Author |
Message |
Wild Zebra
Joined: Apr 28, 2005 Posts: 806 Location: Ohio
Audio files: 5
|
Posted: Wed Oct 11, 2006 11:46 am Post subject:
Whats up with this 8038 Chip? |
|
|
I'm kinda new to all these fancy specialized chips, and was thinking of ordering some for a few of these projects, like the XR2206, LM566, and I ran across this 8038. Are there any layouts for this chip? Has it been optimised Thomas Henry style? Is it worth getting? What about S&H chips like LF398/389? I have a Delton Horn book that has schems for some specialized chips, like S&H and ASDR blah blah
thanks _________________ "your stripes are killer bro" |
|
Back to top
|
|
|
Coriolis
Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark
|
Posted: Wed Oct 11, 2006 11:56 am Post subject:
|
|
|
Well, I read somewhere that the 8038 is supposed to be hopeless for 1V/oct control, but then they said that about the XR2206 (or did they? maybe I'm just exaggerating). But I've never seen it used for anything synth...
C |
|
Back to top
|
|
|
fluxmonkey
Joined: Jun 24, 2005 Posts: 708 Location: cleve
|
Posted: Wed Oct 11, 2006 4:51 pm Post subject:
|
|
|
elby designs sells a circuit board for a thomas henry designed linear VCO based on the 8038. tom's usual elegance & simplicity of design, it uses one quad op-amp and a handful of other components, and is very servicable.
a few limitations of the design to be aware of: * response is linear, like korg and paia but unlike almost everything else which is exponential
* it does not go low (bottoms out around 20hz), so it's not suitable as an LFO. goes up to 20k tho, using a vc sweep of 0 to +15v
* positive cv only
i have 4 behind a dual frac panel, 2CVs with attenuators into each, makes some tasty noise with enough cross-patching.
bbob |
|
Back to top
|
|
|
State Machine
Janitor
Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
|
Posted: Fri Oct 13, 2006 8:44 am Post subject:
|
|
|
Quote: | 8038. Are there any layouts for this chip? Has it been optimised Thomas Henry style? Is it worth getting? |
Its a good chip for a voltage controlled LFO (almost) that has all the common waveforms found in a subtractive synthesizer without having to wire in all the usual waveshaping circuits with discreet OP-AMPS. That is it's main benefit, a compact one chip solution. I have not seen it in precision VCO applications though.
I know the Blacet "Klank Werk" uses it for an internal voltage controlled carrier generator and it works fine in that application.
Another BETTER chip for function generation and LOW frequencies for LFO generation is the MAX038:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1257
http://www.futurlec.com/Maxim/MAX038CPP.shtml
I have one or two in my parts bin and you may be able to find them.
Bill |
|
Back to top
|
|
|
piedwagtail
Joined: Apr 15, 2006 Posts: 297 Location: shoreditch
Audio files: 3
|
Posted: Fri Oct 13, 2006 12:16 pm Post subject:
|
|
|
I'm getting well below 20Hz....
its my TH 3 wave lfo unit.
It doesn't go much below 0.2Hz though and ranges up to 200Hz or so.
Robert |
|
Back to top
|
|
|
State Machine
Janitor
Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
|
Posted: Fri Oct 13, 2006 12:23 pm Post subject:
|
|
|
Quote: | response is linear, like korg and paia |
Linear like PAIA My PAIA VCO design has an exponential response. Which PAIA are you referring to
Thanks,
Bill |
|
Back to top
|
|
|
State Machine
Janitor
Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
|
Posted: Fri Oct 13, 2006 12:28 pm Post subject:
|
|
|
Quote: | It doesn't go much below 0.2Hz though and ranges up to 200Hz or so. |
A 5 second period is good for most applications though It did not occur to me that the 8038 went that low. I know you can make it go well above 200 HZ
Bill |
|
Back to top
|
|
|
fluxmonkey
Joined: Jun 24, 2005 Posts: 708 Location: cleve
|
Posted: Sun Oct 15, 2006 8:52 am Post subject:
|
|
|
piedwagtail wrote: | I'm getting well below 20Hz....
its my TH 3 wave lfo unit.
It doesn't go much below 0.2Hz though and ranges up to 200Hz or so.
Robert |
are you gettng that out of the t. henry circuit? what value do you have for the timing cap? i'm using his suggested 500pf. didn't mean to suggest the chip was incapable of lfo, i was referring specifically to tom's circuit.
State Machine wrote: | Quote: | response is linear, like korg and paia |
Linear like PAIA My PAIA VCO design has an exponential response. Which PAIA are you referring to
Thanks,
Bill |
fatman, and 2700/4700 series... i know, i'm dating myself...
bbob |
|
Back to top
|
|
|
State Machine
Janitor
Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
|
Posted: Sun Oct 15, 2006 7:58 pm Post subject:
|
|
|
Quote: | fatman, and 2700/4700 series... i know, i'm dating myself...
|
Ahh, OK Thats fine, with age, there is wisdom
Bill |
|
Back to top
|
|
|
piedwagtail
Joined: Apr 15, 2006 Posts: 297 Location: shoreditch
Audio files: 3
|
Posted: Mon Oct 16, 2006 9:53 am Post subject:
|
|
|
0.22uF
no problem,just another great adaptable TH circuit!
Robert |
|
Back to top
|
|
|
mediatechnology
Joined: May 10, 2006 Posts: 80 Location: Oak Cliff, Texas USA
|
Posted: Thu Jan 25, 2007 3:14 pm Post subject:
|
|
|
I happened to stumble upon this today while going through an old file. It's a 1975 Electronic Design cite with op amp linearization of an 8038. It would obviously need, in some apps, expo scaling but might make a simple LFO. I'm pretty sure I used this technique once in a sweep generator.
www.ka-electronics.com/images/Electro-Music/VCO_8038_ED30175.pdf
IIRC 8038s are still pretty easy to get. I think I see them at Jameco. |
|
Back to top
|
|
|
State Machine
Janitor
Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
|
Posted: Thu Jan 25, 2007 4:01 pm Post subject:
|
|
|
Quote: | It would obviously need, in some apps, expo scaling |
Yes Wayne, and probably some temperature compensation as I am not sure how much this IC will drift |
|
Back to top
|
|
|
mediatechnology
Joined: May 10, 2006 Posts: 80 Location: Oak Cliff, Texas USA
|
Posted: Thu Jan 25, 2007 5:18 pm Post subject:
|
|
|
Yes 250 ppm/C (max) in the lowest grade for the 8038.
EDIT: The XR2206 in commercial specifies a typical number of +/-20ppm/C but no maximum figure. The MIL version is +/-50ppm max so I would think the commercial 2206 would have a significantly worse-case figure. It might approach the 8038's 250ppm/C.
A linearized 8038 might still be a good candidate for an LFO. |
|
Back to top
|
|
|
Eric G
Joined: Mar 07, 2007 Posts: 19 Location: Sweden
|
Posted: Thu Mar 08, 2007 1:12 am Post subject:
|
|
|
Hi, I'm Eric G and new to this forum (but not new in DIY)
The 8038 and 2206 are OK as modulation generators (LF or audio) or oscillators for crazy sounds, but don't spend time to make them track musically. Neither linear nor exponential (via expo converter). I tried that for months, it really doesn't work. |
|
Back to top
|
|
|
Coriolis
Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark
|
|
Back to top
|
|
|
bugbrand
Joined: Nov 27, 2005 Posts: 846 Location: Bristol, UK
Audio files: 1
G2 patch files: 1
|
|
Back to top
|
|
|
synth_ollie
Joined: Sep 11, 2006 Posts: 149 Location: sweden
|
Posted: Thu Mar 08, 2007 3:20 am Post subject:
|
|
|
Im building one (bugbrands pcb layput) right now ! |
|
Back to top
|
|
|
Eric G
Joined: Mar 07, 2007 Posts: 19 Location: Sweden
|
Posted: Thu Mar 08, 2007 5:09 am Post subject:
|
|
|
Yep, I've seen this one. I don't know anything about it, so maybe I'm wrong. The design is pretty much like what I did. |
|
Back to top
|
|
|
Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
Audio files: 96
|
Posted: Thu Mar 08, 2007 7:24 am Post subject:
|
|
|
Eric,
Are you the Eric G of the EH-30 modular? If so, you must realize, you are partially to blame for my getting back into Synth DIY after a ten year or so hiatus - I think it was your page and Ray's that inspired me to get back into it.
Nice to see you here!
Cheers,
Scott |
|
Back to top
|
|
|
Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
Audio files: 96
|
Posted: Thu Mar 08, 2007 10:17 am Post subject:
|
|
|
Quote: | Regarding my EHS-30 site |
I guess that answers that question
Cheers,
Scott |
|
Back to top
|
|
|
Eric G
Joined: Mar 07, 2007 Posts: 19 Location: Sweden
|
Posted: Fri Mar 09, 2007 12:23 am Post subject:
|
|
|
Scott Stites wrote: | Eric,
Are you the Eric G of the EH-30 modular? If so, you must realize, you are partially to blame for my getting back into Synth DIY after a ten year or so hiatus - I think it was your page and Ray's that inspired me to get back into it.
Scott |
Great! Nice to hear that it did some good. The EHS-30 site will be up'n'running in a couple of months. |
|
Back to top
|
|
|
iorobyy
Joined: Sep 26, 2005 Posts: 65 Location: Italy
|
Posted: Fri Mar 09, 2007 1:48 am Post subject:
|
|
|
8038 is a good misunderstood circuit.
It have linear response but the problem is that is a inverted linerar
response ...not gooood!
The elby circuit is a good point for to start some experiment with a cv driver circuit....uhmmmm....antilog cv driver i think? right?
However the guru thomas henry some time ago made a good vco using 8038.
But response was always linear....is a perfect vclfo! but.... is not the 1V/oct VCO that we like.
Elby use very similar schematic (so linear response again).
However i know that Thomas was studying for 1V/octvize this chip.
Like the xr2206VCO....great!!
So guys.......Thomas go! go! go! |
|
Back to top
|
|
|
Thomas Henry
Joined: Mar 25, 2007 Posts: 298 Location: Southern Minnesota
Audio files: 2
|
Posted: Sat Apr 07, 2007 12:08 pm Post subject:
|
|
|
Try this on for size. This is something I came up with in a book I wrote three years ago but haven't published yet. I used the AD821 because I had one, but feel free to try another matched pair.
This is for Forum users to play with only. Obviously, don't do anything commercial with it without permission, and please don't Web-publish this anywhere, but provide links back to this message.
Note the unusual power supply connections.
Thomas Henry
Description: |
|
Filesize: |
39.56 KB |
Viewed: |
24616 Time(s) |
|
Description: |
|
Filesize: |
41.64 KB |
Viewed: |
24553 Time(s) |
|
|
|
Back to top
|
|
|
goodrevdoc
Joined: Sep 11, 2006 Posts: 288 Location: Philadelphia, PA
Audio files: 1
|
Posted: Sat Apr 07, 2007 12:29 pm Post subject:
|
|
|
Wow! Mr. Henry strikes again! Very cool, unfortunately I recently got rid of my two 8038's as i didn't see myself using them. I'll have to get some more and try them out.
-justin |
|
Back to top
|
|
|
iorobyy
Joined: Sep 26, 2005 Posts: 65 Location: Italy
|
Posted: Sat Apr 07, 2007 2:49 pm Post subject:
|
|
|
Great!!!!! Thomas you're my only Guru!!!
I'm going to search a 8038 in my chips cemetary.
Uhmmmm...2sa798 transistor pair could be ok? |
|
Back to top
|
|
|
|