Why so few balanced phono inputs?


I have been through the posts regarding whether a phono cartridge is a balanced connection or not and per Ralph Karsten etc. I agree it is balanced. It finally hit me why someone like Pass Labs doesn't offer a balanced input on a balanced unit (I wanted one until I saw they only had rca)...There are so few turntables that offer a balanced out connection. I got mine from VPI and it was easily switched and was a huge improvement... but are there other TT brands that offer a balanced connection? I was in a high end shop the other day...first time in a while... and saw none. Even SME didn't show one as an option on their site. Not trying to open the balanced vs. single-ended thing but maybe it is endemmic to the conversation. Thanks
sm2727
Yes this is a BAL vs UNBAL conversation. Real quick ill just say BAL is for long cable runs, that's why you always see them used in professional stage gear. The balanced circuit is a more complex one and for home audio, depending on the engineer/designer they my choose to keep the circuit more basic for whatever reasons...In my listening over 35 years I do not think balanced "sounds better" than unbalanced. Many quality components have one or the other or both? Turntables are simple therefore you see mostly unbalanced outputs. Why take something that works great and make it complex by adding balanced circuitry? IMHO.
Any phono cable can be easily converted into a balanced one. Just snip off the RCA's off and solder the two cable leads onto XLR's. Not all balanced phono amps are more complicated than single ended---in depends on how it is implemented. EAR's Tim Paravicini uses transformers at the inputs and outputs of his balanced connections.

As long as the ground wire is not touching the cold side of the RCA connector, the signal is still "balanced". It's how you wire it not what connector is used. An XLR connector has 3 pins: hot, cold, and ground. If you use RCA, the shell is cold and center pin is hot and the ground wire is, well, ground. With that in mind, you can wire however you want or use XLR adapters. If you want to keep the entire signal path BAL all the way to the power amp output then you need balanced circuits in your phono stage to line stage to power amp.

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Fully Balanced is IMO the only way to play Vinyl, All our BIG phono preamps are fully balanced from input to output.

Even the little Liberty B2B-1 is configured so it can be used as a fully balanced preamp - you'd of course need two of them, one for each channel.

Liberty B2B-1

Good Listening

Peter
Yes this is a BAL vs UNBAL conversation. Real quick ill just say BAL is for long cable runs, that's why you always see them used in professional stage gear. The balanced circuit is a more complex one and for home audio, depending on the engineer/designer they my choose to keep the circuit more basic for whatever reasons...In my listening over 35 years I do not think balanced "sounds better" than unbalanced. Many quality components have one or the other or both? Turntables are simple therefore you see mostly unbalanced outputs. Why take something that works great and make it complex by adding balanced circuitry? IMHO.

If you have ever wondered why tonearms have that ground wire where no other single-ended connection seems to need one, the answer is that its a balanced connection that is being set up to run like a single-ended connection.

Actually the real question here is why take a balanced source, and then convert it to single-ended and introduce colorations along the way? The justification for balanced operation is not long interconnects, it is a **lack of artifact** from the cable. It is the latter that allows the former, but really, length is irrelevant. Lack of coloration is the goal. If you have ever auditioned phono interconnect cables to get the one that 'sounds right' then you know what I am talking about. That is something you won't have to do with a balanced phono connection, unless it is improperly wired. It will simply work.

Our (balanced differential) phono stage has only 2 stages of gain, but works with nearly all LOMC cartridges. Most single-ended phono sections that can do the same thing have 3 stages. So which is more complex? As far as the signal is concerned the balanced is a simpler signal path and one that is lower distortion.

Most tone arms allow a balanced hookup. If you have a 5-pin DIN connection it is very easy- the ground connection (pin 3) is the shield of both channels and is the XLR pin 1 in both channels. If the arm has RCA output its still easy- the trick is to not allow the barrel of the RCA connection to touch ground or be the shield, as that is the job of ground connection (represented by the ground post). I can supply details; they are published in our preamp manuals which are a free download from our website.

Even the old BSRs, Duals and Garrards can be wired balanced without jumping through any special hoops.

We made the first balanced phono sections anywhere in the world. So I can tell you the reason that balanced phono is not more common has everything to do with the dealers who don't like to change the cable when they are doing auditions. This comes from 26 years of seeing that be the main objection; not from customers, but from dealers.
van de Hull and RCM offer balanced inputs on their phono amps.
Balanced Audio Technology (BAT), also has a true balanced phono stage.
NVO (New Valve Order) actually came out with their first units with balanced inputs (also had the RCA inputs as well) but over the last several years no one was using them so now, since these units are all made to order, are still offered with balanced inputs. However the last 25 units we have sold no one wants the balanced inputs which we find very strange indeed.
Steve
Any phono cable can be easily converted into a balanced one. Just snip off the RCA's off and solder the two cable leads onto XLR's.

Some single-ended cables are coaxial. Cut the RCA plug off the end and you will find up with a single conductor and a shield. This would make for a very poor balanced interconnect.
I'm using Ayre electronics all of which are dif. balanced, so I'm naturally using balanced all the way from the cartridge to the speakers. The sound is great...no hum/noise, even with the volume wide open and ear against the speaker.
2nd the response from Stringreen. The Ayre P-5xe mp manual shows the possible wiring for both rca and xlr cables.
I am using the shortest length cable for me system, custom made by moon-audio.com.
So we can tweak the sound with ICs if needed?

It's just like rolling tubes except with wires.

Lot's of other ways to tweak though, probably more effectively but that would require us to be smarter.
If I was really smart I would not have to roll tubes either. I'd know the right one right off. Unfortunately, I am not that smart. So these things take me awhile. :^{
Aqvox

They have some info on their website on which tonearms are wired for balanced operation.

I have a balanced phono stage on my wish list to replace my Trigon Vanguard II. Speakers first though.
2 things:
If you choose to replace an RCA male plug with an XLR, the convention is that the hot wire into the RCA plug should go to pin2 of the XLR. The "other" signal-carrying wire goes to pin3. Ground and only ground attaches to pin1. But as John Tracy intimated, the shield of a typical RCA-terminated single-ended cable, if used to connect to pin3 (carrying the negative phase), may cause issues in sonic quality. Which I suspect has something to do with why many say that balanced is inferior to SE. If you choose to connect the cartridge in balanced mode, best to have two conductors of equal quality for the plus and minus phases of the signal. It's not hard to make such a cable for yourself.
Maybe that was only one thing, not two.
Well length does matter a lot in professional audio and that's why they use XLR, much lower noise floor and 110ohm vs 75ohm. If your trying to FIX a problem with detail and/or sound quality by switching from RCA to XLR, it dose not always make things better. If your company uses balanced circuts for its audio products that's great. That is a designers choice...But to say that all balanced designs are going to sound better than unbalanced ones is horse shit! Talk to EveAnna Manley at Manley labs who among many others who don't see using unbalanced as a step back in sound quality over balanced. IMO balanced is not the last word in sound quality.
I agree that balanced connection is not per se necessary for superb sound reproduction. But where do you get the "110 ohm vs 75 ohm" idea? The impedance in a typical audio system will be only be that which is reflected by the interconnect, depending upon the output impedance of the driving device and the input impedance of the driven device, no matter how you slice it. Further, I thought "pro audio", where distances are great at times, use 600 ohms.

Further, it has been my experience that those manufacturers who offer true balanced connections are prone to say why it is superior to SE connections. Conversely, those who make only SE devices (like Manley Labs) are prone to diss the notion of balanced connections. So, I would take Ms Manley's opinion with more than a grain of salt. If done well and properly, there is no doubt in my mind that there is an advantage in noise issues associated with balanced connections, especially from cartridge to phono stage, if only because of fewer problems with grounding. That's just a "feeling" based on 3 decades of experience with both types.
I feel that I should point out that the type of connector (RCA vs. XLR) does NOT determine whether or not a connection is balanced. What determines this is equal impedance to ground from the two signal carriers. Both for the source and the input. With single ended connections one signal carrier is at ground potential (zero impedance to ground). If you have an input transformer and the primary winding (input side) is left "floating" (no connection to ground) and the cartridge is not grounded you have a balanced connection, whether you use XLR or RCA jacks. This will be true even if the preamp itself is single ended. As long as it has an input transformer and the input is floating. I use RCA jacks on my fully differential, balanced phono pre for convenience (XLR plugs would not fit through the tone arm pod on my Nott. TT).
^^ The thing you have to be careful about with this statement is the cable used. If a shield is involved and it is tied to pin 3 while pin 2 has the inside connection, its not going to work regardless of the impedance to ground.

IOW the balanced connection should be at the very least a twisted pair. If there is a shield, it should shield both conductors simultaneously.
thank-you all for the great response.
Sean
Hi Ralph, I always have this question in mind and you are probably one of the best persons to answer.

I noticed that some supposedly full balanced phonos, even when offering both XLR and RCA input jacks, actually have single-ended circuit for the first input stage (the XLR jacks are really single-ended connection), and then convert the signal to balanced mode.

I always wonder why the designers are doing this when they have full balanced circuit and have XLR input jacks already. Is the main reason, as you have mentioned, just dealers don't like to change the cable when they are doing auditions, or there are some intrinsic difficulties in making a balanced phono input stage, such as noise or needing very tight match of parts etc.?
The thing you have to be careful about with this statement is the cable used. If a shield is involved and it is tied to pin 3 while pin 2 has the inside connection, its not going to work regardless of the impedance to ground.

Ralph, if you would note my earlier post on 5/08 I already mentioned that a coaxial cable would make for a very poor balanced line. I was trying to make the point that just because some piece of equipment has an XLR jack on its panel, that doesn't necessarily mean it's truly balanced. The definition of a balanced output or input is equal impedance from the two signal lines to ground. As an example, with some OP amp based balanced to single-ended conversion circuits the impedances do not exactly match and are off by a few ohms. Doesn't sound like much but it can seriously degrade the CMRR.
^^ got it John!

Thekong, you hit the nail on the head- dealers don't like to change cables- removing a tone arm cable from its connector under the 'table can be a bit of a pain. Anytime you see an XLR connection but the circuit is single-ended, its likely that the connector is just there for show, unless it is connected to an input transformer, in which case the connection might be entirely legit, as transformers can have excellent CMRR numbers.

Building a balanced phono stage itself is another matter. There are a lot of ways to do it, some overly complex (feeding into that notion that all balanced circuits have to have twice as many components, which is otherwise not true). You do have to have matched parts and I think the one that stymies many designers is how to do the EQ. That can be quite tricky if you don't know what you are doing!! But overall one of the nice benefits is lower noise per given stage of gain, which might mean that you don't have to have as much gain to make it work (we have two stages in our phono section for example)...
You do have to have matched parts and I think the one that stymies many designers is how to do the EQ. That can be quite tricky if you don't know what you are doing!!

Ralph, thanks for the reply! When I discussed the issue with some local DIYers, they did mention having difficulities in doing the EQ in balanced mode !
I run balanced all the way to the pre amp. Balanced cables from the tt-Trans Fi, to the phono pre-BAT, to the pre-Zesto. Balanced for the CD Player-NAD M5 to the Pre-Zesto.
Got hum in the phono chain. Dead quiet in the CD chain.
Bought a Buss bar and tried every kind of ground. Amps are Mac 60s across the room single ended. High efficiency ZU speakers.
Bought a BPT 3.5 with all sources into it. Still got hum.
Suggestions or just wish me luck?
If you have hum in the phono its because its not wired correctly or the interconnect is not built correctly.

We built the world's first balanced line phono preamps; whenever we ran into a hum problem it was because of either a wring error or a cable simply was not built correctly.

If you remove the tone arm interconnect from the phono input, does the hum go away?
You may also want to confirm whether your BAT phono really has true balanced input.

Members with more knowledge on BAT please correct me if I am wrong. If I understand correctly, the early BAT phonos really had single end input. The later / current units (not sure starting when) has full balanced inputs.
"Conversely, those who make only SE devices (like Manley Labs) are prone to diss the notion of balanced"

This is not true. Manley Labs makes many products that have balanced circuitry. Take a look at there much sought after commercial products and home audio amplifiers like the NEO Classic.
Thekong, the Bat VK-P5 has RCA connections for input and XLR for output. The VK-P10 used XLR for both input and output. I assume the same for their newer models, P6 and P12, though probably not a good idea to assume!