harhaug,
I have a factory schematic for this and the 4000A. This is the second request to come up in the last week or so. I don't have the facilities to scan files so I have put these and others into the snail mail to Mr. Pass. He should have them in a few days. Perhaps he would be kind enough to post them.
Graeme
I have a factory schematic for this and the 4000A. This is the second request to come up in the last week or so. I don't have the facilities to scan files so I have put these and others into the snail mail to Mr. Pass. He should have them in a few days. Perhaps he would be kind enough to post them.
Graeme
I believe Jon Soderberg at vintageamp@earthlink.net sells
copies. If not, maybe Jam has it. If all else fails, I can reconstruct
most of it from memory.
copies. If not, maybe Jam has it. If all else fails, I can reconstruct
most of it from memory.
400A schematic
Mr. Pass,
I also have a 400A schematic. I reversed engineered the main
circuit board along with the power output stage board/heasink
assembly of one of the channels some time ago.
It shows all the components.(I think)
It has all the resistor values, some of the semiconductor numbers
and some of the capacitor values.
Perhaps you could fill in the unknown electrolytic capacitor values.
I am planning to change the electrolytics soon in my 400A.
I can copy it and send it to you.
Tom
Mr. Pass,
I also have a 400A schematic. I reversed engineered the main
circuit board along with the power output stage board/heasink
assembly of one of the channels some time ago.
It shows all the components.(I think)
It has all the resistor values, some of the semiconductor numbers
and some of the capacitor values.
Perhaps you could fill in the unknown electrolytic capacitor values.
I am planning to change the electrolytics soon in my 400A.
I can copy it and send it to you.
Tom
Sorry about the delay. I edited a swell copy of this schematic
but I keep forgetting to bring it in and I can't ftp from home.
so use the original 500K tif:
www.passlabs.com/np/400a-4000.tif
but I keep forgetting to bring it in and I can't ftp from home.
so use the original 500K tif:
www.passlabs.com/np/400a-4000.tif
Nelson Pass said:Sorry about the delay. I edited a swell copy of this schematic
but I keep forgetting to bring it in and I can't ftp from home.
so use the original 500K tif:
www.passlabs.com/np/400a-4000.tif
My god Mr Pass, you've come a long way indeed!
Jan Didden
lumanauw,
The 4000A was (is) an amplifier in the best Nelson Pass tradition. It was very robust with a large power supply and lots of output devices. It sounded very dynamic and relaxed. Compared to the later Stasis two it had a bit of a darker sound. The Statis sounded a bit drier and more detailed in the midrange. These are very small nits. however. I should point out that it's been a long, long time since I've heard either one.
To answer your question, I believe that the cascodes contribute a great deal to the dynamic sound of these amplifers. I am a fan of cascoding.
There are two additional things about this design that should be mentioned. First: note the absence of VI limiters. This was the first high power commercial power amp I had come across without this feature. I had Dayton Wright XG8 MkIII speakers (modified ala the NP app note). The 4000A was easily the best sounding SS amplifer I had heard driving them.
Note too that there is no output inductor - also the first time I had seen this in a large commercial design.
Graeme
The 4000A was (is) an amplifier in the best Nelson Pass tradition. It was very robust with a large power supply and lots of output devices. It sounded very dynamic and relaxed. Compared to the later Stasis two it had a bit of a darker sound. The Statis sounded a bit drier and more detailed in the midrange. These are very small nits. however. I should point out that it's been a long, long time since I've heard either one.
To answer your question, I believe that the cascodes contribute a great deal to the dynamic sound of these amplifers. I am a fan of cascoding.
There are two additional things about this design that should be mentioned. First: note the absence of VI limiters. This was the first high power commercial power amp I had come across without this feature. I had Dayton Wright XG8 MkIII speakers (modified ala the NP app note). The 4000A was easily the best sounding SS amplifer I had heard driving them.
Note too that there is no output inductor - also the first time I had seen this in a large commercial design.
Graeme
Some of what you may think of as cascode is the series
output stage, which I suppose technically is, but not in
the usual sense, as it's function was simply to divide the
voltage across the output devices by about 2 to share
the dissipation and keep the output devices well away from
the second breakdown region of BJT's.
By the way, if you want to see the massive output stage of the
Stasis 1, take your browser to www.passlabs.com/np/Stasis 1.tif
output stage, which I suppose technically is, but not in
the usual sense, as it's function was simply to divide the
voltage across the output devices by about 2 to share
the dissipation and keep the output devices well away from
the second breakdown region of BJT's.
By the way, if you want to see the massive output stage of the
Stasis 1, take your browser to www.passlabs.com/np/Stasis 1.tif
hello to everyone!
Today I've bought a 400a amp; realy cheap price; well, one chanel is silent; i'm planning to rejuvenate both! (i've allready succeded with a stasis II recently)
I seem to like NP stuff!
BTW, thanks for the 400/4000 drawings;
question : how much bias for optimal operation?
any info welcome!!
Today I've bought a 400a amp; realy cheap price; well, one chanel is silent; i'm planning to rejuvenate both! (i've allready succeded with a stasis II recently)
I seem to like NP stuff!
BTW, thanks for the 400/4000 drawings;
question : how much bias for optimal operation?
any info welcome!!
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