I had REF1. At the time the source was ARC CD3MkII. System ran balanced.
I found the REF1 nice in some ways but it was a bit too colored for my listening tastes. I tried the original tubes and the set of NOS Amperex and eventually sold it.
Things I didn't like about it:
1. It had over-emphasized bass that seemed to slow the presentation. If you have speakers that do not need extra oomph generated by a preamp, then cross the REF1 out,
2. Midrange had an almost weird coloration where voices would have this metallic flavor. I would call it glare. It did not have that pure crystal clear midrange.
3. Highs didn't sound completely natural. There was also slight glare in certain parts of the treble.
Its strengths included, as pretty much all ARC preamps, the ability to throws a huge soundstage and provide great dynammics. It did wonders on classical large scale orchestral music. I liked it with the classical music and instrumental jazz, as long as there were no vocals.
I had an LS-25 with the same NOS Amperex tubes and liked it better than REF1. It had no glare in the midrange and was overall much more neutral and natural sounding.
If you want to try an ARC preamp, I would recommend you start with the REF2(if you want to experiment with 6922 tubes) or even REF2MkII which did address some issues of the earlier REFs. But at the going prices of the REF2MkII, I would probably opt for the LS-26.
