ASM-2

loss1234 · Posted: Wed Nov 12, 2008 8:03 am Post subject:

strange update

i tried it with a +/- 12 volt (not 15 volt psu as is required) and the LFO sounds were almost entirely gone!! i am wondering if the other PSU just couldnt give a clean voltage?

any guesses?

this just might work itself out

thanks

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

sneakthief · Joined: Jul 24, 2006 Posts: 569 Location: Berlin

i have no lfo bleed-through whatsoever.

i don't understand what you've done here - are you bypassing the internal psu?

from the ASM-2 PSU schematics:

loss1234 · Posted: Wed Nov 12, 2008 8:59 am Post subject:

yes i AM USING the wire links

the power one is good because A: i had it handy
and B: i am powering 4 other boards in this same project.

according to laurie it shouldnt matter either way as long as i fit the wire links.

but i am wondering if the first supply i tried was having loading issues.

as this second one has no bleed through

thanks

loss1234 · Posted: Wed Nov 12, 2008 5:30 pm Post subject:

oh and as far as running grounding to different sections...NO i would have to cut too many traces to isolate the grnds of the VCO from the grnds of the lfo's and other circuits.

it DOES have a A gnd and a D gnd though. I am under the impression my original PSU has some sort of issue as the 2nd psu which works fine (and the 3rd i tried) are less amps and work better!

anyway...thanks

Uncle Krunkus · Posted: Sat Jun 06, 2009 5:32 pm Post subject:

Just a quick note here to say that after a lot of thought, I've decided that if I had the chance to do it all over again, I would not use the front panel, semi-patched out version which I documented in this thread.
This is specifically because I have enjoyed building other Synth DIY modules, and have found that only having partial control of input/output connection options has actually hindered my ability to get the most out of this synth.
However, if this was the only DIY analogue synth module in your kit then the layout as documented may be just right.
I think the best option, (and one which I may yet convert it to! Rolling Eyes

) is a "no switch", controls and attenuators only, main layout, with a connection matrix (like the VCS Synthi) and a bank of 8->? generic in/out sockets.
If anyone wants anymore details of how I think this could be implememented, just ask.
I don't mean to be a wet blanket for anyone who has gone a different way. I just wanted to share some hard earned experience. Very Happy

loss1234 · Posted: Sat Jun 06, 2009 6:58 pm Post subject:

what would you use for the matrix?

thanks

Uncle Krunkus · Posted: Sat Jun 06, 2009 8:44 pm Post subject:

I'd use 3.5mm box type sockets. The switching mono type ones. Mainly cos I've already built up a collection of about 70 of them. I'd bus solder them into a slab and back them with a piece of stripboard. That way, you don't even need the nuts and washers on the front. I'd have them normaled along input rows, so you could have multiple outs but only one input per summing resistor. Using 3.5mm plugs as patch pins would enable cords for extra ins and outs. You can also use different plugs/pins as AC or DC coupling and as rectifiers.
These box type sockets are cheap and nasty, but they're also easy to replace if they fail.

Uncle Krunkus · Posted: Sat Jun 06, 2009 9:08 pm Post subject:

Okay,
Maybe I should re-think all that.
I just had a quick look, and there's 54 possible inputs and 31 possible outputs! Shocked

That would mean a matrix made up of 1674 sockets! And using those sockets, the matrix would be as big as the whole front panel is now! Surprised

Well,
Probably heaps of those connection options are invalid or redundant. So I still think the basic idea is sound.
I'm gonna look into it a deeper and see what I can see.
I need to have a look at the patch matrix from the VCS and get an idea of what's important and what's not. Anyone got a clear pic of it?

sneakthief · Joined: Jul 24, 2006 Posts: 569 Location: Berlin

My experience has been a little bit different. I chose to use as many of the inputs and outputs as possible within the space I had for each "module". It's been pretty satisfying so far.

I really like having the pots near their respective jacks. As attractive as the Wiard modules are, I don't think I like having the jacks lumped together in one section because I end up having to hunt around too much so I can figure out what the corresponding knob is. YMMV.

crochambeau · Joined: May 18, 2008 Posts: 31 Location: earth.

Uncle Krunkus · Posted: Sun Jun 07, 2009 4:09 pm Post subject:

Uncle Krunkus · Posted: Thu Jun 11, 2009 4:15 pm Post subject:

Can someone have a look at this and tell me if the red zones really are "unusable"?
I know you can feed an LFO back into it's own CV in, (with varying useability), but I haven't done much "free patching" and wondered if the red zones on this matrix map represent connections which literally can't be used or not.

Patch Matrix.xls

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chriswilliams · Posted: Sun Jun 28, 2009 3:26 am Post subject:

Hey everyone,

I've finally finished my ASM-2 board and have been doing some testing of the VCO's.

As per Laurie's instructions I've been testing with no voltage connections and leaving the wire link out.

Good news is - it oscillates. The strange thing is, after looking at the output on a scope, the frequency is up around 25khz - adjusting P101(P151) doesn't seem to shift it much. The waveform on the output of the CA3140 looks a little strange too (attached). It seems the cap is being discharged when the comparator kicks in, but then immediately jumps to 2.5V or so before ramping up.

Both VCO circuits seem to be doing this as well.
Does anyone have any ideas or have seen something similar?

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Uncle Krunkus · Posted: Sun Jun 28, 2009 4:47 am Post subject:

My VCOs are actually running really well now, but I did have an early incarnation of the PCB which needed a little kludging and newer sync circuits added.
I don't think I looked specifically at the 3140 outputs, but I did scan the whole circuit compared to my original schem and found a few anomalies.
Make sure you have the latest schem (I'll attach it here)
I've got pretty good waveforms on all outputs now, so I'd say you need to start double checking everything. Get out the highlighter! Smile

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chriswilliams · Posted: Tue Jul 07, 2009 8:59 am Post subject:

Got the VCO's sorted !! Very Happy

Turns out the JFETs were at fault - I replaced them with J111's I had sitting in an unused project and all is well - oscillating at an (now audible) 880Hz Smile

These J111's were Fairchild branded , whereas the J108's I had were from Futurlec and without an obvious manufacturer. A warning to others perhaps? Confused

Quite annoying, but I guess in the whole process of debugging this circuit I now understand he VCO design!

Thanks Uncle Krunkus for the PDFs - I think Laurie has updated them again on his website since - I think very minor changes though

Sine · Joined: Sep 10, 2007 Posts: 111 Location: Netherlands

Jup, I had about the same problem with ken stones bi n tic filter that uses a very close oscillator core

http://electro-music.com/forum/topic-30620.html

Skrog Productions · Posted: Fri Jul 17, 2009 8:34 am Post subject:

Hello ASM builders, I've had my bare board sitting around for 6 months now and i'm itching to get stuck into it, but i've been thinking of sorting out all possible mods i might do beforehand.

Will be mostly used for melody / bass / lead sounds.

One idea is to have a 5 or 6 Oscillator ASM2 in semi modular form, but im wondering if it would be easier to get a super thick sound using simple wave folders (cgs) and sub osc's/ frequ. dividers to enhance the original 2 vco's (8+ audio input mixer for each vcf).

Using a switch to select vcf's in parallel or series (with input/output gain control) and a another switch to lock both vcfs to vcf 1 c.v. bus.

If i were to go for 5 osc's would i need to buffer the one incoming c.v. from my ELBY poly-dac , almost like an internally wired 1 to 5 multiple as on my modular system ???.

Seeing all these fantastic ASM 2 creations so far is inspiring.

Cheers
David W

State Machine · Posted: Fri Jul 17, 2009 9:36 am Post subject:

sneakthief · Joined: Jul 24, 2006 Posts: 569 Location: Berlin

Skrog Productions · Posted: Sat Jul 18, 2009 4:26 am Post subject:

Thanks Sneakthief.
I was initially thinking of cloning the vco section a few times to make a sort of real version of an old softsynth called the Pentagon i have .

I like the idea of the yusynth saw animator (I've built his triple clock divider for my 2 mfos sequencers) .

It's good to do most of this pondering first instead of half way thru a build as usual ha ha.

Re think....
ASM vco's on the board with a saw animator / wave folder / sub osc
added per vco.
Maybe just 1 mixer with 2 raw waves from each vco and 3 modifiers per vco ( 5 detuned against 5) into selectable vcf's.

Ok, i'll start doodling some block diagrams on scrap paper.

synthnl · Joined: Oct 19, 2007 Posts: 33 Location: Ede

I finally resumed work on mine after building a new studio and recording a new album:

http://synthnl.blogspot.com/search/label/asm-2

difficultdave · Joined: Jan 04, 2011 Posts: 1 Location: Sydney Australia

I emailed elby_designs@ozemail.com.au to see when the next batch of motherboards would be out and the reply was he has a few back-orders but is still finalizing the new layout with a sub-oscilator for each vco.
He promised it would be out soon.

Skrog Productions · Posted: Tue Jan 04, 2011 8:52 am Post subject:

Cool , sub osc's , Smile

i'd build another but i don't have the space , ASM-2 is a very good diy synth , i use mine alot Smile

http://electro-music.com/forum/topic-36475.html

Dave W.

moogasm · Joined: Dec 29, 2009 Posts: 13 Location: San Diego

This is my first post. I just finished my ASM-2 and following the calibration procedure in the ASM-2 manual the VCOs only track over 4-5 octaves in the low frequency range. A few questions:

What should my expectations be for the VCO tracking?

Is there an alternative procedure that might give better results?

Are there any modifications or part substitutions that can improve the VCO's v/oct performance?

Why did the ASM-2 use a 1.5M resistor in the current mirror as opposed to the ASM-1's 150K?

Does it make sense to add high frequency compensation to the design?

I have already changed the resistor value in sawtooth level shifter to get the sawtooth centered about +-5V.

I bought the MAT-02 and tempco from Laurie. I got the rest of the parts from Futurlec. Should I rebuy some of the critical parts from Mouser or Digikey just in case?

Thanks,
Mike