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In Reply to: RE: Anyone ever build a clone of Citation V? posted by PeterI on May 12, 2015 at 19:18:21
"I have the parts for CCS, can be added later. What is the supply for the CCS though? I can't invent it."
The CCS in the tail of a LTP need not be "super/duper", when the non-inverting triode's grid is at AC ground potential.
AFAIK, no additional PSU is needed if the tail resistor in a Cit. 5's LTP is replaced by a 10M45S integrated circuit.
Eli D.
Follow Ups:
Thanks. I used 10M45S in my first amplifier build 3 years ago, the "Music Machine" triode EL34 version. Nice sound but not nearly enough gain. I had to use a preamp, which defeated the purpose, so it ended up sitting on the shelf.In that application the CCS required a supply of -66V DC and a 100ohm adjusting pot. It went to the cathodes of the 6GK5 input tubes.
Incidentally, I used those Cree Schottky diodes in another build, they're great.
Edits: 05/14/15
It takes roughly 30 V. to operate a CCS. Additional volts are needed to "track" the I/P signal. Now, consider the potential at which the LTP cathodes "sit", in both Poinz's "Musical Machine" and a Mullard circuit.In the "Musical Machine", the cathodes "sit" a few volts above ground. The negative rail is needed in order for things to work. The grids "sit" at 0 VDC.
OTOH, in a Mullard circuit, the cathodes "sit" a few volts above where the voltage amplifier's plate "sits". Remember, the grids of the LTP's triodes "sit" at the same potential as the voltage amplifier plate they are DC coupled to.
BTW, before Poinz went to the CCS tail load, he too used a resistor. The negative rail was also necessary in that situation.
Eli D.
Edits: 05/14/15
This number is very dependent on the actual CCS in question. I could think of some that would operate with much less (LM334) or potentially much more (pentode CCS).
The battery biased, depletion-mode MOSFET CCS operating envelope is dependent on how many batteries you use. With 3x 3.3v LI button cells, 15V is about the minimum it should ever see under maximum signal condition.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
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