Questions about tubes and their subsitites

The gain factor of a 5814 and a 12AU7 are the same! Also the 5963 and the 6189 can be used in place of a 12AU7!!

The JAN-Philips 5814-A preamp tube type is equivalent to the common 12AU7 vacuum tube and European ECC82 tube. It can be used in any 12AU7 or ECC82 circuit.

For some reason, I swore I'd read that the 5814 had 70 db gain but I am obviously wrong. It does make more sense now. I have used Sylvania GP 6189's and still have them. I have a pretty fair collection of vintage tubes.

Next question is alittle more weird. I have a very low output MC cartridge. Fidelity Research FR1MK3F which has .14 mv output. I use an SAEC SUT, which only provides 10db of gain. I have often thought that I'm still a tad low in gain for this cartridge so I tried an experiment. I put a second pair of Sylvania Gold Pin 5751's in the AU7 spots. 

This obviously provides more gain and to my surprise, it sounded very good to my ears, and to my wife's as well. Everything seemed to sound better than it should. My system has undergone many changes over the past few months as old pieces began to fail and I inserted multiple new (used) pieces into the system and would evaluate each with mostly disappointment and a few pleasant surprises. Things may not be perfect back to where I started but it has become very pleasant to sit and listen. I've gone through half a dozen preamps or more, 2 turntables and several cartridge tries. It's been fun and frustrating at the same time. 

Anyway, the question is this: Am I hurting anything by having 5751's in the Cary where it was designed to have 12AU7's?

Thanks,

Bill

I doubt that you would hurt anything. But just to make sure you should ask Cary if it is okay to do that. I swap preamp tubes in my phono preamp to lower the gain and I never had a problem. It never hurts to ask the manufacturer!!