Anyone ever built these (old circuits by Christian/Hemmo)?

[earthtonesaudio]

http://personal.inet.fi/koti/holmberg/images/wave.jpg  This looks interesting.
http://personal.inet.fi/koti/holmberg/images/fm_osc.gif  This looks insane.   

Anyone messed around with either of these?

[MikeH]

What does that first circuit even do?  Second one looks pretty sweet.

[sean k]

Funnily enough I was over at electronics anonymous earlier today and came accross the second of these two. It seems the man Hemmo is quite the hero in the circuit bending fraternity for those who have gone on to the simplfy the analog synthesizer and mix it up brigade.

But as for this, the bottom FM thing I'd love to know what goes in and what could be coming out.

Hes got the normal resistor between 7 and 6,2 and the cap to ground which makes it an oscillator with the output at 3 but then that pnp transistor  pulses  pin 7 to change the frequency of the 555 oscillator so you end up with a type of sequencer... I don't know but I suspect the FM inputs would be fed by LFO's... or am I wrong.

Then the sync input is ... Good Golly, a reset pin and 4 usually goes to VCC.

Please somebody work out what goes in where and what might come out.

[earthtonesaudio]

The first one makes more sense to me than the second one.  Basically it's an ADC/DAC that probably makes some healthy square wave fuzz.  The input is buffered/amplified and goes into several parallel "comparators."  They're not quite comparators but close enough.  Anyway, each set of comparators has a certain voltage threshold, so it will trigger at a different signal level than the others.  The result would be a bunch of parallel square waves with different pulse widths.  The centermost comparators would have maybe a 50% duty cycle, the outermost ones would have much higher/lower duty cycles.  Then you mix all those with a summing amplifier and see what kind of mess you get out. 

The 555-based one, I think is supposed to just make crazy noise, but on the website, Christian says something like "hook up your guitar to the inputs and whambam!"  ...And if that isn't tantalizing to you, well... you're a lesser geek than I.

[earthtonesaudio]

I think I saw a newer circuit, by someone else, that used a similar flash ADC/comparator chain like this, but the reference was variable and symmetric, op-amp controlled... maybe Nelson, I can't remember who drew it.  I remember the schematic looked like it was done in Eagle, with the black background and red traces...

[sean k]

From the same site and maybe it clarifies the first.

[sean k]

I've read up a little on the 555 and heres some quotes with my take on them.
( about the AM and sync inputs)
""All good, but then we have two more inputs at pins 4,5 on the 555. Pin 4 is the reset pin and 5 is control voltage.

"Pin 4 on the 555 is called the reset. In all the circuits up to now this pin has been tied to Vcc. If the reset pin is taken to 0v, the internal flip flop is reset, the output goes low and the discharge transistor turns on to discharge Ct. If the reset pin is taken back to Vcc the 555 will remain in its reset state." from Babani Books IC 555 projects.

This pin four is the Am input which I suppose is Audio modulation but how often does an audio signal crash into the rails?

Pin 5 is labelled the sync input on Hemmo's schemo.

"If, however, the control voltage is varied by external means the astable frequency can be varied. The higher the control voltage the lower the astable frequency; the lower the voltage the higher the astable frequency." Babani Book.

So Mr Hemmo may have gotten his pins labelled wrongly. Pin 5 might be better as the AM input so any audio source, like a guitar or voice modulating the output, and pin 4 might be the sync input by having it switch between the supply rails.""

[karsten_h]

glad you´re all here and g´d bless hemmo.

found an internet archive of his old page here: http://web.archive.org/web/20020806082556/http://www.angelfire.com:80/ego/sitruuna/tech.html

and wonder if someone probaly knows about the missing schematics? i am especially interested in a file called modosc1.jpg it is linked as Non frequency modulated oscillator.

thx for your help.