Long tail phase inverter [was Re: [music-dsp] Frequncy smear?]

Darren Reid shokwave at nbnet.nb.ca
Thu Jan 18 13:56:28 EST 2001


"Kursad Kurt" <kursad_kurt at hotmail.com> sez:

> Maybe. As an analog deficient I cant analize that circuit. But considering
> the transient DC shifts that Thomas Serafini mentions in his article "A
> perceptual approch on clipping and saturation", section 4 static/dynamic,
I
> guess that the cathode follower before the tonestack, and the capacitors
in
> the tone stack may play an essential role. Because the cathode follower
has
> a low impedance output, unlike other tube circuits, and again unlike other
> tube circuits you have 3 coupling capacitors there (in the tonestack), not
> just one.

Hmmm. Sounds like (possibly) a multitap delay line.

> > Good news for me! I'm eying the AX84 homepage...eventually I want to
build
> > my own tube amp, and stick a DSP board in it.
>
> You are smart:). How have you found that page? I had not told:))) Good old
> altavista...
> If so have a look at the project 'Railrocket'. It needs a dsp board
because
> a tonestack cant do the job well.

I saw that one. I probably will make myself do the AX84 first, as it's "for
beginners".
Have you personally built any of the amps from that site? It's definitely a
great resource.

> > I wonder if there is a practical way to do this in RT in the freq
domain?
>
> Perhaps you could erase all the odd order harmonics in the freq domain and
> end up with something that makes weird noises... Ah what's wrong? FFT is
> always surprizing at the hands of someone who doesnt know what he is
doing.

Hey, that's me!

>> > Thanks for the code. Which language is that?
> >
> > Octave, which is a variant of Matlab. Octave is free, Matlab is
commercial
> > SW. Octave is indispensable for testing out DSP algorythms and plotting
> the
> > results in a billion different ways.
>
> Where can I download that one? C/C++ is my favorite. Has Octave any
> advantages over it? (besides perhaps I can understand your code after
> learning a bit about octave)

C/C++ is my faveorite programming language too, but Octave/Matlab are
definitely great for design/prototyping/plotting type stuff.

Octave homepage: http://www.octave.org/
But if you are a Windows user without Cygwin currently installed, you should
go to:
http://matlinks.sourceforge.net/

...and click on the link for the painless Windows install. It will point to:
http://download.sourceforge.net/matlinks/octave-windows.exe
(so I guess you could just click on that....but I wanted to tell you pages
you might wanna bookmark <g>).

That exe will painlessly install everything.

-Darren


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