by deepee99 Mon Mar 21, 2016 11:01 am
peterh wrote: Dave_in_Va wrote:I've got a used SP 14 coming in this week. I don't know too much about it but I know it has EH 6SN7's in it. I'm super excited as I'm also getting the PH14 with it.
I'm sure the EH tubes are fine but I'm pretty sure some USA made tubes would probably sound better. I have a stash of old 6SN7's that test good on my Eico 666 but I'm not familiar with the concept of "matched quads" of preamp tubes. I get it for power tubes in guitar amps.
Am I okay using some of my stash in the SP14 without any "matching"? I have GE, Raytheon, Sylvania, Zenith, etc. Of course, I don't have any way to tell if these tubes might be microphonic.
Or should I buy a "matched quad" of NOS 6SN7's from a dealer? I've noticed the prices on these vary WIDELY.
Thanks for the advice. I'm sure I'll have other questions after the gear arrives as I've never used a stand alone phono pre-amp.
There is usually no need to "match" tubes in a preamp.
Matching is a confusing term. Yes, no need to match one tube with another in a pre-amp tube, unlike the big outputs, but the triodes should be matched internally in preamp tubes. Most reputable sellers will do this for you.
About the only way you're going to find out if your tubes are microphonic is to plug them in and when they're good and warm, give the chassis (or the selector switch) a good thump. You'll hear kind of a "boing" through the speaks. This doesn't mean they're bad tubes; some of my best are quite sensitive in that way but unless it affects the sound that's just a fact of life.
Start with the Sylvanias and work your way down. Most of the Syls (VT-231s) I have are quite microphonic if you tap the chassis anywhere near them, but that has no impact on how they sound. As a friend recently said, "How often are you going to go tap-dancing on the top of your pre-amp?" It's a non-issue in the SP-14, but might be of greater concern in the phono section, however I would yield to higher intelligences on that topic.