I'm still not quite sure what you mean 🙂
This one with the PNP's in place is clipping at the bottom because you are over driving it slightly.
Reduce the input voltage to 0.9 volts and its OK. Zoom in at the bottom and its fine. You can see what look like quantisation errors but those are artefacts of the simulation.
If you compare with the input which is 'perfect' it is the same:
This one with the PNP's in place is clipping at the bottom because you are over driving it slightly.
Reduce the input voltage to 0.9 volts and its OK. Zoom in at the bottom and its fine. You can see what look like quantisation errors but those are artefacts of the simulation.
If you compare with the input which is 'perfect' it is the same:
way to rough and has a lot of issues but i made a practical power amplifier circuit, im also intrested in potentially replacing q5 and q6 with jfets
Quick thoughts on your latest sim.
1/ High DC offset because of imbalance in input stage bias currents. R15 and R7 should be equal value and R2 must be AC coupled to achieve that.
2/ VR1??? That should be fixed and bias current adjusted with R14. Set the value of VR1 to a fixed value that gives about 6 to 8 milliamps.
3/ No Zobel network.
4/ R4 and R11 need to be higher.
1/ High DC offset because of imbalance in input stage bias currents. R15 and R7 should be equal value and R2 must be AC coupled to achieve that.
2/ VR1??? That should be fixed and bias current adjusted with R14. Set the value of VR1 to a fixed value that gives about 6 to 8 milliamps.
3/ No Zobel network.
4/ R4 and R11 need to be higher.
Try this one. You will need to alter the model directive and possibly remove the 'C' from the four BD39/140 transistors if you haven't the C version in the model file. Its not perfect and more can still be done but it addresses many of the issues. Notice the bootstrapped current source of R17 and R3.
Frequency response:
Distortion at 1 watt into 8 ohm:
FFT at 1 watt/8ohm:
Frequency response:
Distortion at 1 watt into 8 ohm:
FFT at 1 watt/8ohm:
And the sim. Some of the caps are altered in this to 1F and 0.1F to get a better sim result on the FFT. C1 should be 470u and C3 6.8 or 10uF.
i hate low power distortion measurments since they are mostly used as a marketing scheme thats why id like to make all my measurments at full power.
Wrong!
We listen most of the time at very low power. If you have oscilloscope, set it to 2.83 volts and connect to speaker at normal listening volume. Most of the time power will be few hundred milliwatts. Rarely above one watt. Its important how amplifier sounds at one watt.
Who cares how it sounds at 100 watts? How much time signal spends at 100 watts?
We listen most of the time at very low power. If you have oscilloscope, set it to 2.83 volts and connect to speaker at normal listening volume. Most of the time power will be few hundred milliwatts. Rarely above one watt. Its important how amplifier sounds at one watt.
Who cares how it sounds at 100 watts? How much time signal spends at 100 watts?
Main advantage of classA is that with decreasing power distortion gets lower (untill noise takes over) unlike in classAB, where it often shoots up.
Its exactly the marketing scheme that classAB amplifier has reported distortion at full power, which is often much better figure than at one watt or less.
Its exactly the marketing scheme that classAB amplifier has reported distortion at full power, which is often much better figure than at one watt or less.
Can you post some measurements of classA amplifiers you taken at full power? Since you hate low power distortion measurments?
yeah thats a somewhat valid point but then you go into a random datasheet and see companies advertise their max power at 10% thd and the thd at 1 watt 2 watts.
@adason makes a valid point. Most listening is done with a very low voltage output from the amp.
Try this:
https://www.diyaudio.com/community/...h-voltage-power-do-your-speakers-need.204857/
Anyhow, this is your Rotel based amp (same sim as above) at max output into 8 ohm.
And this is the very highly regarded ACA (Class A) at the same output level:
Try this:
https://www.diyaudio.com/community/...h-voltage-power-do-your-speakers-need.204857/
Anyhow, this is your Rotel based amp (same sim as above) at max output into 8 ohm.
And this is the very highly regarded ACA (Class A) at the same output level:
i dont own any speakers i want to build an amp and then buy a pair of speakers. (i do have a whole box of random drivers thought)
i read the review on asr and someone said that this amplifier gets to whopping 3,4% thd at 7w.
It may well because on a 24 volt rail 7 watts rms into 8 ohm is just getting to be outside its performance envelope but the fact remains it sounds amazing as a normal domestic amp to listen to music through.
depends who you ask, science audiophiles who obsess over flat lines and everything being good enough to cover the human hearing range would call it an overpriced space heater and then talk about how amazing their overpriced fosi audio whatevers are. im not one of these people becuse i have a pair of ears and i can tell that most things class d sound matte no matter their frequency response or thd.
You have to decide what you want and the best place to start is perhaps for to build a couple of simple designs. Build an ACA, it is a simple design that is easy to construct and also build something like a Class AB design such as in this thread. Then listen for yourself.