Favorite designs

[mark verbos]

gstopp at fibermux.com wrote:
> 
>      Good response. To this I would add the following:

me too.
> 
>      Synth chips are best used in either polyphonic systems or machines
>      that otherwise rely on their accuracy, repeatability, and unit-to-unit
>      matching. To use them as a parts-saving tactic in DIY machines is a
>      bit of a waste, if there is a scarcity of them. Perhaps this will
>      change when the new parts runs become available, but for now, that's
>      my feeling.

yes. I am VERY fond of the sound of the Putney oscillators. I wish they
tracked volt/oct. 
I think the ARP-style oscillator has its place (I use them), but I
wouldn't put them in my dream synth.

       In the
>      discrete world, you can get some very sexy VCOs by using a mixture of
>      some old Electronotes ideas plus a careful choice of modern components.
>      The MAT series of matched transistor pairs from good ol' Analog Devices
>      will solve all of your exponential converter worries with the exception
>      of that pesky little tempco term, and if that last little drift factor
>      bugs you then you *can* find the resistors if you're really determined.

I am interested in this idea.

> 
>      2) VCFs - They're all different. Revel in their diversity. The Moog
>      ladder is beautiful. A good stable multimode is always fun. The
>      cascaded 3080 4-pole actually sounds very smooth. The 2040 causes
>      extreme pleasure. etc. etc. etc.

Amen. Veriety is the spice of life. aren't fat moogy sounds boring yet?
get experimental. 
The Korg MS series have a cool filter, I think because it is all cheep
components.
> 
>      3) Envelopes - 

What I really want are Buchla designs. Some that run their corse from a
short trigger and send a trigger when they finish. Anybody have a
design?


>      6) Power supplies - yup, sure enough, what should be the simplest
>      part sometimes can be the hardest to perfect. Power electronics is an
>      artform. The 78xx/79xx devices present us with yet another compromise
>      - so easy, yet not quite good enough. But they're good enough for
>      bench projects. The 723/4195's are good for small systems. The 723
>      with pass transistors will get you into the multi-amp high-wattage
>      regions, but with a lot of complexity. By this time it becomes more
>      efficient just to go out and buy some Power-One supply (which will be
>      a 723/pass transistor design anyway!).

musicians buy power supplies.


mark
> 
> ______________________________ Reply Separator _________________________________
> Subject: RE: Favorite designs
> Author:  Paul Schreiber <synth1 at airmail.net> at ccrelayout
> Date:    4/17/97 9:27 AM
> 
> 
> I'll take a stab.
> 
> 1) For VCOs, really can't beat a CEM3340. Extremely well behaved, =
> excellent tempreature tracking. Designs using uA726s should be avoided =
> at all costs (can't get uA726s at all for <$200). Not real sure if the =
> necessary +3300ppm temperature resistors are still around. Probably best =
> bet for a new discrete design would be a VCDO. Although not necessarily =
> "DigiKey friendly", it skirts the temperature issues (and introduces a =
> few quirks of its own). It really depends on the cost vs quality. The =
> original Moog VCOs are VERY drifty. Any transistor, by default, is an =
> exponential generator. But the temperature dependance of the Ies term =
> (not the kT/q term, although this is a small contributor) makes any EE =
> cringe. Heating up the transistor (like the uA726 does) is not really =
> solving the problem.
> 
> 2) For a VCF, no contest: Moog ladder filter. If you can't beat 'em, =
> join 'em. The CEM3328/3378 comes close, but really there is no =
> substitute. Now, the "downfall" of a Moog is just that: it's a certain =
> sound associated with synthesizers. ARPs sound like ARPs. Most Oberheims =
> sound the same. The particular "sound" of a synth is 95% in the filter =
> characteristics. I really encourage everyone get a copy of Wendy Carlos' =
> CD "The Secrets of Synthesis" (I found mine at www.cduniverse.com) and =
> listen VERY CLOSELY to what she is saying. The message is: A Moog is a =
> Moog is a Moog. And I beat that dog to death.
> 
> 3) For envelope generators, really can't beat a CEM3310 + a 555 for =
> variable gate delay.
> 
> 4) For VCAs, really can't beat a CEM3381/3382. The OTA approach =
> (CA3080/LM13000) are just too noisy. Cheap, but noisy. Why build a whole =
> modular and run it out of a 45dB SNR part??? The CEMs have 100dB SNR! At =
> least use MAT-04 matched transistors for the front end.
> 
> 5) For op amps: use AD or Linear Tech parts. The TL07x parts are just =
> OK, there are MUCH nicer parts. Rule #1: ALWAYS use dual, NEVER use =
> quads. Why? All of the really cool parts are duals, and quads crosstalk =
> too much (If you really need a quad, use the AD713KN. Awesome!) For =
> duals, look at OP275 or LT1113CS8. Stay away from junk like 1458s. Think =
> of a TL072 as the BOTTOM rung of the food chain.
> 
> 6) The single most overlooked component is the power supply. Remember, =
> ever the lowly LM7815 was not around for the first analog synths. For =
> really good designs, check out the Audio Amateur Magazine (603)924-9464. =
> Folks, this mag is REQUIRED reading for all DIYs. Since the somewhat =
> demise of Electronotes, this is really the only source of precision =
> analog design. Stereos and CD players share alot with synths. For a =
> really good design, the 3 terminal stuff is NO GOOD. Perhaps I can =
> address this later.
> 
> 7) The Electronotes series is simply the best way to get all the world's =
> knowledge of synth design. Call Bernie Hutchins 9PM to 11PM Eastern time =
> at 607-273-8030. At the very least, get the "Preferred Circuits =
> Collection". Then, save your money for the $265 (I think) "full set" =
> which is about 2000 pages.
> 
> Please, no "your the CEM chip guy" flames. Yes, I am. But I'm also the =
> "former Moog designer with 20 years experience designing this stuff" =
> guy.
> 
> Paul Schreiber
> Synthesis Technology
> 
> ----------
> From:  Steve Jones[SMTP:sj2393 at ansys.com]
> Sent:  Thursday, April 17, 1997 3:53 PM
> To:  synth-diy at horus.sara.nl
> Subject:  Favorite designs
> 
> Foregoing the hotter flames, what are some of our favorite
> designs here for the various analog modules.  I know this
> is an incredibly general (and perhaps dangerous) question.
> But I'm currently at square one and I'm trying to plot
> out a course of action.  Modularity and flexibility are
> definite criteria.  So is frugality.  My plan is to procede
> incrementally, maybe starting with a single VCO and adding
> pieces as I go (sound familiar to anybody).
> 
> I have been encouraged by some to leave the CEM chips to
> those that really need them.  That sounds reasonable to me;
> so what are some discrete designs?  Gimme shematics! 8^)
> 
> This is indeed a general question.  But since there is no
> FAQ file per se, it certainly is, if rudimentary, on topic
> (or nothing is).
> 
> One more, slightly more specific, question: what is the
> difference between hard and soft syncing (surely a FAQ
> candidate)?
> 
> thanks, you guys are so cordial to beginners like myself,
> steve
> 
> 
>