Is there a strategy in preamp tube placement?

Lowrider57, On tubes most of the time you get what you paid for, I agree with you, after paying premium price for my globe 6sn7 at Grant Fidelity , it made me realize what a high quality tube is all about.Though I did have luck buying tubes from Chinese 6sn7 dealers o  Pavanedirect and HiFi ...

@lowrider57 The advisory is registered.

When I enter into the exercise of re-visiting 6SN7 Tubes used on my system I will be cautious of the Linlai E Types I buy into.

Especially as I have also discovered the option to use an adaptor for the Pins and use them on a owned Phono- Pre and DAC which are using early 60's Vintage E88CC Tubes.

The additional comparisons for myself, will be a voyage into the unknown. 

The only principle that holds water is to put your best tube in the gain stage. The last tube before the output jacks is almost always a cathode follower. Cathode follower does not add gain and therefore has little effect on SQ. Except the CF by its nature can add a coloration that won’t be entirely overcome with even the best sounding tube.

while I think this talk about tube rolling as if it was a panacea is blather, I too prefer the KenRad VT231 over all other 6SN7s. But they’re microphonic.

@curiousjim - A buddy came over yesterday and we installed 4 of his olderTelefunken's in the phono stage in place of the Electro Harmonics. It was really really nice.

@lowrider57- I bought my Linlai's from Vivatubes, so I'm on the fence about buying a 2nd set from Grant Fidelity or finding a set of Ken Rad's

Presently, I have a set of Tung-sol's in the Gain position and the Linlai's in the Buffer spot. I still need to experiment a little more.

@decooney - The Full Music seems reasonably priced, might have to experiment.

I too have a Cary preamp that I bought earlier this year.  I got the SLP-05, and it has a pair of 6SN7 tubes for the balanced input buffer, and 2 pairs of 6SN7 for the left and right gain stage.  The stock EH tubes have good details in the treble and decent slam in the bass, but I found them to be a little too bright for my system.

So I bought 3 pairs of NOS RCA black plates to replace them all.  The RCA's are much warmer, less details but no harshness at all at the high end. The bass does get pretty low, but lack a little bit of slam.  Overall, I found them to be a little bit too dark.

So I changed the pair for the balanced buffer back to the stock EH tubes.  It sounded much better now with that setup (EH in the buffer, and RCA in the gain).  It restored some details on the high end, but without the brightness, and just a tad of improvement on the tightness of the bass.  So I kind of agree with @lewm that the tubes at the gain stage seem to have bigger impact on the SQ.

Anyway, I also recently bought some Ken Rad VT-231, based on all the praises I read here, and sure enough, they have very bad microphonic.   One minute into the first song I played with these KR, there was a sudden loud hum coming out of my speakers, and I ran to lower the volume down to zero, but the hum was still there.  I ended up having to power off the preamp to stop it.   I tried playing some songs again after a few minutes, and by chance I noticed a loud knocking sound coming out of the speaker when I just happened to tap the volume knob while trying to adjust the volume.  I then tried tapping the surface areas of my preamp, and every time it would be amplified and heard through my speakers.   I ended up returning them to the dealers and asked if he can find me some without the microphonic, but I haven't heard back.

Questions to you guys with the Ken Rad with microphonic.   How do you guys deal with this issue? or do you simply just live with it?   Thanks.