I also mention to a bit off the record.
The feedback resistance from the collector to the base determines the gain along with the impedance of the MC cart, and should also play a role in determining the collector voltage of Q1 and Q6. In the circuit shown above, the DC servo operates so that the base voltage is 0V, but I think either Q1 or Q6 will be saturated and will not operate normally.
I think it is necessary to ground the collector through about 100R or make U1 a transimpedance configuration (an I/V conversion circuit).
Of course, Q1 and Q6 operate without feedback, but this is unavoidable.
The feedback resistance from the collector to the base determines the gain along with the impedance of the MC cart, and should also play a role in determining the collector voltage of Q1 and Q6. In the circuit shown above, the DC servo operates so that the base voltage is 0V, but I think either Q1 or Q6 will be saturated and will not operate normally.
I think it is necessary to ground the collector through about 100R or make U1 a transimpedance configuration (an I/V conversion circuit).
Of course, Q1 and Q6 operate without feedback, but this is unavoidable.
Hi Mason,
I do not get what you mean.
It’s not the collector who drives the feedback resistor back to the bases, but the LT6203’s output does the job.
There is no collector saturating, all the collectors have to do is to drive the opamp’s high Zin input.
And the servo is responsible for setting the input to zero volt.
The circuit is already working flawlessly for several years and can be used as a voltage amplifier or as a transimpedance amp.
Hans
I do not get what you mean.
It’s not the collector who drives the feedback resistor back to the bases, but the LT6203’s output does the job.
There is no collector saturating, all the collectors have to do is to drive the opamp’s high Zin input.
And the servo is responsible for setting the input to zero volt.
The circuit is already working flawlessly for several years and can be used as a voltage amplifier or as a transimpedance amp.
Hans
Just regard the shown circuit diagram as an op-amp with a positive and a negative input.
I used this in a differential head amp, as voltage amp and as transimpedance amp, here as an example with a low output 1R Cart and 50X gain.
The op-amps at the left are the above circuits, and the third op-amp at the right is a LT6234.
Hans
I used this in a differential head amp, as voltage amp and as transimpedance amp, here as an example with a low output 1R Cart and 50X gain.
The op-amps at the left are the above circuits, and the third op-amp at the right is a LT6234.
Hans
So perhaps you should add that the circuit in post 20 (and 15 also) is not a working pre-pre,
but a simulation exercise, at least not due to the missing input bias path.
It is a completely different task to build a head amp using two transistors or three op-amps.
This thread is about a discrete head amp I thought.
but a simulation exercise, at least not due to the missing input bias path.
It is a completely different task to build a head amp using two transistors or three op-amps.
This thread is about a discrete head amp I thought.
You misinterpreted the two op-amps at the left.
They are as discrete as discrete can be based on the John Curl patent.
These are the circuits as shown in #25.
And there is no missing bias, sorry.
Hans
This thread is essentially about two transistor head amps, Mark Levinson John Curl JC1 xx .
Of course you can define your op amp triangles as being set up in a discrete way, but this is
not the point.
Your post 15 schematic is not complete, and so the statement "The circuit below is also a JC
design" can not be true.
The same applies to post 20, not complete without input resistor etc - but if it is only part of
a later revelation (post 25) you should mention this.
I expect the same precision here as we are used from your earlier contributions.
Of course you can define your op amp triangles as being set up in a discrete way, but this is
not the point.
Your post 15 schematic is not complete, and so the statement "The circuit below is also a JC
design" can not be true.
The same applies to post 20, not complete without input resistor etc - but if it is only part of
a later revelation (post 25) you should mention this.
I expect the same precision here as we are used from your earlier contributions.
as_audio, Thx for having high expectations.
But since this is not your thread, let the O.P. be the judge of that.
Sorry Tiefbass to intrude your thread once more, but as I mentioned before, it was a bit off topic, but could be interesting for those wanting to modernize their JC-1 with components that were not available at the time JC applied his patent, while still keeping as close as possible to the essentials.
@as_audio, with all your remarks it seems you are having a problem in reading electronic circuits.
So let me start telling that a triangle is the universal defined way to display an amp.
Telling that that is incomplete, is telling that every op-amp is incomplete.
So starting with the first attachment, this is most rudimentary version of the JC-1.
Second attachment is the Triangle filled with JC's patent.
Third one is the version with two modern low noise transistors.
The fourth one is the version with a buffer to improve characteristics plus a servo to keep input at zero volt.
Hans
But since this is not your thread, let the O.P. be the judge of that.
Sorry Tiefbass to intrude your thread once more, but as I mentioned before, it was a bit off topic, but could be interesting for those wanting to modernize their JC-1 with components that were not available at the time JC applied his patent, while still keeping as close as possible to the essentials.
@as_audio, with all your remarks it seems you are having a problem in reading electronic circuits.
So let me start telling that a triangle is the universal defined way to display an amp.
Telling that that is incomplete, is telling that every op-amp is incomplete.
So starting with the first attachment, this is most rudimentary version of the JC-1.
Second attachment is the Triangle filled with JC's patent.
Third one is the version with two modern low noise transistors.
The fourth one is the version with a buffer to improve characteristics plus a servo to keep input at zero volt.
Hans
