Hi all,
I have at last been able to install the NOS 7308 tubes in my GK-1, listen, and do a comparison to the stock 6ES8 tubes. I’ve had two comparative listens, one by myself, and one with another listener, Listener B shall we say. The system consisted of a Marantz 8260 sacd player, Aksa 55N+ amplifier, Osborn Titan Reference speakers, Critical Q subwoofer, and my diy cables. My listening habits are mostly classical sacd’s with a few others mixed in. For these comparative listens I used just two pieces of music, so as not to confuse one musical memory, and require note taking; the first few minutes of Rachmaninov’s Third Symphony on a fine new Exton Japanese recording, and a familiar (to me anyway) song from blues singer guitarist Eric Bibb, an sacd from a 10 year old Opus 3 recording, with only the singer, his guitar, and a bass player.
Both sessions were conducted the same way, back and forth between tubes and selections until differences/opinions were fully formed. With the second listener, no mention of which tube was in the GK-1 at any given time until the session was complete.
The differences between tubes were consistent to me in both sessions. Listener B and myself both heard essentially the same differences between tubes, though there was some difference.
7308Me – bigger sound on orchestra strings and the orchestra as a whole
much better bass and bigger sound presentation on the blues singer
Listener B – smearing of string sound, though slightly larger presentation,
tube bloom on the orchestra
smearing of leading edge to notes, and stereo image better bass on the blues tune
6ES8Me- smaller sound on orchestral strings and orchestra as a whole
smaller sound presentation on blues song with a little less bass
clean lines to notes, somewhat solid state like in presentation
Listener B – clean sound to the strings on the orchestra with no smearing
much clearer stereo image with the blues singer, with a clean, clear leading edge to the notes
In the end we both agreed that the stock tube gave a somewhat solid state like presentation to the music while the NOS tube gave a bit of tube bloom to the sound.
I preferred the NOS tube, and Listener B preferred the Stock Tube.
Listener B was the GK-1 designer. And I don’t find it surprising that he chose the stock tube as preference.
Myself, I’ve come to enjoy the sound with the nos tubes. Since 90+% of my listening is to classical music, I’m not really concerned with leading edges and such, preferring the small bit of tube bloom with the nos tubes.
In the end it really does all come down to personal preference, irregardless of all else.
As for the NOS tubes, these were a pair of 1964 Amperex USA that I purchased from Andy Bowman at
www.vintagetubeservices.com. Andy’s price of $130 plus shipping was cheaper than the dac grade Siemen’s Rohre 1980’s 7308’s from Upscale Audio, and WAY less than the other tube vendors of NOS tubes, where these Amperex tubes are often listed at $300-400 per pair.
For the money, I dunno, could have bought quite a few discs and enjoyed them just as much. But sometimes curiosity and doability overcome everything else.
