If I were to plug in a battery into the phono, would you also consider this a balanced source? And why the quotes????
Is better sound with RCA cable or XLR cable?
- Thread starter gian60
- Start date
If I were to plug in a battery into the phono, would you also consider this a balanced source? And why the quotes????
If a cart had two opposing coils per channel, it could be a better "balanced source". I doubt you could do that in the space. And as I said before, the carts are not necessarily guranteed to be very balanced on phase that will go to each circuit in a balanced config - so you get a little bit of RF rejection as the main benefit.
Running balanced helps you cancel some common mode noise, mainly RF. But that doesnt mean SE cant mitigate any RF in phono stage design. There are many high end designers that don't bother with balanced phono. I would say the phono preamp design itself matters more. Maybe some work better balanced than some others, but it would be inherint to design not balanced/SE.
OK now we agree. I assume you saw someone else's post on an alleged 6-pin cartridge(s) from yesteryear?!?! Apparently someone did it.
I am more content now for having picked XLR-out from the VPI, and an XLR phono cable, even if going to an RCA-in-only phono.
IMHO this would be needed in a RF transformer to keep symmetry, but not in a micro audio generator such as a cartridge. Anyway the question being debated is that a balance signal can be floating - see the figure. Both inputs are balanced signals. Which is better depends on designer objectives.
Attachments
You pretty much have the definition of a balanced source right there. The arm has nothing to do with it.
The way I look at it, if I compare two interconnect cables and there's a difference, the likelihood is high that both are wrong.
Actually center taps should not be used on a transformer- they work the same way as a cartridge in that regard. A center tap degrades performance.
The phono preamp doesn't 'split the difference' as you say. It merely amplifies the two phases of the signal. The centering of the stylus has nothing to do with whether the cartridge is balanced.
The short answer is yes. The 'how' is- that's pretty much the definition.
I'm going to say something like that... essentially, single ended phono operation leaves some performance on the table.
Our phono section is truly balanced and differential from input to output. We were the first to do that but these days its a much more common practice. The benefits are several- for a given gain stage, theoretically up to 6 db less noise compared to single-ended. So if you have two gain stages, that becomes 12db and so on. In practice you don't get the 6db but you do get something; 5 db is common. So our phono preamp works with LOMC down to about 0.15mV or so; despite that we have only two stages of gain in the phono section, so about 10db less noise; which is why we don't have to have as much gain (and more gain stages) as when operating single-ended. With two gain stages we get about 66db, which includes passive EQ.
Another benefit is greater immunity to noise from the power supply, since the power supply is applied to both phases at once- any signal thus derived is common mode and thus rejected. Also, balanced circuits present less noise to the power supply, so this is a desirable synergistic effect.
Finally, you get the neutrality of the tone arm interconnect cable. If you've ever had to audition cables to figure out which one works best in your system then you know exactly what I mean. This means IOW that the cable merely needs to by built right (twisted pair within a shield, otherwise low capacitance) and it will sound as good as any other cable. Cost becomes minimal; no sacrifice to sound.
Now anyone that's into vinyl knows that getting it right at the front end of the system pays off- if the front end loses information, the best amp and speakers in the world won't get it back for you.
This statement is false. A set of coils would have reduced performance compared to one, for the same reason that a center tap doesn't work as well: reduced CMRR.
Both drawings are complete nonsense. You don't do balanced that way!
One coil on the input, one winding on the output, that's all you need. Anything else is degraded performance.
Yes, I know about it, these are RF designs, not audio - it is clearly stated! I have just presented it to show how varied can be balanced items, not commenting on performance. Did you read my previous posts?
I will agree to disagree with some of what you're saying, Ralph. You are defining the rules that suite you, not the discussion. Both micro and I have mentioned conditions to what we're saying, to which you care not. Audio is fascinating because what matters for sound is not always what one thinks when measuring.
Al, I did see the post but know nothing about it. Micro & Al, I did use quotations since I doubt it matters for audio.
Al, I did see the post but know nothing about it. Micro & Al, I did use quotations since I doubt it matters for audio.
So here's what I heard so far: take any balanced amplification component with XLR-in (obviously) - be it phono, preamp, amp or other - and the moment you plug in a floating source to its input pins 2 & 3 you then consider that floating source a balanced source. I understand where you are going with this, but it's quite a bit tough to swallow, so we will continue to disagree, if that even matters.
Perhaps *someone* would like to draw some diagrams or something for Al? I can see why it is confused to think about how you get the two phases going out as a balanced signal from the preamp, starting with a phono cart.
Yes, I know about it, these are RF designs, not audio - it is clearly stated! I have just presented it to show how varied can be balanced items, not commenting on performance. Did you read my previous posts?
I did, but was compelled to point out that this sort of scenario simply does not work for audio, and isn't in practice. No-one does that.
You can disagree if you like, but that won't help you understand how balanced operation works. The first part of your post here is in fact correct. Balanced operation ignores ground. What that means is there are no ground connections needed to complete the circuit. The signal occurs entirely between pins 2&3; ground is only used for shielding. This is how we connect a phono cartridge to our balanced phono inputs.
Now in the input section of our preamps, we do need a grid resistor circuit for the input tubes. And the industry standard for LOMC cartridge loading is 47K. So we have a pair of precision matched resistors that go to ground that if put in series are 47K. That takes care of the cartridge load, and the input grid resistors for our tubes. But in doing so, we degrade the CMRR (Common Mode Rejection Ratio) of our circuit by doing so- in fact those resistors are a big part of why our CMRR numbers are only the low 100db range. To be clear here, we don't use the resistors to balance the cartridge coils somehow; they are only there for the benefit of the tubes.
I can see that putting up a primer on how balanced operation actually works for audio purposes would be a good thing on our website. I find that these misconceptions about balanced operation are quite common.
Here is a diagram of how a cartridge operates balanced.
And this is exactly how it should be in theory. Annoyingly, i once spent a week arguing with my ears. Me playing the engineer while the ears were happy to be the misguided audiophiles. At the end the ears prevailed.
I have been developing a balanced line stage for a few years. The topology has seen a lot of variations, and so have the output transformers, just the PS always stayed the same: mercury + huge amorphous chokes. For a number of reasons it was increasingly tempting to use a transformer with no centre tap at output. Problem is than none sounded good this way. As soon as the centre tap was disconnected, the sound changed dramatically with respect to bass solidity and dynamics. It doesn't particularly matter what exactly is the input of the power amp: transistor differential, valve differential, transformer. No technical, or measurable issues at all, just unpleasant to my ears sound.
The claim that balanced cables in a balanced system magically lose their sonic flavour...should we even discuss it in a forum where practically everyone has a first hand experience to the opposite?
Perhaps we should just agree to disagree
And this is exactly where we disagree. Balanced operation references ground, does not "ignore it". For example, see https://en.wikipedia.org/wiki/Balanced_circuit and specifically "A balanced signal is one where the voltages on each wire are symmetrical with respect to ground (or some other reference)". So from the source perspective, where's your point of reference? Nowhere, it's imaginary.
Well, yes, I understand it works, but it's not true balanced.
Here's how I interpret the underlined: pin2 is signal positive; pin3 is signal ground; pin1 is the shield, probably connected to chassis ground. Great, but that's not balanced. It's exactly what I am looking for: a shield through the entire cable length, end to end, but otherwise, a typical single-ended connection. This is exactly how all RCA-in phono stages work, the only difference is that the typical ground connection is your pin1 - but so what, it's the same thing, just different physical connection location for it.
Let me know what I am missing.
No ground reference is required, balanced connections work perfectly fine with no ground reference, only, IMHO sound better when a ground reference is provided. Absolutely no idea as of why, perhaps something to do with the mysterious effects of uniting grounds. If Atmaspehere's products employ 2-wire balanced connections, the use of any ground box will transport them into a different class.
And this is exactly how it should be in theory. Annoyingly, i once spent a week arguing with my ears. Me playing the engineer while the ears were happy to be the misguided audiophiles. At the end the ears prevailed.
I have been developing a balanced line stage for a few years. The topology has seen a lot of variations, and so have the output transformers, just the PS always stayed the same: mercury + huge amorphous chokes. For a number of reasons it was increasingly tempting to use a transformer with no centre tap at output. Problem is than none sounded good this way. As soon as the centre tap was disconnected, the sound changed dramatically with respect to bass solidity and dynamics. It doesn't particularly matter what exactly is the input of the power amp: transistor differential, valve differential, transformer. No technical, or measurable issues at all, just unpleasant to my ears sound.
The claim that balanced cables in a balanced system magically lose their sonic flavour...should we even discuss it in a forum where practically everyone has a first hand experience to the opposite?
Perhaps we should just agree to disagree
We can discuss the cables. As a point of fact quite often we do hear differences as everyone here knows. What is less well-known is that when the balanced standard is observed, the differences between cables goes away. That's very nice- an inexpensive cable then takes on the excellent properties of a really expensive cable.
If you want tips on your balanced line stage I might be able to help. We've been building them since 1989, with both direct coupled outputs and also transformer coupled outputs. PM me.
OK. What you are missing is that while there is a symmetrical impedance to ground, ground isn't referenced, and further, no signal return currents (like you have in an RCA cable) are present in the shield. You know what I'm talking about here- if the shield connection of an RCA cable opens up you get a big buzz because the circuit isn't complete, so the cable acts like an antenna. So in a balanced system, quite often you don't even need the ground connection, yet its perfectly hum-free. And its 'true balanced', no if, ands or buts.
About the 'imaginary reference': Well, you do have a reference- pin 2 is referenced to pin 3, and pin 3 references to pin 2. In other words, the signal on pin 2 is seen with respect to its opposite on pin 3.
Pin 1 is ground *shield only*, pin 2 is non-inverted signal and pin 3 is inverted. Forget about 'hot', 'cold' or pin 3 being 'ground', that stuff just leads to confusion and misconceptions.
Three paragraphs down from the Wiki quote you used this statement appears:
(emphasis added)
Note how the line is isolated from earth ground. This is a good thing- helps ground loops (which are inevitable) from messing with the signal.
So that is why the balanced cartridge hookup I posted works. The cartridge is in no way a single-ended source, and if you want proof of this, try reversing the phase at the output of the cartridge. You will note that the act of doing so does not introduce a really loud buzz like it would if your source was really single-ended. It merely inverts the phase. That's how balanced connections work (which also means you have to be more careful when building cables and equipment to get those phases right).
Our preamps do the balanced output part by using a Circlotron, for which we got a patent. Normally a true balanced output is hard to do without an output transformer, since it has to be floating while (usually) at ground potential. The Circlotron allows us to do that, and has the benefit of a direct-couple vacuum tube output, which gives us a lot of transparency.
The key is in the some other reference words. This reference is established by the voltage of the signal receiver when you connect the source to it. It is precisely defined, not imaginary! Again, being balanced is a system attribute. Sources that can be used in true balanced mode are considered balanced.
In the strict sense of the word "balanced" in instrumentation refers to matched impedance and differential mode - you can have a balanced signal with asymmetrical phases. We debated it years ago in WBF, unfortunately I could not find the thread.
Perhaps people will believe in the classical reference on the subject: Design of High-Performance Balanced Audio Interfaces, Bill Whitlock, Jensen Transformers, Inc., 9304 Deering Avenue Chatsworth, CA 91311.
THE BALANCED INTERFACE
The purpose of a balanced audio interface is to efficiently transfer signal voltage from driver to receiver while
rejecting ground noise. Used with suitable cables, the interface can also reject interference caused by external
electric and magnetic fields acting on the cable.
The true nature of balanced interfaces is widely misunderstood. For example “Each conductor is always equal in
voltage but opposite in polarity to the other. The circuit that receives this signal in the mixer is called a differential
amplifier and this opposing polarity of the conductors is essential for its operation.” [3] This, like many explanations
in print (some in otherwise respectable books), describes signal symmetry – “equal in voltage but opposite in
polarity” – but fails to even mention the single most important feature of a balanced interface. SIGNAL
SYMMETRY HAS ABSOLUTELY NOTHING TO DO WITH NOISE REJECTION — IMPEDANCE IS WHAT
MATTERS!
The full article is accessible on the net .
THE BALANCED INTERFACE
The purpose of a balanced audio interface is to efficiently transfer signal voltage from driver to receiver while
rejecting ground noise. Used with suitable cables, the interface can also reject interference caused by external
electric and magnetic fields acting on the cable.
The true nature of balanced interfaces is widely misunderstood. For example “Each conductor is always equal in
voltage but opposite in polarity to the other. The circuit that receives this signal in the mixer is called a differential
amplifier and this opposing polarity of the conductors is essential for its operation.” [3] This, like many explanations
in print (some in otherwise respectable books), describes signal symmetry – “equal in voltage but opposite in
polarity” – but fails to even mention the single most important feature of a balanced interface. SIGNAL
SYMMETRY HAS ABSOLUTELY NOTHING TO DO WITH NOISE REJECTION — IMPEDANCE IS WHAT
MATTERS!
The full article is accessible on the net .
There you go. This is the statement that really matters. I get what you and Ralph are saying, and it all boils down to this statement; that's what the debate is all about. Ralph's argument is effectively all about isolation. I get it. Let's all enjoy some good wine over this debate, I know we all here find it useful and fruitful.
Why are guys fencing with Ralph, whose life-long profession is audio electronics and audio engineering? He is one of the most experienced inventors, designers and builders of balanced audio circuits in the entire world.
There may be a disconnect in terms of you not understanding Ralph’s explanations, or in Ralph not explaining himself clearly to laymen.
If the question is “whose technical answer is factually and electrically correct,” I think it is extremely likely that Ralph is the one here who is correct. I’m impressed that Ralph has the patience for this thread.
There may be a disconnect in terms of you not understanding Ralph’s explanations, or in Ralph not explaining himself clearly to laymen.
If the question is “whose technical answer is factually and electrically correct,” I think it is extremely likely that Ralph is the one here who is correct. I’m impressed that Ralph has the patience for this thread.
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