VTA ST-120

Hello guys,

I bought my VTA ST-120 in February 2021 from Bob with the following options:

VTA ST-120 amp wired with no tubes
220/240 volt power transformer wired in
Both capacitor upgrades
Stepped attenuator wired in
TDR wired in
Triode/pentode switching kit

As tubes, I'm using:

4 x KT 120
1 x Mullard GZ34
1 x 12BH7A
2 x Genalex 12AU7

I saw on tubes4hifi website that are couple of upgrades for the amp:

- dual rectifier mod
- Bias display (replace octal socket) For use with VTA driver board only

Do you recommend one of these as an upgrade?

I want also to add an autobias board. Do you recommend any model?

My room is not big, it's around 475 square feet.

At this time I'm running a pair of A20 speakers which I like very much, but in the near feature I want to change with a pair of standfloors, something like B&W 703, Klipsch RF 63 or something like that.

I read about for tube amps, the sensitivity of speakers must be higher than 90 db. Even for ST-120?

I'm not listening loud, I just love the quality over quantity . As music I listen mainly electronic music (chill, progressive house, deep house) and jazz.

Based on my experience egarding the sensitivity of speakers with a VTA, more efficient speaker is not really required. I had Klipsch Fortes, Klipschorns, Zu Druids and no run a pair of Fritz Carerra Be bookshelves on stands I truly love and everone is amazed at. I have a VTA ST-70. The Klipsch's we ranging form 96-103 SPL and the Fritzies come in around 88. The coparison to SPL an sound is another topic and very individual.

Did the panel meter mod and its a very nice addition. Get some window tint, grade 35 darkness (scraps from a window tint shop) for the Lexan so you don't see the meters when turned off. Dan is working on upgrading the kit with potentially darker Lexan. The blue displays are nice a subtle. For bias setting, I will install panel mount test points for a DMM since it is a bit more accurate. However, these displays make the look of a VTA very appealing versus the old Dynaco preamp sockets and are good indictors if something goes wonky. Highly recommend.

I've thought of building a VTA ST-120 but its strictly a want not a need. Really enjoy my ST-70 set-up and so does everyone else. However, if I were to do that I would definately to the dual rectifier mod and panel meters with self installed panel jacks for bias adjustments.

Hope that helps.

Nice looking amp! I'm glad my digital bias display is such a hit!

Love the powder coat if that it what it is. Nice craftsmanship indeed all around. I like my panel meters on my ST-70. Had to remove the resistor to eliminate some stray pulsating / flickering of the dispalys but all good now. Also added test plugs for a DMM. Great addition of the displays, well worth it.

Brap wrote:Love the powder coat if that it what it is.  Nice craftsmanship indeed all around. I like my panel meters on my ST-70. Had to remove the resistor to eliminate some stray pulsating / flickering of the dispays but all good now.  Also added test plugs for a DMM.  Great addition of the displays, well worth it.

I took the transformer sides off and had them powered coated, also the case and knobs. I made a SP-14 Pre Amp and color powder coat matched it.