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Hi Everyone,
I have made All changes as per Ed Browns Super expert advice! back to the original Parallel SE output, but; with the exception of The 1N5408 3A Diodes for biasing, and I replaced the Ground lift from the power supply to the 1626 cathodes, that will work better in this case but may not be as high a voltage, but still will float the filaments DC. Here I also placed a new drawing showing extra PLLXO's off of the Selector cap switch. Much appreciated from everyone who helped!! Pianolydia P.s. Ed Brown, Thank you!!!!!

The first main problem is, the 3K output transformer primary would need a coupling capacitor, in order to block the DC from the relatively low (DC) resistance of the OPT primary. Otherwise the top 1626 is going to take all of the "heat" and break down. This configuration would be very inefficient, and output power would be minimal,
approximately 200 mW at best.


The only SRPP power stage I've ever seen referenced uses SRPP EL86 / 6CW5s, and it drives a 1K load, originally a special speaker with a 1K coil,
details can be found here:

http://frank.pocnet.net/sheets/129/e/EL86.pdf

though a 1K:8 OPT would work very well. About 4.5 W output, it could be driven with SRPP 12AU7 / 5963 stage. Since there is no DC flow through the primary,
a decent quality 10 watt, 70 volt "line matching" transformer would work well, using the primary's 5 Watt tap..

/ed B

EWBrown wrote:The first main problem is, the 3K output transformer primary would need a coupling capacitor, in order to block the DC from the relatively low (DC) resistance of the OPT primary. Otherwise the top 1626 is going to take all of the "heat" and break down. This configuration would be very inefficient, and output power would be minimal,
approximately 200 mW at best.


The only SRPP power stage I've ever seen referenced uses SRPP EL86 / 6CW5s, and it drives a 1K load, originally a special speaker with a 1K coil,
details can be found here:

http://frank.pocnet.net/sheets/129/e/EL86.pdf

though a 1K:8 OPT would work very well. About 4.5 W output, it could be driven with SRPP 12AU7 / 5963 stage. Since there is no DC flow through the primary,
a decent quality 10 watt, 70 volt "line matching" transformer would work well, using the primary's 5 Watt tap..

/ed B

I changed the configuation back to original SE Parallel, but I need help to see if I can Bias 1-pair of Parallel output tubes at the same time with only one meter and one LM317!

The LM317 should be good to cathode bias two 1626s in parallel, the cathode voltage (also on theLM317 input) should be around 25 to 27 volts DC, for 25 m per tube. The main thing is to be sure that both tubes are drawing current equally, and not one drawing in 30 or more ma and the other 20 or less (which would be a worst case scenario).

The low cost way for paralleled 1626s,would be to use a 500 to 600 ohm 5W resistor, bypassed with a 470 uF / 50V to 100V Low ESR capacitor).

HTH

/ed B