Magnus freq doubler.

[Magnus Danielson]

From: "Bjorn Julin" <bnillson at hotmail.com>
Subject: Re: Magnus freq doubler.
Date: Sun, 17 Sep 2000 20:09:49 GMT

> Hi.
> 
> >Which irony... I used the frequency doubler as an inspiration to an >90 
> >degree phase shifter for sawtooths, a version of that you will >find in 
> >Jörgen Bergfors LFO section.
> >
> >Now, to fix this, change the comparators reference voltage, that >is... 
> >have the pos input of U1A go into a trimmer...
> 
> Comparators!!! arrrhhh,,! What the hell.!, I have misintepeteted
> your design intention, ofcourse it works when its a comparator function..

Phew... I just thought I made a fool of myself just because I did not actually
build it..

The whole trick is to build a 50 % PWM to be used to add another reset jump.

When one makes a sawtooth phase shifter, one takes the same idea but instead
moves the jump. This causes a DC error, but since this is linearly dependent
with the phase voltage, it is just a matter of adding the phase voltage at the
output summing to be home free.

> >Also, Jörgen skiped the diode, which is a smart move. The comparator >will 
> >go rail-to-rail without the diode, so then the DC correction R3 >could be 
> >skiped.
> 
> Yepp.
> 
> >So, you say I have made a saw-to-tri converter... hohoum...
> 
> Not anymore, since i "now" see that you actually drive the sawtoth
> directly onto the neg input of the TL082. i had intepreteted it
> as that a input resistor was missing!

Ah.

I guess I should have made a more comprehensive explanation of the curcuit,
others would have been even more confused about this little trick.

> Sorry my fault.

Well, OK. You got my tired brain confused too, so...

> >Maybe time to breadboard this thing...
> 
> Haven't bread boarded yet, will now when its a comparator function.
> 
> BJ (going blind in the desperate shearch of a freq doubler)

Hopefully will this one do the trick, or at least act as an source of
inspiration. Maybe I should redo it without the diode...

Cheers,
Magnus