I'd like to share my experience on tubes rolling for my ST120.
First of all, I'd like to thanks to Bob, Roy & also Troy who built such a high quality products.
After almost a year using NOS Mullard 5U4G rectifier, 2x French brand 12AU7's for L&R + EH's 12BH7 on the C for the drivers (with monthly bias adjusment), I decided to do some tubes rolling.
Yesterday I put a NOS Mullard GZ34R for the rectifier, 2x matched NOS 1954 Raytheon 5814 for the L&R + Genalex ECC82 on C for drivers channels.
After readjusted the bias setting (0.500 dcV), then I fired up the amps.
My impression was:
1. On CD.
I played "Jazz at the pawnshop" & "Marantz's High End Audiophile Test" CDs.
The result was: I heard a bigger sound stage compared to previous tubes setting, the stereo is wider with clearer details and easy to pint point the instruments with no hars on the highs. I could hear the fingering on the straight-up bass much clearer. One of the track on the Marantz cd (Harumi played by Circle Percussion), the low was sound nicely tight (not boomy) with alot of details on the highs. On of the track which had a trumpet lines, it was nicely presented with no harsh on my ears.
2. On Turntable.
I played some Ben Webster, it brings the saxophone sound much forward/bigger. I could hear Webster's breath clearly with details on others instrument. The only downside, the stereo image is not as wide as the CD, maybe it's the way they recorded.
3. Digital music from my Itunes collection (in Apple Lossless format) using Schiit DAC.
I played some "vocals" such as Jenna Mammina, Roberta Flack, Norah Jones, Nat King Cole, Diana Krall.
Their vocals were so clear & details with forward soundstage which I love it.
Overall, I love this tubes setting compare to my previous tube set up. I'm not sure which tubes from the mixed that brings up the big diferences and sorry I'm not a techy guy, this was just my observation.
Here's my set up:
A pair of 1981 Cornwall I.
VTA120 in pentode mode (purchased new in 2013).
SP12R/PH12 pre-amp from tubes4hifi (purchaed new in 2014).
The same 4xEH KT-90 for the output tubes (with bias set to around 0.500 dcV).
Schiit Bifrost DAC.
Marantz CD player.
Project Carbon turntable.
Any one has good experiences using Mullard GZ34R, Raytheon 5814 or Genalex ECC82 on their VTAs are welcome to share their experiences & opinions on this thread.