Preamp for audio research ref110

Don't be too harsh on ARC, the SP 9 is an old "entry level" (for them) unit, built and sold back before ARC went all balanced with their equipment--that didn't start till they brought out the LS 5 (a terrific sounding line stage, by the way).  I'd go with later ARC preamps for the long term--the LS 16 was their first full-function preamp that had balanced outputs, as I recall, but it will sound different than the SP 9, which was less "tubey".  For the short term, initforthemusic has some good ideas, you might also ask ARC or a good tech if there's a way to give the SP 9 true or faux balanced outputs for your purposes.

For short term you could run an RCA to balanced cable from the SP9 to Ref.110.

I suspect that like most or all of the the more recent ARC Reference series amps the Ref 110 won’t work properly when provided with unbalanced signals via adapters or adapter cables. In the more recent designs, at least, apparently only half of the balanced signal path within the amp would see a signal in that situation, resulting in a drastic reduction in power capability among other consequences.

If ARC confirms that is the case with the Ref 110, what I would suggest is that you purchase a Jensen Transformer, probably their model PI-2RX (similar to the PI-2XX shown at the link except with RCA input connectors). Give Jensen a call to confirm that would be the best model to use in your specific application. It would convert the unbalanced signal for each channel to a true balanced signal pair. It would also eliminate any possibility of ground loop issues between the preamp and power amp, and would provide noise rejection comparable to the performance of a fully balanced interface. It would require that you use a very short length of XLR cable on its outputs (no more than about 2 feet or so), but the length of the RCA cables connecting to its inputs is not critical.

Good luck. Regards,
-- Al

For short term, IMO it's not reasonable to invest into Jensen Transformer. spending extra $200-ish, it's wiser to sell SP9 and get fully balanced preamp. There are active balanced converters sold by major pro-audio internet retailers along with B&H photovideo and J&R stores of Manhattan for much lower price point, but even that can wait till you get REAL stuff...

BAT VK3i normally with no phono, but VK installs phono-board there for $500 and it will be HUGE step above SP9.

Sell the SP-9 MK II.  You could get at least $800.

The Sp-9 MK II is from around 1990.

Buy a more modern preamp with balanced, or both single ended and balanced outputs.

I called ARC and they said RCA to XLR converters would not work, for the reasons almarg mentions, above.