transistors
I was thinking 2SA970 and 2SC2240 or BC550 and BC560.
And batteries 😉
Can't wait!
atb,
Audiofanatic 😎
I was thinking 2SA970 and 2SC2240 or BC550 and BC560.
And batteries 😉
Can't wait!
atb,
Audiofanatic 😎
I would use BL grade ( Idss ca. 8mA ). My circuit degenerates that to 6mA. That is about optimum for least distortion. In a line stage there is no need for sub nV noise so we can afford some degeneration.
There is a very symmetric N and P channel pair from NEC that EUVL found that should also work well in my circuit. I just forgot the names.
You mean 2SK163 / 2SJ44 ?
It is even more impossible to get than the Toshiba's.
I ordered a few pairs as NOS fron Japan and had to pay a premium for those.
Patrick
It is even more impossible to get than the Toshiba's.
I ordered a few pairs as NOS fron Japan and had to pay a premium for those.
Patrick
That was what i am afraid of. When i look at the NEC-Tokin website they do not make transistors any more.
What can work is 2SJ103BL and 2SK246BL. If we degenerate them to 3mA we need a 900
Ohm trimmer and the drain resistors should be 2.5kOhm. That way we lower the gain of the input stage compared to the 2SJ74, 2SK170 combination. That could help linearity. What i do not like is the wide spread of Ugs with this Fets. The 2SJ103 needs 2.2V and the 2SK246
needs only 0.5V to degenerate to 3mA. So a conflict can arise between the output offset trim and the zero trim in distortion. Maybe i am wrong here because when both Fets drop 3mA over the drain resistors output offset should be fine even when the trimmer is a lot off from the mid position.
Ohm trimmer and the drain resistors should be 2.5kOhm. That way we lower the gain of the input stage compared to the 2SJ74, 2SK170 combination. That could help linearity. What i do not like is the wide spread of Ugs with this Fets. The 2SJ103 needs 2.2V and the 2SK246
needs only 0.5V to degenerate to 3mA. So a conflict can arise between the output offset trim and the zero trim in distortion. Maybe i am wrong here because when both Fets drop 3mA over the drain resistors output offset should be fine even when the trimmer is a lot off from the mid position.
I told you that the transimpedance line stage can be arranged to include global feedback. So here it is : the full monty Transimpedance Line Stage Buffer. Actually it includes transimpedance and conventional feedback in one circuit.
Feedback
Hi Joachim,
It looks OK but for whatever reason, I think the feedback, I prefer the other.
I will (perhaps) try this one also but still I prefer the one without feedback.
Just a personal thing not based on measurements or technical specs.
I hope you don't hold it against me 😉 again it's nothing personal 😀
atb,
Audiofanatic 😉
Hi Joachim,
It looks OK but for whatever reason, I think the feedback, I prefer the other.
I will (perhaps) try this one also but still I prefer the one without feedback.
Just a personal thing not based on measurements or technical specs.
I hope you don't hold it against me 😉 again it's nothing personal 😀
atb,
Audiofanatic 😉
No, i like the non feedback version too. It is more simple and different and has low enough distortion and output impedance to not introduce audible problems . The feedback version will just measure better in terms of distortion and speed but that does not imply that it sounds better. Charles Hanson of Air may like the simple version better too. He thinks that negative overall feedback always sound worse. It is just hard to explain in conventional measurements. Maybe it is the time domain behavior. A transimpedance circuit rolls of with 6dB octave in the treble and a feedback amp with 12dB octave and the transimpedance circuit is unconditionally stable. Add more capacitance at the output and it will get even more stable because the treble will be rolled of and the distortion in the treble goes down because of local current feedback.
Call it degeneration if you will. At first glance that is hard to understand but the output of a transimpedance amp is a current source and the output of a global feedback amp with emitter follower is a voltage source. Put a cap behind a high feedback amp and it sure will oszillate.
Call it degeneration if you will. At first glance that is hard to understand but the output of a transimpedance amp is a current source and the output of a global feedback amp with emitter follower is a voltage source. Put a cap behind a high feedback amp and it sure will oszillate.
Funky brainset on that man..😉
Why not build it like your pure JFet transimpedance riaa, just with oppesite current lowering of the mirrors and a resitor to gnd. With the jfet buffer and funky servo....I'll run a simulation....
Why not build it like your pure JFet transimpedance riaa, just with oppesite current lowering of the mirrors and a resitor to gnd. With the jfet buffer and funky servo....I'll run a simulation....
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Yes, i thought about that too. Would be more then happy to see a simulation. This transimpedance thing brings us into the uncharted territories. I hope Scorpius and the Peacekeepers do not catch us ! We can always Starburst to the rescue though.
I'll do tomorrow, I think we can use some lower gain fets so the initial gain will be lower..an then just shunt to gnd with a resistor to get app 6 dB gain.