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Old 13th April 2009, 04:14 PM   #1
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Default Pass A20


Here is a picture of an amplifier chassis I built very early in the 80ties. It was ment for a Threshold 400A clone. I had obtained a schematics at the time. Later I changed my mind and planned for a A40. Then I found I did not have the time to finish it - allthough all the metal work was ready! - and sold it. The amplifier then became a Pass A20. Which it still is to this day.
The article with schematics can be found here at Pass labs http://www.passdiy.com/pdf/classa_amp.pdf
The article was published in "Audio" February 1977.

I publish these pictures as inspiration to fellow builders.
The front panel is purchased Schroff 19" one. The heatsinks was purchased as one meter parts, and then cut up. We bought several meters of heat sinks. (Still stored to this day - except the ones used here.) All other metal panels where cut from large aluminium panels. The top panel ventilation was BTW added after I sold the parts.
The heat sinks are joined by a thick horizontal metal bar. A la 400A. The TO-3 transistors where also mounted in the 400A fashion.
Rear panel fuses are BTW the same as used in some F-16 electronics from way back when.

Rolv-Karsten RØnningstad
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Old 13th April 2009, 04:32 PM   #2
valo is offline valo  Norway
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Nice metall work, and it looks like it was made in the early 80ties

here is my Mini Aleph chassi
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Old 13th April 2009, 04:45 PM   #3
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Thank you.
Your chassis looks great, and seems Electrocompaniet inspired with plexiglass front(?).
Yes, mine was constructed maybe as early as 1980. I cannot remember exactly. What I remember though is that the Threshold 400A was soooo desirable when it arrived. And expensive. So I had to get one/build one!
Well. What happened was that I instead of finishing this first bought a Hafler DH-200, then an Electrocompaniet Ampliwire 2, then an Audio 60 (still around) (http://home.online.no/~jandors/audio.html), then Mark Levinson ML-2s, then Borbely Class As, and now I am playing retro Threshold NS-10 and 400A at last!
That old A20 chassis now has a future as a Pass DIY ZV9 (F3-like) or F5.

RK
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Old 13th April 2009, 05:30 PM   #4
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Quote:
Originally posted by R-K Rønningstad
......... then an Electrocompaniet Ampliwire 2,.........

RK

knowing you - you probably have schematic stashed somewhere ...... ?

regarding that fugly! ancient case - maybe you can try this one :
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Old 13th April 2009, 08:43 PM   #5
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Thanx!
I have the schematics for the original EC "2 channel power amp" somewhere. (But that is Regarding the latter Ampliwires I don't know. True! Besides, this is the Pass forum....)

Fugly ancient case.....
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Old 13th April 2009, 10:09 PM   #6
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Quote:
Originally posted by R-K Rønningstad
Thanx!
I have the schematics for the original EC "2 channel power amp" somewhere. (But that is Regarding the latter Ampliwires I don't know. True! Besides, this is the Pass forum....)
...
well - I can always ask (politely) to send me that schmtc .......
if you don't mind ......


Quote:
Originally posted by R-K Rønningstad
......
Fugly ancient case.....


certainly greatest compliment ZM can give .......

reminds me of story about one pictorial critic ( is that right word? ) , on one picture exhibition ....... he just trow enormous compliments in front of every picture ;
in front of one , he make loooong silent pause , and just said : " this one is really good ."

so - for me that's fugly! ancient case ..... not awesome or superb as every second one , easily seen in Stereophile ..... and in every one is newest breakthrough amp , almost Mana from heaven ... ( 'till next one )

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Old 13th April 2009, 10:25 PM   #7
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I'll send you the "2-channel power amplifier" schematics when I find it!
In the mean time top/rear view of A20:
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Old 13th April 2009, 10:26 PM   #8
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A20 front:
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Old 13th April 2009, 10:31 PM   #9
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Old 13th April 2009, 10:32 PM   #10
valo is offline valo  Norway
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Do you have a inside picture ?

Zen-mod: trye this link you may have to use Google Translate
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