Looking at the specs for your amp, I'd surmise you're going to have 6 dB higher gain on the balanced input. You might not need that gain, but you could also think of it as 6 dB better s/n ratio. Using the balanced amplifier inputs also gives it a higher input impedance. That might be a friendlier load for your streamer. |
You will get a volume boost... but the only thing that probably means is that you will generally move the volume button one twentieth of an inch less clockwise on your preamp. Most likely the quality of the wire will make a much bigger difference than then connection type. But it can make a difference because component manufacturers do a better job of internally converting from the topology of the component to the opposite output. For instance, I have Audio Research Equipment. It is of balanced design and that is what is recommended. However, it is very good equipment, so they spent a lot of time making sure the single ended connections were good. So, when I compared the same brand and tier of interconnect, I could hear no difference between single ended and balanced. I spent some time doing this. But I did not spend a couple week intervals with one, then the other... maybe then I would have detected a difference. I am sure Audio Research spent a lot of time make sure they sounded the same. So, of course, you have to try to find out. You have different components. But you must compare using the same brand and model of interconnect. |
I think two things are going on. First, Paul McGowen at PS Audio has always been a fan of using balanced cabling over single ended. Second, and probably the most important reason, is that the S300 is a fully balanced design. If you use RCA's, then the input has to be converted to a balanced signal first. Thus adding another layer to the circuit. I currently have a S300 amp with the PS Audio Gain Cell preamp in a secondary system. When I got those two pieces, I did a comparison between using a balanced cable and RCA's (both were Audioquest Columbia's) and the balanced cable did sound better. Not by much, but it is tighter in the treble and midrange driving my Martin Logan electrostatics. - Jeff |
PS Audio S300 is not fully balanced. "Bridged" output might suggest that, but it isn't a bridge of two amps but 4 Mosfet bridge to flip speaker direction between V+ and GND, since output is single voltage supplied. Some class D modules, like Hypex, use dual +/- supply and only 2 output Mosfets. S300 is based on 300AS1 Icepower module, almost identical to 200ASC (in my Rowland 102), but with stronger output Mosfets. Both my amps Benchmark AHB2 and Rowland 102 don't have RCA inputs. |
You might want to check the specs of the amplifier here. They certainly reflect those of a balanced amp. |
@cleeds I don't see anything in specs showing fully balanced operation. |
Look here. Big clue: Input impedance Unbalanced 50KΩ
So? You seem to not understand how a balanced amp works. This amp looks like it's differentially balanced, a perfectly valid approach. This is taken from the data sheet you provided: Input Stage Output Stage
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@cleeds It is amplifier with balanced input and not the "Fully Balanced Amplifier". "Fully Balanced Amplifier" term refers to amplifier consisting of balanced input followed by two separate amplifiers - each driving one terminal of the speaker. |
Of course you are free to define terms for yourself anyway you like. But a "fully balanced amplifier" doesn’t require two separate amplifiers. You simply do not know what you’re talking about and your claim conflicts with the manufacturers' published literature. An amplifier using balanced inputs, balanced circuits and providing balanced outputs is, by definition "fully balanced." It’s as simple as that. |
@cleeds Input stage can be either "balanced" or "true balanced". "True" refers to inputs that are not referenced to GND, like in instrumentation amp or transformer. |
@invalid S300 output is supplied from single supply only. To achieve net zero output at 50% duty cycle speaker is "flipped" between V+ and GND by bridge of 4 Mosfet transistors. Some modules achieve it with dual +/- supply and only 2 Mosfets. To me it is more "bridged" than "balanced", but it doesn't matter, as long as we know what it is. |
I understand that intuitively what you wrote seems "true," that it "feels" like it's correct. But it is completely false. You don’t know what you’re talking about. Here’s a guy who actually understands balanced circuits and who notes the myth of your claim. (I suspect you’ll reject this, just as you have the information I’ve quoted from other manufacturers. I’m including it for the benefit of others): Balanced line equipment is often also fully differential, like our amps and preamps. A differential amplifier has two inputs, and in theory only amplifies what is different between those two inputs ... A differential circuit isn’t double the number of parts of a single-ended circuit, although it does have more parts. |
@cleeds He talks about benefits of balanced cables and differential inputs. It has nothing to do with "Fully balanced power amplifier" vs power amplifier with balanced differential inputs. I will leave it at that. |
Actually, it has everything to do with "fully balanced" amplifiers, and @atmasphere is especially well known for his balanced amps. Owner Ralph Karstens even holds an interesting patent covering his topology. I've now provided to you three original sources that reveal your beliefs to be myths. |
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At the risk of dragging out the "balanced" discussion, and for what it's worth, my statement about the S300 being fully balanced came directly from a conversation with PS Audio and from their literature. They state the S300 is a dual mono amp with separate power supplies (which I can confirm because I had to fix it when I bought it) and, I quote from the 'features' list, "XLR 'True' Balanced Input". Is it just advertising speak, maybe... Here is the link to their product literature (same link that @cleeds posted): |
@kr4 I'd put it the other way 'round. We audiophiles are very used to hearing interconnect cable differences. But recording engineers, who use balanced lines in a studio, are not. When the balanced line system is set up properly (as usually seen in a studio) the 'sound' of different interconnect cables goes away. Having done many auditions of this difference over the last 40 years I can say that RCAs usually don't sound as good as a result and nothing is defective; this providing that the balanced line equipment actually supports the balanced standards (such as AES48).
@kijanki Could you explain what is meant by 'two separate amplifiers'? Do you mean two single-ended amplifier circuits or two push pull amplifier circuits, or something else?
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@atmasphere "Fully Balanced Amplifier" is in my opinion an amplifier that consists of true balanced input stage, like transformer or instrumentation amp, followed by two amplifiers - each for one leg/phase of the signal. Speaker is connected between outputs of both amplifiers. |
@kijanki Our OTL tube amps are fully balanced and differential. But to the best of my knowledge, there's only one output section (which is push-pull) driving the speakers. Does this meet your definition? |
@atmasphere Fully Balanced, in my opinion, would require two output stages - in your case two Push-Pull stages, which probably wouldn't make much sense. |
@kijanki Its hard to know what Emotiva is talking about since there appears to be a typo or complete misunderstanding of what is happening in the opening sentence of the quote of the description; power amps do not drive the input, if you see what I'm talking about. A preamp might do that though... Anyway, IMO/IME your definition is a bit too restrictive. Our OTLs are an example that flies in the face of it and are one of the oldest fully balanced differential amplifier designs in production.
This statement is false if the circuit is also differential. You do have more parts but not double. Depending on the gain of the circuit the CMRR can be quite high. There are amps that are fully balanced but not differential. I see no advantage to them at all, since they often offer no CMRR and do indeed have double the parts. Apparently Douglas Self doesn't know about our stuff since he makes the claim at the link you provided:
We've been doing exactly that for 40 years although its been with tubes, but he might be right depending on what is meant be 'high volume production'. Now if you want, you can build a conventional tube amplifier using a differential Voltage amplifier and transformer coupled push-pull output. In fact that is exactly how our little Gem integrated amplifier works (it only makes 5 Watts/channel, meant for headphone, bedroom or desktop use, but you could use it in a main system with high efficiency speakers). Depending on how you execute the ground at the output, you could have balanced feedback loops or single-ended. Yet the amp is fully differential and balanced from input to output. I really think you need to expand your definition, since as you have stated it so far makes a good deal of your arguments false, for example the bit
This statement would only be true if the word 'amplifier' meant only a single-ended circuit. Obviously there's a bit of a contradiction were that the case since the input allows for differential circuits which are not single-ended. Further, whether the embodiment is tube or solid state is irrelevant. For example, I'm sure you've heard of GAS, who made the Ampzilla. That amp used an output circuit known as a Circlotron, the same as our OTLs. If that circuit were used with a differential balanced input (like we do), you'd have a fully differential balanced amplifier with only a single amplifier section driving the speaker terminals and it would be up to the designer as to whether a single or balanced feedback network would be used. So I really think your definition/opinion has you painted in a corner unnecessarily. |
@atmasphere Perhaps my definition is too restrictive, but IMHO amp with one of speaker terminals at GND is not "Fully Balanced" Do you agree it is "Fully Balanced"? |
@kijanki It looks like that amp is. But: I would not use a speaker terminal at ground as your definition, although our OTLs have both speaker terminals ungrounded and floating. Many ARC amplifiers do not have a grounded 'common' terminal; the impedance to ground of the common connection is the same as their 16 Ohm connection. IOW that is not the defining character of a fully balanced amplifier although it is a characteristic they are likely to have. We are experimenting with a tube amp that has a speaker terminal grounded, yet its fully balanced from input to output with dual feedback loops. |
@atmasphere Amplifier in question PS Audio S300 has only balanced input with single ended stages following. I don’t believe that adding, for instance input transformer, makes any amplifier "Fully Balanced". In my opinion such amp is an amplifier with true balanced input. |
@kijanki Did you not mean to use 'S300' twice in the above post? |
@atmasphere I replaced second "S300" with "such amplifier" to make it general. To me something that is "Fully Balanced" has all stages, including output stage, balanced. One criteria of balanced output is lack of GND return current. |
Agreed. I was not limiting my "something" to the physical cable. It could include associated equipment and/or the observer. |
@kijanki So if one side is at ground, but there is no ground return current to any other part of the amp, your criteria is satisfied? Or is the fact that the speaker circuit is not complete without a ground connection a problem? Audio Research used to ground the 4 Ohm tap of their output transformers rather than the common tap, so they could cathode cross couple the output tubes; IOW the cathodes of one half of the amp were tied to the common tap and the 16 Ohm tap was tied to the other half of the amp's cathodes, as a feedback mechanism. To do this obviously the feedback was balanced. Does this meet your criteria? |
@atmasphere Tube design is your domain so it is not wise for me to argue, but grounding tap of transformer’s secondary won’t make current return to GND. Transformer output is balanced, but stage driving primary might be not with one transformer tap returning current to GND. I’m sure we can find many exotic configurations that could qualify as Fully Balanced, but PS Audio amp, that started all this, is not. It is single ended class D amp with differential input stage. Something should differentiate between this and fully balanced design, like one in the schematic I referred to. To me it is word "Fully" suggesting, all stages are balanced. |
@kijanki Right. (We introduced a class D amp of our own design about 4 years ago FWIW.) The question then becomes, in the context of this thread 'is it important?' WRT the thread title, it isn't. Ampex made a tape machine that was used for quite a lot of the recordings made in the so called Golden Age of stereo (1958-1963); that machine had a balanced input and output using transformers but the internal electronics was mostly single-ended. Its use of transformers allowed it to be immune to interconnect cable differences. |
@atmasphere I agree, "Fully Balanced" design doesn't have to be better - net result is what counts. There are many imprecise popular or marketing terms in use, why to argue. I noticed that many great companies still use erroneous "watts RMS" and wonder if it is on purpose. They likely know it should be just watts or watts average, but that is what most customers think of (product of RMS voltage has to be RMS power) - cannot blame them. |
I've always preferred single ended over XLR.. I think it sounds smoother, more detailed, more analog and has better contact rather than the little pins on XLR... XLR really is for broadcast studios, military, commercial systems for noise rejection where there are hundreds of cables going hundreds of feet from studio to studio and lots of grounding issues, I've worked soldering racks full of XLR cables that are all super long runs of mogami cable... That being said, some equipment is specifically designed to sound better with XLR, but my vote is RCA |
Hey @fastfreight When an amp or preamp has XLR inputs there are three things that may be done:
The first case looses any noise / long distance benefits of the XLR cables. The connector is a convenience feature. The second is fully discrete but subject to bandwidth and distortion limitations of the transformers, may add character all its own. Third is the most common and I’m sure you don’t even know how many times that was used in creating the music you listen to. Professional devices, from microphone preamps to mixing boards and tape recorders almost all rely on op amps as the inputs and convert the signal from differential to single ended before doing whatever they will do with them, so keep that in mind when evaluating whether this is good enough for you. Like any active devices they may add noise or distortion, but it is only at the end of the chain that Audiophiles become obsessed with them! I would not say they have any specific sound by themselves or their use, so it IS good to test with them. Also, while XLR is "professional grade" and bigger and more complicated there’s no guarantee at all in a home away from radio towers and machinery that you’ll ever hear a difference. If you have a long run to a subwoofer, or to active speakers in your surrounds you might as well go with XLRs to ensure the least likelihood of noise pick up though. |
PS Audio's Paul McGowan recommends to use XLR when that is an option and indicates that virtually all their equipment is true balanced. Makes sense to follow manufacturers recommendation. He has a number of youtube videos on the topic, one is referenced below. https://www.youtube.com/watch?v=PzEmKPTb18g
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Besides the 6db of gain, you MIGHT have a quieter signal from your preamp to amps withe XLR. Years ago I had a system that was crazy sensitive. Some of the issues were from the built in phono preamp, and XLR IC’s did help. Since then, I’ve haven’t gone longer than 3 meters between my preamp and amps and in my current home, with my current system, RCA’s have worked just fine. All the best. |
