The ST70 is not the last word in either power or low-end. That being said, even in this age of multikilobuck products being de riguer, I'm hard pressed to find a more satisfying amplifier.
A few questions:
1) Are you sure the ST70 is working properly? Have you measured the bias on the tubes, as well as the typical voltages inside the amp that Dynaco spec?
This is ALWAYS the first thing to look at. You may well have a weak pair of output tubes, drivers, or rectifier. A tired rectifier tube will take all of the gusto out of your ST70
2) Have you tried the Dynaco with the speakers before you upgraded to the Triode Electric board? Of course, you may not have had the amp without the mod
3) Loudspeakers prior to what I call the Tube Renaissance beginning in the late 1990s are often far more difficult to drive than those of today. Solid state amplification was the far more common topology, and loudspeakers featured difficult impedance curve and featured more complex crossover networs which serve as "speed bumps" for an amplifier.
Further along those lines, What is the woofer size and alignment of your loudspeakers? A lot of products of that era are sealed aligment, which is a difficult task for a tube amplifier.
In my experience, the ST70 works beautifully with a couple of my loudspeakers, and not at all with others. In the end, presuming your amp is OK, you may just have a poor match
A few questions:
1) Are you sure the ST70 is working properly? Have you measured the bias on the tubes, as well as the typical voltages inside the amp that Dynaco spec?
This is ALWAYS the first thing to look at. You may well have a weak pair of output tubes, drivers, or rectifier. A tired rectifier tube will take all of the gusto out of your ST70
2) Have you tried the Dynaco with the speakers before you upgraded to the Triode Electric board? Of course, you may not have had the amp without the mod
3) Loudspeakers prior to what I call the Tube Renaissance beginning in the late 1990s are often far more difficult to drive than those of today. Solid state amplification was the far more common topology, and loudspeakers featured difficult impedance curve and featured more complex crossover networs which serve as "speed bumps" for an amplifier.
Further along those lines, What is the woofer size and alignment of your loudspeakers? A lot of products of that era are sealed aligment, which is a difficult task for a tube amplifier.
In my experience, the ST70 works beautifully with a couple of my loudspeakers, and not at all with others. In the end, presuming your amp is OK, you may just have a poor match