Balanced or Not


I own a preamp which has both balanced and single ended jacks. I assumed that since I was using the balanced jacks I was getting the benefit of a balanced circuit. I have just now realized that just having balanced plug-ins doesn't mean your preamp (or any other component) is "balanced." Just wondering what sonic compromises are being made with equipment which has balanced inputs and outputs but that change the signal to single ended as it passes through it. If you are using the balanced outputs, what good is that if the signal going into this jack is single ended? Why would manufacturers do this? What is the advantage to not following the balanced circuit through completely?
frepec
My preamp manufacturer mentioned to me that "RCA" is much more "musical" than XLR, even though he provided XLRs on the preamp.
For me it was an issue of "gain" in my system. XLR provided me with the necessary gain (twice the volts over the + and i terminals) and I am pretty happy with it. This is from a very recent upgrade from RCA to XLR between the preamp and amp.
Roscoe50, the best way of interfacing a balanced output to an unbalanced input is most likely with a Jensen transformer, as explained in section 3 of this paper. Examples of those transformers are shown near the bottom of this page. They cost around $200. If you want to pursue that approach, give them a call to obtain a recommendation of a specific model.

A less expensive alternative would be an ART DTI, specs shown here, although I can't vouch for its sonic quality.

Another alternative would be to have an adapter cable made up by a cable vendor, that connects XLR pin 2 to the RCA center conductor, and XLR pin 1 to the RCA ground sleeve. In theory a Jensen transformer is a better approach, but as a practical matter an adapter cable MIGHT provide results that are just as good.

The least preferable approach, IMO, although it still might provide satisfactory results, would be to use an adapter plus a separate cable, as you seem to be considering. If you want to try that I think it would probably be best to use an XLR-female to RCA-female adapter at the output of the Fostex DAT recorder, with an RCA cable connected from there to the Denon receiver.

The adapter cable approach and the adapter + cable approach will not provide any of the potential benefits of a balanced interface, regardless of the type of cable that is used, although as I say that might not make any difference in your particular setup.

Be aware, also, that most XLR to RCA adapters short XLR pin 3 (which is usually the inverted signal in the balanced signal pair) to ground (XLR pin 1). I suspect that won't cause any problems with your pro-oriented DAT recorder, but if you pursue that approach you might want to consider purchasing an adapter made by Cardas, which as I understand it do not short those pins together, at least on XLR-female to RCA-female adapters. Pin 3 SHOULD be shorted to pin 1, btw, when adapting an RCA output to an XLR input.

Regards,
-- Al
Al, I think I know a better way than that, but it requires a mod to the amplifier. But it is a very simple mod!

Any amplifying device (tube or transistor) has two inputs. On a tube this would be the grid or the cathode. Taking that a step further, you can drive both on a single-ended amplifier. I have done this a lot in the last several years. You just set up the cathode circuit of the amp to accept a signal (add a coupling cap, equal to the value of the cathode bypass cap; if the amp has a cathode bypass cap you use that).

For a tube amp it literally is that easy. With transistors its a little trickier but still easy. IMO this sounds better than a transformer and the CMRR is quite high.