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crashlander42
Joined: Oct 21, 2006
Posts: 292
Location: Orlando, FL (US)
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 Posted: Fri Sep 12, 2008 5:30 pm Post subject:
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| Tronato wrote: | Hello!
I can't figure it out... if the tempco (R7) must be as close as possible to the LM394 and even the use of Thermal Compound is recommended, where do you physically fit in the extra 100R resistor?
Could you post a picture of that detail?
Thanks!
TRON |
I really wouldn't worry about it unless you run into the same problem, and odds are you won't.
I'll post a pic if need be, it's just a bit of component sculpture. I don't think any of the other SN-Voice builders ran into that problem, so it's probably just an isolated incident (or something I screwed up).
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Tronato
Joined: Sep 21, 2007
Posts: 274
Location: Florida
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| Posted: Fri Sep 12, 2008 5:41 pm Post subject:
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Hello!
You're probably right!
I'll let you know... but take the picture anyway... just in case...
Thanks!
TRON |
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State Machine
Janitor
Joined: Apr 17, 2006
Posts: 2809
Location: New York
Audio files: 24
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| Posted: Sun Sep 14, 2008 6:15 am Post subject:
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| Quote: | | 'm running my SN-voice on 12V supply. Do I need any modification to lower the Tri further? I'm thinking about the values of R52 and R21. |
I would say, bump just R21 up to 22K and see what that gets you. You want to increase the positive voltage into the inverting input of the buffer to achieve waveform symmetry. 
Bill |
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Pehr
Joined: Aug 14, 2005
Posts: 1307
Location: Björkvik, Sweden
Audio files: 2
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State Machine
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Joined: Apr 17, 2006
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Location: New York
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| Posted: Sun Sep 14, 2008 9:19 am Post subject:
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| Quote: | Thanks for the answer Smile
I decreased R52 to 150k instead and now I got it down to the correct level Smile
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Hell, that works also ............ Good ............ I am glad you have success using the board with 12V supplies as I just had a guy from Belgium wanting to purchase three boards but wanted confirmation that it would work on these voltages. I referenced your work and told him it would be fine ......... I did however, based on your observation, tell him about the TRI waveform symmetry issue. I don't believe you had any other issues right? You tuned your SN to 4 or 5 octaves right. Thats about what I was able to get. After this, the units just goes flat with more and more error as you increase in frequency, (higher control voltages). I suppose a refined corrective circuit could be employed as an improvement to get things back on track ........ I say refined because there is one already. I know that D1, R25, and R58 compensate for the error at higher control voltages by presenting a dynamic impedance at R2 wiper to sort of delinearize the control voltage. Knowing TH though, he probably rung out as much ccuracy as he was going to get with minimal parts count.
Great stuff here !!
Glad so many have built these synthesizers !!!!!
Bill |
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Pehr
Joined: Aug 14, 2005
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State Machine
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Joined: Apr 17, 2006
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Location: New York
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| Posted: Sun Sep 14, 2008 3:47 pm Post subject:
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| Quote: | | I just love the digital noise of it too |
I happen to agree with that and the filter really provides all sorts of sound modification which makes it stand out even more.  It's got the classic arcade digital noise character to it. Brings back memories of the many hours spent in the game rooms through the 80's
Oh, and thanks for the feedback with regards to using 12 volt power supplies.
Bill |
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