Single ended to balanced conversion....

[farflungstar]

So I've just put a payment down on this lovely amplifier (no more looking for Leben) but I have slight problem - the amp only has balanced inputs and my the Truth is single ended - so can I have a pair of interconnects made up that are single ended to balanced? Are there any high quality converter plugs?



https://uploads.tapatalk-cdn.com/20171102/117b3be87fec601f511461616263d109.jpg

[struth]

ooohhh, very nice Adrian.. that is a bosker

[farflungstar]

Thanks - it's the Ref 75 - after a lot of reading and chat wth Tom it won me over.

[Barry]

The quick answer is yes - XLR to RCA adaptors are readily available. All they do is connect the -ve going input to ground. (I use a pair on my Quad 520 amp.)

[farflungstar]

The quick answer is yes - XLR to RCA adaptors are readily available. All they do is connect the -ve going input to ground. (I use a pair on my Quad 520 amp.)World you recommend a custom build? Or is the quality okay?

[Barry]

The quick answer is yes - XLR to RCA adapters are readily available. What they do is connect the -ve going input to ground. (I use a pair with a Quad 520 amp in one of my systems.)

If you are looking for high quality adapters, then I would recommend those made by Neutrik: https://www.amazon.co.uk/NEUTRIK-SILVER-NA2MPMF-POS-ADAPTOR-BLISTER/dp/B00MOF8DLC/ref=sr_1_35?ie=UTF8&qid=1509656222&sr=8-35&keywords=xlr+rca+adapter

[Spectral Morn]

Go with a Cardas Rca/XLR adaptor there is a difference in sound quality between that and cheap Chinese crap, and I think they have the edge on Neutrik. Cardas do two levels of quality I would go the extra and get the better of the two.

http://www.cardas.com/adaptors.php

[farflungstar]

Thanks guys - Cardas looks like a good choice.

[RothwellAudio]

This is a far more complicated subject than it may appear. Your Truth has a single-ended output so you can really only feed the Audio Research with an unbalanced signal. The simple solution is to use one of those adaptors which was linked-to above, but all it does is feed the unbalanced signal to pins 1 and 2 of the XLR and link pin 3 (the unused pin) to pin 1. At least, I assume pin 3 is linked to pin 1 - they rarely bother to tell you in the adverts.
However, there's another option: instead of linking pin 3 to pin 1 you could use balanced cable and link pin 3 to the the ground side of the RCA plug at the RCA end. The idea is that you still get some of the benefits of a balanced line. Wire it like the top picture in this image
https://www.audioexchange.co.za/wp-content/uploads/2016/08/RCA_to_XLR.gif

Will there be much difference in practice? Somehow I doubt it, but bear in mind that I'm one of those cloth-eared fools who thinks mains cables don't make any difference. :lol:

[RothwellAudio]

BTW, I just found this from Genelec:
https://i.imgur.com/aEnPnHC.png

[hifinutt]

fabulous , one amp on my listening list . when i had a ref 5 i had an expert in cable making make me a xlr to rca set of cables . as my power amps were only rca inputs . we had rather a job as they hummed and despite our best efforts i never succeeded so went onto rca to rca . i am sure someone could do it though

incidentally the xlr were cardas

[farflungstar]

Hmmm - so maybe I'm going to have a problem with hum... Bugger...

[farflungstar]

I've emailed the maker of the Truth to see if there is a solution - I thought the 75 was like many other amps, not true balanced operation but it is - so it really needs a truly balanced preamp. FFS...

[Puffin]

Do these powered units work?

https://www.studiospares.com/ProductDetail.aspx?p=368360 There are cheaper alternatives around.

There are also passive ones that use transformers to carry out the conversion. Are these worth having?

https://www.studiospares.com/Microphones/Mic-Transformers/ART-DTI-Dual-Balancing--Isolating-Transformer_325310.htm?gclid=Cj0KCQjwp_DPBRCZARIsA GOZYBQpxWytbN4h8VWqiqWI8d_Mz30P2CRKcpN15R-RJkrPHL1Cc79ur3AaAkE4EALw_wcB&gclsrc=aw.ds

[farflungstar]

Ok so I'm stupid - can someone explain to me what a balanced circuit actually is...

[RothwellAudio]

Hmmm - so maybe I'm going to have a problem with hum... Bugger...

I've emailed the maker of the Truth to see if there is a solution - I thought the 75 was like many other amps, not true balanced operation but it is - so it really needs a truly balanced preamp. FFS...
Eh? No, there shouldn't be problem. You don't need a "truly balanced" preamp for it to work without humming. I'm pretty sure the Nuetrik adaptors will work without producing hum - I only said it's more complicated than it appears because there are several wiring options which will work but they're all a bit of a fudge. For example, you could leave pin 3 completely unconnected - but that would introduce some noise. Still, it would work and wouldn't (shouldn't?) hum.
Generally pin 3 is grounded somehow. It could be grounded at the AR end of the cable (as it would if you used an adaptor) or it could be grounded at the preamp end of the cable (but that would require making a cable for the job).
BTW, I wouldn't expect Cardas cable to be any better than anything else - what's more important is having it wired correctly. personally, I would make up a cable (two core plus screen) wired as in the diagrams on the previous page.

[Puffin]

This is fairly well written for the layman (me included)

http://www.aviom.com/blog/balanced-vs-unbalanced/

[farflungstar]

Eh? No, there shouldn't be problem. You don't need a "truly balanced" preamp for it to work without humming. I'm pretty sure the Nuetrik adaptors will work without producing hum - I only said it's more complicated than it appears because there are several wiring options which will work but they're all a bit of a fudge. For example, you could leave pin 3 completely unconnected - but that would introduce some noise. Still, it would work and wouldn't (shouldn't?) hum.
Generally pin 3 is grounded somehow. It could be grounded at the AR end of the cable (as it would if you used an adaptor) or it could be grounded at the preamp end of the cable (but that would require making a cable for the job).
BTW, I wouldn't expect Cardas cable to be any better than anything else - what's more important is having it wired correctly. personally, I would make up a cable (two core plus screen) wired as in the diagrams on the previous page.That's exactly what I initially thought David. Live to pin 1, return to pin 2, and earth shield to pin 3. But having checked forums no one, it seems, is running it that way - all are using balanced preamps.

[RothwellAudio]

Do these powered units work?

https://www.studiospares.com/ProductDetail.aspx?p=368360 There are cheaper alternatives around.

There are also passive ones that use transformers to carry out the conversion. Are these worth having?

https://www.studiospares.com/Microphones/Mic-Transformers/ART-DTI-Dual-Balancing--Isolating-Transformer_325310.htm?gclid=Cj0KCQjwp_DPBRCZARIsA GOZYBQpxWytbN4h8VWqiqWI8d_Mz30P2CRKcpN15R-RJkrPHL1Cc79ur3AaAkE4EALw_wcB&gclsrc=aw.ds

Yes, it is possible to take an unbalanced signal and generate a balanced signal from it using op-amps or balanced line driver chip but you're introducing a bucket load of additional electronics that isn't really necessary.
It's also possible to use a transformer to balance the signal but there are likely to be audible sonic effects.

[RothwellAudio]

That's exactly what I initially thought David. Live to pin 1, return to pin 2, and earth shield to pin 3. But having checked forums no one, it seems, is running it that way - all are using balanced preamps.
Who's David? :scratch:

[RothwellAudio]

That's exactly what I initially thought David. Live to pin 1, return to pin 2, and earth shield to pin 3. But having checked forums no one, it seems, is running it that way - all are using balanced preamps.
Who's David? :scratch:
BTW, do you trust the people on forums? :lol:

[Barry]

Pin 1 on an XLR connector is always the ground or earth connection. Pins 2 and 3 are usually the +ve going and -ve going signal connection respectively, though it ought to mentioned that this convention is not always followed: on some equipment the polarity of pins 2 and 3 can be reversed. The latter will cause no harm but it will invert the polarity, which some claim to be audible.

http://theartofsound.net/forum/showthread.php?3849-Basics-amp-General-Audio-Connectors

I believe there are in-line balanced to unbalanced converters available which use transformers.

https://www.canford.co.uk/Images/ItemImages/large/49-277_01.jpg

https://www.canford.co.uk/BALANCED-TO-UNBALANCED-CONVERTERS

They are expensive and are not really necessary: an XLR to RCA lead wired using shielded two-core cable as Andrew has described above ought to be quite sufficient. I use such when I need to connect an amplifier with an unbalanced input to my preamp which has a true dual-differential balanced output.

The only other thing to bear in mind when feeding a balanced amplifier from an unbalanced source (preamp), is the sensitivity of the amplifier will be halved.

[farflungstar]

Who's David? :scratch:
BTW, do you trust the people on forums? [emoji38]Why did I think your name was David? Dementia.

[farflungstar]

Pin 1 on an XLR connector is always the ground or earth connection. Pins 2 and 3 are usually the +ve going and -ve going signal connection respectively, though it ought to mentioned that this convention is not always followed: on some equipment the polarity of pins 2 and 3 can be reversed. The latter will cause no harm but it will invert the polarity, which some claim to be audible.

http://theartofsound.net/forum/showthread.php?3849-Basics-amp-General-Audio-Connectors

I believe there are in-line balanced to unbalanced converters available which use transformers.

https://www.canford.co.uk/Images/ItemImages/large/49-277_01.jpg

https://www.canford.co.uk/BALANCED-TO-UNBALANCED-CONVERTERS

They are expensive and are not really necessary: an XLR to RCA lead wired using shielded two-core cable as Andrew has described above ought to be quite sufficient. I use such when I need to connect an amplifier with an unbalanced input to my preamp which has a true dual-differential balanced output.

The only other thing to bear in mind when feeding a balanced amplifier from an unbalanced source (preamp), is the sensitivity of the amplifier will be halved.Yes you're right...
Technical specs from the maker
Output power: 75 watts
Frequency response: at full power 7Hz - 60kHz (-3 dB), at 1W -0.7Hz - 75kHz
Input sensitivity: 1.4V (25dB to 8Ω)
Input impedance: 300*
Absolute phase: not reversed (pin 2 = hot)
Negative feedback: approximately 15dB
Rise time: 10V/ms
Hum and noise: < 0.06 mV RMS (-112dB)
Dimensions: 483 x 222 x 495 (WxHxD)
Weight: 21.3 kg

[Pharos]

Generally, connecting an unbalanced O/P into a balanced I/P is never a problem, but the reverse can be.

ATCs are often fed from unbalanced preamp ccts, and without problems, I have done it with three pairs using Sumo and AVI preamps.

[RothwellAudio]

Actually, at the risk of putting the OP right off the idea of feeding a balanced power amp from an unbalanced preamp, there is one more complication, and it's this:

Pin 1 on an XLR connector is always the ground or earth connection.
Is pin 1 ground/earth or 0V? Depends what you mean by ground. The amplifier's metalwork should be earthed to the mains for safety (unless it's double insulated). That doesn't mean it has to be connected to 0V though. So what do you do with the little earth tag inside the XLR connector? It's there so you can make a link between the XLR's metalwork and pin 1 if you want to. But do you want to? :scratch: If you do make the link and the amplifier's casework is connected to 0V then you're making a link between mains earth and 0V. Is that a good thing or a bad thing? Depends on how the preamp is wired. Is the preamp's 0V also connected to mains earth or is it floating?

It would be nice if balanced equipment actually did live up to its goal - that you can connect anything to anything and there'll never be a problem - but things don't always work out like that.
Having said all that, I'm not claiming that there's trouble ahead for the OP. Just wire up an RCA-XLR cable and see what happens. Most likely there won't be any problem at all.

[farflungstar]

Actually, at the risk of putting the OP right off the idea of feeding a balanced power amp from an unbalanced preamp, there is one more complication, and it's this:

Is pin 1 ground/earth or 0V? Depends what you mean by ground. The amplifier's metalwork should be earthed to the mains for safety (unless it's double insulated). That doesn't mean it has to be connected to 0V though. So what do you do with the little earth tag inside the XLR connector? It's there so you can make a link between the XLR's metalwork and pin 1 if you want to. But do you want to? :scratch: If you do make the link and the amplifier's casework is connected to 0V then you're making a link between mains earth and 0V. Is that a good thing or a bad thing? Depends on how the preamp is wired. Is the preamp's 0V also connected to mains earth or is it floating?

It would be nice if balanced equipment actually did live up to its goal - that you can connect anything to anything and there'll never be a problem - but things don't always work out like that.
Having said all that, I'm not claiming that there's trouble ahead for the OP. Just wire up an RCA-XLR cable and see what happens. Most likely there won't be any problem at all.I'd be lying if I said I wasn't worried but I've spoken wth the maker of the Truth (hes sent me 3 messages) and he assures me there won't be a problem. For extra info there is a ground lift on the Truth - there's also a second set of outputs - could these be utilised in any way?

[Spectral Morn]

Fully balanced is dual differential with separate left and right channel audio paths, basically everything doubled up, and while I personally think a suitable/matching balance pre will sound better, you are over thinking things, just buy an adapter. I use adapters for some of my single ended kit into my fully balanced pre and its fine, no issues and I use the Cardas ones, and I think they sound better..... you pays your money and makes your choice.

My gear is Balanced Audio Technology, not Audio Research.

[farflungstar]

Fully balanced is dual differential with separate left and right channel audio paths, basically everything doubled up, and while I personally think a suitable/matching balance pre will sound better, you are over thinking things, just buy an adapter. I use adapters for some of my single ended kit into my fully balanced pre and its fine, no issues and I use the Cardas ones, and I think they sound better..... you pays your money and makes your choice.

My gear is Balanced Audio Technology, not Audio Research.Jajaja I overthink everything.

[montesquieu]

Jajaja I overthink everything.

I've used RCA-XLR adaptors with no issue in the past and I had some XLR/RCA cables at one point as well ... either way you should be fine. Personally, I'd have some cables made up (I'm sure Paul at RFC could help you there).

As well as single ended all round I have balanced outputs available on my AN DAC (4.1x fancy balanced transformer output), balanced inputs and outputs on my EAR 912, and balanced inputs on my Radford STA100. So I could in theory use balanced all round and have tried things that way. However I hear precisely no improvement from balanced wiring. I can see the point in a studio over metres and metres of distance, but not over 1m cables in a domestic setting.

Deep breath and relax.

[Spectral Morn]

I've used RCA-XLR adaptors with no issue in the past and I had some XLR/RCA cables at one point as well ... either way you should be fine. Personally, I'd have some cables made up (I'm sure Paul at RFC could help you there).

As well as single ended all round I have balanced outputs available on my AN DAC (4.1x fancy balanced transformer output), balanced inputs and outputs on my EAR 912, and balanced inputs on my Radford STA100. So I could in theory use balanced all round and have tried things that way. However I hear precisely no improvement from balanced wiring. I can see the point in a studio over metres and metres of distance, but not over 1m cables in a domestic setting.

Deep breath and relax.

Lower noise floor, which benefits everything if the two items being connected are genuine balanced designs. You can't hear it, I and others can. As they say other folks mileage will vary.

[farflungstar]

I've used RCA-XLR adaptors with no issue in the past and I had some XLR/RCA cables at one point as well ... either way you should be fine. Personally, I'd have some cables made up (I'm sure Paul at RFC could help you there).

As well as single ended all round I have balanced outputs available on my AN DAC (4.1x fancy balanced transformer output), balanced inputs and outputs on my EAR 912, and balanced inputs on my Radford STA100. So I could in theory use balanced all round and have tried things that way. However I hear precisely no improvement from balanced wiring. I can see the point in a studio over metres and metres of distance, but not over 1m cables in a domestic setting.

Deep breath and relax.That's almost exactly what the maker of the Truth said Tom.

[montesquieu]

The only other thing to bear in mind when feeding a balanced amplifier from an unbalanced source (preamp), is the sensitivity of the amplifier will be halved.

Having said all the rest, Adey's Truth is (as I understand it) some kind of LDR attenuated buffer device with no gain. Since the Vida isn't a gain monster either this **might** be an issue. Hard to tell in advance.

[farflungstar]

Having said all the rest, Adey's Truth is (as I understand it) some kind of LDR attenuated buffer device with no gain. Since the Vida isn't a gain monster either this **might** be an issue. Hard to tell in advance.Yes I've thought about that but Ed, the maker of the Truth says it won't be a problem. I'm truly hoping not as I cannot imagine in a million years changing the Truth, it would be a retrograde step no matter what preamp.

[farflungstar]

What would the effect of halving the amps input sensitivity be in real terms? I'm assuming it would be more difficult to drive to high levels?

[Pharos]

Yes, as dealt with previously, the main benefits of the balanced approach are for broadcasters and studio setup engineers when assembling different combinations of equipment, which they do frequently, they not having to worry about hum problems with long leads.

In our case we setup and leave, mostly.

I think the cable method is neater, and not hard to do, and with fewer interfaces.

[RothwellAudio]

Lower noise floor, which benefits everything if the two items being connected are genuine balanced designs. You can't hear it, I and others can. As they say other folks mileage will vary.
Balanced connections don't have inherently lower noise - in fact they can be noisier.

[moodybuilder]

im using psuedo balanced cables as my pre amp is balanced and my monos are single ended, with good results and no hum,

[RothwellAudio]

im using psuedo balanced cables as my pre amp is balanced and my monos are single ended, with good results and no hum,
With a single-ended source and a balanced destination you can run a psuedo-balanced line, but not the other way round. The power amps are single-ended, what can possibly be balanced about line? :scratch:
Of course, you can connect the two together and get no hum, but there's nothing balanced - or psuedo-balanced - about it.

[moodybuilder]

sorry trying to do to many things at once, i ment single ended pre and balanced mono amps

[Primalsea]

Everything has been pretty well covered but I would add that the input impedance of balanced circuits is usually lower than unbalanced, so the preceeding equipment will need to be able to dive the load. This is rarely an actual issue as most equipment can handle this additional anyway, but in some cases can result in increased distortion. In real life this is not usually a real issue.

Also balanced nominal line level voltage is a fair bit higher than unbalanced nominal line level. In some cases this can be helpful as you can crank your volume up abit further than if you were going into an unbalanced amp. I find that some equipment sounds better cranked up a bit.

[Barry]

Actually, at the risk of putting the OP right off the idea of feeding a balanced power amp from an unbalanced preamp, there is one more complication, and it's this:

Is pin 1 ground/earth or 0V? Depends what you mean by ground. The amplifier's metalwork should be earthed to the mains for safety (unless it's double insulated). That doesn't mean it has to be connected to 0V though. So what do you do with the little earth tag inside the XLR connector? It's there so you can make a link between the XLR's metalwork and pin 1 if you want to. But do you want to? :scratch: If you do make the link and the amplifier's casework is connected to 0V then you're making a link between mains earth and 0V. Is that a good thing or a bad thing? Depends on how the preamp is wired. Is the preamp's 0V also connected to mains earth or is it floating?

It would be nice if balanced equipment actually did live up to its goal - that you can connect anything to anything and there'll never be a problem - but things don't always work out like that.
Having said all that, I'm not claiming that there's trouble ahead for the OP. Just wire up an RCA-XLR cable and see what happens. Most likely there won't be any problem at all.

Sorry - I was being sloppy with my terminology. Yes Pin 1 is 0V or the signal ground, whether that is the same as the mains earth will depend on the design of the amplifier. Certainly the housing of the receptical will be earthed as it is connected to the case metalwork, so the shell of any plug mated will also be earthed. When it comes to the 'little earth tag' inside the shell, I don't use them, the shells are electrically safe and there is no possibility of creating an earth loop.

I'm a big believer in the idea of using balanced-line systems. If the equipmant is designed to be fully dual differential, there are noticable benifits to be had. There is no a priori reason why they should be any noisier, or the impedance should be lower, than with unbalanced systems; 600 Ohms is a legacy from the telecoms industry.

I use them because I have balanced input monoblock amplifiers located behind each speaker and run 15m lengths of balanced-line cable back to the preamp (which has fully balanced outputs), which in turn is fed by a CD player also having fully balanced outputs.

And since pick-up cartridges are inherently balanced devices, I am looking for a phonostage that is also fully balanced, but haven't, as yet, found anything suitable.

[Pharos]

Yes balanced is reliably very good, but often has a theoretically doubled distortion, although this is already so low these days that it is still near zero. (AVI pre 0.0001%, ATC pre 0.0002%)