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12AT7s--Genelex, Shuguang Treasure, CV4024, JJ, Sylvania--compared

Posted by jeffreybehr (A) on February 27, 2011 at 22:26:10

WARNING--I am NOT a golden-eared audiofile; sometimes I feel more like a tin-eared audiofool...BUT..I try to keep my mind and ears open, so FWIW...

Equipment that uses 12AT7s is a pair of newish Monarchy Audio SE-160 hybrid poweramps, one tube per amp. One triode is used for gain; the other as a constant-current source. Associated equipment was an Oppo 83SE discplayer playing mostly SACDs; Audioquest Panther* ICs to a c-j MET1 6-channel preamp that has been much improved with SoniCap Platinum ('SCP'; Teflon-film) coupling caps and Jupiter HT/SCP-combo PS caps; a long pair of Audioquest Niagara silver-conductor IC to the poweramps; DIY speaker cable made of all-Neotec-OCC conductors (2 pairs 18g. copper to the MR and 1 pair of that copper plus a pair of 23g. silver to the tweeter). This is hardwired to the crossover board and continues to the drivers, and all 4 commons are unbroken from the spadelugs to the drivers. The crossovers' filters include huge SoniCap Platinums to the tweeter, SoniCap 'propylene MR shunt caps, Mills MRA-12 resistors, original chokes, and NO...as in NOT ANY...MR high-pass caps in the crossover**. Speakers are Audio Physic Avanti IIIs with a diffractionbegone.com antidiffraction pad around the tweeter. Altho the 2 MR drivers are driven full-range on the bottom, the 'main' section of speakers that are driven by these Monarchy amps have little output below c. 80Hz***. The amps had only about 125 hours on them; each of the 5 tubes has about 24 hours on them, so these are first impressions.

Tubes are current-production JJ, Shuguang Treasure, and Genelex, plus NOS Mullard CV4024 and Sylvania JHS 12AT7WA with gray plates about 0.45" tall and triple top-micas.

So far, I can characterize only a difference in the treble output of these tubes, with the Sylvanias, Mullards, and JJs having slightly more and the Genelexes and Shuguangs having slightly less. None of the treble is harsh (altho the JJs MIGHT sound a little smoother), and all tubes sound quite musical. Occasionally I thought I heard slight differences in low-level detail but couldn't confirm it. (My sonic memory seems to be about 2 seconds long.) I expect such differences will become more audible as the amps get lots more hours on them.

I'll add more impressions as the amps and tubes get more hours on them.

BTW I had been using small tubed amps--Music Reference EM7-12 SET monoamps--on these speakers for a few months. The combination sounded quite good, but I went stupid and sold the amps, feeling I didn't have enough power. Saturday while playing music for a visiting friend, I heard a cymbal simply explode out of the orchestra as I've never heard before. I guess enough power (320 into 4) makes a difference. ... :-)

* That was AQ's best copper-conductor IC a generation ago.
** That function is replaced by a small coupling cap in the poweramps, but I've not yet done that in the SE-160s.
*** The speakers have a quad of 7" woofers per channel that are actively filtered and amped; they were NOT turned on for these tube-listening sessions.

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Schiit Audio

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