Why Single-Ended?

Yep,
Manufacturers develop and sell what they believe in and there're no shortage of beliefs.  This suits the marketplace which has listeners of many different sonic and musical preferences. Every single genre of amplifier type will have its adherents and of course detractors.  Subjectivity drives the High End and keeps it viable with the many choices. Be your desire a 1 watt SET or a 2000 watt class D beast,  there's something for everyone. Preference and individual taste are the dominant determinants of final decisions about which audio component to buy/own. 
Charles 

Not sure of that.  Perhaps, since it is done without input transformer there is ground reference for instrumentation amp that is usually connected with higher value resistor (and small cap) to a chassis. Signal is still differential and I cannot understand why would it reduce effect that cable brings.  Cable capacitance, inductance and dielectric absorption are still there.  Do you think that extremely dirty copper would sound wonderful in balanced cable?

The way balanced line eliminates cable artifacts is twofold. First, ground is ignored, so the shield is not part of the sound (nor the is noise to which its exposed; in a single-ended system the shield is part of the signal path).

Second, the source impedance is low and so is able to swamp the inductance and capacitance of the cable.

In fact in our tests and auditions we have frequently used an aged (60 year old) microphone cable that used rubber dielectrics and tin-plated multi-stranded copper, with obvious corrosion on the shield. When driven by a balanced passive control (which did not meet AES file 48) the cable literally sounded broken compared to other cables (Purist, Kimber, Audioquest and also Mogami)- broken enough that you wondered what the heck was wrong with the stereo. When we then ran the same set of cables with a source that supported file 48, the differences between the cables, including the one with the 'dirty copper' vanished.

IOW, what the technology is **for** is to eliminate a problem that audiophiles are well aware of- which is that cables sound different and often not as musical as one would hope. Put another way, if you can hear a difference between cables in an audition, it means that **both** cables are wrong, as everyone knows full well that next year someone (likely the manufacturer of the better cable) will have a newer cable that sounds amazingly better. This has been going on decades (one would think an audiphile would just like to finally get to where that is all going and not have to search for the holy grail anymore), yet somehow recordings made in the 1950s (using balanced lines) just sound better and better as the playback equipment improves...

It does not make sense.  I understand how even harmonics are eliminated but don't know of any mechanism that would remove odd harmonics in fully balanced amp.  Remember we're talking about Fully balanced amps in general - not only your designs.

I get that it does not make sense for you. But that does not mean it does not make sense. The idea here is to remove distortion sources (now this is strictly my opinion). If you can't use feedback to get rid of distortion, how do you get rid of it? Eliminate distortion sources! A common complaint about tubes: 2nd harmonic (ask any solid state guy). OK- fully balanced differential design gets rid of the even orders. Now we are left with the odd orders. To reduce them, we set bias points in the voltage amplifier such that it cancels the odd orders. Then design the circuit to use as few stages of gain as possible (in our amps there is only one stage of gain, making them a simpler signal path than an SET). Use triodes throughout. Get rid of the output transformer (which may or may not add distortion). Take care to avoid obvious diode issues (proper metallurgy) in component selection. Stuff like that.

Kijanki, you have made one of the most reasonable cases for the sonic advantages of the single ended circuit and its simpler design. This positive perspective is rarely seen. Well done gentlemen!

For the most part I agree, however just for the record as I pointed out above, our amps have only one gain stage with no phase inverter circuit. They are a simpler signal path than most SETs. This should be possible with any **fully** differential circuit- it does not have to be an OTL.

BTW despite what Ralph contends phono cartridges are NOT balanced as there is no ground, no ground  pin connection, only 2 lines out.

This statement has long been debunked. Herman, take this from someone who has apparently made a career of balanced line operation, who also understands single-ended (I've built many SE amps; type 45, 2A3 and 300b):

Any source that employs a magnetic pickup, like a phono cartridge, dynamic microphone or tape head, is an inherently balanced source. The proof of this is simple: reverse the connections to the device and all that happens is you reversed the phase. If it really was a single-ended source, reversing the connections from it would get you a whole lot of hum and buzz!

The reason is simple- all of those sources are simply a winding.

Now I think I see where the disconnect is happening: you probably think that balanced line requires three connections, and that somehow something like a cartridge would too. It does not work that way. If you refer back to my initial post in this thread, you will see that a balanced line **ignores ground** (and so uses two connections, not three, as ground is only used for shielding).

To put that in perspective, let's take the example of a transformer driving a balanced line. I suspect you think that such a transformer would use a center tap for the ground, but that is not the case. The reason is simple: you want the best Common Mode Rejection Ratio you can get. If you use a center tap of a transformer, the CMRR will be degraded because the center tap can never be placed perfectly in the center of the winding). Instead the winding of the transformer floats- its output (or input) is merely tied to pins 2 and 3 of the XLR and nothing else. No ground connection- that is only for shielding and the chassis and is not tied to the transformer, cartridge, tape head or dynamic microphone.

So only two connections are needed, and in many cases you can operate a balanced line without the shield (sometimes its actually lower noise this way, particularly in shorter runs of less than 3 feet). IOW you don't need three connections to be balanced.

One thing here I like to point out:

Running balanced lines is an entirely different matter from having an amp or preamp that has a fully balanced differential circuit! By this I mean that you can have a single-ended circuit but run balanced lines outside the box and retain all the advantages of balanced line as it pertains to cables (a good example of this is the venerable Ampex 351 tape electronics, which is almost entirely single-ended, but runs balanced line inputs and outputs; many fabulous recordings exist in many audiophile's libraries that were recorded on those electronics). 

IOW its important to not conflate the two.

Now as it happens, there are advantages to running a fully balanced circuit. I think that one of them is the simplified signal path. For example in our preamps we have three stages of gain from low output moving coil input to the line stage output (which can drive headphones). In the amps we have one stage of gain. That's about as simple as a signal path can get!

I too prefer higher efficiency loudspeakers with an amplifier of simple design and signal path. So that is one thing that Herman and I have in common.

You could ask the same of Atmasphere. Why don't they offer an SET amp? The reason is they are dedicated to optimizing the topology that they are committed to.

Hm. I think you could be mistaking pragmatism for being dogmatic. Take a look at this:
http://www.atma-sphere.com/Products/#UV-1

I've often defended SET amplifiers on account of they can do something that very few push-pull amps can do: As the output power is decreased, the distortion becomes unmeasurable. The only push-pull amp I know of that does that is our own amps (now you can see why I defend SETs in this regard) although there will be others if the designers take the right steps.

Fact XLR is not better necessarily for common or usual runs of 1/2 meter to 1.5 meter.  

Atmosphere.....great post...thanks.  I have a fully balanced system and wondered why when evaluating cable interconnects....there was such very little difference.....speaker connections much more obvious.

grannyring
Fact XLR is not better necessarily for common or usual runs of 1/2 meter to 1.5 meter.

+1, In fact it’s worse in many cases as I outlined before.

" Many amps, preamps, and sources have fake balanced inputs and outputs In that they just put in an extra opamp in the signal path to create a balanced input or output.
Where their single ended input/output is better, as that fake balancing opamp is then not in the signal path."

Cheers George

Thanks Almarg

if you google around you will find debate on whether a cartridge is balanced, as I see it that really doesn't matter. The important thing is how you deal with it. if you transformer couple it with a center tapped secondary then that would definitely be balanced. Of course you could take any SE source and do the same thing.

Thanks for the spell check. My point is that when the air compressions and rarefactions hit the microphone it is equivalent to a single ended source. The diaphragm vibrates back and forth. There is no equivalent diaphragm moving forth and back. Same for a speaker, the cone moves back and forth driven by a balanced or SE amp. At the end of the day does any of that matter? probably not. 

As I see it any "advantages" of balanced are outweighed in the home environment by the simplicity and linearity of an SET amplifier. At least that's what my ears tell me. 

 I will admit the only extended listing I've done to OTL amps were Atmasphere at some dealer I believe in San Jose years ago. Can't remember the name or anything else about the system except they were playing vinyl and it did sound excellent, so I get it that many would prefer it. I do remember the guy had a lot of vinyl for sale, they all smoked cigars so the place smelled foul, and the owner was an arrogant jerk, at least he was to me.

So Ralph, you have come over to the dark side with an SE preamp. There is some hope :>)

Full disclosure; my preamp is the Atma-sphere UV-1, single-ended. I decided to buy this unit based on it's sonics and simple design. To me, it does everything right; wide and deep soundstaging, realistic imaging, deep bass extension. It presents a clear, yet classic sound using 6SN7 tubes.
  My CDP and DAC are a balanced design, thus the reason I posted my question. If this preamp or a CJ or Coincident offered a balanced input thru a transformer, it might introduce artifacts thru the circuit.

The way balanced line eliminates cable artifacts is twofold. First, ground is ignored, so the shield is not part of the sound (nor the is noise to which its exposed; in a single-ended system the shield is part of the signal path).

You cannot eliminate capacitance between wires.  Low output impedance helps to lower effect of it, but it so does with single ended design.  It will be difficult to get rid of shield to wire capacitance since many preamps have balanced output referenced to ground.  It will be pretty much any transformerless output stage including my Benchmark DAC1.

I get that it does not make sense for you. But that does not mean it does not make sense. The idea here is to remove distortion sources (now this is strictly my opinion). If you can't use feedback to get rid of distortion, how do you get rid of it? Eliminate distortion sources! A common complaint about tubes: 2nd harmonic (ask any solid state guy). OK- fully balanced differential design gets rid of the even orders. Now we are left with the odd orders. To reduce them, we set bias points in the voltage amplifier such that it cancels the odd orders. Then design the circuit to use as few stages of gain as possible (in our amps there is only one stage of gain, making them a simpler signal path than an SET). Use triodes throughout. Get rid of the output transformer (which may or may not add distortion). Take care to avoid obvious diode issues (proper metallurgy) in component selection. Stuff like that.

You forgot that we are discussing Fully balanced topology and not design of particular amp in general.  Setting bias point, as you described, can be done to single ended amp and has nothing to do with issue that we're discussing.  Please tell me how Fully balanced amp topology reduces third harmonic better than single ended amp.

So Ralph, you have come over to the dark side with an SE preamp. There is some hope :>)

Ha! We've been making some variant of that since the company was founded. Not sure that 'come over' is the right phrase...

if you transformer couple it with a center tapped secondary then that would definitely be balanced.

I very much doubt that there even is such a thing as a center-tapped SUT for the reasons I outlined earlier. We have made up SUT boxes that were entirely balanced using Jensen SUTs. All transformers (including SUTs) are capable of operating single-ended or balanced; no center tap required- works better without it.

You forgot that we are discussing Fully balanced topology and not design of particular amp in general.  Setting bias point, as you described, can be done to single ended amp and has nothing to do with issue that we're discussing.  Please tell me how Fully balanced amp topology reduces third harmonic better than single ended amp.

It doesn't. The 3rd harmonic (which is musical to the human ear) occurs at about the same level or slightly less (see below) than the 3rd shows up in a single-ended design (this is assuming open loop).

Because the 2nd is pretty well eliminated, the result is (due to the ear's masking principle) greater low level detail since there isn't a 2nd order to obscure it. That there is more low level detail in such amps is not a subtle thing- its quite easy to hear. Its nice when the measurements and the subjective experience agree.

When I was speaking of the bias point I was not referring to the output tubes, but the bias point at which the voltage amplifier is set. This is not an adjustment; its the value of resistor in the cathode circuit, which can affect the distortion and gain structure of the voltage amp. In the case of a differential amplifier, this resistor is in the CCS circuit and its value can be critical. In essence the value can have an outcome on the kind of distortion the voltage amplifier makes, particularly when it overloads. I prefer to set that value so that the stage is clipping in a symmetrical fashion. This makes for more of a 3rd harmonic rather than a 2nd, but also can have the effect of reducing the amount of the 3rd harmonic.

You cannot eliminate capacitance between wires.  Low output impedance helps to lower effect of it, but it so does with single ended design.  It will be difficult to get rid of shield to wire capacitance since many preamps have balanced output referenced to ground.

I hope you are not suggesting that single-ended cables can run as far as balanced... I'm going to refer you to Wikipedia on this one.
https://en.wikipedia.org/wiki/Balanced_line

I also refer you to AES file 48 which I've mentioned several times. The Rane site has a great little article that should help clear things up:
http://www.rane.com/note110.html

The final statement in the quote above points to the possibility that you did not read my opening post in this thread. I will therefore repeat myself in saying that many high end audio products don't support the balanced standard, such as the preamps to which you are referring in that last sentence.

When the balanced line standard is not supported the interconnect cables become audible and then audiophile tend to spend a lot of time and money trying to eliminate the audible artifacts that result (IMO/IME its simply easier to just support the balanced standard). This is the reason why this debate is still around (as Herman points out) years on after we introduced balanced line to high end audio.

To Ralph's point about the audibility of cables; I settled on DIY CAT 5 cables as interconnects and speaker cable years ago. They are neutral configured as single ended over any practical length in the home. I encourage anyone who is on the cable merry go round to do the same and focus on things that have more impact. If you are a million dollars into your system and want to play around with mega buck cables then have fun. If you have a budget like me then cables are the last thing to spend any money on. IMHO playing with the placement of your speakers will have much more impact than cables and it is free. On the other hand, you can go with Ralph's approach and eliminate cables from the equation

However, as a DIY guy that builds his own SE amps I have the luxury of tuning the sound to my preference with the active circuits and don't have to feed the coffers of ridiculously overpriced cable makers. It is inconceivable to me that someone would pay $20,000 + for speaker cables. That tells me 2 things; PT Barnum was right and I'm in the wrong business

Honestly you need to audition all kinds of amplifiers (I have). They work best with different speakers as well. I personally don't like SET amps at all (and I've owned 101db and now 91db speakers and tried at least a half dozen of them). I tend to prefer 3rd harmonic over 2nd I guess. But the people who are adamant that only one way is technically correct or sounds right are to be ignored. 

Ironically, the best I've ever heard Avantgarde was Trios w/ basshorns on BAT tubes years ago. The audience gave standing ovations - but darn those complicated balanced amps :)

Thank you Ralph for explanation about third harmonics. I understand that advantage of the fully balanced configuration is removal of second harmonic to better hear the third one (that you try to lower?). As for the balanced cable - yes it can run further because of superior noise rejection but still suffers from effects of the capacitance between wires. There is no way of getting rid of it. Capacitance to shield is different story. Reducing it would require usage of low capacitance signal transformers. Otherwise - even if you completely "float" signal ground in preamp and amp it will find return, by substantial capacitance of power transformer, to chassis (that you earth ground) hence to shield attached to it. Am I missing something?

Rane paper shows XLR cable (pattern1) with shield grounded at female end only, while common XLR cables, sold in stores, have shield grounded at both ends.

It would seem so.

In order to support the balanced line standard:

1) pin 1 is ground, pins 2 and 3 carry the signal
2) the signal occurs between pins 2 and 3.
3) Ground (shield) is ignored
4) the system is low impedance.

Again as I pointed out earlier, most high end audio systems don't do so well with 3) and 4) nor for that matter 2).

If they did though, the capacitance becomes a non-issue in lengths of 200 feet or so (which should be practical in most homes- at my place they are only 30 feet).

So, Again. If the equipment supports the balanced standard, you won't hear the effects of the cable. IOW if you can hear the effects of the cable, its likely that your gear does not support the standard.

I come from the 'pro audio' side. Looking for a reasonably priced ( OK, cheap) 5 channel amp, I couldn't believe that so many 'hi-fi' amps are unbalanced. I've never used a fully balanced topology (may be, probably is, superior!), but I've come to the conclusion that an XLR connector (with a short cable run)  just introduces yet another circuit into the audio chain ( balanced->unbalanced op-amp) which is to be generally avoided, notwithstanding that companies often choose to shave-off a few cents of quality at this junction.

Can somebody give definitions and explain differences  between:
single ended
balanced
truly balanced
fully balanced
differential
differential balanced 
full differential
truly full  balanced
truly full differential balanced

Can somebody give definitions and explain differences between ....

First, keep in mind that these terms are often bandied about in a loose manner, and some are inherently ambiguous. So you may frequently see a given term used to mean different things. And there may be legitimate disagreement about some of the following definitions. But FWIW I’ll give it a shot.

Single-ended: Either not balanced or not push-pull, depending on context. I have interpreted the OP’s question as referring to "not balanced."

Balanced: If referring to a pair of signal lines, the two lines have equal impedances relative to the ground of a circuit, or the two lines are not referenced to a ground. If referring to a pair of signals, the signals have nominally equal amplitudes but opposite polarities. If referring to a circuit or component, the circuit or component processes signals having nominally equal amplitudes but opposite polarities in a symmetrical manner.

Truly balanced: Not a technical term, but sometimes used to distinguish between an XLR connector on which a balanced pair of signals is present, and an XLR connector on which just one signal is present. Also sometimes used to mean "fully balanced."

Fully balanced: The entire signal path of a component is balanced.

Differential: A circuit within a component, or the entire signal path of a component, responds to the difference between two input signals. May also refer to a form of balanced design in which the signal path of a component consists of a series of differential circuit stages.

Differential balanced: Usually used in a loose manner to mean "fully balanced."

Full differential: Usually used in a loose manner to mean "fully balanced."

Truly full balanced: Usually, a somewhat redundant way of saying "fully balanced."

Truly full differential balanced: Usually, a somewhat redundant and clumsy way of saying "fully balanced."

Regards,
-- Al

Home audio, especially 2 channel systems with analog being the primary source will rarely benefit from balanced connections. Adding balanced operation in this scenario will only add more circuitry with no real benefit and likely have deleterious effects.  One should attempt to have a full-featured preamplifier that includes a well designed phono stage. This approach has significant advantages. The installation is much simpler, the cabling requirements are simpler as this approach has a concentrated purpose. Avoiding ground loops is generally not a problem with this approach and cable lengths can be kept to a very reasonable length. Plus the number of cables is minimized.
Balanced topology imposes twice the circuitry into the signal path.  Abandoning single-ended connectivity is not an advancement.

"But the people who are adamant that only one way is technically correct or sounds right are to be ignored. "

Surely there is best way for any individual. You and I may not agree on what is best since we may value different virtues, but having on opinion on what I find best does not mean that opinion should be ignored.

To the question about single ended versus balanced. Single ended has 2 potentials (voltages). One is fixed commonly called the ground, the return, or the reference level. The outside shield on an RCA plug. The other varies and carries the information (music) which is the center conductor.  

In balanced you have 2 lines carrying the information so typically 3 pins on the connector. Two for the signals and a third is the ground reference. In an ideal world they are exact opposites with one going positive the exact same amount as the other goes negative. The balanced circuit amplifies the difference between the two so it is differential. One advantage of that is if the cables pick up noise they tend to pick it up equally. The differential amplifier doesn't amplify the noise signals because they are not different. One debate here is if that is important in the home environment.

One approach amplifies the difference at the input and another keeps them separate until combined at the output leading to some of the terminology you asked about. 

Some circuits have a balanced 3 pin input but once inside convert it to single ended or simply don't use one of the signals and are therefore not really balanced or not fully balanced. 

Beyond that you can have combinations of the 2 like a balanced input followed by some SE amplification converted back to balanced at the output.

As Almarg points out, there is no universal agreement on what to call the various configurations so you get a variety of terms which mean different things to different people. Unless you look at the schematic and understand it you are at the mercy of whoever is describing it.

https://en.wikipedia.org/wiki/Differential_amplifier
 

Balanced topology imposes twice the circuitry into the signal path.

It is not quite that simple. There are many was to implement either one so it all depends on the design. There are very complex SE circuits and very simple balanced ones. Since a differential amplifier has more gain than a comparable SE circuit you could easily end up with less stages and less circuitry. In any case the amount of circuitry is not a design criteria. If additional circuitry leads to better sound then its a good thing.

perazzi28

Home audio, especially 2 channel systems with analog being the primary source will rarely benefit from balanced connections. Adding balanced operation in this scenario will only add more circuitry with no real benefit and likely have deleterious effects. One should attempt to have a full-featured preamplifier that includes a well designed phono stage. This approach has significant advantages. The installation is much simpler, the cabling requirements are simpler as this approach has a concentrated purpose. Avoiding ground loops is generally not a problem with this approach and cable lengths can be kept to a very reasonable length. Plus the number of cables is minimized ...

It's rather vague to state "analog being the primary source" in your premise. If you're referring to LP, I think you couldn't be more mistaken.

A phono cartridge is an inherently balanced source. If you feed it to a truly balanced (differential) phono preamplifier, you'll add gain where you need it most, and reject noise and interference where you need to most. And you'll avoid having the cable influence the signal. Again, that's where you need it most.

To state that " balanced operation in this scenario will only add more circuitry with no real benefit" is absurd. Yes, differential amplifiers add more circuitry - but there are multiple real, measurable benefits - especially when a turntable is the source.

@herman 
I like the way you write.
B

Well I can Say the Atma-Sphere amplifiers with the Classic Audio Loudspeakers sounds Sublime with Clarity, Musicality, Frightening Dynamics, Smoothness its just plain Truth Full!

I learn more from Ralphs Writing than i ever have reading other professional designers post here at Audiogon!!!
 Stuff justs clicks so much faster the way he explains it.

Surely there is best way for any individual. You and I may not agree on what is best since we may value different virtues, but having on opinion on what I find best does not mean that opinion should be ignored.

Impossible to argue with that, Herman (nor would I want to, I agree 100%), unless of course you are a dogmatist, in which case you know what is best for everyone!  I don't claim to speak for keithr, but I suspect that he was referring to someone who presents their ideas as dogma.  And I agree with gdnrbob, it's refreshing to read someone who writes clearly. 

Well I can Say the Atma-Sphere amplifiers with the Classic Audio Loudspeakers sounds Sublime with Clarity, Musicality, Frightening Dynamics, Smoothness its just plain Truth Full!

+1, dragon-vibe.  Wish I could afford those Classic Audio speakers!  If I ever hit the lottery...well, if I ever buy a ticket and then hit the lottery ;-) 

Its a prize possession to behold. The Sheer Size of the speaker at first was overwhelming. I wanted something that would stir emotions when listening to a setup. This does that and more in spades. Im running my pair on the New Nirvana Amplifier Atma-Sphere has soon to release.

Home audio, especially 2 channel systems with analog being the primary source will rarely benefit from balanced connections. Adding balanced operation in this scenario will only add more circuitry with no real benefit and likely have deleterious effects.

The only place in my room where I didn't have significant interaction between the room nodes and where the equipment might be set up was about 15 feet from the loudspeakers (there just seemed to be less bass in that spot; a nice place to start if you don't want microphonics affecting the sound). So this has meant either a set of very long speaker cables (28' if I was to keep them out of sight), or moving the amps to a location right beside the speakers and running long interconnects.

The latter was not possible single-ended without audible high frequency rolloff and loss of detail. But when I went balanced, that changed significantly and by also running short speaker cables, I suddenly has more detail without brightness; a more relaxed presentation overall. There was no going back unless I placed the front end of the system between the speakers (where it just did not sound as good due to room interactions).

So the quote above is false in anyway I can make out. In the case of a phono cartridge which is balanced to begin with, its helpful to not be getting any artifact from the tone arm cable. The source is always the best place for things to not get messed up!

 Two for the signals and a third is the ground reference.

+1 on your post above Herman, but I spotted this bit in it and though I might point out that this is a frequent area of confusion: the ground is not a reference in a balanced system (or shouldn't be; if it is, the balanced system isn't being set up correctly). The **reference** is pin 2 is referenced to pin 3 and ground is ignored (used only for shielding). This may be one of the most misunderstood aspects of balanced line operation. 

Ralph, I get that the signals in balanced can float relative to ground. I'm not knowledgable about how you  configure your circuits but I'm thinking you do not float the signal from input to output so eventually the signals do get referenced to pin one. I see what you are saying though. Balanced will work without pin one attached 

+2 ??

I'm not knowledgable about how you  configure your circuits but I'm thinking you do not float the signal from input to output so eventually the signals do get referenced to pin one.

We try to avoid referencing signal to ground as much as possible in our preamps as it decreases the Common Mode Rejection Ratio. One area that is tricky though is the volume control. Since two of the five inputs of the preamp are single-ended only line connections (with RCA connectors), the volume control is built with 4 decks (one for each phase of each channel) and it has to have a ground reference to work right with the SE inputs. 

How much potential sonic performance would I lose by using my SE preamp into the unbalanced inputs of a fully differential amp? e.g., my UV-1 preamp into the SE input of an Atma-sphere amp, or using this preamp with a Pass Labs amp.

There’s an impedance difference between fully-balanced and SE inputs, but in what way would sonics be different using unbalanced in a fully-differential design?
Or is it recommended to use a fully-balanced preamp to gain high quality sound?

An addition to my post;
The unbalanced cable runs would be short, 1 to 1.5 meters.

Lowrider, if you were to change from an amp having a single-ended internal signal path to a fully balanced amp I would expect that the differences in the intrinsic sonic characters of the two amps, and perhaps also differences in their interactions with the particular speakers, would most likely greatly overshadow whatever difference may result from providing that amp with an unbalanced vs. a balanced input. Also, my guess would be that finding a fully balanced preamp providing sonics that are as much to your liking as those of the UV-1, for a comparable price, would be a tall order if not impossible.

Regarding your mention of impedance differences, many amps providing unbalanced and balanced inputs connect the center pin of the RCA connector directly to one of the two signal pins on the XLR connector, usually the non-inverted input on XLR pin 2. When the RCA input is used in those cases the unused signal pin on the XLR connector is simply grounded, via either a jumper inserted into the XLR connector or via a switch on the rear panel. And in those cases the doubled impedance that is usually specified for the balanced input, compared to the unbalanced input, simply reflects that the balanced input spec is based on the sum of the input impedances of the two balanced signal lines. So in those cases connecting an unbalanced signal to the XLR input via an adapter, for example, would result in the same input impedance as connecting the unbalanced signal to the RCA input.

Best regards,
-- Al

Al,

"When the RCA input is used in those cases the unused signal pin on the XLR connector is simply grounded, via either a jumper inserted into the XLR connector"

It is correct that some manufactures use a jumper pin from 1 to 3 when a input are configured with two options - XLR and RCA.  IMO there is several issues with this. First one being that pin 1 of a XLR should have Chassis ground (earth) potential - not signal ground which is what the inverting amplifiers input needs connected to when only feeding the non inverting amplifier to get a balanced output. 

Second one being that the non inverting amplifier is connected to ground via the volume control, which means that a varying resistance ( depending on Volume control setting ) is inserted between signal ground and the inverting amplifiers input.

Our preamps are configured so that when a RCA input is selected the inverting amplifiers positive input is connected to signal ground via a relay AFTER the volume control.  

Good Listening


Peter

Thanks, Peter. Regarding the first point, yes, a provision that an RCA input is to be used in conjunction with a jumper inserted between pins 1 and 3 of an XLR input likely reflects a grounding approach in the design that is non-optimal at best.  Such as pin 1 being connected to signal ground, or signal ground and chassis ground being common.

Regarding the second point, my comment addressed the inputs of power amps, that do not provide a volume control.

Best regards,
-- Al

How much potential sonic performance would I lose by using my SE preamp into the unbalanced inputs of a fully differential amp? e.g., my UV-1 preamp into the SE input of an Atma-sphere amp, or using this preamp with a Pass Labs amp.

If using our amps, the difference essentially amounts to the sonics of the cable, as that comes into play when running single-ended. The amplifier input really doesn't care because the voltage amplifier in our amps is a differential amplifier. It simply amplifies what is different between its inputs. If one side is ground it still works the same way.

@atmasphere , thanks, that's the answer i was hoping to hear.

"my guess would be that finding a fully balanced preamp providing sonics that are as much to your liking as those of the UV-1, for a comparable price, would be a tall order if not impossible"
Al, that is quite true.

It is correct that some manufactures use a jumper pin from 1 to 3 when a input are configured with two options - XLR and RCA. IMO there is several issues with this. First one being that pin 1 of a XLR should have Chassis ground (earth) potential - not signal ground which is what the inverting amplifiers input needs connected to when only feeding the non inverting amplifier to get a balanced output.

When using a SE input to a differential amp, I thought the ground was tied to pin 1 of the XLR input and to the chassis. What are the consequences of also being tied to the safety ground?

I was offered a Pass amp at a great price, but don’t know if I should use a SE pre with their fully-differential design.

Lowrider,

In order to prevent ground hum most have 2 different grounds, one being Chassis Ground (earth, safety ground) which should also be connected to pin 1 of all XLR connectors both in and outputs.   Typically Signal ground is isolated from chassis ground with a dual diode in reverse parallel and a resistor - or something similar.  Signal ground should not be present on pin 1 of the XLRs

I have  referred to this paper before - it contains some very useful information about grounding 

https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf


Good Listening

Peter

@pbnaudio , Thanks, I’m familiar with the Whitlock paper, probably time for me to read it again.

Typically Signal ground is isolated from chassis ground with a dual diode in reverse parallel and a resistor - or something similar. Signal ground should not be present on pin 1 of the XLRs

Peter, your components are magnificent. I like the toggle between balanced and RCA on the back of the amps.

I appreciate the info provided by yourself, Ralph and Al. It makes me realise that the design of an amplifier needs to be examined carefully before making a purchase. It’s easy to check for a balanced signal, or for fully-differential by reading the specs, but how an amp deals with safety and signal ground is not always disclosed. Atma-Sphere states clearly that their amps use a star grounding topology.

^^Just FWIW, star grounding is nice but the real issue is how the chassis and circuit grounds are handled!

I have a balanced preamp and XLR inputs into my power amp, but the amp inputs are likely not balanced at all (Jolida 502p). Thus when I hooked up a pair of balanced Mogamis to replace whatever the unmarked weird green XLRs (that sound fine by the way) are that came with my preamp, the Mogamis sounded awful…weirdly since I’ve used Mogami balanced cables in pro audio for years. I can now assume the Mogamis just didn’t mesh with the "unbalancing" of the amp inputs, so back they went to Guitar Center (I tried). I use Mogami Neglex for my turntable "din to RCA" and they’re much quieter than the stock Linn cable they replaced, so Mogami is still OK by me. I use an AQ balanced cable to the amp now, and it works fine. Note that when I was recording songs by "folkie" artists for a cable TV interview show we had in Maine years ago, I did notice that high quality XLR mic cables all around sounded somewhat better in my headphones than el cheapo cables…so there’s that.

Why doesn't Magico build horn speakers?  They are.... wait... oh, they do.

i have a balanced preamp and XLR inputs into my power amp, but the amp inputs are likely not balanced at all (Jolida 502p). Thus when I hooked up a pair of balanced Mogamis to replace whatever the unmarked weird green XLRs (that sound fine by the way) are that came with my preamp, the Mogamis sounded awful…

If the Mogami's are truly balanced and the Jolida shorts pins 1 and 3 of the XLR inputs, could this cause a change in sonics?

Yes! It brings the shield into play as part of the signal. IOW its not just for shielding any more. As soon as that happens, then the cable imposes considerably more artifact.

Thanks Ralph, I get it now. My many questions have been answered.

I have found most of the time that users go to XLR connections because they think they are "cool"... the fact is that RCA sounds better the majority of the time anyway.

The "artifact" or whatever it was that sucked using the Mogami XLR cables was just with them specifically as other XLR cables sounded fine, so hey…it’s still a little mysterious. Also, after years of using XLR cables in pro audio I am absolutely in the camp of them being a way better idea if only in the mechanical aspect of the plugs, although they do sound exactly the same as RCAs in my Jolida (I checked, and figured yeah…not really a balanced input)…they lock on and don’t move so mo bettah in my view. I use RCAs also of course, but they seem in need of a better design like phono plugs…phono plugs are something from a 1920s switchboard, and are a pain in the ass and a lame design really, but I use ’em all the time of course since I mix shows and play guitar and somehow the things work mostly. I like Neutrik Speakon plugs also, and they’re made in Lichtenstein.