Earlier this year I finished updating the first of my two 55+ year old Dyna ST-70 tube amps with the VTA driver boards, new tubes, new quad caps, and new input and output jacks (a significant upgrade to an already good amp). About 6 weeks later I finished amp number 2, and began experimenting with bi-amping them. Less than 30 minutes in, the 2nd amp started showing some problems, so it went back to the bench for debug. After fixing some issues, bi-amp attempt number two was going nicely, when my Lazarus Cascade Basic tube pre-amp also started having issues. What are the odds?! 25 years of good service, and it acts up within hours of finishing the amps! So the Lazarus got some new resistors and electrolytic caps to the power supply, and new poly caps in the audio circuit. That seemed to bring the Laz back to life, so the third time attempting to bi-amp these two old Dynas was the charm, and all is well. I ended up with a vertical bi-amp configuration, tri-wired, which is one amp per side...that configuration tends to have less crosstalk, and better separation.
I've gotta say that the VTA updates are a phenomenal upgrade. Gone are the 7199 driver tubes, replaced by three 12AU7s, and more filter capacitance. The Dynas with the VTA PCB are performing at a whole new level, and I'm hearing details and beauty I had not noticed before. Support from Bob Latino at Tubes4Hifi was superb, and greatly appreciated too. Highly recommended if you're at all contemplating such an upgrade.
The bi-amping makes an audible improvement, especially in the soundstage separation and clarity, but it's not quite as dramatic of a difference as adding the VTA circuit. I'm glad I did it, because I already had both amps, but relative to the value of the system, I'm not convinced bi-amping would necessarily be the most improvement for the money if I actually had to buy another amp to do it. Nonetheless, the system sounds really good to me....just wish the family would give me some quiet time listen a bit more!
I've gotta say that the VTA updates are a phenomenal upgrade. Gone are the 7199 driver tubes, replaced by three 12AU7s, and more filter capacitance. The Dynas with the VTA PCB are performing at a whole new level, and I'm hearing details and beauty I had not noticed before. Support from Bob Latino at Tubes4Hifi was superb, and greatly appreciated too. Highly recommended if you're at all contemplating such an upgrade.
The bi-amping makes an audible improvement, especially in the soundstage separation and clarity, but it's not quite as dramatic of a difference as adding the VTA circuit. I'm glad I did it, because I already had both amps, but relative to the value of the system, I'm not convinced bi-amping would necessarily be the most improvement for the money if I actually had to buy another amp to do it. Nonetheless, the system sounds really good to me....just wish the family would give me some quiet time listen a bit more!