|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
64.122.72.31
In Reply to: RE: CCS in a circlotron??? posted by Lew on December 17, 2014 at 13:20:54
Its pretty hard to keep that one supply from being part of the load of each half of the circuit. That's why having 4 supplies in the output of the MP-1 allows it to drive stereo headphones- the power supplies don't represent a shunt to the circuit.
If you employ a CCS, it has to go in the tube bank it serves- IOW you would need two CCS circuits, one for each half. There is very little current through the two reference resistors (which in most of our amps are a pair of 600 ohm resistors) that reference the circuit to ground. A CCS would have no effect in that part of the circuit, as grid current is all the flows through them. They complete the circuit that allows a conventional driver to drive the power tubes.
The latter is the thing (innovation??) that we brought to the table when we created our OTLs. Prior to this, the Circlotron employed an integrated driver circuit that ran off of the Circlotron power supplies. Its a simple thing, but its what made the circuit practical in a number of ways.
Putting a CCS in the circuit might be a bit of a trick; due to the desired impedances I think a 2-stage solid state CCS is what is needed. It would have to handle the power of the output section without failure should a tube fail.
Follow Ups:
It sounded as if you were giving me a good reason why a CCS (two CCSs, really) will not do much to "help" the circuit. Then at the end it seems like there is a rationale for the modification, provided it's done right. I am thinking ONLY in terms of the MP1, not any amplifier, where currents in the output stage are comparatively very high.
I brought this up for theoretical discussion, not necessarily because I am about to try it. Sounds like you would not place a CCS where I theorized one could be used, in the negative rail(s), connected to the common junction of all the cathodes of the tubes in the output stage, above the 600 to 1K ohm resistors. Because, as you wrote, very little current flows through those resistors. So, maybe if one takes the output of the circlotron from between the float resistors and the "bottom" of each of the two CCSs (where the output or "top" of the CCSs are in turn connected to the cathodes) that would be the way to go???
The CCS would be in series with each tube in the circuit. In the MP-1, it would be in series with a pair of 6SN7 tube sections on one half of the circuit.
The output would be taken at the junction of the CCS and the cathodes of the 6SN7s. You would have a few hoops to jump through to set up the bias on the 6SN7s, but it seems very doable.
You wrote, "The output would be taken at the junction of the CCS and the cathodes of the 6SN7s. You would have a few hoops to jump through to set up the bias on the 6SN7s, but it seems very doable."
Where is the float resistor in this topology, below the "bottom" of the CCS (in series with the CCS to ground, as I proposed above) or in parallel with the CCS, such that only the float resistor is connected to audio ground? (That actually seems like the only way to go, now I think about it more.) Sounds like you might be saying that the latter is correct, to connect the float resistor to the cathode(s), AND the CCS to the cathode. Thus the CCS is in series in the circuit, as you say. Do I have that right?
Need a discrete CCS for every cathode?
Sounds like you got it.
I don't think you need a CCS for each cathode, but it wouldn't hurt.
only the float resistor is connected to circuit ground. Which makes sense.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: