Bi-pulse convertor (ON-topic)

[danial stocks]

>The term I've heard is "phase reversal"
yup thats what I meant!

>
>Whay can you do... build an active limit circuit that takes effect before 
>you
>reach that point.  A zener diode, bridge rectifier, and two resistors can 
>make a
>very symmetrical
>clamp that is fast to boot. There are also tricks using two transistors (1 
>NPN -
>1 PNP)
>but its a little harder to guarantee symmetry.
>
If you used the inv amp on the CV instead of the saw, feed the CV to + in of 
amp 1, invCV to + amp 2, then you feed saw to - of both amps, use a 10k res 
or so for each, and inv parallel diodes on each amp feedback loop... maybe a 
cap on the f/b too to damp down the high freq gain.. these op amps then 
simply mix in another summing op amp.... neatly done in 4 opamps [singl 
pkg], no trims, no instability, no phase rev..
Cheers,
Dan




> > > > >Nope, but let's make one... this is done by using three op-amps and
> > > > >four resistors...
> > > > >
> > > > >                           |\
> > > > >                       +---|+\    ___
> > > > >  CV ------------------|-+ |  >--|___|-+
> > > > >          ___     ___  | *-|-/    1k   |
> > > > >      +--|___|-*-|___|-* | |/          |
> > > > >      |   10k  |  10k  | |             *---- Out
> > > > >      |        |  |\   | | |\          |
> > > > >      |        +--|-\  | +-|+\    ___  |
> > > > >Saw -*           |  >-+   |  >--|___|-+
> > > > >      |        <|-|+/    +-|-/    1k
> > > > >      |           |/     | |/
> > > > >      +------------------+
> > > > >
> > > > >That ougth to do it. Throw in buffers as required.
> > > > looks good but I'd add in inverse parallel diode clippers after the 
>1k
> > >res,
> > > > then mix in an op amp summing stage... this circuit is making the
> > >assumption
> > > > that the + clip on the op amp occours at the same level as the - 
>clip..
> > >and
> > > > this is not always the case [LM324.. etc ..]
> > >
> > >Right, it assumes balanced clip-levels. There are many ways to handle
> > >this, but in this particular schematic I went for the quick-and-durty
> > >level just to show how easy it can be. It is not a precission
> > >curcuit for sure. It is just sufficient to explain how it could work
> > >and it can also be made to work.
> > >
> > >If you assume that the +clip and -clip is fairly stable, then
> > >individually trim the levels from each op-amp/comparator and then have
> > >a common offset trimmer should improve the situation alot. Possibly up
> > >to the level where nobody would preceive much audioble difference.
> > 3 trimmers or 4 diodes? I'd take the diodes myself.. less stuufing 
>around
> > calibrating.. but a sep lvl for the + & - pulse setting could be 
>interesting
> > as a user controls...
> >
> > >
> > > > also probs with phase inversion?
> > >
> > >Phase inversion? Please elaborate!
> > >
> > never mind about that .. I was thinking back to over driven TL0.. phase
> > inversions and looking at this with no feedback path in the op amps.. 
>high
> > voltage between the inputs.. prolly nothing to worry over, just out of 
>bed
> > so I dont fully got my head on just now..
> >
> > > > OTOH a comparators should work well here, but the o/p res should
> > > > be high to the op amp in mix,...
> > >
> > >The two output op-amps could very well be comparators.
> > >
> > > > also, feeding with a triangle wave will give interesting other
> > >waveform..
> > > >
> > > > _           _
> > > > | |___   ___| |___   ___
> > > >       |_|         |_|
> > >
> > >Oh dear...
> > >
> > >Have anyone considered what happends if you feed diffrent waveforms
> > >into this little device? Or maybe just diffrent frequencies...
> >
> > dont reckon different freq's would change too much  in the waveform 
>unless
> > you get to freq limitations of the op amps [pull out all you vintage pre 
>741
> > op amps?] but this could be the basis of an interesting new fx thingo...
> > like a distortion, maybe then feed the o/p thru a filter, nothing too
> > resonant, just round off the corners a little or something.. maybe you 
>put a
> > envelope follower to generate a CV off the incoming audio signal so that 
>the
> > volume modulates the pulse width.. ok thats it Im gonna try it out...
> > Cheers,
> > Dan
> >
> > 
>_________________________________________________________________________
> > Get Your Private, Free E-mail from MSN Hotmail at 
>http://www.hotmail.com.
>

_________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.