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Trumpet1
Joined: Aug 02, 2007 Posts: 10 Location: Long Beach, CA
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Posted: Thu Aug 02, 2007 3:26 pm Post subject:
TH PAL Filter |
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I have a couple of CEM chips and the schematic for this TH Polyphony mag design, and have always wanted to build it. Does anyone know of a PCB, or even just the PCB layout? As I recall, one was never provided with the article.
-David |
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Dan Lavin
Joined: Nov 09, 2006 Posts: 649 Location: Spring Lake, Mi, USA
Audio files: 21
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Posted: Thu Aug 02, 2007 3:58 pm Post subject:
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Trumpet1,
Welcome to the electro-music forum!
I forgot about the PAL filter! Yeah, it would be awesome to build! I still have that Polyphony issue. But to answer your question: no, I don't believe I've ever seen a pcb pattern for this. Generally speaking this group stays away from CEM and older SSM chips (with the exception of Fonik's SSM2040 LPF). Unfortunately the asking price for the chips is really high and folks are leery of making a new pcb for parts they can't easily replace.
Do you have pcb design experience? It could be possible to use ExpressPCB which would be ~$51 for 3 boards and you could maybe talk 2 others into buying the other 2. I might consider it, but no promises right now. |
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Dan Lavin
Joined: Nov 09, 2006 Posts: 649 Location: Spring Lake, Mi, USA
Audio files: 21
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Posted: Thu Aug 02, 2007 4:05 pm Post subject:
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Sorry. For those that don't know what a PAL filter is: Phaser, Allpass, Lowpass switchable filter |
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Danno Gee Ray
Joined: Sep 25, 2005 Posts: 1351 Location: Telford, PA USA
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Posted: Thu Aug 02, 2007 5:22 pm Post subject:
Subject description: More info |
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Fill us in!
Some of us don't have the Poliphony mags.
What CEM chip was used? Some of them still pop up on Ebay once and a while.
Don't tease... |
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Dan Lavin
Joined: Nov 09, 2006 Posts: 649 Location: Spring Lake, Mi, USA
Audio files: 21
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Posted: Thu Aug 02, 2007 6:31 pm Post subject:
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DGR,
The PAL uses the CEM3320 along with two 4066 and the 1980's obligatory 4136. A mechanical switch triggers 2 banks of 4066 switches to configure the filter as either low pass or all pass filter. In the all pass mode, there is a original signal blend-in pot so that it becomes a phaser. |
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etaoin
Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL
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Posted: Thu Aug 02, 2007 10:34 pm Post subject:
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I have a "spare " CEM3320 as well. Actually, it's in a Digisound module, but the PAL sounds far more interresting. Is the schematic publicly available somewhere or is the schematic even more unobtainable than the 3320 itself? _________________ http://www.casia.org/modular/ |
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Trumpet1
Joined: Aug 02, 2007 Posts: 10 Location: Long Beach, CA
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Posted: Thu Aug 02, 2007 11:47 pm Post subject:
TH PAL Filter |
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Thanks for the welcome. The PAL was a 1982 TH design and I actually wire-wrapped one then, but lost track of it, if you can believe. I still have a couple of CEM VCOs, and ADSR, and the CEM 3320. I recognize it is dated, but since I've got it...
I have done simple PCB layout using ExpressPCB, and even did an EAGLE schematic of the PAL circuit to see if the Eagle autorouter could possible layout a single sided, or at least minimum jumper PCB. No such luck - the board needs two sides and about 20 vias. I wanted to etch it myself, since I have never actually used the ExpressPCB service. (I use their free software to make my own transparencies, but only for simple, single-sided boards.)
Anyway, the Eagle schematic and board files are available if anyone can use them, and if TH doesn't mind, and you let me buy a board. You would need the original magazine schematic and instructions, since I left off all the panel controls and jacks from the Eagle version - just used labeled connectors. I have that info too, again if TH (or would it be PAIA) doesn't mind. BTW, back issues are still available, or were not too long ago.
Regards,
David |
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etaoin
Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL
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Dan Lavin
Joined: Nov 09, 2006 Posts: 649 Location: Spring Lake, Mi, USA
Audio files: 21
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Posted: Fri Aug 03, 2007 5:18 am Post subject:
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Trumpet1,
Thomas also designed a 12dB state variable (LP,HP, BP,notch) VCF around a CEM3320 in one issue of Polyphony. Actually that's what I was thinking about doing with my spare CEM3320. I'm a big Oberheim SEM fan and thought it would be cool to make a not-quite identical clone. There is artwork for the pcb and it is single-sided. |
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Trumpet1
Joined: Aug 02, 2007 Posts: 10 Location: Long Beach, CA
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Trumpet1
Joined: Aug 02, 2007 Posts: 10 Location: Long Beach, CA
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Trumpet1
Joined: Aug 02, 2007 Posts: 10 Location: Long Beach, CA
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Trumpet1
Joined: Aug 02, 2007 Posts: 10 Location: Long Beach, CA
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Posted: Fri Aug 03, 2007 9:41 pm Post subject:
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antman49443 wrote: | Trumpet1,
...There is artwork for the pcb and it is single-sided. |
Hey, this sounds right up my alley. Got a URL?
Thanks,
David |
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Randaleem
Joined: May 17, 2007 Posts: 456 Location: Northern CA, USA
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Posted: Sat Aug 04, 2007 1:33 am Post subject:
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antman49443 wrote: | Trumpet1,
Thomas also designed a 12dB state variable (LP,HP, BP,notch) VCF around a CEM3320 in one issue of Polyphony. Actually that's what I was thinking about doing with my spare CEM3320. I'm a big Oberheim SEM fan and thought it would be cool to make a not-quite identical clone. There is artwork for the pcb and it is single-sided. |
Hi,
Here's one that sounds like it may be similar to the Thomas Henry PAL.
Craig Anderton's MIF (Multiple Identity Filter), using the 3320 for a filter with switch selectable LP,BP,HP,AP and Notch response. Most modes have 12, 18, or 24dB slopes available. It uses a LOT of Panel toggles. I was going to try some analog switches and a PIC in an updated version.
The complete Contemporary Keyboard magazine article (From Nov '79, running three issues) is available somewhere online. No PCB layout, but the circuit is pretty simple with only 3 IC's. Looks more complicated due to the switches in the schematic. So far, it's the most comprehensive circuit I've seen for a 3320.
Randal |
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v-un-v
Janitor
Joined: May 16, 2005 Posts: 8933 Location: Birmingham, England, UK
Audio files: 11
G2 patch files: 1
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Posted: Sat Aug 04, 2007 1:55 am Post subject:
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fwiw, the Elektor Formant 24db/oct filter had similar specifications but used cascaded CA3080's (like the Oberheim design), however it also used a notoriously difficult to find ua726 matched transistor pair.
I've got the plans still for this filter
But I do like the sound of this filter. Very buttery. _________________ ACHTUNG!
ALLES TURISTEN UND NONTEKNISCHEN LOOKENPEEPERS!
DAS KOMPUTERMASCHINE IST NICHT FÜR DER GEFINGERPOKEN UND MITTENGRABEN! ODERWISE IST EASY TO SCHNAPPEN DER SPRINGENWERK, BLOWENFUSEN UND POPPENCORKEN MIT SPITZENSPARKSEN.
IST NICHT FÜR GEWERKEN BEI DUMMKOPFEN. DER RUBBERNECKEN SIGHTSEEREN KEEPEN DAS COTTONPICKEN HÄNDER IN DAS POCKETS MUSS.
ZO RELAXEN UND WATSCHEN DER BLINKENLICHTEN. |
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Dan Lavin
Joined: Nov 09, 2006 Posts: 649 Location: Spring Lake, Mi, USA
Audio files: 21
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Posted: Sat Aug 04, 2007 5:40 am Post subject:
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I agree with Randal, the MIF is a much more versatile filter and not that hard to build. Your panels have enough real estate to handle all the required switches. I just downloaded that article a couple days ago after googling "CEM3320 circuits" The file was MIF.pdf, but I don't remember the exact website.
Your panels and pcbs look pretty good! You obviously know what you're doing. |
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Trumpet1
Joined: Aug 02, 2007 Posts: 10 Location: Long Beach, CA
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