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I have studied some threads about what I assume is a very nice kit by Shannon (and therefore ordered a PCB myself). But ...
If it is easy to change various components, making it possible to use various tubes like the (original) 1626 and 6L6, it is easy to configure the PCB to handle other tubes that, at least, have the same pin config as 6L6?
The tubes that come to my mind are 6V6, 6A6 (12A6), maybe even EL34. Guess the 6F6 also has the same config.

Basically with any tube that has a separate suppressor grid connection going to pin 1 instead of being tied internally to the cathode, you will tie pins 1 and 8. My old 6L6GAs and EL34s needed this mod and it makes a handy test point clip for my DMM monitoring cathode bias. I tested some EL34s and KT90s in my Clementine and got great numbers. The EL34 gave me about 4.7W with the exact same biasing as the Russian 6L6s. As far as using flying wires, like with the 807 and 1625, you can mount about any triode strapped tube. Just check if you need to re-bias and minimum grid resistor requirements.

Note that the Clementine 6L6 is the design to experiment with, since it has a higher voltage rated power supply compared to the Darling version.

Shannon

I really wanted tobuild a working and noisefree Darling, but an idea could be to make some kind of switching arrangement for various components and B+:es as well as heatervoltages and try different tubes that would work.

What about using 6W6/12W6 as the output tubes? Same 7AC basing as a 6L6, 10W plate dissipation, rated for 300V in triode mode, both heater voltages are cheap (<$4) and plentiful. Envelope scratching gives about 2.1W output with a B+ of 250V, 5K transformer, 1K 2W cathode bias resistor (31V @ 31mA). Only drawback is a thirsty heater (6.3V at 1.2A for the 6W6, 12.6V at 0.6A for 12W6).

I was thinking of making my build a sort of convertible to go between the 1626 and maybe 12V6, 12A6 or other 12v filament tubes. I'm guessing the difference is the cathode resistor?

The main "variable" would be the cathode resistor value for the output tube, Since there are two sets of pads for two cathode resistors for each of the powe rtubes, it is relatively easy to use appropriate parallel resistor combinations, or perhaps connect the second RK through an under-the-chassis switch.

For an example, if you needed 1K and 500 ohms, use a 1K 2W resistor for the "main" RK and then another 1K 2W which can then be switched in for 500 ohms.

just my dva rubles' worth...

/ed B

I have 12A6 (G's and no G's), 6L6 (Russian 6P3S - not the type w/o base however). I also have 807's but need a convertor for the socket. I also have some 6V6 (Russian again).

The 12A6 would be similar to the Darling circuit with the lower B+ (Hammond 269EX) and bias current. Its much higher plate impedance almost necessitates negative feedback. The 807 and 6L6 would be biased up per my Clementine 6L6 info. The 6V6 would probably be somewhere in the middle and use a different power transformer, though you could just plug it into the Darling circuit and re-bias.

Shannon

Couple more WWII era oddball tubes which can be used with the Clem,

1614 which is essentially a metal envelope 6L6, with a "military" number.

1631 is nearly similar, but has a 12.6V, 0.45A filament and a slightly lower max plate dissipation rating (16W).

Both tubes have the same "7S" basing as a 6L6 / 6L6GC, so no board surgery would be required.

The 1631 would require using the voltage doubler (and a 12SL7 driver) or just use a 12.6VAC filament source and forgo the voltage doubler.

If you like going way out on a limb, the 6DZ7 could be used, it just requires two added jumper wires (1 to 5 and 3 to 6) on the V2 and V3 sockets:



The one "weird" characteristic of the 6DZ7, is that in paralleled operation, the grid resistor has to be significantly lower than useds with most power tubes, when I built my 6DZ7 PSE last year, I found the tubes to be unstable with 470K or 270K grid resistors, and worked the values downward, until it became unconditionally stable, and 150K was the highest value, and 100K oe 120K would probably be better.

The B+ should be approx 365VDC, and the cathode resistors, 200 ohm, 5W, for each 6DZ7.

The 6SL7 driver should still be good with that, just increase the coupling caps to 0.33 uF, from 0.1 or 0.22 uF. (this is described in my "Weekend 6GK6 Project" posting, in the last parts of the topic).

http://diytube.com/phpBB2/viewtopic.php?p=33067#33067

6DZ7s were designed for PP operation, and with the paralleled G2s and cathodes, for some reason, the control grids need the lower resistance value, in parallel operation. My SWAG on this phenomenon is tha the paralleled G2s and cathodes create a rather high G1 capacitance to the adjacent elements, when they are connected in parallel, as opposed to operating in PP, 180 degrees out of phase. ALso, the increased transconductance from paralleling the two sections, would be a major factor in dealing with instability issues. 100K grid resistor takes care of that nicely.


/ed B

With only one minor wiring change, the 6BQ6GTB / 6CU6 and the 6DQ6B can be used onthe Clem board.

The only difference is thatt hese tubes have a plate cap, whereas the 6L6GC uses pin 3 for the plate connection.

6BQ6GTB / 6CU6 is nearly identical to the 6AV5GA's operating characteristics.

6DQ6B is heftier, with a 18 watt plate dissipation rating.

/ed B

The metal octal 12A6s should work in the Clementine, use the same voltages and values as with 1626s, but change the V2 and V3 cathode resistors to 390 -400 ohms, 2 Watts, for approx 30 mA cathode current and 12 to 12.5V on the cathode. Bypass with 100 to 330 uF / 25 or 35V.

THe Hammond 269EX or 369EX should be a good choice for this one. In pentode mode, it should be good for about 3.4 WPC with a 7500 OPT primary. The Triode Electronics TF103-48-UL OPT would be a good match for the 12A6s.

http://frank.pocnet.net/sheets/049/1/12A6.pdf

Should also be good for triode strapped operation, probably about 1W RMS out.

/ed B in NC

OH NO!!! I forgot that I have a half built Clementine lying around ...