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Subject: tube circuits
I have got a question about a possible circuit that I have been tossing around in my head for awhile now. This involves the use of tubes in a hybrid, tube-IC, surround sound processor. I know that some commercial processors are based on the PMI 2126SA , IC for pro-logic surround. Shouldn't it be possible to utilize some of that circuitry along with tube circuitry (especially differential amp circuits) to produce a simple but fantastic sounding surround sound processor? I would be interested in your thoughts on this.
Cal
USA
Bless you. I knew that such a circuit must exist, but I did not want to find it. Using this IC and a tubes
could make for a sweet sounding setup. I bought a Dolby surround processor over ten years ago. I listened to it for a little over one month and then put it in closet where it remains. The effects were impressive, but the sound was as bad as is found in movie theaters, harsh and brittle. I will look into this chip and see what can wrested from it.
Subject: auto bias in a cathode follower
I read with great interest your articles about automatically regulating bias in a common cathode circuit using a small voltage sensing resistor in the cathode. I was wondering if this could be transferred to a cathode follower design? I am trying to make a cathode follower with a constant current source on
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the cathode. I want the output of the CF at 0v which would be at the top of the CCS and the bottom of the voltage sense resistor. Is there a way of using your automatic fixed bias circuits to really lock in the cathode current of a CF with the constant current source on the cathode? I am aiming to use a pentode as the CF.
Richard
?
Check out the circuit at the GlassWare Tube Circuit of the Month web site. It makes use of what I call a compliant current source. It meets the quiescent current presented to it, rather than proscribing a fixed amount. As the tube heats up or ages, the circuit matches its idle current. Furthermore, at the same time that it presents a near infinite impedance to audio frequency, it works to maintain an output referenced to ground.
Subject: Triode-connected beam tetrodes?
What happens to the operational characteristics of a pair of 6L6 beam pentodes (push-pull, Class-AB1) when their screen voltage is slowly brought up to equal the plate voltage?
Does the power supply choke (or ripple-reducing resistor) provide sufficient feedback (or, conversely, isolation) to cause the tubes to "behave" more like triodes than pentodes? Would the amplification factor, mu, decline from 171.6 down to 7.99; the transconductance, gm, lower from 0.0052 S to
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