This is the finall version of the amplifier I`ve been working on lately. It is a class A amplifier single ended with impemented "aleph ccs".
30W on 4Ohm load
Open loop distortion @ 1W/4Ohm = 0.03
Open loop bandwidth 48KHz (-3dB)
CL distortion @ 95% power = 0.08%
CL bandwidth 480KHz
30W on 4Ohm load
Open loop distortion @ 1W/4Ohm = 0.03
Open loop bandwidth 48KHz (-3dB)
CL distortion @ 95% power = 0.08%
CL bandwidth 480KHz
Attachments
A few thoughts:
1) The phrase "low negative feedback" should be followed by "wide bandwidth." What is the open loop bandwidth of your circuit? If your circuit has, say, 1kHz open loop bandwidth and you're counting on 26dB of feedback to increase that to 20kHz, you're going to be disappointed with the results if you use less feedback.
2) As a corollary, a circuit has to be built from the ground up to be low feedback; trying to do it after the fact doesn't usually work well. Most people design in too much gain and once it's there it's hard to get rid of without resorting to feedback. Yes, you can toss in emitter resistors and such and degenerate the gain, but then you throw off the operating points and things get confused. Which leads to->Putting in a JFET as a drop-in replacement isn't likely to produce good results--everything else has to be adjusted to fit.
3) Assuming that the closed loop gain of an amplifier remains constant, higher open loop gain directly translates as higher negative feedback. More negative feedback generally leads to a "tinkly" or "brighter" sound in the upper midrange that some people associate with "detail." A quick trip to a concert hall will show that instruments don't really sound like that--even close up. That doesn't mean that the sound isn't popular, though. Plus it's an easy way to meet specs.
Grey
1) The phrase "low negative feedback" should be followed by "wide bandwidth." What is the open loop bandwidth of your circuit? If your circuit has, say, 1kHz open loop bandwidth and you're counting on 26dB of feedback to increase that to 20kHz, you're going to be disappointed with the results if you use less feedback.
2) As a corollary, a circuit has to be built from the ground up to be low feedback; trying to do it after the fact doesn't usually work well. Most people design in too much gain and once it's there it's hard to get rid of without resorting to feedback. Yes, you can toss in emitter resistors and such and degenerate the gain, but then you throw off the operating points and things get confused. Which leads to->Putting in a JFET as a drop-in replacement isn't likely to produce good results--everything else has to be adjusted to fit.
3) Assuming that the closed loop gain of an amplifier remains constant, higher open loop gain directly translates as higher negative feedback. More negative feedback generally leads to a "tinkly" or "brighter" sound in the upper midrange that some people associate with "detail." A quick trip to a concert hall will show that instruments don't really sound like that--even close up. That doesn't mean that the sound isn't popular, though. Plus it's an easy way to meet specs.
Grey
bogdan_borko said:
So C10 and C11 are bootstrapping the load of the input
transistor. Maybe you should consider a current source there.
On the other hand, the caps are also loading the emitter of the
second transistor.... You might want to try to isolate these
effects to see which is making the difference.
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