Hi amp-guy.
I have, and yes, according to the original article it is 1000uF.
I did enjoyed my 20W ClassA right until my voltageregulator fried not only itself, but the ampboards as well
My ClassA amp
Good luck building it, but don't take lightly on the Pass' warning: "For this amplifier, there is no such thing as too much heat sinking for the output stage. Extravagance in this area is no vice, and good ventilation is similarly very important."
I have, and yes, according to the original article it is 1000uF.
I did enjoyed my 20W ClassA right until my voltageregulator fried not only itself, but the ampboards as well
My ClassA amp
Good luck building it, but don't take lightly on the Pass' warning: "For this amplifier, there is no such thing as too much heat sinking for the output stage. Extravagance in this area is no vice, and good ventilation is similarly very important."
20W/8Ω - Class A Mosfet (Nelson Pass 1977 project)
Would be really interesting if someone else did it successfully...
https://www.passdiy.com/project/amplifiers/construct-a-class-a-amplifier
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Would be really interesting if someone else did it successfully...
https://www.passdiy.com/project/amplifiers/construct-a-class-a-amplifier
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R3 is 10k.
if you use 1mF for the input filter you end up with an F-3dB of around 0.016Hz
The 10uF suggestion brings the F-3dB to around 1.6Hz. Much more sensible in limiting the passband and yet letting ALL the the lowest bass frequencies through.
1000uF would have to be an electrolytic and then you have to choose between Polar and non polar and polar+ralop and nonpolar+ralopnon.
Using 10uF allows you choose a plastic film. Then it's either FKP, or MKP or MKT
if you use 1mF for the input filter you end up with an F-3dB of around 0.016Hz
The 10uF suggestion brings the F-3dB to around 1.6Hz. Much more sensible in limiting the passband and yet letting ALL the the lowest bass frequencies through.
1000uF would have to be an electrolytic and then you have to choose between Polar and non polar and polar+ralop and nonpolar+ralopnon.
Using 10uF allows you choose a plastic film. Then it's either FKP, or MKP or MKT
If you refer back to Walter Jung's clasic article Picking Audio Capacitors he has
a little discussion about electrolitics used as coupling capacitors. It seems that
the closer you get to F-3 the more distortion you have in the signal. I read this
article more than 30 years ago I don't remember figures but i believe he showed
that even at 10x the F-3db point the distortion was still quite high and a lot of it
showing up in the higher frequencies hence the subjestion to use a cap much larger
than you need.
a little discussion about electrolitics used as coupling capacitors. It seems that
the closer you get to F-3 the more distortion you have in the signal. I read this
article more than 30 years ago I don't remember figures but i believe he showed
that even at 10x the F-3db point the distortion was still quite high and a lot of it
showing up in the higher frequencies hence the subjestion to use a cap much larger
than you need.
yes.
1.6Hz is a factor of /12.5 less than 20Hz.
0.16Hz is /125 less
0.016 is /1250 less.
are we still talking about 10times?
I located that article and the effect I was talking about isn't as pronounced as I seem to remember. But heck I read that almost 40 years and many many beers ago. Even though its an old article it's still a worthwhile read. This is a link to the first part of the article but near the conclusion of the second part of the article a mention of runing the coupling cap into a lower resistance ofton makes the cap sound better. http://waltjung.org/PDFs/Picking_Capacitors_1.pdf
There is a series of much newer articles done just as thoroughly.
Worth finding and reading.
I was surprised to see that a pair of series connected non-polar electrolytics are close to polypropylene for low distortion.
And that a pair of series connected back to back polar electrolytics were not that far behind.
Worth finding and reading.
I was surprised to see that a pair of series connected non-polar electrolytics are close to polypropylene for low distortion.
And that a pair of series connected back to back polar electrolytics were not that far behind.
i never built this, but always wanted to when i saw the original article in audio magazine many years ago. it would be cool if mr pass came by for a visit and dropped a few ideas about anything he might do differently in modern version of this amp ... still using bipolar output devices instead of mosfets though.
mlloyd1
mlloyd1
Well, some years ago he published a little blurb about parts substitutions...
https://www.passdiy.com/download.ph...ssdiy.com/images/uploads/project/part-sub.pdf
https://www.passdiy.com/download.ph...ssdiy.com/images/uploads/project/part-sub.pdf
Truth is, I look at it now and see how much it could be simplified.
Understand, I want these project to be built, which is why I don't
complain about boards and kits based on them.
Over the years, I have learned that apart from aesthetics, sound quality
and reliability, simplicity has the value of attracting more DIYers to a project.
I was surprised by popularity of the Son of Zen, which was just about the
dumbest circuit you could do (not that it didn't sound good), but it seems
that lots of guys who were not afraid of cutting wood or machining metal
or soldering up heavy wires were still intimidated by the little 3 legged beasts.
SOZ seemed to lower that hurdle just enough to tempt a lot of these guys,
and I have never forgotten that lesson.
Understand, I want these project to be built, which is why I don't
complain about boards and kits based on them.
Over the years, I have learned that apart from aesthetics, sound quality
and reliability, simplicity has the value of attracting more DIYers to a project.
I was surprised by popularity of the Son of Zen, which was just about the
dumbest circuit you could do (not that it didn't sound good), but it seems
that lots of guys who were not afraid of cutting wood or machining metal
or soldering up heavy wires were still intimidated by the little 3 legged beasts.
SOZ seemed to lower that hurdle just enough to tempt a lot of these guys,
and I have never forgotten that lesson.
If you can't see it with your eyes, it's got to be harder to figure out, right?
Emulation IS the best form of flattery, so they say...
I'm kind of one of those guys, am now having fun trying to educate myself here in a new hobby, and I feel a bit like I was as a youngster working on cars on my own.
Emulation IS the best form of flattery, so they say...
I'm kind of one of those guys, am now having fun trying to educate myself here in a new hobby, and I feel a bit like I was as a youngster working on cars on my own.
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