Hi Nico,
I can see your getting some stick over all this but you can't leave us all dangling.
The figures do sound almost to good to be true -- do you have a zobel network on the output.
To slew that kind of voltage across even a few nano farads will cause huge currents, even the on resistance of laterals if they could be switched instantaneously would be a limiting factor.
Where in the amp are you making this measurement ?
Maybe you have developed something a bit radical, a different topology but you can't just leave it like this.
Even a slew rate of 1/10 your figure is pretty amazing.
A few clues maybe
I can see your getting some stick over all this but you can't leave us all dangling.
The figures do sound almost to good to be true -- do you have a zobel network on the output.
To slew that kind of voltage across even a few nano farads will cause huge currents, even the on resistance of laterals if they could be switched instantaneously would be a limiting factor.
Where in the amp are you making this measurement ?
Maybe you have developed something a bit radical, a different topology but you can't just leave it like this.
Even a slew rate of 1/10 your figure is pretty amazing.
A few clues maybe
Nico Ras said:
Nico,
I can think of a few things, but they are more related to how the
amp will perform in a real world environment.
- Ability to drive difficult loads, say 1 or 2 ohms, but obviously within
the OP stages current capability.
- Composure when driving capacitive loads. The usual square wave
into 1uF / 8ohm load.
- Ability to preserve linearity when driven from a higher source
impedance, say 10 or 12k representative of a passive pre amp
for example. A lot of designs will perform significantly worse
when driven from source Z's much higher than a few hundred ohms
due to IP stage CM distortion and capacitance modulation.
I'm assuming from your ultra low 1MHz distortion that it should
do well in the latter, but it's worth checking.
Good luck with the venture.
Terry
fab said:
...at best, for a couple of minutes. Unless you are using some sort of special cooling that would help dissipate 50-60W average power per device. Not realistic for 2SK1058/2SJ162 plastic case, you would need to keep the case temperature to max 60-70 degrees. Very large heatsink, and probably forced cooling, certainly way more expensive than throwing another 1-2 pairs of output devices.
And that's before any SOA considerations under reactive loads.
And that's before any considerations regarding the claimed performance (0.005% IMD) in a Miller compensated single pole design.
syn08 said:
Hi syn08, it is not uncommon to measure high power under instantaneous conditions, few listen to sine wave for a continuous period. Square wave is even worse. Few class AB amps are designed to operate under 100% conditions continually.
However, as you rightly state SOA considerations are very important.
Nico
Congratulations on your amplifier design. I wish I could design an amplifier to even a close approximation of what you have achieved.
I hope you can give some information later but I do appreciate that you may be completely limited by the contract you signed. I am an engineer and I am also a lawyer so I understand that a contract obligation needs to be adhered to.
None the less any hints on the directions that audio amateurs, such as myself, should be looking in would help. You could maybe list the 5 or 6 aspects of the design or layout that you thought contributed most to your achievement. That would help some of us a lot.
It souds as though you now need a loudspeaker to match your amplifier design as the loudspeaker is likely to be the weakspot in your system now.
Congratulations.
Don
Congratulations on your amplifier design. I wish I could design an amplifier to even a close approximation of what you have achieved.
I hope you can give some information later but I do appreciate that you may be completely limited by the contract you signed. I am an engineer and I am also a lawyer so I understand that a contract obligation needs to be adhered to.
None the less any hints on the directions that audio amateurs, such as myself, should be looking in would help. You could maybe list the 5 or 6 aspects of the design or layout that you thought contributed most to your achievement. That would help some of us a lot.
It souds as though you now need a loudspeaker to match your amplifier design as the loudspeaker is likely to be the weakspot in your system now.
Congratulations.
Don
Hi Guys,
The project is now over. There were six companies contracted that we know of, but we do not know whose design will eventually prevail. But the IP to this particular R&D project belongs to ...
It was not a discreet hi-fi but the circuit is earmarked for a audio chip for high-end TV receivers 35 to 50 watt and OLG of the amp is about 100 dB.
The design was based on a 15 MHz linear amplifier I did and found in a very respectable function generator of about 18 years ago.
I am working on another low power amp that will use a similar topology and I intend to post it on this forum when completed.
Obviously this will be in the public domain and DIYers can use it as they see fit.
Thanks for the interest anyway.
Nico
The project is now over. There were six companies contracted that we know of, but we do not know whose design will eventually prevail. But the IP to this particular R&D project belongs to ...
It was not a discreet hi-fi but the circuit is earmarked for a audio chip for high-end TV receivers 35 to 50 watt and OLG of the amp is about 100 dB.
The design was based on a 15 MHz linear amplifier I did and found in a very respectable function generator of about 18 years ago.
I am working on another low power amp that will use a similar topology and I intend to post it on this forum when completed.
Obviously this will be in the public domain and DIYers can use it as they see fit.
Thanks for the interest anyway.
Nico
darian said:
I am returning to work tomorrow after my summer vacation and will use the next two or so weeks to knock together a public domain system for those DIY guys who would like to tamper with a real world circuit.
I must admit in the past few weeks some interesting output stages cropped up that I may want to include in the circuit as there is some real merit in lazy cat's output stage. I have also looked carefully at the Dunlap output and am thinking to maybe combine these features into an interesting design.
It would be a new thread with PCB layout and participation from you all I hope and it will be a DIY Audio amp by the DIY Audio crowd in its own right.
Kind regards
Nico
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