Odp: [sdiy] ic question

[Theo]

Hi Ruud ,
I found this circuit a while ago, it is just a variation on the
clock>counter>MPX CV sequencer theme.
But the "load" feature of the counter is used to implement a random mode,
nice touch :)
http://www.geofex.com/Article_Folders/udrand.htm

Expanding to 16 steps is easy, just add another 4051.
The left over inverter can be used to make /Qd out of Qd.
Next feed Qd to pin 6 of one 4051 and /Qd to the other 4051 to get 16 steps.
However you need a extra clock for the random input Dd too,
you may use the squarewave output of your "audio oscillator" (the 3909 in
the other circuit) for this.
Why add more components if you don't need to ;)

A other option could be to hook up input Dd with 100k to GND and a switch to
the positive supply rails.
The RND function then is limited to the 4051 selected by the switch.

HTH,
Theo


From: Rude 66 <r.lekx at chello.nl>

>
> ----- Original Message -----
> From: "Brock Russell" <brockr0 at shaw.ca>
> To: "synth-diy" <synth-diy at dropmix.xs4all.nl>
> Sent: Sunday, November 24, 2002 10:31 PM
> Subject: Re: Odp: [sdiy] ic question
>
>
> > Roman wrote:
> > >Why would anyone want to use 2 decoders and 4016s if there's
> > >4051 that can replace those 4 chips?
> >
> > I agree. This looks like a mid to late 70's circuit designed from
> > parts on hand. A bunch of regular TTL, a 555 and a 3909?
> > Not to say there weren't a lot of great designs from this era
> > that still stand up today, but this isn't one of them.
>
> i wanted to build it as an addition to some circuit bent speak & spells
and
> my 76477 box.. find a way to interface it. use the led's to trigger
things..
> i dunno. it just caught my eye..;-)
>
>
> >
> > >this 3909 generator can be replaced with any oscillator.
> >
> > I'm not sure this is true. The 3909 is driving an 8 ohm speaker
> > directly and most oscillators would have some trouble with this.
> > Not that I would suggest using the 3909. It is obsolete, (although
> > readily available from many surplus dealers), noisy and sucks a
> > lot of power in this configuration.
>
> i'd replace the speaker anyway with a normal line out..
>
>
> > >Simplest
> > >would be made of one schmit gate and capacitor. Resistor
> > >(pot)
> > >adjusting frequency would be connected via switching 4051.
> > >And you could use another scmit gate from same chip for
> > >tempo
> > >control, i.e. U1 replacement. Plus you need 1000s times less
> > >power to run such circuit than original.
> >
> > Yes, this design is probably a better heater or low RF generator
> > than a tone sequencer. At least there are LS and HC parts listed
> > as alternatives but to suggest running the thing from a 9V battery
> > makes me think it would be a good idea to figure out how much it
> > costs to run per hour.
>
> ;-) thanks for the analysis.. my idea was to either run it off a battery
or
> a small ps..
>
> >
> > >Mail me if you need exact
> > >drawing.
> > >
> > >This only my suggestion tho...
> > >
> > >Roman
> >
> > Take his suggestion...
>
>
> i have..;-)
>
> thanks for the replies so far.. i figured it's time to actually start
> building things instead of modifying and circuit bending them.. though i'd
> like the things to be sort of half circuit-bent.. or have some weird boxes
> that interface with a speak & spell.. that sort of thing.
>
> ruud
>
>