Review: ARC SP-15 and LS3 preamps

Note: After the big job of re-labeling I just performed on this Blog, as part of my re-organization, I'm going to eliminate my other sister audio Blog (Review and Overview), to let everything be archived here. Today I'm duplicating all reviews from my sister Blog here. This may cause inconvenience for a few users who follow some of my items; my apology. In the long run, this shall be a lot more efficient. For regular posts, scroll down to 01, Spetember and below.

Review: ARC SP-15 and LS3 preamps

(posted in R33 in 06):

jules' ARC SP-15 has been playing flawlessly in my house for the last 10 days.

I haven't exactly matched the SP15's linestage against the SP10/11, but after many hours of listening I am pretty sure I prefer it to the all ss linestage LS3 (stereophile class A).

The SP15 does not quite have the LS3's superior analytical power, yet it is smooth on top, never even giving you a sense of stridency. As in the best of ARC ss gears, images and dynamics mimic tubes, and do not have that ss artificial flavor (apparent even in the Cello Suite). Well done.

The 3 tubes in the phono does wonders. The phono is dead quiet, in this aspect superior to SP10 and SP11.

Overall this is a smooth sounding preamp. Without direct comparison, I suspect it to be actually more polite than the SP10/11. This preamp can still match with the "best" of today and need not fear.

An incident:

There is just one thing I wish someone can tell me something about. I cannot yet use the balanced out. When I inserted the Neutrix Balance-to-RCA adaptors in the balanced out, the preamp produces no sound, not even through the RCA outs. It shorts itself. Obviously this preamp had worked with true balance connection between preamp and amp, but it does not work with adaptors.

Can anyone tell me why?????????

I was really irked by the balanced-out problem of jules' ARC SP15, so I just opened it.

I found the following:

-A reasonable balanced output, with 2x symmetrical circuit for the XLR + (pin 2 for USA) and XLR - (pin 3 for USA). The RCA SE out derived from these.

-Interestingly, the XLR +/hot (pin 2) also connects to the RCA INVERTED +/hot pin

-Correspondingly, the XLR - (pin 3) connects to the RCA DIRECT +/hot pin

My conclusion are:

-the polarities are reversed at the XLR output. Which caused a short when I used the US convention balanced-Neutrix adaptor (+/hot/pin2)

-ARC, being US manufacturer, should have XLR pin 2 as +/hot. This unit had been modified and phase reversed at the XLR by a previous owner, so as to use DIRECT in the correct phase. probably in conjunction with some Japanese or European amp.

-To back this up, I noticed that a) one of the screws of the XLR socket is not original; b) The solder looks too new at the XLR sockets.

-The main RCA outputs are likely not affected, and the phase there can be adjusted at the flip of a Invert/Normal switch (defeated when using DIRECT).