Audio Research Sp-6a-Should it be modified?

First, thanks for all the input. With your help, I have found an amazing repairperson, and will write about his work after the repair.

He said he could modify the pre-amp and bring it to current levels of performance.

What do you think? Should I have it modified or leave the circuits original? What do you recommend?


it depends on the price and the level of performance upgrade. The 6a is pretty good without an upgrade, maybe the money should be put elsewhere...
The best bang for the buck, and relatively simple to do, would be to replace the Wondercap metalized coupling caps with higher quality caps.
I would upgrade the parts but leave the circuit the same. The caps are old and much better ones are now available. Resistors have also improved. I would stick to original values for both. Modifications to the original circuit will produce a different sound than the original which you may or may not like better. The first approach is likely to give a significant improvement without altering the basic nature of the sound.
I recommend that you ask Steve Huntley at Great Northern Sound Co. He's honest and his work is exceptional.
I got my first ARC pre-amp in 1989- an SP-6b. A buddy of mine who was experienced and competent with modifying ARC gear did a nice upgrade for me. He replaced the film capacitors with WonderCaps, changed the resistors to metal film, new trim pots on the tube voltage bias circuits, Litz wiring throughout and gold RCA jacks. I enjoyed that preamp up through 2003 and only changed so I could experiment with low output MC cartridges.
I had similar questions with my ARC SP-8. In the end I sent it back to ARC to be refurbished, rather than to another specialist to have it modified/changed. My logic was that while an upgraded SP-8 might be an improvement, it simply wasn't going to turn it into a REF 3, SP-17, or LS-25, so in the end it made more sense to me to save up for a really improved model, rather than try to increment my way up. It made sense to me to have aged components replaced with current equivalents (i.e. ARC replaced the old caps with better current caps) but not to make any circuit changes.
Not if you want any one to buy it should you decide that. I have noted people like all original pieces when it comes to buying older or classic gear.
Hi MilesD77,

First of all SP6 is a GOOD Pre-amp. If I am not mistaken, The circuit went back and similar to SP3. I suggest that you maintain the original circuit and change the caps & resistor available today.

Good Luck,
it may have a similar circuit as the SP3 (I do not know) but the SP6 is way more neutral and extended - if a bit dry (compared to the carmel colored SP3)...