Dear Metako,
you are right, but these effects can't be seen without the topology of the circuit.
My rough estimation according to the drawing of GUS:
(i see there an interesting schizzophrenic Transistor Q5 trying to
be on two positions the same time) :
Cap B is for smoothing the negative power
for the grid and capsule polarization. life is easy for this cap, high impedances, DC.
(As well I have the feeling there should be one more resistor to ground).
CAP A (.1uF) righses the impedance of the input reference point, microphonics
might there be an issue, a big ceramic cap on long leads won't be a good idea.
bigger influence at lowest frequencies.
The 15p integrator cap is not so easy to judge, but it is inside the feedback loop
and it's distortion should be 10000 times under the rest of nonlinearities.
220uF are paralleled by 15 Ohms of the LED, no issue.
The circuit might even work without it. affects the bias in the output.
The impedance on this point is around 100kOhm (load/ beta of Emitter followers.)
C1 has a good deal of polarization Voltage, cause the star point of the emitter followers is below ground level.
The impedance of this cap is Z=100 @34Hz. For a better sleep bypass it with a film cap or replace it.
C2 does not see a polarization voltage, which is not ideal, but otherwise not a big issue.
This cap affects the sound of the unwanted noise from outside , which should be cancelled out
by your balanced input.
Impedance on the output pins should be matched for noise suppression. This does not mean same Resistor values(100Ohm)
but nearly identical cap values, cause pin 2 sees the Impedance of the emitter follower in series with C1 and 100Ohms.
This circuit has a high amount of internal feedback but:
The biggest influence has the parasitic capacitance from plate to grid. This will
be summed to the input and will determine the frequency response and sound the most.
1.5pf versus 50pF (capsule) . . 3% feedback of the Plate signal to the input signal.
Plate signal is not output signal.
You can take off the capsule, feed a signal to the input with a cap of 47 pF and measure the signal
at the plate. and check how high the level of the plate signal is. Stage Q1 might have a gain of 2, so
it might be that the plate signal is lower than the input signal (less influence on the input though)
It is possible to change the gain of stage Q1 if you like to modify around.
As mentioned in the thread before: parasitic effects caused by the dimensions of the cap can have substantial
influence on the circuit. As well there is in most film caps an outer foil connected to a marked lead.
This is often overseen.
Most of the sound is caused by the capsule design.
Most annoying for me would be the uneven response of the capsules, where the rode seems to be fairly good.
In any case would say, that minimal tweaking of the EQ in your channel should do much more
than cap swapping. Changing the valve might have a bigger influence, but not as much
as in a single valve circuit with substantial gain like the Neumann U47 or KM54.
________________________________
Non-electrical thoughts:
I think I underrated the desire of the cap-swappers to have a personalized tool or mechanical/electrical friend.
This gear, spit out of the factory in anonymous mass quantities is definitively lacking some kind of aura.
So better degrade it with some critical soldering attempts, let a fly, which is living in your creative space
puuh on the diaphragm and here it is:
The mic , which you can believe in.
all the best, Tito
you are right, but these effects can't be seen without the topology of the circuit.
My rough estimation according to the drawing of GUS:
(i see there an interesting schizzophrenic Transistor Q5 trying to
be on two positions the same time) :
Cap B is for smoothing the negative power
for the grid and capsule polarization. life is easy for this cap, high impedances, DC.
(As well I have the feeling there should be one more resistor to ground).
CAP A (.1uF) righses the impedance of the input reference point, microphonics
might there be an issue, a big ceramic cap on long leads won't be a good idea.
bigger influence at lowest frequencies.
The 15p integrator cap is not so easy to judge, but it is inside the feedback loop
and it's distortion should be 10000 times under the rest of nonlinearities.
220uF are paralleled by 15 Ohms of the LED, no issue.
The circuit might even work without it. affects the bias in the output.
The impedance on this point is around 100kOhm (load/ beta of Emitter followers.)
C1 has a good deal of polarization Voltage, cause the star point of the emitter followers is below ground level.
The impedance of this cap is Z=100 @34Hz. For a better sleep bypass it with a film cap or replace it.
C2 does not see a polarization voltage, which is not ideal, but otherwise not a big issue.
This cap affects the sound of the unwanted noise from outside , which should be cancelled out
by your balanced input.
Impedance on the output pins should be matched for noise suppression. This does not mean same Resistor values(100Ohm)
but nearly identical cap values, cause pin 2 sees the Impedance of the emitter follower in series with C1 and 100Ohms.
This circuit has a high amount of internal feedback but:
The biggest influence has the parasitic capacitance from plate to grid. This will
be summed to the input and will determine the frequency response and sound the most.
1.5pf versus 50pF (capsule) . . 3% feedback of the Plate signal to the input signal.
Plate signal is not output signal.
You can take off the capsule, feed a signal to the input with a cap of 47 pF and measure the signal
at the plate. and check how high the level of the plate signal is. Stage Q1 might have a gain of 2, so
it might be that the plate signal is lower than the input signal (less influence on the input though)
It is possible to change the gain of stage Q1 if you like to modify around.
As mentioned in the thread before: parasitic effects caused by the dimensions of the cap can have substantial
influence on the circuit. As well there is in most film caps an outer foil connected to a marked lead.
This is often overseen.
Most of the sound is caused by the capsule design.
Most annoying for me would be the uneven response of the capsules, where the rode seems to be fairly good.
In any case would say, that minimal tweaking of the EQ in your channel should do much more
than cap swapping. Changing the valve might have a bigger influence, but not as much
as in a single valve circuit with substantial gain like the Neumann U47 or KM54.
________________________________
Non-electrical thoughts:
I think I underrated the desire of the cap-swappers to have a personalized tool or mechanical/electrical friend.
This gear, spit out of the factory in anonymous mass quantities is definitively lacking some kind of aura.
So better degrade it with some critical soldering attempts, let a fly, which is living in your creative space
puuh on the diaphragm and here it is:
The mic , which you can believe in.
all the best, Tito
