New TT : Balanced vs. Unbalanced Connection?

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.

atmasphere

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 ...

Pedantic.

I’m going to do you a favor, Ralph. After this post, I’m going to allow you the last word on this matter in this thread. You have my word. Based on your past practice, I know you’ll have many!

For the last time let’s look at that phono cartridge into a ARC Ref Phono 2SE using its balanced out into an ARC Ref5SE. That is the exact combination I’ve mentioned in this thread, and its results are not unusual.

Here is the ARC factory specification for the Ref Phono 2SE:

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.

Ralph,

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

I agree, I have many times said I like that XLR positive lock, perhaps desirable for that feature in residential systems with no other advantage.

However:

Did you watch the video? (posted above by veerossi)

What this guy did is far from robust as he readily admits.

I repeat: stubborn or obsessive absurdity.

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.

I can tell you my experience with my Esoteric E-02 phono preamp which has balance and unbalance inputs.  Since my Din cable is RCA, that was what I was using until I decided to see how the balance input of the Esoteric compares.  I use a couple Cardas RCA to XLR adapters and Wow, the sound opened up and was considerably clearer sounding which was a surprise since I added a extra piece and connections in the signal path.  But the design of the phono preamp is fully balanced, so XLR should be used for best performance.

@lewm : “I hope you get the salient point that ICs per se count for nothing if the phono stage (in this instance) is not capable of balanced operation. Therefore you can’t have one without the other.”

That is quite misguided. Single ended is in fact differential, with respect to signal ground. Using the signal ground of the unbalanced differential signal from your typical phono cartridge as a shield is utter madness. To understand why, you must look at the point of origin and understand that while it is not referenced to the phono stage chassis ground, that is the only ground available and appropriate for a shield, and it is well proven to be effective.