Asking $949 / or best offerFor sale is an upgraded / refurbished pair of Dynaco Mk 3 / Mk III monoblock tube amplifiers. I completed them 5 months ago and they function perfectly. The only parts from an original pair of Dynacos are the output 1974 454216 PENTODE ONLY output transformers, tube cages and fuse holder. New power transformers, chokes, and chassis are from Dynakitparts. The new signal / power supply boards are the Mk-3 System on Board Premium Version from Curcio Audio Engineering. The signal tubes are a pair of matched 6922 type tubes. Bias and signal tube power are regulated supplies. There is individual bias for each of the power tubes (near new testing Sino 6550 ) with potentiometers on the board and test points for your multimeter on the back of the amp. Put the black lead of the multimeter in the black jack, and red lead in the right or left test point. With multimeter set to read millivolts, set the bias point for each tube to 450mV (45mA of current through the cathode of the tube) and you are ready to go. These amps have live HIGH VOLTAGE that can be lethal present under the tube cage, so you must feel comfortable using an insulated screwdriver on the powered up board to adjust bias. If not, please do not purchase these. The Curcio boards are set to run the amps in Pentode mode, not the traditional Ultralinear mode as used in most other Mk3 setups. This works well with these particular Dynaco output transformers that do not have Ultralinear taps. If you want to run ultralinear, this is not the set of monoblocks for you! For safety I have 3 prong grounded power cords in these amps, and that requires a good ground isolation circuit to prevent ground loops. I have one in each monoblock, and it works well to prevent hum. Sound is accurate, full frequency, with deep articulate bass and open highs. Not a romantic pair of amps. The tube cages were recently media blasted and professionally powder coated a textured black. The upgraded 5 way speaker binding posts are set for 8 ohm speakers. They can be rewired to 4 or 16 ohms. I am selling as I have made a speaker change that does not require these fine monoblocks. They run HOT, as all Mk3 amps do, and I recommend having them positioned with good ventilation available. These will ship in 3 boxes, one double box as shown for each monoblock and a separate box with the tubes carefully padded. Sold AS IS as I do for all DIY and vintage gear.
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