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

Showing 4 responses by atmasphere

^^ 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.
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.
^^ 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)...
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?