The original Dynaco 6AN8 design we believe was inferior to the 7199 driver used in the Stereo 70. Therefore applying the same circuit that we developed for the Stereo 70 to the Mark 3 resulted in a dramatic improvement over the stock amplifier topology. This design coupled with the robust and high quality output transformers in the Mark 3 produced a truly stunning amplifier - both balanced and delicate yet powerful. The spectral balance is perfectly neutral and the imaging has the depth and focus of the best amplifiers. The circuit is identical to our upgrade circuit for the ST-70 (cascode gain stage direct coupled to the split load phase inverter) with higher current capacity in the phase splitter to drive the 6550's or KT-88 output tubes. Like the ST-70, it retains its musicality with both standard as well as premium audiophile components (although the benefits of the latter are evident). We included a few optional features that many of you requested as well including a DC Balance potentiometer (to balance the DC bias in the output tubes) and an AC Balance potentiometer to perfectly balance the phase inverter stage. Installation is perfectly straightforward since the board is exactly the same size as the original including the exact labeling of the connectors. You simply de-solder the connections from the original board, drop in the upgrade board, and reconnect the wires to the same pads. So, within an hour you will be enjoying your Mark 3 like never before. Download our comprehensive installation manual to see for yourself just how easy it is. You may purchase the board blank or fully assembled & tested. You may also purchase the board and parts as a kit.
Blank Board Pair (PWB-1U) = $80
Blank Board Pair w/Parts (KIT-1U) = $122
Assembled Board Pair (ASM-1U) = $150
Driver Tube Option, 4 Premium 6922 Dual Triodes (OPT-V-4) = $64
DC Bal Adjust Option per Pair (OPT-DCB-1U) = Add $24
AC Balance Option per Pair (OPT-ACB-1U) = Add $24
Polypropylene Capacitor Option per Pair (OPT-PPC-1U) = Add $27