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Broadwave
Joined: Feb 16, 2007 Posts: 347 Location: Manchester UK
Audio files: 6
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Posted: Thu Apr 09, 2015 9:00 am Post subject:
"Okita" Vocoder (Roland SVC-350) - Adding more channels? |
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I've just found the details for building N. Okita's 10 channel vocoder, based on the Roland SVC-350.
I'd like to double up on the channels, but I'm not quite sure if what I have in mind is the right way to go about it.
I should be able to add them simply by changing the value of the caps - as it stands, Ch1 uses 0.05 (0.047), Ch 2 uses 0.033 etc.
If I replace Ch 2's caps with 0.039 and put the 0.033 in Ch 3, then 0.027 in Ch 4 etc. then this would "fill in" the gaps of the current 10 bands, up to the desired 20.
BUT, should I also change the basic 4 pole BPF's shown, to 8 pole which would help create "space" for the extra channels... or is it just a case of changing the value of the resistors (which ones???) to narrow the bandwidth of each channel by 50%-ish.
I'm not sure where I should go from here. Any help/advice would be grateful.
Either way, I'm probably having one of my mad moments and maybe all this is bunkum
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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Posted: Wed Apr 15, 2015 9:31 am Post subject:
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Hi Andy.
My non pro advice would be to search another vocoder project with more Channs then 10, and see how they handle things over there.
Maybe it will give you direction or an idea.
Hope it helps in some way
Cheers,
Isak E. _________________ http://www.myspace.com/mgmtrance |
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Broadwave
Joined: Feb 16, 2007 Posts: 347 Location: Manchester UK
Audio files: 6
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Posted: Fri Apr 17, 2015 1:10 am Post subject:
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I've taken a look at other designs, particularly Senheisser & Syntovox. They both add the extra filter cells on the analysis side.
Luckily, Okita's board layout makes it easy to insert them via an add-on PCB
I'll build the basic version, then tinker with it to see what happens. |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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StephenGiles
Joined: Apr 17, 2006 Posts: 507 Location: England
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StephenGiles
Joined: Apr 17, 2006 Posts: 507 Location: England
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StephenGiles
Joined: Apr 17, 2006 Posts: 507 Location: England
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AlanP
Joined: Mar 11, 2014 Posts: 746 Location: New Zealand
Audio files: 41
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Posted: Fri Apr 17, 2015 11:23 am Post subject:
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The NE570 has me worried. It adds clarity, from what I understand, but with one for each channel...
Smallbear lists the V571 (a NE571 clone from CoolAudio) at $3.25, for 10-24 each. The original NE570 is $5.95, and the next price break is $4 at 100 each. |
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Broadwave
Joined: Feb 16, 2007 Posts: 347 Location: Manchester UK
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Posted: Fri Apr 17, 2015 9:27 pm Post subject:
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AlanP wrote: | The NE570 has me worried. It adds clarity, from what I understand, but with one for each channel...
Smallbear lists the V571 (a NE571 clone from CoolAudio) at $3.25, for 10-24 each. The original NE570 is $5.95, and the next price break is $4 at 100 each. |
I'm using the NE571 (same as the 570 but slightly different temperature specs) I got 12 of them from Futurlec $2.80 each
They're used as the Envelope Follower/VCA for each channel, and compressor on the input board.
@StevenGiles - Many thanks for the EH schems, they will definitely come in handy. Okita's BPF's use different value caps, but the resistors are the same value, EH's version use the same 1% caps, but vary the resistor (but only one filter cell?)... I'll think I'll go a similar route, but keep the 4 cell idea. At least I don't need to source odd value 1% caps now, and calculating the resistor values for the extra bands will be far simpler. Looks like another order for Futurlec is on the cards - they stock all the resistors needed
Much appreciated. |
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xpmtl
Joined: Aug 10, 2007 Posts: 162 Location: Brussels, Belgium
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Broadwave
Joined: Feb 16, 2007 Posts: 347 Location: Manchester UK
Audio files: 6
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Posted: Mon Apr 27, 2015 12:17 am Post subject:
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@AlanP - The good news is that NE571's work fine.
@xpmtl - Yes, I saw this and used his mod (470k resistors from pins 1 & 16 to ground) to stop bleedthrough on the VCA's - it cleans things up really well.
I've decided not to add extra channels for the time being, I wanted to get it built as per Okita's original plans to see how good it was before messing around with it... The results are in this thread.
I had no idea that Korg's VC-10 was a 20 band Vocoder - looks pretty simple too, so I *might* have a go _________________ Kronos 2-88, Kronos 61, Studiologic Sledge V2/SL, Broadwave ARP 2600EX, Broadwave 18U ARP based Eurorack Modular, Broadwave Minimoog Clone, GEM S2 Turbo.
Synth DIY Projects
Musical Doodlings |
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zephyrin
Joined: Feb 15, 2012 Posts: 10 Location: Switzerland
Audio files: 2
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