by audiowize » Sun Jan 13, 2008 2:32 pm
Ok, I don't see any issues with using the Poseidon, except that you are using cathode bias currently, and the Poseidon is setup for fixed bias. If you wanted my 2 cents, I would convert the amplifier to fixed bias first. You would remove the 470uf cap and 250 ohm resistor, and then connect a 10 ohm 1 watt resistor between pin 8 and ground on EACH tube. Next, you will need to add a small 40-50VAC transformer and a negative bias supply, then a pot to bias each tube. Basically, you can copy the bias scheme for the Dynaco MK IV, but double up on the bias setting pots. This will get you "around" those scorching resistors, and you can easily measure the current each tube draws. You will want to have have .55-.60 volts between ground and the pin 8 end of each 10 ohm resistor.
When this is done, then you might consider the Poseidon, otherwise, there will be no change in terms of burning out resistors. Also, just for the sake of being meticulous, you might want to measure the DC voltage at pin 5 on each KT88 while the amp is running and report back. If you have a coupling cap that's leaking voltage onto the grid(s), you can easily draw more current than you should.