ASM-1 Information

gstopp at gstopp at
Mon Jan 13 18:48:16 CET 1997

     Hi DIY List,
     Due to popular demand I figgered I'd re-post some info about the ASM-1 
     to the list. Our good friend Magnus Danielson has been kind enough to 
     put a bunch of ASM-1 data up on his web page, so I can point to that 
     as a reference. The URL is:
     He did a pretty good job, only a few typos :)
     He didn't include my snail mail address (which can be a good thing I 
     suppose, serious inquiries will get to me somehow) so it's included in 
     this post towards the bottom.
     As far as quantities go, I have 9 left. Looks like I'll have to place 
     an order for another 50, which takes about 4 weeks.
     Just to recap, here's some text from old e-mails, from April 1996, 
     that tell the story:
     ************* Beginning of e-mail snippets **************************
     Hi DIY List,
     I've had a circuit board made. I just got the prototype back and 
     started to stuff the parts, and so far it looks like it's a cool 
     It has two saw/pulse VCO's, a multi-mode VCF, two ADSR's, two VCA's, 
     an LFO, and a White/Pink/Random Noise Source. It's basically similar 
     to an Oberheim SEM, except for the noise source and extra VCA. All 
     circuit sections are discrete - in other words, no hard-to-find custom 
     synthesizer chips! The circuits are based on the Electronotes modules 
     that I've experimented with lately.
     Here's a brief description of each module:
     VCO - based on the Electronotes sawtooth design, with a CA3140 
     integrator with FET reset, controlled by an LM311 comparator. The NPN 
     exponential converter can be an Analog Devices MAT-02 matched pair, or 
     a pair of hand-matched 2N3904's. A 1K tempco resistor can be used for 
     best stability but is optional. There are 6 exponential CV inputs, 2 
     linear FM inputs, 2 pulse width inputs, a sync input, a sawtooth 
     output (-5v to +5v), and a pulse output (-5v to +5v).
     VCF - based on the Electronotes state-variable design. The exponential 
     converter is based on one 2N3904 and two 2N3906's. The integrators are 
     CA3080's buffered by CA3140's. There are 4 exponential CV inputs, one 
     inverted exponential CV input, 4 audio inputs, and one buffered output 
     each for Lowpass, Bandpass, Highpass, and Notch.
     VCA - based on the Electronotes 3080 linear design. There are 3 CV 
     inputs, one (+) signal input, one (-) signal input, and one output.
     ADSR - my own design from a couple months ago, using an LM358 for the 
     input comparators, a CD4002 for the attack flip-flop, a CD4053 analog 
     switch, and a TL082.
     Noise Source - based on an Electronotes design. It uses a 
     reversed-biased NPN transistor junction followed by a series of op-amp 
     LFO - typical tri-square manually-controlled design.
     PCB dimensions are 4.8" by 11". Power required is +/- 15 volts.
     I wanted to try out my CAD package and local circuit board vendors, so 
     for the first project I decided to make something useful instead of 
     just a single module. I would like to offer this circuit board to 
     other people on the mail lists. I want to make a run of circuit boards 
     and sell them, and I need feedback to get some commitments on just how 
     big an order I should place. The more I order the cheaper they'll be.
     Note: I do not have any unrealistic ideas on making a huge profit 
     here. This is my hobby and my only monetary goal would be to recoup 
     the film and PCB setup costs (a few hundred dollars) plus some time 
     and energy spare change. I expect that I'll be able to sell the bare 
     boards for around $60 each.
     Any interest?
     - Gene
     gstopp at
     Hi List,
     I've received my batch of ASM-1 circuit boards, and built one up. It 
     works great. So - I'm sending off a few to some "beta tester" list 
     memebers so they can try them and report back to the list.
     So - I'll take orders via mail, *not* email. When I get a check I'll 
     ship out the boards. I've kept all of the responses from people who 
     have stated their intention to purchase, and I used that data to come 
     up with the quantity (50) buy I just made. Besides, I tend to delete 
     emails by mistake all the time.
     I'll post my address for orders soon. In the mean time the beta 
     testers will get their boards and I'll finish up my documentation.
     - Gene
     gstopp at
     I've sent a few of the ASM-1 circuit boards out by now and they appear 
     to have been received in good shape, so I guess I'll go ahead and 
     offer them to the DIY list in general.
     Price is US $60 apiece, or $50 apiece for four or more in one order.
     While I haven't heard from anybody who has one built completely and is 
     currently making noise, by now I've got three working modules of my 
     This thing should be perfect for the beginning modular synth builder. 
     For example if I were to take the three units I've built so far and 
     stick them in a single modular, I'd have the following machine:
     6 VCOs
     3 VCFs
     6 ADSRs
     6 VCAs
     3 LFOs
     3 Noise Sources
     3 Lag Processors
     for a circuit board cost of $180.
     The first thing I'm planning on making is a four-voice poly synth, and 
     maybe add four more voices after that.
     Anyway send checks to me at:
     Attention: Gene Stopp
     21415 Plummer Street
     Chatsworth, California
     Orders from the US can use personal checks. Orders from Canada can use 
     money orders in $US. Orders from elsewhere - I have no clue - anybody 
     out there have some advice???
     Regardless, I'll throw in the shipping and hope it all evens out.
     - Gene
     gstopp at
     Hi DIY list,
     Here's the parts list for the ASM-1 circuit board:
     Active components:
     (5)  CA3140
     (4)  CA3080
     (19) Dual op-amp, TL082, LM358, etc.
     (2)  CD4002
     (2)  CD4053
     (2)  LM311 Comparator
     (2)  2N4856 N-channel JFET
     (6)  2N3904 NPN transistor
     (2)  2N3906 PNP transistor
     (13) 100K 10-turn trimpot
     (2)  10K 10-turn trimpot
     (1)  100 ohm 10-turn trimpot
     Passive components:
     (6)  1N4148 Diodes or equivalent
     (4)  22   ohm resistor
     (6)  220  ohm resistor
     (1)  390  ohm resistor
     (2)  470  ohm resistor
     (2)  680  ohm resistor
     (10) 1K   ohm resistor
     (2)  1.5K ohm resistor
     (3)  2K   ohm resistor
     (2)  3K   ohm resistor
     (2)  3.3K ohm resistor
     (7)  10K  ohm resistor
     (4)  15K  ohm resistor
     (2)  18K  ohm resistor
     (1)  27K  ohm resistor
     (1)  33K  ohm resistor
     (5)  47K  ohm resistor
     (2)  56K  ohm resistor
     (51) 100K ohm resistor (at least 2 1%)
     (1)  150K ohm resistor
     (2)  200K ohm resistor
     (1)  270K ohm resistor
     (1)  330K ohm resistor
     (6)  560K ohm resistor
     (7)  1M   ohm resistor
     (4)  1,5M ohm resistor
     (2)  2M   ohm resistor
     (2)  18pf     capacitor
     (2)  30pf     capacitor
     (4)  100pf    capacitor
     (2)  330pf    capacitor
     (1)  0.001uf  capacitor
     (2)  0.0022uf capacitor
     (3)  0.01uf   capacitor
     (24) 0.1uf    capacitor
     (2)  1uf      capacitor, unpolarized
     (2)  4.7uf    capacitor, 16V
     (2)  10uf     capacitor, 16V
     (2)  100uf    capacitor, 16V
     (2) 1K or 2K +3300ppm/C' tempco resistors
     (2) MAT-02 matched NPN pair (or equivalent)
     * If you use the MAT-02 matched NPN pairs you won't need four of the 
     * You should use all metal film resistors.
     * The caps over 1uf are tantalums, except for the 100uf's which are 
     * The 100uf caps can be any value, really, since they are just power 
     conditioning caps on the +/- 15 volt inputs. They do need to be at 
     least 16V however, and not too big to fit on the PCB.
     * The 1uf unpolarized cap can be made from two 0.47uf non-polarized 
     caps in parallel.
     * There are many places where the resistor values may be changed by 
     the builder, such as the input structures or places where the ratio of 
     two resistors sets a parameter level. These will be discussed in the 
     documentation that I haven't written yet.
     This parts list might have a couple errors in it - it is only intended 
     to give a preliminary idea to those who might want to build one.
     - Gene
     gstopp at
     ***************** End of e-mail snippets ****************************

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