This amplifier reminds me a bit of a Zen amplifier in the output stage but has a servo so no output cap is needed. The PDF is in Russian but the schematic is on page 3
http://www.next-power.net/next-tube/articles/hybrid/HAmp4I.pdf
I would like to discuss this topology and see if it could be adapted to something a bit more powerful than the 3 watt design.
http://www.next-power.net/next-tube/articles/hybrid/HAmp4I.pdf
I would like to discuss this topology and see if it could be adapted to something a bit more powerful than the 3 watt design.
I'm a little rusty on my Russian since they took 3CP1 off the
air, but it looks like a 3 stage amp - 1 tube voltage gain stage
loaded with a bipolar cascoded current source and a cathode follower driving a Mosfet follower biased by a bipolar current
source. No feedback loop. An imaginative circuit that probably
sounds very good. No reason you couldn't scale it up quite a
bit, since there is enough internal buffering to allow for a
larger output stage. As it sits, though, the distortion will
continue to climb with power (not that we care....)
air, but it looks like a 3 stage amp - 1 tube voltage gain stage
loaded with a bipolar cascoded current source and a cathode follower driving a Mosfet follower biased by a bipolar current
source. No feedback loop. An imaginative circuit that probably
sounds very good. No reason you couldn't scale it up quite a
bit, since there is enough internal buffering to allow for a
larger output stage. As it sits, though, the distortion will
continue to climb with power (not that we care....)
Konnichiwa,
Well, the circuit is rather basic and simple.
Working backwards, we have a mosfet as source follower (VT3).
This has a current source with BJT's as source load (VT4/5), the current source is an open loop type, but with NFB broyght back through the backdoor as Compound Feedback Pair.
An Op-Amp servo deals with output offset (DA1).
So far a very straight forward Source follower. You can scale this to any power level you like, Powersupplies and heatsink sizes are your limit. No reason why you should not scale this up to use bigger power transistors and many more volts and ampere plus liquid helium cooling and a powerplant in the backyard....
The Valve Frontend is equally straightforward.
Working from input, the input Valve (VL1:2) operates as common cathode amplifier, the anode load is a traditional C4S.
The Anode is buffered by a "Miss piggy" plain jane cathode follower. This drives the Mosfet follower poweramp part.
The name given by the author "The simple hybrid amplifier" is entierly aproipriate.
Sayonara
MIKET said:
Well, the circuit is rather basic and simple.
Working backwards, we have a mosfet as source follower (VT3).
This has a current source with BJT's as source load (VT4/5), the current source is an open loop type, but with NFB broyght back through the backdoor as Compound Feedback Pair.
An Op-Amp servo deals with output offset (DA1).
So far a very straight forward Source follower. You can scale this to any power level you like, Powersupplies and heatsink sizes are your limit. No reason why you should not scale this up to use bigger power transistors and many more volts and ampere plus liquid helium cooling and a powerplant in the backyard....
The Valve Frontend is equally straightforward.
Working from input, the input Valve (VL1:2) operates as common cathode amplifier, the anode load is a traditional C4S.
The Anode is buffered by a "Miss piggy" plain jane cathode follower. This drives the Mosfet follower poweramp part.
The name given by the author "The simple hybrid amplifier" is entierly aproipriate.
Sayonara
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