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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Digivox
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slabman



Joined: Sep 01, 2005
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PostPosted: Mon Jul 13, 2009 2:37 am    Post subject: Digivox
Subject description: Useful PDF on the Bernie Hutchins Electronotes website
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There's a useful PDF on the Bernie Hutchins Electronotes website.

Quote:
The Digivox one note at a time music synthesizer' uses predominantly low cost RTL circuitry with a single low voltage power supply. The circuits have been reduced to the bare minimum required to produce a reasonable variety of electronic sound effects. The digital synthesis method results in a great simplification of the pitch and timbre generating functions and ease of tuning over most any 36 note range with all notes always in tune with respect to each other.


There are some shift-register timbre generators and a keyboard controlled master oscillator that, if translated from RTL into CMOS, might yield useful building blocks.

PDF here - http://electronotes.netfirms.com/S007.pdf
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slacker



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PostPosted: Mon Jul 13, 2009 1:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Very cool, thanks for sharing that.
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DGTom



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PostPosted: Mon Jul 13, 2009 5:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Shocked

the oscillators & the timbre generator look really interesting.

does anyone know where to get info on RTL in order to swap them out for CMOS?

All the logic is pretty easy, but some of the ICs seem to be represented by blocks, googles not been much help so far, but woah! these RTL chips go for some serious scratch these days!
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droffset



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PostPosted: Mon Jul 13, 2009 7:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

Awesome info, thanks for that. Smile

I don't have experience with RTL, would a NAND from this family act like a NAND in another?

Only one way to find out I suppose, I think I have NAND in TTL and CMOS. MIght need to NAND it up.
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DGTom



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PostPosted: Tue Jul 14, 2009 7:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

richard64 posted some vital info here that seems to have dissappeared in the wake of the spam attack.

*I think* it was something along the lines of RTL using 'negative logic' whereas CMOS uses 'positive logic'

So, in RTL High = 0 & Low = 1 so the NAND gates in these ccts are actually NOR gates in CMOS.


I BB'd the transistor sine wave generator yesterday, it worked... for awhile, quite a nice sine, but, it was a very sensitive arrangment & I could not get any control of the frequency except by touching the 330k resistor, altho running a pot to ground here didn't work as expected & neither did the VR in the schem. I played for awhile & it stopped working, I decided to come back to it Embarassed
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droffset



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PostPosted: Wed Jul 15, 2009 1:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Whoa, thanks for bringing that up(NAND/NOR), it hadn't occured to me.

DGTom wrote:
richard64 posted some vital info here that seems to have dissappeared in the wake of the spam attack.

*I think* it was something along the lines of RTL using 'negative logic' whereas CMOS uses 'positive logic'

So, in RTL High = 0 & Low = 1 so the NAND gates in these ccts are actually NOR gates in CMOS.


I BB'd the transistor sine wave generator yesterday, it worked... for awhile, quite a nice sine, but, it was a very sensitive arrangment & I could not get any control of the frequency except by touching the 330k resistor, altho running a pot to ground here didn't work as expected & neither did the VR in the schem. I played for awhile & it stopped working, I decided to come back to it Embarassed
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v-un-v
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PostPosted: Wed Jul 15, 2009 1:54 am    Post subject: Reply with quote  Mark this post and the followings unread

I may be worth mentioning here that a very rare but well used 1970's classic synth called the Davolislint used a very similar architecture to this Digivox. The Davolislint was used by Cluster/ Harmonia and Soft Machine too Cool There's a review of the Davoli at SOS mag.
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richardc64



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PostPosted: Wed Jul 15, 2009 6:59 am    Post subject: Reply with quote  Mark this post and the followings unread

I built this!

Well, part of it. OK, I only used the VCA/VCF and the Envelope Generators.
http://www.sdiy.org/richardc64/rtlsynth/rtlsynth.html

The rest of the circuitry seemed to me to be too complex for a mono instrument. Using a shift register to create different tonal qualities was intriguing, but the skimpiness of information about that part of the DigiVox put me off, so I used simpler methods.

(My post about negative logic wasn't a casuality of the spam clean up: It was deleted by ME. Although I am certain that the MC724 is a NOR in the more usual positve logic, I can't be certain about the other gates in the design.)

edit: updated link

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Last edited by richardc64 on Tue Aug 24, 2010 4:06 pm; edited 1 time in total
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richardc64



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PostPosted: Wed Jul 15, 2009 7:14 am    Post subject: Reply with quote  Mark this post and the followings unread

OMG! I can't believe I found it!

I don't know why Burhans drew it as NAND. Full data sheet is the last one listed here:
http://www.datasheetarchive.com/search.php?q=mc724


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DGTom



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PostPosted: Thu Jul 16, 2009 12:01 am    Post subject: Reply with quote  Mark this post and the followings unread

richardc64 wrote:
(My post about negative logic wasn't a casuality of the spam clean up: It was deleted by ME. Although I am certain that the MC724 is a NOR in the more usual positve logic, I can't be certain about the other gates in the design.)


Embarassed sorry.

Thanks for the info & links.
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