Intuition can be a reliable guide, but only when it is well educated by facts and appropriate principles. If not it is a most unreliable guide however sincerely someone believes in it.
I would like to comment on post 260 by kokoriantz, but I cannot make enough sense of it. It appears to suggest that feedback makes things worse when the speaker generates back emf; if so, this is another 'true believer' myth being trotted out. Perhaps that is not what he meant.
I would like to comment on post 260 by kokoriantz, but I cannot make enough sense of it. It appears to suggest that feedback makes things worse when the speaker generates back emf; if so, this is another 'true believer' myth being trotted out. Perhaps that is not what he meant.
When I was seven years old a kid at the end of the block told me he knew how a periscope works. Your eyesight reflects off the mirrors bounces off the object and comes back to your eyes. There are times that I feel nothing has changed.
The point, never had a single science class yet but simple observation of magnifying glasses, etc. and I knew this was nonsense.
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With a high enough damping factor, this is not an issue. No back emf can be introduced into the feedback loop if the output impedance of the amplifier is low enough.
In other words, it is another feedback bugaboo that is cured by - get ready for it - more feedback.
A two stage amplifier can partially address anyway. It's been done - Nakamichi Stasis topology. But the output stage still has voltage gain, and it still has a feedback loop around two transistors.
Furthermore, modern speakers with magnetic circuit shorting rings greatly reduce back emf and distortion. Try a set!
To change the tone of this, since I don't know what feedback is, or anything else, I am ready to bet that if everyone here had the 'free' money they would get a no feedback amplifier or as less as possible, like the Pass, high power transmission tubes and so on.
“The formula is simple: More hardware for more power with few stages and lower distortion with less feedback.. {...} — bigger hardware biased more deeply into the Class A operating region.” (quote from N.Pass)
“The formula is simple: More hardware for more power with few stages and lower distortion with less feedback.. {...} — bigger hardware biased more deeply into the Class A operating region.” (quote from N.Pass)
You are not very smart are you? Being surrounded by lots of people that advocate high feedback, and then say 'I bet you all want a zero fb amp' doesn't strike me as a good career move
Jan
Seems plausible. But what is an amplifier lambda? Please explain.
Did you mean the schoolyard bullies cannot discern a resistor from a transducer?
We could build one ourselves much easier than a conventional amplifier.
So much for that theory.
Actually I have been using the same DIY power amplifier since 1994.
In the early 1990's, my first DIY audio power amplifier design was a variant on the Blomley amp that I never got to work well. When one day the emitter resistors of the output transistors spontaneously caught fire after turn on, I abandoned it. In the meantime I had also learned about the Tol/Huijsing class-AB bias loop technique and decided I liked it more than the Blomley concept anyway. I then made a second amplifier with a class-AB bias loop which I still use today.
I have experimented more with preamplifiers, because I was never completely satisfied with them. For example, I experimented with simple stereo crosstalk cancellation/generation circuits that never worked well. The chassis in post #198 still has holes in it from features that I added and later removed again.
Besides, I have designed and built many circuits for a local radio station here, such as microphone amplifiers, filters to equalize the line between studio and transmitter, a downward expander that automatically turns itself off when not in use, a DIY digital field recorder and various converters from balanced to unbalanced and back.
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Long time ago ,the living room was heavily smelly .Feedback was invented to clean it up . Nowadays amplifiers are so clean that the floor is lickable, but there is still some slight smell still perceptible . To my exotic opinion ,because Zout is not remaininig resistive for the whole range . Conclusion ,to use non-millard amplifiers ,one or two stages ,like my bi-circletron which is resistive up to 100khz . But the millard ones are not doomed . I show one who's millard is so active that it has no resistive range at all ,100% inductive as the phase angle shows .To get rid of the smell from such amplifier, my exotic opinion ,is to clean also the toilet. By applying a negative current feedback ,the one that reduces the damping factor to 16 , when it kisses the frog ,it transforms it into a charming resistor. The one which had non, now is resistive up to 700khz and as bonus ,instead of becoming inductive ,it becomes capacitive , no more resonance with capacitve loads.
This is just an exotic opinion and nothing else . you like it? adopt it ,you don't, forget it.
Kokoriantz
This is just an exotic opinion and nothing else . you like it? adopt it ,you don't, forget it.
Kokoriantz
This thread could be titled "from technical to folklore".
There are many factors involved in waveform perception, not just the waveform. Neurons require many substances to be accurate. Neuronal networks have topological requirements to be accurate. Increasing perception resolution involves using neurons at higher gain. Every unsolved deception is a "double-zero at the origin" in frequency response of neuronal networks (a "blind spot" in perception, it does "motorboating" as soon as enough gain is attempted, failing any convergence criteria).
When these factors are not under control, you never know if the subject being discussed is loss-less waveform amplification, or the factors involved in waveform perception.
When a neuronal network is pushed into higher resolution, the first cycle of motorboating can be already interpreted as reaching its limit of precision.
There are many factors involved in waveform perception, not just the waveform. Neurons require many substances to be accurate. Neuronal networks have topological requirements to be accurate. Increasing perception resolution involves using neurons at higher gain. Every unsolved deception is a "double-zero at the origin" in frequency response of neuronal networks (a "blind spot" in perception, it does "motorboating" as soon as enough gain is attempted, failing any convergence criteria).
When these factors are not under control, you never know if the subject being discussed is loss-less waveform amplification, or the factors involved in waveform perception.
When a neuronal network is pushed into higher resolution, the first cycle of motorboating can be already interpreted as reaching its limit of precision.
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Hi Jan . If you feedback an amplifier of more than 2 stages it becomes an oscillator. To make it back a stable amplifier,you must add a capacitor to one of the stages to make it the dominant phase shifter ,smashing the open loop frequency response . This capacitor is called miller capacitor. Example, if you end up with an amplifier who's fr is 20khz after applying 40db nfb to have low distortion, than the miller capacitor has smashed the open loop frequency response to 200hz. The output impedance is now resistive only for the subwoofer.
miller,millerred, millard
miller,millerred, millard
Billshurve : please ,permit me share my knowledge of loudspeakers with you. I fully agree with you that the voice coil can generate current only by its inductance .However ,it transformes the acoustic and mechanical impedances into electrical ones . How these inductive components are generating current, I cannot explain . If you have a look to phase measurements, example Harbeth Monitor 30.2 40th Anniversary Edition loudspeaker Measurements | Stereophile.com
You can see, it is rarely resistive nearly half of it is inductive . All these inductors are spitting current into the mouth of the amplifier . For triodes to swallow currents is in their nature but current elements need to be controlled . If the amplifier becomes inductive also than, instead of damping it is jut shifting the frequency . The measurement shown as example than,includes the impedance of the measuring lambda amplifier.
You can see, it is rarely resistive nearly half of it is inductive . All these inductors are spitting current into the mouth of the amplifier . For triodes to swallow currents is in their nature but current elements need to be controlled . If the amplifier becomes inductive also than, instead of damping it is jut shifting the frequency . The measurement shown as example than,includes the impedance of the measuring lambda amplifier.
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