An externally hosted image should be here but it was not working when we last tested it.
Lars you have deleted this picture..but i caught you...red handed.
hi there,
actually it's been long before this post.......
Lars, I could not find nowhere in your website your 500watt N-channel
design....
can you send it to me.
email: hienrichb@yahoo.com
actually it's been long before this post.......
Lars, I could not find nowhere in your website your 500watt N-channel
design....
can you send it to me.
email: hienrichb@yahoo.com
Hello Heinrich
I only have the published version, as far as i remember there was something updated in the bias circuit. Anyway you can see the published sch here
Please note: I am not supporting this circuit in any way, and not answering questions about it. Take it as is. Sorry...
The problems with the ZETA, that lead me to give it up, are fundamental, and related to the Id/Rss characteristic of the MOSFET's. They produce huge amounts of third harmonic distortion (the nasty type).
The voltage amplifier stage is actually very good with a low distortion, around 0.001%. However at the recommended bias current the total THD is 0.3%. Way too high.
You can improve it somewhat by increasing the bias current, at 1A per set of output MOSFET you get something like 0.03%, which is starting to be acceptable, but not exactly excellent. And now you have a colossal power loss to get rid of / and pay for.
Using Audio MOSFET's might help, but i haven't tried.
In theory you could improve the MOSFET's intrinsic distortions by either increasing the idle current and running them in Class A, but it leads to very low efficiency, low output power, and requires a big heat sink. IMO a bit of a relic from ancient times.
You could also increase the loop gain, and try to make the feedback eat the cross over distortion. But IMO that have never proven a successfull solution, because the sound will still be hard and cold. And in today's demanding audio world, that is simply not acceptable.
The conclusion is, that industrial MOSFET's are cheap, rugged, and easy to come by, and therefore tantalizing to use as output devices. However they have inherent problems that prevent you from getting even useful results in Class A/B amplifiers.
In Old-Style Class A amplifiers they may still be good, and of course in Class D amplifiers too. But the ZETA was a Class A/B amplifier, so i had to abandon it, as what it really was, a fun experiment.
I only have the published version, as far as i remember there was something updated in the bias circuit. Anyway you can see the published sch here
Please note: I am not supporting this circuit in any way, and not answering questions about it. Take it as is. Sorry...
The problems with the ZETA, that lead me to give it up, are fundamental, and related to the Id/Rss characteristic of the MOSFET's. They produce huge amounts of third harmonic distortion (the nasty type).
The voltage amplifier stage is actually very good with a low distortion, around 0.001%. However at the recommended bias current the total THD is 0.3%. Way too high.
You can improve it somewhat by increasing the bias current, at 1A per set of output MOSFET you get something like 0.03%, which is starting to be acceptable, but not exactly excellent. And now you have a colossal power loss to get rid of / and pay for.
Using Audio MOSFET's might help, but i haven't tried.
In theory you could improve the MOSFET's intrinsic distortions by either increasing the idle current and running them in Class A, but it leads to very low efficiency, low output power, and requires a big heat sink. IMO a bit of a relic from ancient times.
You could also increase the loop gain, and try to make the feedback eat the cross over distortion. But IMO that have never proven a successfull solution, because the sound will still be hard and cold. And in today's demanding audio world, that is simply not acceptable.
The conclusion is, that industrial MOSFET's are cheap, rugged, and easy to come by, and therefore tantalizing to use as output devices. However they have inherent problems that prevent you from getting even useful results in Class A/B amplifiers.
In Old-Style Class A amplifiers they may still be good, and of course in Class D amplifiers too. But the ZETA was a Class A/B amplifier, so i had to abandon it, as what it really was, a fun experiment.
Lars,
If you donot know how to solve the issues with vertical mosfets in a descent way, Please donot atleast blame mosfets for your inadequacies in designing vertical mosfet amps...
Hi Richie...
Niether Rod elliot has an experience with vertical mosfets, nor he knows how to deal with them....
There are many ways to design a descent amp with verticals...such as EC,TGC etc...
regards,
Kanwar
If you donot know how to solve the issues with vertical mosfets in a descent way, Please donot atleast blame mosfets for your inadequacies in designing vertical mosfet amps...
Hi Richie...
Niether Rod elliot has an experience with vertical mosfets, nor he knows how to deal with them....
There are many ways to design a descent amp with verticals...such as EC,TGC etc...
regards,
Kanwar
Kanwar: I am aware of techniques to get around the shortcomings of the industrial MOSFET, however my purpose of the ZETA was not to design a amplifier to make a product or useful amplifier. Rather i wanted to make an experiment to see how far one could go with a clean N-channel layout in a Class A/B setup.
I think you will agree with me, that this type of amplifier is today somewhat outdated compared to the much more efficient, rugged and far better sounding Class D technology.
I think you will agree with me, that this type of amplifier is today somewhat outdated compared to the much more efficient, rugged and far better sounding Class D technology.
Lars Clausen said:
Donot compare Class-D with Class-AB...its a total different phenomena.....
If you do want to compare than compare Class-AB amps with BJT's and Vertical Mosfets....This would be a much sensible comparision....
Could you compare Formula 1 Ferrari with Mercedes Benz SL600....
Well the fact is, that the vast majority of new amplifiers produced today (on this earth ) are based on Class D. And with good reason..
Especielly if you were to consider what credentials a Class A/B amplifier has to make it worthwhile compared to Class D.
I have found none myself.
ClassD has better sound, better efficiency, lower cost (when you include the heat sink and large power supply required for Class A/B) smaller size, better sustainability towards heavy loads, lower CO2 footprint, etc etc
But maybe i have missed something, so if you can come up with any reasons to make new Class A/B amplifiers, i would like to hear it (Well unless you happen to own an aluminum factory, short of orders for heat sinks .. hmm i guess you would opt for Class A then )
) are based on Class D. And with good reason..Especielly if you were to consider what credentials a Class A/B amplifier has to make it worthwhile compared to Class D.
I have found none myself.
ClassD has better sound, better efficiency, lower cost (when you include the heat sink and large power supply required for Class A/B) smaller size, better sustainability towards heavy loads, lower CO2 footprint, etc etc
But maybe i have missed something, so if you can come up with any reasons to make new Class A/B amplifiers, i would like to hear it
(Well unless you happen to own an aluminum factory, short of orders for heat sinks .. hmm i guess you would opt for Class A then )
The arguments cannot be reconciled......
There will still be good and bad examples of each technology, and there is always the perception distorting effect of 'bleeding edge thinking', which always favours the latest technology regardless of its disadvantages.
But Class AB and Class D are not the same sonically, somewhat like comparing tubes to SS.
Greetings Lars, you have done many good designs in both technologies, I salute your design abilities.....
Cheers,
Hugh
There will still be good and bad examples of each technology, and there is always the perception distorting effect of 'bleeding edge thinking', which always favours the latest technology regardless of its disadvantages.
But Class AB and Class D are not the same sonically, somewhat like comparing tubes to SS.
Greetings Lars, you have done many good designs in both technologies, I salute your design abilities.....
Cheers,
Hugh
Greetings and thanks Hugh
I would have to partly agree with you. Nothing beats the glow of a SE triode amplifier for intimate chamber music, classical violin and soft jazz. (Providing the right speakers, such as Audio Note AN-K). Even when the distortion is several percent, you can feel every string on the violin. I have heard it demonstrated by Peter Quortrup a few years back, it was simply amazing!
All the best from
Lars C
I would have to partly agree with you. Nothing beats the glow of a SE triode amplifier for intimate chamber music, classical violin and soft jazz. (Providing the right speakers, such as Audio Note AN-K). Even when the distortion is several percent, you can feel every string on the violin. I have heard it demonstrated by Peter Quortrup a few years back, it was simply amazing!
All the best from
Lars C
You got it right Man!
No, You havenot missed anything....you are right about Class-D...its the future of amplifiers.....100% agree with you...I am also into Class-D from past 2 years....
Lars Clausen said:But maybe i have missed something, so if you can come up with any reasons to make new Class A/B amplifiers, i would like to hear it
No, You havenot missed anything....you are right about Class-D...its the future of amplifiers.....100% agree with you...I am also into Class-D from past 2 years....
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