Audio Research amps - balanced & non

Martykl you are correct! When driving an ARC balanced amp with the SP-10 preamp you will find that you are unable to get symmetrical clipping out of the VT-130. At about half the rated output of the amp, one half of the waveform will indeed softly clip and you will be unable to get anymore output out of the amp period. Since the waveform is asymmetrical, i.e. both halves of the waveform are not clipping at the same point, distortion products go way up because no distortion cancellation takes place. Since the amp puts out approx. 122 Wrms across 8 ohms,( i just looked at one) you would probably get about 55 Wrms. BTW if the SP-10 has not been looked at for 10-15 yrs., there are a few filter caps in the power supply that tend to fail. Look at the end gaskets on the caps with leads that come out of each end of the body of the cap (axial caps) and look for bloating or an actual hole where the cap may be venting. I believe they are located near the power transformer just to the right as you are facing the front face plate, and then look slightly below those caps as well. Hopefully, my memory serves me right. If any of the caps look like that, it's time for service. G

Can't answer that as question as I don't know other manufacturers circuit topology. Even with an XLR/RCA converter
you don't have the inverting half of the balanced input so unless the input circuit can compensate for that, your not going to get proper output. This is true with ARC.

Twenty seven years ago I was, with my business partner, designing a head amp. At that time I had a meeting with a man named Dene Jensen at his facility. I spoke with him for about an hour. He was the first person to actually design a computer program to simulate various transformer designs and how they would react in a given circuit. The man was brilliant.He was in a wheelchair at the time and was not a well man. He made an impact on me. He was passionate about his research into transformer design and materials. After our meeting I was unconvinced that a transformer could work better than an active circuit for stepping up small signals. I was doing research on moving coil cartridge pre-pre amps, and was considering using his step up transformers. For use as an impedance matching device it is far easier to use a transformer. However, both Dene and I knew the inherent problems associated with transformers and frequency extremes for my application. Although his transformers were revolutionary for what they were capable of doing, you can't defy the laws of physics and frankly I wanted to design a very wide bandwidth device. The point is , in some applications transformers work extremely well. In others...not so well. Everything you do is going to be a compromise. Since there is no such thing as a straight wire with gain the only thing you can do is try it and see if it works. I did...it didn't work. Audio Research designed and sold a single ended to balanced converter that used an IC not a pair of transformers and that was their decision. Was it right or wrong? Who knows.

...And the one big disadvantage of a transformer is phase shift and frequency roll off at the extremes. If the transformer is feeding a poorly designed wide bandwidth circuit then in fact the transformer might actually improve the sound over all. And I do agree, an active circuit is more complicated. But I think you missed my point. The point is that basically to each his own. You can't say you don't like something until you have tried it and it fails in that particular application.