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mike page
Joined: Sep 26, 2016
Posts: 134
Location: norwich, uk
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Cfish
Joined: Feb 24, 2016
Posts: 477
Location: Indiana
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 Posted: Sun Nov 13, 2016 4:38 pm Post subject:
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I'm very interested to know how it works if you give it a try.
My math skills aren't the best but it looked like the design frequency is pretty high for audio( if I was even reading it right). What it can do is what is important. Especially in Lunetta.
Might grab a couple to try with my next order |
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Cfish
Joined: Feb 24, 2016
Posts: 477
Location: Indiana
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| Posted: Sun Nov 13, 2016 4:42 pm Post subject:
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| Oh, and I had not noticed you on here yet mike. Welcome, and nice to meet you. |
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mike page
Joined: Sep 26, 2016
Posts: 134
Location: norwich, uk
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| Posted: Mon Nov 14, 2016 2:08 am Post subject:
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| Hiya, yup im pretty new posting here. Mostly asking dumb questions at the moment but I'll share my discoveries once they solidify a bit! I have ordered a couple of these so I'll have a go and report back. wikipedia says its goes from 0.001 hz to 300khz! |
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fluxmonkey
Joined: Jun 24, 2005
Posts: 708
Location: cleve
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| Posted: Sat Dec 24, 2016 12:00 pm Post subject:
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i believe there are designs using the 8038 in Thomas Henry's "Thomas VCO Chip Cookbook"
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elmegil
Joined: Mar 20, 2012
Posts: 2179
Location: Chicago
Audio files: 16
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| Posted: Sat Dec 24, 2016 3:04 pm Post subject:
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| fluxmonkey wrote: | | i believe there are designs using the 8038 in Thomas Henry's "Thomas VCO Chip Cookbook" |
Yup, part 2 of the VCO Chip Cookbook is about the 8038. The book is available from Lulu.com, you can get a PDF or a hard copy.
The datasheet VCO isn't the best you might want. The chip is similar to the NE566 which is linear and 10:1 sweep in the default configuration. Thomas develops some strategies to deal with that and is able to get 1000:1 and exponential response.
Since you're in Lunetta land, you may not care about the limitations, but if you do, I'd recommend the book. |
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trav
Joined: Sep 11, 2012
Posts: 108
Location: Auckland
Audio files: 16
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| Posted: Sat Jan 14, 2017 10:31 pm Post subject:
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| so did you get the chips and try them out? |
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gasboss775
Joined: Jan 02, 2016
Posts: 217
Location: Scotland
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mike page
Joined: Sep 26, 2016
Posts: 134
Location: norwich, uk
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| Posted: Thu Feb 16, 2017 3:56 am Post subject:
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| trav wrote: | | so did you get the chips and try them out? |
I did but couldnt get it to work. So I gave up and made triangle type shapes with the r2r method. |
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stolenfat
Joined: Apr 17, 2008
Posts: 476
Location: Sunny Oakland California
Audio files: 1
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| Posted: Sat Sep 09, 2017 12:00 am Post subject:
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I looked at this thread before and put it on my list of stuff to get... Then I reread the datasheet just now and noticed it works on +/- voltage which my lunetta doesn't run on... Just ground and +v.
I havent dabbled in negative voltages yet but I suspect that would probably take it out of lunetta land as most of us (other than the godly phobos) likely doesnt have a bipolar supply in their machines. Other opinions?
edit: well paint me silly... as I reread the datasheet looks like the darn thing can run on V+ and ground and I spoke to soon... but perhaps thats what caused OP to have some trouble?
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home made noise and electronic ill-logic |
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PHOBoS
Joined: Jan 14, 2010
Posts: 5797
Location: Moon Base
Audio files: 709
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| Posted: Sat Sep 09, 2017 6:49 pm Post subject:
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| stolenfat wrote: | | I havent dabbled in negative voltages yet but I suspect that would probably take it out of lunetta land as most of us (other than the godly phobos) likely doesnt have a bipolar supply in their machines. |
  right,..
Actually, for lunettas I use a single supply. I do have a dual supply in the Asylum
but that's just for the mixer section which I wanted on a seperate supply anyway.
On the rare occasion that you do need a dual supply for a lunetta circuit you can often
get away with creating a fake GND. Not that there is anything wrong with using an
actual bipolar supply of course.
The 8038 is a nice chip btw, reminds me a bit of the XR2206.
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JovianPyx
Joined: Nov 20, 2007
Posts: 1988
Location: West Red Spot, Jupiter
Audio files: 224
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| Posted: Sun Sep 10, 2017 10:25 am Post subject:
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| PHOBoS wrote: | | On the rare occasion that you do need a dual supply for a lunetta circuit you can often get away with creating a fake GND. |
Yes, a virtual ground (here called "fake") may be used, however a note of caution is that the virtual ground is not capable of sourcing or sinking much current, so don't try to build a huge sound making device using that technique. A few chips usually works.
You can also strengthen a virtual ground using an opamp which will extend it's usefulness by allowing more source and sink current capacity.
One method that several people have used instead of virtual ground is that since they already likely have a +5v supply, simply add a -5 volt supply and voila - stable dual supply that can sink or source lots of current without causing problems.
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8038 VCO,
