Favorite 300B: Sophia vs KR

I want to thank Isochronism(Brett) once again for his very generous and trusting loan of the RP tubes to a perfect stranger. Brett, the RP must sound fantastic in your Wavelength amplifier,sonic bliss I`m sure.I know The builder of your amp likes the W.E. but I`d find it hard to believe they beat your combination(unless it`s true old NOS rather than reissue W.E. he prefers, and even then who knows?).
Best Regards,

Charles1dad, many thanks for your impressions, like your way to keep last 5% for the future:-)))

Now that there has finally been some comment and comparisons done on these two heavy weight tubes I would like to add my two cents since I own both of them now and have done a good deal of listening to both. The comparisons were done in a Border Patrol S-10 EXD amplifier with dual power supplies through Edgarhorn Titan l speakers heavily modified @ 107db efficiency.
Since this amplifier is a fixed bias and adjustible I set both tubes up at .685 MA (The recommended is .68-.70 MA from the amp. designer) and gave them some 50 hours of listening before a recheck of bias....more later on this.

I will try to catergize what I think most audiophiles classify would find important and give you a descritption from there.

Nuetrality: I give the nod to the takasuki as it extends top to bottom with no emphasis anywhere. The RP has very slight warm character in the midbass like you can hear the carbon plates at work. They pull this off however by still giving you the full performance and extension and both are as smooth as butter.

Holograpic imaging: I thought the Takasuki was a little wider in the soundstage with greater front to back imaging. The RP was farther back to begin with and a more laid back character. In my set up it was like the Takasuki is row F and the RP is row M. This differs from Charlesdad comparison in my system....welcome to audio as both systems differ as well as our hearing.

Musicality/Tone definition: The richer sounding tube to me was the RP but it is not night and day but I could characterize the Carbon plates of the RP. They still give you the full performance however just that a bit of extra fullness there if you need it. The Takasuki was simply the more nuetral sounding of the two.

Quietness and definition/resolution: The nod goes to the Takasuki as there is simply more air and definition around the performance....things are easier to depict and it could be because the backround is simply quieter who knows. Both tubes are great here however as compared to the Psvang/BT and EH tubes I have encountered.

Since I was curious on rechecking bias on the new tubes I rechecked after some 50 hours or two weeks of listening and found the Takasuki at exactly the same bias I began with .685 MA! The RP had moved lower and needed to be reset again. In the end I find them both very stable but the Takasuki was something special there as I have never experienced such stability. Maybe they liked my amplifier better who knows but thought I would share.

In the end I doubt you will be disappointed with either and would classify both extremely fun to listen to in there own ways and could live with either and find myself very fortunate to own both. I like the Takasuki to be a better fit in my system but your MMV. My suggestion is to save up and buy them both as it is the only way you will surely know!

I have limited time to join in the fun of the forums but from this please realize both tubes are leaders in their class and your system will likely bring out the best in either and you will have to be the judge from there.

Swampwalker & Markus - Let me know if you end up trying the Takatsuki's in your VAC REN amps. Audiogoner "Wavetrader" tried Sophia carbonplates (not RP) in his 70/70 and, if I remember correctly he had at least three of them fail over a 2 year period... so the Sophia RP's might not be a good option for VAC REN amps. Given their local availability, I would have been very tempted to try the RP's if I'd know they would hold up in the VAC REN circuit.

I know I'm taking a bit gamble trying KR 300B's, but Audiogoner "Waltersalas" has been using them in a 70/70 for a few years with no failures. The quad I'm getting are said to be gently used, and I'm getting them at a used price @ 60% of retail, so I figure it's worth a try, vs. spending $2600 on Takatsuki's that have no track record in regards to longevity with the VAC REN amps.

Brent & Kevin @ VAC did recommend Shuggie Black Treasures from a sound quality perspective, but did not know how well they's hold up over the long run. But @ $600 a pair, there's not too much risk, relatively speaking when it comes to premium 300B's.

Terrific post, Gwalt. Thanks so much.

Regards,