hi guys, im building a modular preamp with s typical differential psu (15-20v positive/negative) and modularized active circuits so i can try different designs, and besides the usual discrete suspects the tubes are definitely on my radar.
So im wondering if theres a well documented low voltage tube (or hybrid) preamp that uses differential psu. The only one ive found is the borbely headphone amp but im told its not a safe design?
Thanks in advance 😁
So im wondering if theres a well documented low voltage tube (or hybrid) preamp that uses differential psu. The only one ive found is the borbely headphone amp but im told its not a safe design?
Thanks in advance 😁
I don't see any major problems and its certainly a "straight-through signal " type design .
Getting tubes that work on a lower voltage isn't easy both the Russians & Americans had them in military jets so I know they are around just don't remember the name of them , Russia had them in quite late models of their fighter jets as a precaution against aerial nuke blasts .
Very old portable radios had 45V tubes but their specs don't stand up to modern day hi-fi.
If you are worried about stability very small value compensation capacitors can be added in a "distributed " fashion, b uild one and test it its a pretty simple circuit .
Getting tubes that work on a lower voltage isn't easy both the Russians & Americans had them in military jets so I know they are around just don't remember the name of them , Russia had them in quite late models of their fighter jets as a precaution against aerial nuke blasts .
Very old portable radios had 45V tubes but their specs don't stand up to modern day hi-fi.
If you are worried about stability very small value compensation capacitors can be added in a "distributed " fashion, b uild one and test it its a pretty simple circuit .
Q2 base should be shorted to the collector, not emitter, assuming this was an attempt to create a current mirror.
Merlinb's note is right.
The base of Q2 should be connected to the collector of Q2 for a correct (simple)current mirror operation.
The base of Q2 should be connected to the collector of Q2 for a correct (simple)current mirror operation.
I see only 2 (constant) current sources in this circuit: Q3 and Q4.
Q1and Q2 are part of a current mirror. The current running through Q2 is mirrored by Q1.
Q1and Q2 are part of a current mirror. The current running through Q2 is mirrored by Q1.
But you are arguing the point about the unusual /non standard connection of Q2 a current mirror is not identical to a current source.
It isnt an non standard current source it is an errata, you dont need another current source because you have one in the bottom with Q3 😀
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O.K. you can say that the configuration of the (correctly connected) Q1/Q2 is also acting as a current source.
Q1 follows/mirrors the current flowing through Q2.
If the current though Q2 is constant that also the current
through Q1 is constant.
Q1 follows/mirrors the current flowing through Q2.
If the current though Q2 is constant that also the current
through Q1 is constant.
