Who out there knows about Audio Research Pre's???

There is an issue with the turn-on on the SP-6A that I have not heard about in a long time. The SP-6B has this fixed. At turn-on there is a DC transient that gets passed through the preamp. If you have a DC coupled amplifier (solid state amp designs), you may (and I have) overextend any woofers to the point of destruction. The SP-6B has a warm-up timer which prevents this.

Sounds trivial, but it is incidious. Long time ago, I was listening to stereo, warming up for run. Went running, did not turn off system. While I was out, there was a short power outage. I came back to blown speakers. Ouch.

Anyway, lots of people still interested in SP-6, so I thought I would tell my story from 24 years ago.

Recently, I have switched to an SP-11 and I like the SP-11 better than the SP-6. But the SP-6 (not as good a soundstage) is a warm, wonderous beautiful sounding preamp. Mine has been modified with Sidereal caps. I was actually surprised at how good it was compared to the SP-11. SP-11 is the winner though, bass much better, soundstage much better.

Another feature on the SP-11 that is nice is that the phono stage is much quiter than the SP-6. This can allow one to use a lower output MC cartridge without a step-up device. SP-6 works fine with normal output levels, but I have tried a .2 microvolt cartridge and it just plain is noisy at the gain required.

My impression is in the world of SP-6, the SP-6B is the unit to have. I have owned my SP-6A since 1979 and it is still apparently worth within $100.00 of what I paid for it.

The LS-25mk1 with the right combination of NOS tubes will easily outperform a stock LS5 mK1,2,3, Ref1, LS-15,16,22 and 25mk2, not to mention the Ref2mk2. Beware the 6h30 tube. I would highly advise that you never ever under any circumstances - purchase a tube pre-amp that takes (8) 6922/6dj8 tubes. This is one of the worst tubes ever. but the 6H30 may even be worse. You will never be able to find the right combination with (8) tubes. Nos is mandatory and if you are not educated and have $$$- forget about it. Don't even think that you can get away with that Russian 6h23 tube- garbage. Four 6922/6dj8's is hard enough to deal with. I would also stear clear of the lower resolution SP series if all you need is a linestage. So if you want an ARC linestage with remote control- go for the LS-25mk1 with Amperex/Siemens NOS tube combination. If you think you can handle (8) NOS tubes- go for the LS-5mk3.

I own the LS25 MKI. With NOS 6H23 tubes (6922) it easily out performs the LS25 MKII. It is a very musical preamp. I am very satisfied with its performance compared to some very expensive preamps that I have auditioned in my system.

I went from LS-25mk1 to LS-25mk2- back to LS-25mk1. Have you tried some Amperex 6dj8's and Siemens 6922's. The 6H23 are better than the Sovtek 6922's but they are still far removed from the 1960's European tubes. But I'd still choose the 6H23 over a 6H30.

I agree with tubegroover's recommendation on the SP8 & SP10. I got an SP6C1 with the muting circuit moded. The C1 uses 12ax7 (4) and 6dj8 (2). The 6dj8 has about an 8 db better signal to noise ratio over the 12ax7. Mine is fairly quite running a low output MC. The tubes used on the preamp makes a huge difference. I did lots of tube rolling with Mullards, Telefunkens, GE, Amperex...etc.