This is it! The classic Dynaco Mark IV (mono output). The most desirable of the Dynaco amplifiers. It is basically half of an ST-70, but has a dedicated power supply instead of the split power supply in the ST-70, thus making the Mark IV better in terms of power supply stability, co-channel crosstalk, bass response, and overall power output. I estimate that I have used this unit for less than 20 hours. It was installed in a church before I had it, so it was used about once per week for only a few hours at a time and at a very conservative level, no doubt! This unit surely has a lot of life left in it!!

This unit features:
• NO RUST anywhere!
• NO PITTING anywhere!
• No oxydation.
• No scratches or dings.
• Very low noise (mostly 60Hz harmonics, indicating that a new power supply bypass caps would help, but they are not really necessary).
• Shiny chrome finish (but needs a little chrome polish to bring out the full gleam).
• Original Preamp board.
• 4-, 8-, and 16-ohm outputs.
• Output power ~35 watts.
• Size: 14"L x 6.5" H x 5" W
• Weight: ~17.5 lbs.

Several minor modifications have been made to the original Mark IV, they are:
• Replaced negative power supply diode and capacitors (see photo).
• Replaced EL34's with the Groove Tubes E34L (used as guitar amp), but no bias adjustments were made. The tubes have less than a dozen hours of use on them!
• Grid signal resistors have been replaced with 1% tolerance units (photo).
• Power resistors have been replaced with higher power new units (photo).
• The original RCA jack is still installed and functioning, however, a 1/4" input jack was placed in parallel with it to facilitate its use with guitar. It does not affect the functionality of the unit.
• A triode / pentode mode selector switch was placed in the circuit. In triode mode, this switch basically ignores the ultralinear taps on the output transformer and ties grid #2 to the plate through a 100-ohm resistor, effectively operating the output stage as a high-gain triode. This adds a unique touch to the tone. In pentode mode, the unit functions in the unaltered original mode of operation.