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Old 3rd March 2005, 12:59 AM   #11
adx is offline adx  New Zealand
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Hi - and yes, you're right, my reasoning above was flawed. Roughly the same level of fundimental is present in the second stage as in the first. The 10dB drop I saw IS a sizeable reduction (1/3rd). I'm sure I could null out the 2nd harmonic with ease, if I didn't have to get an amp ready for a demo tonight...

It's a pity audio signals are still shown using the old log scale tradition, the reality is that our response is closer to linear (pressure) and this is a much more "visually relevant" presentation. Even the a linear frequency scale is better than log for some jobs (like designing speaker crossovers). I was going to write an article or some sort of paper on this at some stage, but that was a while ago now!

Oh well, back to this amp. One day I might even sell one.
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Old 3rd March 2005, 01:11 AM   #12
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Hi adx !

Good luck whith the amp. I`m going to sleep to dream about a super-simple amp. Goodnight.

Thorsten
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Old 3rd March 2005, 11:14 PM   #13
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hi all
to be mathematically precise:
exp(x)=sum(x^n/n!)=x+(x^2)/2+(x^3)/6+(x^4)/24+....

so

exp(Asin(t))=Asin(t)+(Asin(t)^2)/2+(Asin(t)^3)/6+.......=
=Asin(t)+0.25A^2 -0.25*A^2*cos(2t)+...

McLaurin series and powering keeps all secrets

sin(t)^3=0.25sin(t)-0.25sin(3t)

regards
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Old 9th March 2005, 08:19 AM   #14
adx is offline adx  New Zealand
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Woaaa! Maths. At least I verified that (ax^2+bx)^2 results in an x^3 term. That's about as high tech as it gets for me.

I think I see what's going on in those formulas, which I think implies x^n results in only harmonic "n" being added to the output, and demonstrates how exponential distortion gives an infinite number of harmonics.

I modified my program to do y = ((1-yy/10)^3-1)*10 and got a 2nd harmonic as well, as shown. I guess this is because the waveform is offset and scaled before it goes into the "cuber" (something I'd usually associate with cooking or garden waste processing or something like that). Interesting to see all this working.

The gif is clearer this time - the latest version of freebasic doesn't scale graphics slightly off any more. BTW I thoroughly recommend this to anyone wanting to do lash up quick utils and programs without a big learning curve. I've been searching for years.

Well, I got my amp going and debugged (a Gainclone), so onto the next one!
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