The Dyna-70 Ultimate Upgrade with Manual Bias is the original version of the Dyna-70 Upgrade kit, introduced 6 years ago. There is no difference in the audio circuit between Manual or Auto Bias versions and they both sound superb when compared to a stock ST-70. In truth, the Dyna-70 Ultimate Upgrade is just that- ultimately, it blows all other ST-70 audio upgrades away– it is the Ultimate Upgrade, or your money back.
If your budget doesn’t have room for the Auto Bias version of the Dyna-70 Ultimate Upgrade, don’t worry, while you still have to manually adjust bias, likely you’ve done it for years with your stock ST-70, or perhaps a competitors driver stage PCB. You will still experience the fabulous 3 Dimensional sound from your “Ultimate ST-70”. We here at Miller Audio LLC started with a manual bias Ultimate Upgrade, when that was all that was available 6 years ago; that amplifier is still going strong, although we have re-tubed the amp twice.
(For those who wish to build and populate circuit card using their own parts)