But chatting is so much fun ! 
Anyway, i am sitting here staring onto the layout and thinking about the inductive coupling of the half waves...
I did some math/sims and was able to reproduce quite exact the harmonic spectrum measured. It perfectly fits my theory and will give a distortion rise with 6db/octave. Even the relative amounts / pattern of the harmonics perfectly fit, resulting in the assumption that symasym could do 0.001% in real world with proper layout.
I didn't know that layout is even more difficult than designing amplifier circuit.
Mike
Anyway, i am sitting here staring onto the layout and thinking about the inductive coupling of the half waves...
I did some math/sims and was able to reproduce quite exact the harmonic spectrum measured. It perfectly fits my theory and will give a distortion rise with 6db/octave. Even the relative amounts / pattern of the harmonics perfectly fit, resulting in the assumption that symasym could do 0.001% in real world with proper layout.
I didn't know that layout is even more difficult than designing amplifier circuit.
Mike
I completely rewired the whole thing, using consequently star grounding. The result was only that i can now measure directly with soundcard and stereoseparation increased to >80db. No change in THD... (but no more fancy spectral lines)
It bugs me seeing that performance of symasym is limited that much by board layout.
Mike
It bugs me seeing that performance of symasym is limited that much by board layout.
Mike
PMA said:
Pavel, it's far from perfect, most of the 50hz junk is captured by RCA-cables, they are too long. (have not enough left right now, they are ~2m each)
But much better, above 1khz is practically nothing left.
I got the soundcard to a level where it does not show any harmonics at all, all harmonics visible are from symasym. (still jfet version)
These harmonics scale linear with impedance of load. (reducing dummy load by factor 5 reduces thd by factor 5)
The peak at 17khz seems to be an issue from RMAA, spectralab does not show it.
Mike
Attachments
mike,
I have a problem - the output stage bias is 1.6mA! I am thinking that this may have something to do with the BD139 (yes, I got a working model). How do you set it? What should be the correct Ib or Vbe? I have messed with it but I can't get the Vbe to go over 570mV. I probably should have asked someone to check my schematic before I started messing with stuff.
I have a problem - the output stage bias is 1.6mA! I am thinking that this may have something to do with the BD139 (yes, I got a working model). How do you set it? What should be the correct Ib or Vbe? I have messed with it but I can't get the Vbe to go over 570mV. I probably should have asked someone to check my schematic before I started messing with stuff.
So the BD139 is just being used because of the casing (as in more heat tolerance?)? What should be the ideal setting for the POT? I would read the original thread, but it's kind of boring reading something that you barely understand 
. I have recently coughed up an old circuit idea and figured out a way to generate odd harmonics. Could something like this be used in the output stage to cancel odd harmonics? It's really simple:
Two transistors, PNP and NPN. They are joined at the base and the emitter of the NPN is connected to the negative rail and the emitter of the PNP is connected to the positive rail, the collectors being connected to the opposite rails as the emitters. I connected a signal source in series with the supply, and the voltage was distorted. I don't remember about the current, but I am wondering if this idea can be used to cancel harmonics.
. I have recently coughed up an old circuit idea and figured out a way to generate odd harmonics. Could something like this be used in the output stage to cancel odd harmonics? It's really simple:Two transistors, PNP and NPN. They are joined at the base and the emitter of the NPN is connected to the negative rail and the emitter of the PNP is connected to the positive rail, the collectors being connected to the opposite rails as the emitters. I connected a signal source in series with the supply, and the voltage was distorted. I don't remember about the current, but I am wondering if this idea can be used to cancel harmonics.
Hey guys!
Think it would be worth it if I tried to make a simple model that would generate noise and implement parasitic properties into circuits in LTSpice? I think that I could do it if someone could tell me what values to use...
I am thinking that maybe the symbol could be semi-invisible and stretches 1 gridpoint per symbol so that it could be used in series to connect parts farther away from each other while accurately adding properties and such. I haver never touched the arbitrary voltage/current sources before, think that these could be used as a form of noise production?
I hope that this is something that I am capable of...
A problem would be layout, though. You would have to arrange the circuit as if it were the PCB...
Maybe someone could request a EMI/RFI LTSpice directive...
Could someone tell me how to make a noise generating circuit with some high-noise transistors such as 2N3904/06? Would amplifying the output of a CCS using noisy transistors work?
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