Balanced vs RCA preamps
How important is it that your Pre-amp has both balanced and RCA capabilities? I’m shopping for another pre, most likely tube, and it seems to make sense with any future component that it offers both XLR and RCA. And to further complicate the search finding both these features plus remote limits the offerings for both tube and SS particularly tube.
Where did you get this from? Have you done your homework before taking 10 seconds to write this? Let me do some homework for you, and you can do the rest to see if you can find anything to support your false statement.
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My preamp has both, XLR Lundahl balanced inputs transformers, since most Digital front ends are balanced ,then on the outputs RCA Because of Linear Tube Audio,originally Designed by David Berning with his unique Micro-Z-OTL output stage ,which the Vacuum tubes run much more efficient ,lower noise ,The team at LTA found over a few years to make it even better a Gen 2 Version , and use the Rays Select 6SN7 vacuum tubes , detailed a bit warmer , and the other tubes 12AT7 or 12AU7 which I am using with some Very rare Medical grade Telefunken tubes a great combo , + using 2 Hifi tuning Supreme CU- Copper Gold - 4 amp 20 mm slow blow fuses on back ,which VH Audio Carry. and as a good option ,and not too expensive a Hifi tuning Supreme Silver gold 20 mm 3.1 amp Fast blow on the main board with a AQ Tornado Source power cord ,Exceptional results and a who who of Excellent top notch parts quality which I know very well ,having 40+ years in Audio ,beating preamps at 2x the price $6350 Retail ,Mike at Audio Archon was very helpful , and fair-in pricing. | |||||||||||||||
@lanx0003 It is a fact in high end audio though that most producers of balanced line products pay no attention to AES48 (the balanced line standard), or the use of dBm levels (more later). That is part of the reason there is a balanced vs RCA debate. You have to be careful about things you read like the specs above! I own the two of the Topping DACs; The 40 Ohm value is actually the two 20 Ohm output impedances put in series when really they should be in parallel, which would be about 10 Ohms. WRT to the ARC stuff they are doing the same thing. FWIW ARC preamps in general tend to have high output impedances. IOW this is a nomenclature issue, not an output impedance issue. The standard for balanced line studio line level input impedance is 600 Ohms. Common accepted good design practice is that the circuit driving a load like that will have an output impedance about 1/10th of the load impedance. So we can assume that the source impedance will be 60 Ohms or less. That's a lot lower than most single-ended preamps... Balanced line levels are usually expressed in dBm. dBm is the VU reading you would get on a VU (Volume Unit) meter when the meter is across a 600 Ohm resistor. So its a measure of power; that requires the output impedance to be even lower. There are two levels that are standards in use: -4dBm and +10dBm; 0dBm is one milliwatt dissipated into a 600 Ohm load. My Neumann U67 microphones are designed to drive a 150 Ohm load. That implies an output impedance of 15 Ohms. Our MP-1 preamp can drive 600 Ohms directly at +10dBm despite using a vacuum tube output. This also suggests a low impedance and in fact they will drive 32 Ohm headphones. My old Ampex 351 studio tape machine was designed to drive 600 Ohms and also supported +10dBm. Most tube preamps will fall flat on their face trying to drive loads like that. In fact most solid state RCA preamps will too. My Otari MX70 1" tape machine has 600 Ohm inputs which expect at least -4dBm. You need a low impedance output to drive that. I designed the first balanced line preamp offered to high end audio back in the 1980s so yes, I researched this quite a lot prior to saying what I did
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Not really, the benefits of balanced designs are pretty well known. Designing to the AES spec is just one approach to balanced design.
The Topping and Audio Research schemes are different than your designs. That doesn’t make your design right or "proper" any more than it makes the ARC design "improper," as you’ve claimed. They each take a different approach to balanced amplification, either method offers improved CMRR. (Similarly, some speaker designers use sealed boxes, some use ported boxes and some use no boxes at all. Each approach can be valid and its success will depend on implementation.)
Most home users have no need to drive 600 ohm loads. | |||||||||||||||
@atmasphere One should be very careful when interpreting the impedance of a true balanced XLR cable. The two conductors (pin 2 and pin 3) carry both positive and negative signals from the source to the load simultaneously, behaving like a parallel connection. However, because they are of opposite polarity, the signals travel in differential (v.s. common) mode. The resulting voltage is the so-called differential voltage, which is twice the amount of the individual phase voltage. This explains why the voltage from an XLR port is twice that of its RCA counterpart. Similarly, the resulting impedance, known as differential impedance, is also twice the impedance per phase. The manufactural reports either impedance per phase or the differential impedance. Hope this helps. | |||||||||||||||
@lanx0003 Actually this isn’t true if the source is AES48 compliant. An output transformer is a good way to look at this if you understand how they work. In the case of a an output transformer driving a balanced line, there is a simple secondary with no taps. One end of the secondary output is tied to pin 2, the other end to pin 3. Pin 1 is typically tied to chassis. Now if you want to run this output single-ended, pin 3 is tied to pin 1. You’ll note that the actual output Voltage is unchanged as is the output impedance. IOW either way the Voltage and impedance of the source is the same, which is to say there’s no 6dB increase when running balanced as opposed to single-ended. The transformer doesn’t care if one side is grounded or not. Your conclusion in the quote above is false WRT AES48 compliant sources, such as our MP-1 or MP-3. Now if you have a non-compliant source (such as a Topping DAC or ARC preamp) then your comment is true. But that isn’t how balanced lines are supposed to work. Here is a link to a Neumann microphone. Note the output impedance and the load its expected to drive (1KOhm). This mic is set up to drive balanced lines properly. A device that behaves as you described above does not. Put another way, the idea that the output impedance of a balanced source is twice as high is true only if the balanced source isn’t designed properly to drive balanced lines! To understand this issue better take a look at this page on the Rane website- its a quick read. If you scroll down to the ’Absolute Best Right Way To Do It’ you’ll see I’m not making this up. You might also read portions of this book by Bill Whitlock who designed most of the Jensen transformers. It gets more relevant to this discussion on page 13; if you look at the diagrams which show balanced connections, you’ll see no connection to ground except when it goes single-ended (such as driving an opamp in the case of an input transformer). Page 15 shows a microphone input. Page 16 shows a line output. I think you’ll see what I’m talking about.
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That is your opinion, and you're certainly entitled to it. You express it here frequently, as is your right. But it is just as opinion, and one which many of the world's foremost manufacturers of audio equipment reject. That appears to trouble you greatly, perhaps because you seek to promote your trademarked and patented Balanced Differential Design® components. And that's fine, too. But when you claim that those whose circuit topologies don't embrace your favored methods somehow aren't "proper," you really make yourself look kinda silly, imo. I have a lot of respect for you Ralph, as do many others on this forum. But for just about everything in life, there simply is no One Absolutely Right Way, and that includes the design of balanced circuits. I'm telling you this Ralph because I think you do yourself a disservice by denigrating the designs of others. | |||||||||||||||
@cleeds I'm not sure that's true; AES48 is an industry standard but you'd have to check with them to see. As far as I can tell, a good number of them don't know what AES48 is. I've seen manufacturers state their gear supports AES48 but then you found out it really doesn't. That makes me wonder if they know what it is. You mistake my reason for being active on threads where balanced line is discussed. The simple fact is I've been doing this longer than anyone else and I've seen an awful lot of misinformation online. Apparently if I don't say something, the chances are high that no-one else will step in and set the record straight. Would you prefer that I just don't participate? Just to be clear WRT to the 'one absolutely right way' remark, I didn't make this stuff up. We use a direct coupled technique in our products, transformers have been in use for the same purpose for the last 70-some years and That Electronics makes a chip at the link that is an example of the other way to drive balanced lines properly. There may be more ways but I am not aware of them and would love to be enlightened- after years of doing this, these three methods are the only ones I know of. You are correct that my way isn't the only way. Before we introduced balanced lines to high end audio the only balanced products you came into contact with was studio gear. To be clear, the innards of the product doesn't even have to be balanced. My Ampex 351 tape machine was single-ended inside. That machine was the recording industry workhorse from about 1957 to well into the 1960s. I am not denigrating anyone else's work; I think you misunderstand. Instead what I am saying is that if AES48 is not supported, then you loose a lot of the benefit that balanced line operation offers: immunity to ground loops and reduced or non-existent cable coloration/interaction issues (this being the 'cable makes a difference' phenomena). No-one would argue stating that you don't have to support the USB standard for cable because such a cable might not even work. Balanced lines are different in that they will still play despite the standards being ignored, much like speakers in this regard; you can throw some drivers in a box but unless you did your homework its unlikely to sound right. If you want a speaker to work right you have to pay attention to Thiel Small parameters, for a USB cable you support the USB specs, for balanced line its AES48.
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It cannot possibly be a "standard" ("something established by authority, custom, or general consent as a model or example") yet at the same time not commonly accepted. Even your website admits that few home audio manufacturers observe this "standard." ("still one of the very few preamps to support the balanced standard (AES48)"
I don't think so. While you provide information about balanced circuits, you are also promoting your patented and trademarked Balanced Differential Design® components. That's fine, of course, but there's no reason to be coy about it. After all, you frequently argue that only balanced designs that respect AES 48 are "proper."
No, balanced lines can work quite nicely and still reject AES48. You're welcome to listen to my mostly-ARC system and judge for yourself, @atmasphere. | |||||||||||||||
@cleeds Just so we're clear, other than our own, I've never put that trademark on any website. As far as I know, that sort of thing might be considered a violation of forum rules.
Thanks!. Just to be clear though, I never said or implied that if you don't support AES48 that it won't sound 'quite nicely'. What I did say was
My DAC at home sounds 'quite nicely' but it doesn't support AES48. So I keep its cables short to minimize cable colorations. | |||||||||||||||
It's a red herring, really and you've already acknowledged that AES48 is not commonly accepted in home audio. You describe your MP-1 preamp as "featuring Balanced Differential Design®" and state it's "still one of the very few preamps to support the balanced standard (AES48)." You then go on to insist that only AES48-compliant designs are "proper" balanced designs. So yes, you're here to promote your products, Ralph, and that's fine. You've earned the trademark and multiple patents and you've earned the right to tout them. But when you insist that you have found The One True Way, and that competing balanced designs aren't "proper," it warrants a reminder that with most things in life, there's almost always more than one way to accomplish a task. And that is certainly true in high-end audio. | |||||||||||||||
@cleeds How is that a red herring?? The topic of this thread is "Balanced vs RCA preamps" so my comments about balanced operation are relevant. I do describe the MP-1 and the MP-3 in that manner. I’ve described other high end preamps in that manner too. The emphasis added bit is false. Nor am I claiming they are The One True Way (in fact listed a couple of other ways including links in prior posts which you seem to be ignoring) nor did I say any competing balanced line product isn’t ’proper’. Please stop trying to put words in my mouth; when you do so you commit a logical fallacy called a Strawman; logical fallicies are false by definition... Regarding the use of ’proper’ I was talking about driving a balanced line ’properly’. I didn’t say anything about some balanced line product not being proper. Do you get the distinction?? Again, for like the 4th time already(!), this is what I claim:
Nowhere in that is any comment about anyone’s particular balanced preamp or the like. Its a simple statement about balanced lines themselves.
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One only has to open up their equipment in order to determine if true balanced, mirrored circuit path, power supplies,power and output transformers, my Coincident Statement even has dual transformer volume control. Also true balanced pre's used with true balanced sources such as dacs may offer even greater beneifits, pseudo XLR inputs on pre may in fact be inferior to single ended inputs such that using the superior balanced outputs on dac may be compromised. | |||||||||||||||
@rwwear That is indeed the common myth. I'll add that the name contributes to the popularity among those having to make a choice with limited info. Balanced sounds like a good thing to most people. Jerry | |||||||||||||||
That depends. Many truly balanced amplifiers do not use "mirrored circuit paths." For example, you can build balanced circuits using differential amplifiers. As for @atmasphere, he simply won't accept that his opinion that the only proper way to build a balanced component is to make it consistent with the AES48 standard is simply his opinion. It's one that most of the high end community has rejected but he disputes that too, arguing that maybe they've never heard of the "standard." Those are the simple facts and I'll grant him the last word. | |||||||||||||||
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Ralph promotes his products here and I've always defended it:
Ralph's issue is confusing his opinion with fact. No more, no less. | |||||||||||||||
@cleeds Please read this thru to the end; you might see there's another explanation. You might have to be a member of the AES to view this document: https://www.aes.org/publications/standards/search.cfm?docID=44 At that link:
You should be able to see something at the link on that page entitled: 'Downloadable Preview'; on page two at that link you'll see an interesting list. Opinion vs fact... where your argument falls apart is where you say the 'high end audio' industry rejected AES48. So hang with me just a bit as there is some history first: You have to jump thru some hoops design-wise in order to support the standard. Traditionally in the 1950s when hifi was getting started no-one thought there was a need since home audio devices weren't built to the same standards as recording/broadcast equipment, no-one thought there would be a need for long interconnect cables and no-one thought RCA interconnect cables might influence the sound if kept short. Back then, to drive a balanced line you needed a line transformer and they cost about as much then as they do now ($500-$1000/channel) once adjusted for inflation. So traditionally all home audio has used single-ended connections. Please keep this in mind. Its that issue about an output transformer that has most tube preamp producers stymied about driving balanced lines. They cost a lot so will raise the price of a 'balanced' preamp by $1000-$3000 depending on how the manufacturer sets pricing. You could use a solid state circuit that's a lot cheaper but tube preamp producers and their market tend to disdain that idea. Or you could use our patented method but we're a small player and to this day a lot of the high end community doesn't know who we are and if they do, don't realize that we are more about balanced line than we are about OTLs (IOW we're still known for OTLs despite the fact that our preamps have traditionally been our best selling products). If they do know this about us, the other problem is in high end audio designer's don't like to use ideas 'that weren't invented here'. Add to that the simple fact that many are simply ignorant of AES48 and you have a nearly perfect storm. I knew there were standard practices for balanced line back in the 1970s but I didn't learn about AES48 until about 10 years ago (it was codified about 2005); and yet we were the ones that pushed harder for balanced lines than anyone else in high end audio worldwide with the first fully differential balanced amps and preamps made back in the 1980s. So from my perspective its hard to see yours. We influenced ARC to do balanced line; Dave Gordon (who might still be at ARC) and I were visiting the same dealer in Studio City CA back in the early 1990s after CES and he saw that we had figured a balanced connection between a tonearm and preamp. He asked how we did it so I sent him a copy of our MP-1 preamp owner's manual which details how its done. A while later ARC produced their first balanced phono section, later discontinued as they found out that dealers didn't like that because they had to change a cable to play it and that sort of thing could cause a customer to walk. I think the rejection argument isn't quite right; here's something we've not yet discussed: When you have a balanced preamp that does not support the standard, it will play nice with single-ended equipment (in particular, a balanced preamp driving an amp with a single-ended input; this because single-ended and proper balanced operation are mutually incompatible, which means if you try to hook one up with the other you can get a buzz problem) and will also cost less. Occam's Razor suggests that between two explanations for a given situation, the simpler one is probably the correct one. So your explanation that 'high end audio has rejected AES48' needs some nuance. I'm also thinking my idea of ignorance isn't quite correct either (although I know of examples where that is clearly the case). I think the simplest explanation is AES48 is inconvenient because it complicates equipment compatibility (solvable but can be an additional hoop to jump thru) between single-ended and balanced, which means dealers will have objections (this is one we've dealt with a lot) and its more expensive. Both of those are money issues; that is the simplest explanation.
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@kckrs wrote:
Nowadays it’s only important to me that any component in my setup, or one that enters it has true balanced in- and outputs, and preferably only that. I’ve simply come to favor the sound of true balanced equipment that is typically also more studio oriented, and where both RCA and (true) XLR connections were offered I’ve preferred the latter. @atmasphere -- Thanks for your insights. | |||||||||||||||
I got 15-feet of XLR for 1 system between the preamp and amp. Though I am not sure if the Schitt Mjolnir v3 preamp and Schitt Wotan amp are AES48 compliant (I will ask today). My Benchmark HPA4 preamp and CODA #16 amp are AES48 compliant and have 25-feet of XLR between them. I hate having anything other than an amp between the speakers. I use the low-cost Benchmark XLR cables for the long lengths. Great cables for these long runs. |
, and yes, balanced outputs generally are usually lower output impedance unless the manufacturer had no intention of supporting common balanced line practices.
