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"if I was buying the kit"

Not that you have anything beyond intellectual interest in the VTA circuit, but in a purely self-serving way, I sure wish you had one. I have no deep objective knowledge of what improvements my (pre-CCS) 12AU7 based VTA might possibly need to improve its objective and / or subjective performance. But I can give you a list of the subjective things I've tried in my VTA, which include:

Increasing the value of the capacitance in the "on board" B+ caps over stock.

Using Panasonic, rather than Xixon electrolytics on the board.

Using a variety of well regarded resistor brands and types instead of Xicon metal films, including Dale RN, PRP, and Riken Ohm carbon films, all the same values as the stock schematic calls for.

Several different brands of NOS 12AU7s

12BH7s

Upgraded coupling caps

Output tubes tried included Gold Lion KT-77, Russian 6P3S-E, and original (not reissue) Mullard EL-34

Despite the above, I still find the amp "musically uninvolving" with the only significant change being the use of the 6P3S-E, which were the best of the tubes I tried.

I email another VTA ST-70 owner who has the later, CCS version. He's taken things further. In addition to the some of the above, he's increased and decreased the amount of feedback, removed the additional "on board" electrolytics, and attempted to change the circuit to use the more linear 12AX7, to name a few that I can recall.

Although we both have very different speakers and musical tastes, we're in agreement in that we both have other amps, both tube and solid state, which we enjoy listening to more than the VTA ST-70.

You can't please all the people all the time, so I thought I'd post my results to add some balance to this thread.





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