I don't know my way around and wanted to ask if it's all right
I measured here
I connected it it is the second circuit in the first was everything soldered on the PCB
As a general rule, you should always measure from GROUND to the pin you're checking voltage on. 1) Because generally, voltages are referenced to ground, and 2) because then you won't be inadvertently introducing a higher voltage at that point through the meter.
If you measure JFET pin voltages relative to ground, nothing bad will happen. DO NOT measure JFET pins relative to B+.
@RuudNL So are you just swapping out the c104 47nf cap for a 100nf cap, and changed the 160nf to 180nf? Is that all?The components to 'fine tune':
View attachment 124050
Measurement | Value |
---|---|
Overall gain, CAL to Vout, 1KHz (measured at 100mV in) | -1.6dB (0.83x) |
JFET open-loop gain (1KHz) | +19dB (9.0x) |
THD, 100mV RMS in, 1KHz | 0.013% |
Max input voltage. THD < 0.5%, 1KHz (RMS) | 530mV |
Drain current at optimum bias | 0.38mA |
Polarization voltage | 45.0V |
What effect would a lower-value resistor have? Right now I converted it from 56kohm to 47kohm now with the 33V Zener. With the 33V Zener and 47K resistor I'm not noticing that much difference compared with the 24V Zener & 56K resistor.Yes, you will have more headroom, more signal output and the transformer will saturate a little faster.
Just put a 33v Zenner and reduce the resistance that feeds it (for example in ORS87 R16 - 22...33kohm , you have to experiment, the Zenner will stabilize effectively if you feed it with a few extra volts, also take into account the possible phantom voltage deviation +/- 4v). For Dani B. U87 get inspired by U87ai.
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