Would an electronically balanced solution along the lines of the SSM2142 Balanced Line Driver be more suitable for balancing the unbalanced synth outputs and bringing up the level to +4dBu?


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Martin WalkerModerator
Watcher Of The Skies


Joined: 28/02/01
Posts: 17409
Loc: Cornwall, UK
Re: After playing around with a few transformers.... new [Re: ketracel]
      #1108986 - 22/06/14 02:31 PM
Hi ketracel, and welcome to the SOS Forums!

Yes, the SSM2142 could work well -it's capable of providing 10volts RMS into a 600 ohm load, which equates to +22dBu, and therefore well up to 'professional' audio standards.

I've seen them advertised on ebay at around £3.50 too


Martin

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


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ef37a



Joined: 29/05/06
Posts: 6698
Loc: northampton uk
Re: After playing around with a few transformers.... new [Re: Martin Walker]
      #1109021 - 22/06/14 07:06 PM
Quote Martin Walker:

Hi ketracel, and welcome to the SOS Forums!

Yes, the SSM2142 could work well -it's capable of providing 10volts RMS into a 600 ohm load, which equates to +22dBu, and therefore well up to 'professional' audio standards.

I've seen them advertised on ebay at around £3.50 too


Martin




I agree if you need a high end booster/driver but, (and I don't mean any slight to synths)for a synth? An NE5532 with 2x 100R impedance balanced out will surely be more than good enough?

If you still want galvanic isolation a couple of OEP 1200s driven from the 5532 configured for "zero" output impedance would be fine.

Dave.


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ef37a



Joined: 29/05/06
Posts: 6698
Loc: northampton uk
Re: After playing around with a few transformers.... new [Re: nathanscribe]
      #1109034 - 22/06/14 09:17 PM
Quote nathanscribe:

Quote ef37a:

I can't find a proper specc' for the Orchid box (shame Orchid!) but the Cleanbox 2 is rated for 0.05%thd at +24dBu at 100Hz and that is pretty good and I doubt the Orchid is any less? In any event the Orchid is available with XLR connectors? Be a bit daft to fit "pro" connectors to a device that cannot handle pro levels? And, AFAIK Orchid lekks are NOT daft!
I suspect the distorting devices are to blame in some way.




The Orchid uses a VTX 101-1604, which is 600:600 - haven't seen distortion specs to compare though. Like I say, it's noticeably better than the ART, whatever the quoted figures. I also know that the Moog and 909 kick put out enough welly in the sub-100Hz range to cause nastiness - even the Radial JDI I had could be tickled into nervousness around the edges by certain bass patches - I don't know why, or even what kind of distortion exactly was happening, but my ears tell me 'tis the case


Quote:

you might as well make two boxes IMHO!




Fair enough! Just pondering.




I would suspect therefore that the two devices are putting out high level, sub sonic crap. I am a great believer in limiting gear to frequencies that humans can hear!

Dave.


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Martin WalkerModerator
Watcher Of The Skies


Joined: 28/02/01
Posts: 17409
Loc: Cornwall, UK
Re: After playing around with a few transformers.... new [Re: ef37a]
      #1109274 - 24/06/14 03:55 PM
Quote ef37a:

Quote Martin Walker:

Hi ketracel, and welcome to the SOS Forums!

Yes, the SSM2142 could work well -it's capable of providing 10volts RMS into a 600 ohm load, which equates to +22dBu, and therefore well up to 'professional' audio standards.

I've seen them advertised on ebay at around £3.50 too


Martin




I agree if you need a high end booster/driver but, (and I don't mean any slight to synths)for a synth? An NE5532 with 2x 100R impedance balanced out will surely be more than good enough?

If you still want galvanic isolation a couple of OEP 1200s driven from the 5532 configured for "zero" output impedance would be fine.

Dave.




Ah, true - I did say the SSM2142 could work well, but it probably is overkill for achieving 12dB gain and a balanced output


Martin

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


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Evie McCreevie



Joined: 06/09/04
Posts: 1028
Loc: Dublin
Re: After playing around with a few transformers.... new [Re: Martin Walker]
      #1109650 - 26/06/14 07:09 PM
Hi Martin W...

I'm posting here as you advised, following my thread re ready-to-go transformer boxes:
http://www.soundonsound.com/forum/showflat.php?Cat=&Number=1108798& ;page=0&view=collapsed&sb=5&o=&fpart=1#Post1109619#1108798

Just be be clear: I'm interested in a transformer-based box to run ITB mixes through - purely for the sonics. I love what good transformers do in quality mic pre-amps, and am hoping for a similar effect across the mix buss.

TBH I'm not mad about DIYing, but there seems to be no alternative.

Any help appreciated. Thanks!


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Martin WalkerModerator
Watcher Of The Skies


Joined: 28/02/01
Posts: 17409
Loc: Cornwall, UK
Re: After playing around with a few transformers.... new [Re: Evie McCreevie]
      #1109959 - 29/06/14 12:16 PM
Sorry Evie - only just noticed your post in this thread

Here as promised are some links to DIY 'euphonic transformer' boxes following my own research, that as I mentioned I've yet to follow up with my soldering iron.

Using Transformers to Transform Audio | Allen Farmelo

Tape Op Message Board :: View topic - Building a Transformer/Color Box? School me on transformers

Audio Transformer As Signal Processor | Preservation Sound

DIY Transformer mojo box??? - Gearslutz.com

DIY transformer box to add color - Gearslutz.com

New Output Transformer that WILL Saturate?? - Gearslutz.com

How to Build a Boutique Passive DI

Experiments with transformers

horobooster


Hope these links help, and do let us know (with audio examples ) how you get on


Martin

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


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ketracel



Joined: 14/10/07
Posts: 4
Re: After playing around with a few transformers.... new [Re: ef37a]
      #1110809 - 05/07/14 03:51 PM
Quote ketracel:

What are the variations in addressing the issue of level?

Consider unbalanced synth outputs are usually -10dBv running into mixer inputs which are balanced +4dBu. In this case there is a massive 12dB loss of signal. Sure, significant amounts of gain can be applied on the mixer, also with additional noise mind you is there a cleaner, efficient or optimal solution, can transformers also help here?




Quote ef37a:

I would not consider 12dB to be a "massive" loss nor making it up "significant"! The line inputs on even a cheap mixer should be capable of this without adding noticeable noise. Indeed, any noise that does intrude is likely to come from the synth!




Hi again Dave,
Dave, 12dB would be the minimal loss!!! Consider the quieter sounds from a synth, these are going to need much more than 12dB of gain to get to unit in the mixer on inputs.
The mixer input is only one such path. Would you not consider 12dB a large loss of signal, if for instance we were to run direct from the synth output into an fx unit (balanced +4dB I/O) , instead of going via a mixer input + gain > AUX send/return? Surely a tonne of additional noise would enter the path no??

Quote ef37a:

Note I said "good" transformers? The products from OEP/Walter at about £10 each (600R:600R) are actually a bit too good for synths! I would not go for exotics.




What type of synths do you have on your mind and what components of these synths do you consider not good enough when you mention certain transformers "too good for synths"? If you could clarify the elements of consideration, i'll have a better understanding of your opinion, because another bit of advice you offer is more than perplexing given the available info:

Quote ef37a:

If you still want galvanic isolation a couple of OEP 1200s driven from the 5532 configured for "zero" output impedance would be fine.




If I have the correct product data sheet in front of me for the OEP1200 tranny, (which can't be found under audio transformers but under Telecom transformers) its frequency response is 300hz-4khz. This frequency range wouldn't be wide enough for any synth I can think of.

Product page:
http://www.oep.co.uk/products_listing.php?page=1&cat=6&subcat=23&a mp;subsubcat=50
Data sheet:
http://www.oep.co.uk/pdf/OEP1200.pdf

While I still need to analyse the output levels of each unbalanced device I have, I'd still like to know if there is any advantage or disadvantage in having this 12dB gain added close to the source by way of a isolation balanced line matching device connected directly to the unbalanced outputs of the synths or at the destination (mixer line input gain, or any other balanced +4dB fx, processing device).

Apologies original thread creator if this is taking your conversation out of context.


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ef37a



Joined: 29/05/06
Posts: 6698
Loc: northampton uk
Re: After playing around with a few transformers.... new [Re: ketracel]
      #1110824 - 05/07/14 05:09 PM
Quote ketracel:

Quote ketracel:

What are the variations in addressing the issue of level?

Consider unbalanced synth outputs are usually -10dBv running into mixer inputs which are balanced +4dBu. In this case there is a massive 12dB loss of signal. Sure, significant amounts of gain can be applied on the mixer, also with additional noise mind you is there a cleaner, efficient or optimal solution, can transformers also help here?




Quote ef37a:

I would not consider 12dB to be a "massive" loss nor making it up "significant"! The line inputs on even a cheap mixer should be capable of this without adding noticeable noise. Indeed, any noise that does intrude is likely to come from the synth!




Hi again Dave,
Dave, 12dB would be the minimal loss!!! Consider the quieter sounds from a synth, these are going to need much more than 12dB of gain to get to unit in the mixer on inputs.
The mixer input is only one such path. Would you not consider 12dB a large loss of signal, if for instance we were to run direct from the synth output into an fx unit (balanced +4dB I/O) , instead of going via a mixer input + gain > AUX send/return? Surely a tonne of additional noise would enter the path no??

Quote ef37a:

Note I said "good" transformers? The products from OEP/Walter at about £10 each (600R:600R) are actually a bit too good for synths! I would not go for exotics.




What type of synths do you have on your mind and what components of these synths do you consider not good enough when you mention certain transformers "too good for synths"? If you could clarify the elements of consideration, i'll have a better understanding of your opinion, because another bit of advice you offer is more than perplexing given the available info:

Quote ef37a:

If you still want galvanic isolation a couple of OEP 1200s driven from the 5532 configured for "zero" output impedance would be fine.




If I have the correct product data sheet in front of me for the OEP1200 tranny, (which can't be found under audio transformers but under Telecom transformers) its frequency response is 300hz-4khz. This frequency range wouldn't be wide enough for any synth I can think of.

Product page:
http://www.oep.co.uk/products_listing.php?page=1&cat=6&a...
Data sheet:
http://www.oep.co.uk/pdf/OEP1200.pdf

While I still need to analyse the output levels of each unbalanced device I have, I'd still like to know if there is any advantage or disadvantage in having this 12dB gain added close to the source by way of a isolation balanced line matching device connected directly to the unbalanced outputs of the synths or at the destination (mixer line input gain, or any other balanced +4dB fx, processing device).

Apologies original thread creator if this is taking your conversation out of context.




Ok my remarks were a bit tongue in cheek but it is hard to find data on a synth's dynamic range?
How quiet are the very best ones? A synth with an output at "consumer" neg ten is hard likely to be of high audiophile quality?

The OEP1200 are actually used in some commercial gear for audio distribution in the home. Running at the same -10dBV level they give quite a good account of themselves. Distortion from transformers is reduced as the source Z drops so driving a 1200 from a "zero" Z opamp (at -10dBV) would be a good plan. But no, if you want studio levels pay for better.

I don't quite follow all the noise criteria but my point was that a 5532 line amp with 12dB of gain would have a noise output of rather better than -100dBu and you should be so lucky to find a synth that quiet?

Dave.


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