Posted by PakProtector [ 205.188.116.67 ] on December 21, 2005 at 19:02:42:

In Reply to: Re: Merlin front end simlple-er posted by Damir on December 18, 2005 at 11:22:32:

Hey-Hey!!!,
In the original amp, built with a 290V B+ for its 1619 finals, I liked the 6AU6 a lot. I upgraded the output Iron from the little Z565 to the E-Linear modified Peerless S265. I saw no reason to swap out the Iron and went on to play with the cascode.

The cascode has the advantage in the single series path, where the pentode has g2 in parallel with the plate( on theway to the cathode ). Been wanting to experiment with the pentode again. Mounting two of them allows the switch to triodes if the hybrid front end is employed. Easy as strapping the pentodes as triodes, and adding the extra hardware.

But which pentode? low noise is always good, and plenty of gm so a low-value plate load can be employed and do best interacting with the grid choke at LF. I have a bunch of 6CL6 I'd like to play with. Looking for the same sort of characteristics as I'd look for in a power final. A low mug1-g2 for one. The EF184 is 50+, the 12BY7 is ~30. Looks like 6CL6 is ~20. The g2 current is more constant and to lower plate voltages with this sort of tube than the higher triode mu types. I think it will be fine. Unfortuneately the CB and Ham guys have put this tube in demand.

The 6CL6's anode Z is a comfortably high 150kOhm, and I don't have to worry about a MOSFET's gate-source voltage sensitivity. The higher voltage ones seem to have a 30V limit instead of the usual 20.
cheers,
Douglas

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