Let me lite fire - Nelson Pass F1

Crying like a baby, one small girl was afraid of walking into the operation room . . . I said it's a small thing . . . I pushed her back into the room . . . It was not a cancer, but something under the skin . . . Mmm . . . she was born with it . . .
Waiting outside . . . I was thinking about . . .
Pass Zens and the First Watt . . .
Yeah, it's time . . .

Here is my concept darwing.

I will not draw any details . . . I am afraid of Nelson Pass . . .

My target is [email protected] and [email protected]
A-class of efficiency about 5%.
Of course, the current source amplifier.

Nelson Pass, is the concept feasible?

Will it drive normal 2-way 90dB speakers too?
Or, should I change the x-over network?

Or, should I go with the efficient single unit speakers?



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Hi JH,

Mr. Pass has already given away most if not all of the F1 design in the form of small hints on this board and in the ZEN articles on PASSDIY. I would start off by doing a search on the subject.

I have built a transconductance SOZ from this information. I am still debugging a few things but it does work and it does make music. Some other people have already had good luck converting some of the other Zen's to work as current amps, if you need something right away.

Your other questions on 2 way speakers and crossovers are already answered in the current source amplifier and crossover papers on the PASSDIY website.


Oh . . . the limited number of the first edition is almost slod out . . . ?
In one month . . .

gl, I will read his writings.
Thorsten, thanks for the hint about the input R.
acaudio, mine is almost the same as yours. Did you build it?

Actually, mine was inspired by Zen V6 and Zen V7 . . .
I will go out to find IRF240 and collect them and others . . .

Mr. Pass,

The specifications in the F1 owners manual states that the input impedance in balanced mode is 100K and unbalanced is 50K. However, the FirstWatt product page for the F1 gives the input impedance (no qualification) as 80K. Which number is correct?

The output swing is also given as +-20V but the amp has a single voltage PS and the outputs are biased to sit at +13.8V. Should the spec read 20V P-P perhaps?