Topic: Balanced to Unbalanced vs. Unbalanced to Unbalanced

[Cheesecadet]

Hey All,

Just curious what the consensus is on the best way to hook up these cables?

1.)  Balanced Dual XLR out to Unbalanced 1/8" Stereo TRS Cable

OR

2.) Unbalanced Dual RCA out to Unbalanced 1/8" Stereo TRS Cable

Wondering if there is any advantage or disadvantage to either scenario or if they would be equal in sound, noise, etc.?

Thanks

[Ronmac]

It will depend on the output and input impedance and nominal levels.

What products are you connecting?

[Cheesecadet]

PCM r500 > Sony pcm m10

[Ronmac]

I would go RCA unbalanced to 1/8 unbalanced, since both are -10dB nominal.

[DSatz]

Ronmac's answer seems right to me. If a piece of professional equipment has unbalanced, consumer-level outputs, then the manufacturer has already solved several potentially tricky problems for you. By all means use those outputs unless you have a very good reason not to.

There are several different types of balanced output circuits--some are symmetrical (with both signal lines driven by active circuitry); others have active circuitry only on one signal lead or the other. And at least three different wiring schemes for converting balanced signals to unbalanced are in common use.

If you choose a conversion scheme that's not appropriate for the output circuitry, you could get increased noise and distortion, a faint, tiny signal that's just the residue of crosstalk, and/or potential damage to the output circuitry. The majority of these schemes connect one signal lead to ground, which can mean "shorting out" an output transistor; not all devices can tolerate being short-circuited on an ongoing basis.

Moral of the story: It's impossible for any one passive balanced-to-unbalanced converter / adapter / patch cable to be optimal, usable, or even safe for all situations. So the first principle is RTFM.

(OK, and that's also the second and third principle.)

Fourth-level suggestion is that the "most nearly universal" passive solution is to use coupling transformers at the inputs of the equipment receiving the signal. But the good ones are expensive (see for example http://www.jensen-transformers.com/product/pc-2xr/), and the cheap ones aren't very good.

--best regards

[capnhook]

If a device such as a Henry box is half its price, what are you getting with the Jensen PC-2XR?  They are both passive devices, eh?  The Patchbox II has multiple XLR, TRS and RCA outs.

https://henryeng.com/patchbox-ii/

About $150

[DSatz]

capn, I couldn't reach the Web page that you linked to. But in general what you're paying for (and getting) with the Jensen boxes is the highest-quality audio transformers in the world (that I know of), first-rate design and construction quality, and full engineering support in case of any questions or problems.

If your point is that not everyone requires that, I agree. There are plenty of alternatives all the way down to the $15 price level. But most pro audio equipment is designed mainly for public address, broadcasting and other communications-type applications. For straightforward economic reasons, the bandwidth, frequency response, overload limit and distortion specifications of many widely-available coupling transformers aren't entirely suitable for wide-range music recording (meaning both dynamic range and frequency range). If a person wants to minimize the potential loss of audio quality, that will cost a non-trivial amount.

Which was my point in the first place--if a piece of professional equipment has unbalanced outputs available, use them (unless, as I said, you have a very specific, very good reason not to). That way you don't have to pay even the $15 for a transformer that probably has rather uneven frequency response, limited bandwidth, and a risk of saturating at high signal levels depending on the lowest frequencies in a recording and how strong they are.

[capnhook]

Thanks DSatz, sorry for the confusion.  Here, have another try at the links.

Henry Engineering Patchbox II (about $150):

https://henryeng.com/patchbox-ii/

Product description and Technical specifications (not much here, thus hard to compare to the PC-2XR):

https://henryeng.com/specs/PATCHBOX.pdf



How much "loss of audio quality" can I expect to give up, by using the Henry box, and not the Jensen box?

[DSatz]

capn, this is a sidetrack of a sidetrack by now, so let me just summarize a reply. A few types of components in recording equipment really are critical, such as the capsule and the first-stage FET or tube of a condenser microphone. Audio transformers fall close to being in that category--not quite to the extent that microphone capsules do, but considerably more than (say) 44.1 kHz vs. 96 kHz makes a difference in music recording.

Or you know the descriptions of various recorder mods that some vendors offer, that some people here swear by? Those descriptions are at about the same level of difference that different audio transformers can definitely, actually make.

Many issues affect the quality of audio transformers--and as I said, the really good ones (i.e. the ones that are reliably audibly transparent) tend to be expensive and somewhat bulky. But there is definitely a "law of diminishing returns" in this area, since more than half the benefit can often be obtained for less than half the cost. Plus the problems of audio transformers aren't always a matter of quality as a generality--often they're a matter of the transformer's suitability (or lack thereof) for the specific use to which it's being put, plus certain tricky details of the way in which the transformer is actually used in practice.

The main technical issues are (a) bandwidth, (b) flatness of the frequency response within that bandwidth, (c) distortion levels at ordinary signal levels, and (d) the overload limit. (d) then breaks down further into the midrange/high-frequency overload limit vs. the low-frequency limit. Other technical issues include shielding and the limits on cable-driving ability--it is often imperative that the cabling between the output of the transformer and the input of "whatever comes next" be as short and as low in capacitance as possible to avoid high-frequency signal losses and/or high-frequency slew-rate limiting, though as with all source and load effects, the degree of this problem varies with different transformer configurations.

In general, all these problems are most apt to matter when (a) the transformer is small or even "subminiature" (as in the kind that can be built in to an XLR connector, or a metal tube with XLRs on both ends), and/or when (b) the transformer features a voltage "step-up" (= its secondary winding has significantly more turns than its primary winding, which both multiplies the voltage and causes an impedance transformation equal to the square of the turns ratio).

All in all, transformers introduce numerous variables that need to be looked out for. If they're well made for their specific application, and used with proper awareness, they can solve certain kinds of problems very effectively. If not, though, they can screw things up. There's an off-chance that they'll screw things up in an interesting or pleasing way in a given instance--but if so, that's a serendipitous outcome that you can't rely on.

--best regards

[Cheesecadet]

No mention of any of this in the manual fwiw

Thanks for the replies.

[DSatz]

> No mention of any of this in the manual fwiw

One of the things that studio engineers find most troublesome about their jobs is having to connect consumer equipment to professional equipment. Often this must be done under time pressure at the start of a session--the worst possible moment--as a courtesy or accommodation for clients who bring their own gear along ("Where can I plug my portable recorder into the board?"). Clients often don't understand that consumer and pro audio equipment follow different connection standards--not just mechanically but also electrically, such that simple plug or cable adapters don't suffice. The introduction of consumer equipment into the studio can also bring nasty hum and RFI problems along with it. I've seen sessions held up due to such problems.

The experience is often irritating and time-consuming--as I mentioned earlier, no one standard method of connection can be counted on to work optimally, or even at all--and it is quite a sore point for many engineers. Some studios at various times have had, or tried to maintain, a rule against doing it at all. It requires you to keep special cables and interface boxes on hand that you wouldn't otherwise need; it threatens to delay the session while you try this and that or go get another engineer to deal with the problem; and it requires a different, more technical mindset from the music-and-sound-oriented mindset that you want to be in. But the client is the client.

At any rate, the convenience value of separate unbalanced, consumer-level (and -impedance) inputs and outputs on pro audio equipment is immediately recognizable to any audio engineer, and I hope I'm not "burying the lead" here, but the PCM-R500 is from Sony's professional audio division; its manual was written mainly for professional audio engineers, and it does what it has to do: On page 5, it shows the location of the unbalanced analog outputs on the back panel and gives the type of plug connector they are compatible with, while the electrical specifications of these inputs and outputs are listed on page 32. Those are very ordinary specifications for consumer inputs and outputs, and a professional audio engineer would immediately recognize this.

If the deck didn't provide unbalanced, consumer-level inputs and outputs, its manual (to be reasonably complete in the modern context of "prosumer" equipment) would likely explain the best way to connect its balanced inputs and outputs to unbalanced equipment. But since the unit does provide those inputs and outputs, evidently no such explanation was considered necessary.

It's not the only possible decision that Sony could have made, but it's typical where professional equipment is concerned. On the other hand, on page 6, the manual tells you to "Connect the AC power cord (supplied) to the AC IN socket on the rear panel and connect the plug on the other end to a wall outlet" which I would have thought superfluous. It's always a process of guessing what needs to be said vs. what is better to leave out (or did I not need to say that here?).

--best regards

[Cheesecadet]

Thanks Dsatz,

I read that through that whole thing and actually missed what was in plain sight. Thanks for hw follow through.