Sun Audio SV-2A3:: Direct or not?

Hi, I use a tube preamp with my SV 2A3. I have tried my cd player directly in. They both have their advantages IMO. More detail and more high end content directly in, but i still prefer the tube pre for its warmth and sweeter mids. To me, going direct is a little anemic sounding. Tube swapping can even things out to a degree, so it's a close call. The gain should be set at fullwhen using a pre, but my pre has so much gain, that i run the pots at 1/2 volume. Experiment! For running direct, try a couple Ked Rad 6SN7/VT-231 jan and a older RCA 5U4 rectifier, that should warm things up a bit. Good luck, have fun and enjoy, Alan

If you go with a pre, you can reduce the gain somewhat (it only takes 150mV to drive the Sun to full output) and IMHO improve the sound by leaving off the cathode bypass cap on the input voltage gain stage. I did this on mine and didn't notice any loss of high response that could be caused by the increase in output impedance of the first gain stage by leaving off the bypass cap. Leaving it off creates some degenerative feedback (hence the loss of some gain) and should reduce distortion. Try it. You might like it.

I use a custom built tube preamp with the Sun SV 2A3, which I also mod to replace 6SN7s with WE 417A tubes. They sound perfectly awesome with spatial, detailed and sweet.

Yeh, but have you checked out the price of NOS Western Electric WE417As?

Average price of a pair WE 417A right now on ebay is USD$60-80. Whereas top line of 6SN7s are sold with untoucheable price USD$150-200 like Mullard ECC33 or rare TungSol VT231 round plated. To me WE417A is best choice of input tubes for 2A3 and/or 300B amplifiers. Do not underestimate the little tube like WE417A/5842!!! You will be surprised if you know how to mod.