I understand that replacement of transistors undesirable.... but as far as it maybe to apply 2SA2031 / 2SC5669 ?
I had a quick look. The fT is quoted at 10 MHz and output capacitance at 200 pF Vs. 30MHz and 600 pF for the devices specified.
You could try them, but you may need to change the compensation. The existing compensation has 80 dev phase margin and about 15 dB gain margin.
You could try them, but you may need to change the compensation. The existing compensation has 80 dev phase margin and about 15 dB gain margin.
to choose the capacity of indemnification(68пф) ? what criterion for the choice of capacity = absence of excitation ? rectangular impulse on an oscillograph ? how is it correct to pick up a capacity ? on what criterion ? will I be very thankful for an answer or where reading it is possible ?
I used FJAF4210\FJAF4310 . works perfectly. distortions not more than 0.01%. excitation is not present. a parasite generation is not present
Hi, I checked the voltages as in the diagram and everything is ok, but I hear the mid-high and high frequencies decreasing compared to my reference. I have tried with many sources and preamps. Can you help me? I have no oscilloscope to measure.
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The kx2-Amplifier is coming that wrinkles out some of the issues builders had with the original kx-Amp.
I am in the middle of build 2 and once this is measured and meets the same performance as build 1, the Gerbers will be released to Jim’s Audio - another 2-3 weeks at most.
Olopolo,
I will make a list of things for you to check to try to solve your problem - not easy without a scope.
Do you have this problem on both channels?
How bad is it compared to your other amplifier?
The problem is quite evident in two channels. Light low and medium frequencies also a little analytical. High down. I used no matched transistors.
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I measured with inexpensive oscilloscope, no problem. I tried to disconnect ZN and the sound changed, it is now more airy. !!! ???
You cannot omit the Zobel network on any feedback amplifier where it is part of the design. Please make sure it is connected and the wires are tightly twisted to the PSU.
Check that R4 and R5 are 1 k Ohms and not 10 k
For you HF loss problem, can you check C15 (270 pF) and R31 (1k). If one/both of these are high, you may get excessive treble roll-off
Check that R4 and R5 are 1 k Ohms and not 10 k
For you HF loss problem, can you check C15 (270 pF) and R31 (1k). If one/both of these are high, you may get excessive treble roll-off