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Amp [message #31013] Fri, 18 March 2005 21:27 Go to next message
cheetah is currently offline  cheetah
Messages: 70
Registered: May 2009
Viscount
Het T,

Couple questions!

Is the B+ tied to the grid of the 5687 in the cascode? Its not clear on the schematic.

Also thoughts about using center tapped filament transformer, AC heating on output tubes, in place of the balance pot. Should be easy to implement, but how does the sound compare?

Joe

Re: Amp [message #31015 is a reply to message #31013] Fri, 18 March 2005 21:35 Go to previous message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
The upper grid ( Ec2 as refered to in cascode plate curves ), is attached to an ohmic voltage reference. Fed a regulated current by the CCS 2, it is attached to the low-impedance output for maximum stability. See the CCS2 sub-assembly for the detail. B+ to the top of the CCS, grids to the lower source, and the other end of R-set to the R-bias( V_bias=i_regulated*R_bias ) and with a pair of 5687's V_bias ought to be ~60V. +5/-0 V. As drawn with LND150's i_regulated is ~0.2 mA so ~270k is a reasonable guess.
regards,
Douglas

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