New TT : Balanced vs. Unbalanced Connection?

There are two separate sets of inputs, with selectable gain between Low (51dB BAL / 45dB SE) and High (74dB BAL / 68dB SE).

I can confirm that these products meet specification. My best to you.

@cleeds If this is correct then the input isn't differential. It might be balanced, but differential amps don't behave that way.

If you run a cartridge "balanced" (technically, it's floating) into a differentially balanced phono preamp such as an ARC Ref Phono 2SE, you will have 6 dB more gain in balanced mode than unbalanced.

@cleeds Emphasis added, and no, you don't. 

I think this might be coming from a misunderstanding of how differential amplifiers work. So let's look at that:

A differential amplifier gets its name from the fact that it amplifies what is different between its two inputs. In a balanced phono situation, normally that would be pin 2 and pin 3 of the XLR input.

However, what if the cartridge was connected to pin 2 and pin 1 (ground) instead (as would be the case if running that phono section single-ended)? It wouldn't work right unless you tied to pin 3 to pin 1; otherwise you'd likely have a lot of hum and buzz.

So you tie pin 3 to ground and there's your signal. Exactly the same as before, not increased by 6dB, for the simple reason that the differential amplifier is amplifying what is different at its inputs, and that difference is the cartridge signal. The diff amp doesn't care that one side happens to also be ground.

That's is your opinion and I respect it. But many others think the advantage is:

... good rejection of common-mode noise and interference ...

... as noted in the Wikipedia link I previously provided.

Wiki isn't wrong on this point. Those are advantages of balanced line operation. But imagine a recording studio, with 50 or 60 different devices- a mixer, tape machines, mic preamps, compressors and other effects devices. You can see that if you had a ground loop it might take days or weeks to find it! So one of the advantages of balanced line operation is also ground loop immunity. (that's also a Wiki link FWIW)

I knew Robert Fulton (as did Bill Johnson, founder of ARC, and Warren Gehl, Kalvin Dahl, who still work there, along with Rich Larson, who was ARC's engineer for a long time; I know or knew those people too and they knew me as well since we did listening sessions at Bob Fredere's house in south Mpls). Fulton created the first high end audio interconnect cables and speaker cables, and thus founded the high end cable industry. We all know what happened after that.

So what do you suppose was going on prior to Robert Fulton? How were record labels able to run 200 feet of interconnect cables between their microphones and the inputs to their tape machines as Mercury did when they recorded at Northrup Auditorium in Minneapolis?

I know you know- they used balanced lines. This was to prevent the cables imposing an artifact (in addition to all those other benefits). Quite literally with the equipment they used, you could swap out a cable with one a lot more expensive and not hear any difference. That is still true today (get yourself a refurbished tape machine and some Neumann mics and you can see for yourself). Put simply, the system is immune to the artifacts of the cable as long as the standard is observed.

I'm sure your preamp works fine, but as you've already noticed, you have audition the cable and find the one that works best that you can also afford. That's up to you; all I'm saying is if the standard is supported you no longer have to worry about that.

And where this makes the most difference is the phono cable, where the signal absolutely must arrive intact if you want best performance.

You muddy the waters when you mistakenly claim they aren’t balanced.

@cleeds  I've not once anywhere on the web made the claim as you suggest above. I think you misunderstood something, since what I posted previously did not contradict this statement of yours:

It’s a simple fact that designs such as the excellent ARC products will yield 6 db greater gain when run in balanced mode.

My comment was regarding a phono cartridge. So let's examine that and you'll see I was right. Let's start with the single-ended connection: the output of the cartridge is applied to the input of the phono section and ground. The total output of the cartridge might be 0.5mV. Now if you apply that same cartridge to a balanced phono input, the output of the cartridge is unchanged- its still 0.5mV. So there is no '6dB increase in output' of the cartridge- it is in fact exactly the same.

As I mentioned in my post, at the output of a balanced preamp that does not support AES48, there can be a 6dB in the apparent increase in gain if that output is connected to a balanced amp as opposed to single-ended. That is because a non-compliant balanced circuit simply has two single-ended outputs, one out of phase with the other. So if you use one and get a Volt out of it, if you use both you get 2 Volts which is a 6dB increase.

If the circuit supported AES48 then neither output references ground- they reference each other (like you see at the output of a phono cartridge). Its worth noting that this means that to drive balanced lines correctly (IOW to winnow all the benefits of the technology, such as interconnect cable artifact immunity and immunity to ground loops) what ever is driving the balanced line has to be floating source.

You don't have to do it that way of course but if you do it gets better.

@gemoody The cartridge screws was a tip from @mijostyn, not me.

@elliottbnewcombjr That is a bit odd- XLRs are a lot more rugged than RCAs.

Oh, and one more thing, phono cartridges produce a differential signal that is not referenced to any ground

@sleepwalker65 Actually this is the literal definition of a balanced source. So the output of a phono cartridge or tape head is inherently balanced.

What balanced gets you, mostly, with phono is a few db of gain.

I say, residential, short runs: no advantage, 

RCA single ended is just as good  as balanced xlr unless your running long spans of cable 

@willy-t , @elliottbnewcombjr , @rmdmoore , If I can straighten some things out here:

You don't get any more gain. That only happens with active outputs that don't support the balanced standard, AES48. When you run a cartridge balanced, it supports the standard. So no increase in gain.

For home use, the advantage is that a properly set up balanced line will minimize the 'sound' of the cable. If you've ever auditioned cables and heard a difference, that's what I'm talking about. The tonearm cable is the best place to really get that right; no matter how good the rest of your system is, it can't make up for colorations and loss from the tonearm cable. Even if the cable is only 1 meter, you still get a benefit as opposed to an RCA cable. Keep in mind the cartridge is a balanced source to begin with.