DEC Littleton was a relatively sedate place compared with bustling "The Mill".
We could have used a 12lb turkey that DEC used to give out to each employee around this time every year. Yellow_Light_Colorz_PDT_12
deicide67 wrote:Does anyone know what the voltage swing on the poseidon boards is? I'm not too limited on space, but I also want to keep it simple.
At B+ of 440V (max for in the triode mode according a spec sheet), a pair of triode-connected KT-88s/6550s would require an input signal of around 70V-80V peak-to-peak to achieve full power.
In a fixed bias scheme you want to have a grid-to-ground resistance that is much lower than 470K that is used for a cathode bias scheme.
For example, in the HK-10 the bias voltage is applied to the KT-88's grid via a 100K resistor from the
"fixed bias adjustment" Yellow_Light_Colorz_PDT_17 resistor network. Therefore, each KT-88 has a grid-to-ground resistance of ~110K or so. Both Citation II and Mark III use a similar scheme.
Looking from the driver's side, the tri-paralleled output stage will present 1/3 of the impedance of the non-paralleled output stage which makes it a more difficult load to handle. Which brings to Ed's post regarding the PPP KT-88 amplifier and its driver stage:
EWBrown wrote:I ran a sim on tubecad, with 12AU7s and with 6CG7s, and the 6CG7s come out a little better. The overall gain with 12AU7s seemed to be marginal for driving 6550s or KT88s to full power, but they have more than enough drive (even without the CF stage after the LTPI) for driving PPP EL84s.
Can the Poseidon board drive the Tri-PPP KT-88 stage to its full power?
I have to get back to you on that unless someone already knows the answer. Yellow_Light_Colorz_PDT_12
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