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And now for something completely different: the aluminum acid experience...

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jojjelito

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Lately I've been working on the proper control surface of the 6582 having run the mighty 6582 in a somewhat completed state with a perfboard control surface just for lulz. I followed Hawkeye's excellent tutorial on the CS construction but mixed and matched with the older methods from Wilba's construction hints where applicable just to be non-conformist fat rebel. :bug:

Now I'm at teh "waiting for the glue to cure" stage. :sleep: I wish one could just use superglue or Goop and be done with it. But oh noes, clamping and waiting seems to be the soup du jour... Guess I should detent the encoders or make up a nicer cable to my LCD meanwhile.

Meanwhile, this got me thinking about that elusive external filterbox with VCAs (ze famous EEFV, of which there are only whispers of a handful, being rare as hen's teeth). Wonder which filter to use:

Transistor ladder a la Moog, diode ladder a.k.a ARP stylee, CEM3372 in the Oberheim fashion, Wonky ladder 303 stylee, or IR3109 in the Jupiter 8 fashion. Mebbe I should just stick to LPF using SSM2044's there or CEM3379 and call it a day? Anyone got any suggestions? Gimped late/early MS-20 perchance? SVF based on a SSM2164 quad VCA like the Shruthi is doing it? Decisions, decisions... :frantics:

I smell experiments and a sudden uncotrollable urge to slap something together. It also needs pre/post filter distortion if I can get away with it :sorcerer:


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:-) the glue will cure at some point ;-)

Could you tell us more about the EEFV VCA solution you choose? How does it compare to Seppomans Solution?

Would you create a blog/tutorial on how to connect this to the baseboard? Would be great for electronic noobs like me :-)

I don´t think analog filtering is soo necessary for the excellent SIDs (they really have quite nice filters which add to their specific sound), but VCAs would be a great addition for more expressive live keyboard playability ;-)

Best regards,

Hawkeye

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Hi jojjelito,

I build this one (it's sounds famous!):

Moog VCF

Easy to build, all parts available, only think you need to match some pairs of transistors...

Keep a try!

greetz jonas

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Hi Jonas and Peter!

I see that Yves (YUSynth) uses a transistor array for his take on the famous VCF instead of manually matching discrete transistors the way that René Schmitz and later Jörgen Bergfors of Bergfotron fame did it. That would save work!

After thinking about it over some sleep I decided to keep it as simple as possible: Either use SSM2044 or some other IC I have, or a very simple array-based filter as this will be polyphonic. Also it takes 4xAOUT_NG (expensive, innit?) for control. Add a bipolar PSU and maybe VCAs.

Either I will use Seppos VCAs (as I already planned ahead and got some PCBs) or I'll use what's already in the CEM chips if I go that route. Or I can attempt a 1-transistor VCA the way Korg did it in the PS-series of synths, but that's less than optimal for sound and control. Good for the low parts count though.

But, I'll make up a tutorial once I get there for sure. At the moment I'm at the graphing paper stage. Then I need to do some breadboarding...

Maybe Stophlex has made some progress as I know that he was also looking at an external VCF/VCA box?

However, the JB Weld has cured enough. Time to do the encoders and LEDs!

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Hi jojjelito,

I see that Yves (YUSynth) uses a transistor array for his take on the famous VCF instead of manually matching discrete transistors

Have a look again, there is one for matched BC547's vcf

I build them, so I should know what I am talking about ;) I will take a phote when, I am at home...

I got a source for CEM Chips in Germany, but I need to find the link if you want it?

greetz Jonas

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Hi jojjelito,

Have a look again, there is one for matched BC547's vcf

I build them, so I should know what I am talking about ;) I will take a phote when, I am at home...

I got a source for CEM Chips in Germany, but I need to find the link if you want it?

greetz Jonas

Ahh, I see. I guess I was too quick when just taking a peek while at work. There is no such thing as a free lunch... I dread doing the transistor matching just because I figured I wanted instant gratification :whistle:

BUT, it will take a while before I get to that stage.

Feel free to share to the CEM linky. I'm not sure at the moment how many 3379 chips I have - I stashed some 15 years ago being young and foolish. Now I'm not that young anymore :hmm:

Take care,

Johan

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Hi jojjelito,

Good to hear you have some CEM Chips - and maybe one of them survived your child-hood:) When we already have a talk about electric-child-hood - I am doing electronic stuff for about three or four years. But I don't claim to know anything about it ;) But the minimoog filter is almost easy to build and it sounds like wonder! No digital-filter whatever else I heard (analog modeling, spectral-morphing...how they ever called them, and so on...) have this

sound! So keep up man! You are absolutly Welcome!

greetz Jonas

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Hola stiltz&Rumpel,

I've heard plenty of filters but I think you're on to something: the top 5 analogs are the Minimoog VCF, Korg's early MS-20/MS-10, the dual CEM-3350 of the Syrinx, the OSCar and Thomas Henry's Mankato. But there's plenty of good stuff out there :afro:

The CEMs... what can I say? She's at a nice age, ripe age, ready to be killed by the thrill :poke:

PS: You get brownie points for the lyrics reference (don't Google-cheat!)

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I had have a look for the link, but sorry I didn't found it. Struggling around with four browsers and setting up my system new for about 1 year - there is a lot of stuff going to digital hell! :whistle:

But I keep my eyes off, maybe there is one day I will find it randomzised :sorcerer:

:)

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