Alternative microsynth

[DiyFreaque]

Well - I'll be!  I bet I've seen that pic at the archive site a hundred times, but it never registered!  It's amazing what a small world the DIY community can be.  

Harry Bissell, BTW, has to be one of my all time favorites on many levels.

So - I wonder if a CMOS filter is doable for a guitar synth?  I haven't played it in over 10 years, but I'm going to have to pull my SG out of storage and string'er up, I guess.

Cheers,
Scott

[puretube]

Mark: I`ll bring a bottle of red Italian, and red French - you decide which one first.
Come wintertime, that beer preference steps back a little...  


cc. CMOS: if it weren`t for the output-impedance, I`d almost swap`em for tubes...

("almost" to be read in italics!   )

[DiyFreaque]

Puretube,

Do you know Rene Schmitz?  If you do, one of these days you oughtta run over to Bonn - he's just built an *amazing* tube synth.  You two would probably have a blast.

I visited him back in January while on a business trip, and he had a tube phase shifter going that was enough to convert anybody over to tubes - it was *sweet*.

Cheers,
Scott

[Vsat]

Take a look at the schematics for the ARP Quadra - the "Bass Synth" PCB has a neat two-pole VCF based on the CD4007 and a couple of dual op amps - even has voltage-controlled regen. An envelope generator and VCA are also on the same board.
Regards, Mike

[Maneco]

do you have a schematic link for the arp quadra?
thanks!

[Vsat]

Maneco - I thought the pdf was at www.oldchool-sound.com, but it wasn't there when I looked - the file was a big one, around 24 megs. I gave the URL to Mark H., he might remember where it is to be found.
Mike

[puretube]

Puretube,

Do you know Rene Schmitz?  If you do, one of these days you oughtta run over to Bonn - he's just built an *amazing* tube synth.  You two would probably have a blast.

I visited him back in January while on a business trip, and he had a tube phase shifter going that was enough to convert anybody over to tubes - it was *sweet*.

Cheers,
Scott

Don`t know him in person, nor ever talked to him - just admire his whole web-stuff. (Bonn is quite far away from here...).
Jürgen Haible lives half an hour by bike away - only had some idea-exchanges via email with him, though.
MAM, btw. is from my hometown, too.

and cc. tube-phaser(TM):
http://www.puretube.com/T-PHASER%20cor.2.jpg

[StephenGiles]

My back aches from putting up outside lights and inside decorations, but I found my Klark Technic manuals near our box of Christmas decorations in the attic. The schematics have no part values but I have them in one of my "piles" of stuff - Puretube! Now, I've seen that Arp schematic before now and maybe it's tucked away deep on my laptop, I'll have a look.
Stephen

[StephenGiles]

Not much luck I'm afraid, but I found this VCF using a 4007 as variable resistors.

http://www.uni-bonn.de/~uzs159/
Stephen

[DiyFreaque]

Hey Puretube,

Cool looking phaser!  Looks like you've put in the stuff I like to see in a phaser, too (positive, negative regen, etc.).  Bet it sounds great.

I think the synth DIY guys over there would probably go gaga over it.  You may already know this, but the synth DIY guys have a yearly get-together in Germany.  Last year it was at Bad Berka, I can't recall where it was this year.  You can see pic's at Dr. Joerg Schmitz's site:

http://www.analog-synth.de/

As for the CMOS filter, as soon as I clear off some space on the breadboard, I think I'll give it a try and see what the character of the thing is.

Cheers,
Scott

[gez]

cc. CMOS: if it weren`t for the output-impedance, I`d almost swap`em for tubes...

Yeah, that can be a pain.  I messed around with buffered chips once, for their higher gain, which helps.  Useless for overdrive but excellent for filters.  Just have to watch the gain so that they don't self oscillate.  Had good results with 4000 series chips (as good as an op-amp circuit), but couldn't get 74(HC?) series to work, which was weird.  Current consumption isn't exactly low with buffered chips though...

If you have spare inverters in an unbuffered chip you could use three in a row to get the gain up, or try the trick Nasse mentioned (which I've seen in an old Elektor schematic) of paralleling inverters biased as amps.  I'm sure you know all this though!  

[Nasse]

Did I mention emitter follower trick... :?

[gez]

Did I mention emitter follower trick... :?

It was in a CMOS distortion thread, you mentioned that once you stuck a few inverters in parallel and biased them as a single stage.  

I've seen this approach used in an old Elektor schematic to lower output impedance of an inverter biased as an amp.

[idlefaction]

Here's one i built a while ago...  it's wicked cool and i love it dearly.  :-D

note that you have to put a voltage divider between the osc's and the filter as the signal coming out swings betwen the supply rails!!!  it's using a 4069 hex inverter.  i also ended up using the spare inverter as a square wave fuzz for the guitar signal, and built the whole thing into a guitar.

[puretube]

gone...

[puretube]

Maneco, any news?