Building a An Attack/Decay/Sustain filter?

[bufftonz]

Is there any affordable way, (spending less than $99) to make a DIY ADSR filter device? Has anybody ever done this before, because I know by the time one buys the metal encasing, the circuit board, componbents, wires, and control knobs (after drilling holes into the chassis), it would all eventually add up. I'm trying to enhance my Yamaha YC30 combo organ with a sustain/decay/attack filter so that I can be able to make analog-harpsicord and electric piano sounds...by this I mean I want to build a stomp-box or at least table-top version of a ASDR filter that can use standadrd instrument cable (for keyboard to pass in and out to the amp). Since I already found a few websites that contain simple ASDR schematics and instructions, its a matter of finding the best prices on parts and components. I'm trying not to go over $50, but I'm not sure how well this budget might hold up. If anyone is interested in helping or advising me in this matter, please feel free to reply. Cheers. :-)

--Chris

[Mark Hammer]

I would stronger recommend giving up on this.  Traditional envelope generators assume that you are feeding them a trigger and/or gate pulse representing a single note.  Having multiple envelope-shaping circuits and assigning every one of the notes your combo organ produces to a bank of these might have been worth the effort in 1974, but it will likely cost you less for a portable keyboard that does the same thing polyphonically than it would cost you to do the same thing for one note at a time.  I say, let your combo organ be a combo organ, and get something else to do the harpsichord stuff.

The alternative would be if the various divider circuits (assuming it has them) in the organ would permit you to envelope controlspecific drawbar outputs.  For instance, I have some chips from the early 80's that I kept threatening to make a keyboard of where there is a group 16', 8', 4' and 2' output, that the user can mix down as desired.  One could have some sort of transient control over those 4 outputs on the way to the mixer.  Of course, you still have the problem of determining when to generate the trigger that initiates the transient shaping.

[Fleetdog]

Mark, it seems like your answer here is based on the idea that bufftonz was going to mod his organ to put the filter in the organ.  I think he's really asking about just a standalone effect he could put between the keyboard (or a guitar I would guess) and the amp.  That would basically just be like an envelope filter or autowah with different voicing wouldn't it?

[Mark Hammer]

I reread bufftonz note in response to your note, and my sense is that he/she really does want something that would filter individual notes to produce note voicings not currently feasible with the organ.

Are there interesting funky sounds producable by means of tacking an envelope filter on after an organ?  Within limits (remember that an organ does not really HAVE an "envelope" to be followed), you bet your funky ass there are!  But adapting an organ so as to mimic what a proper synth can do in terms of tone-shaping will be difficult, if not impossible.  And considering how inexpensive some surprisingly decent-sounding keyboards can be these days, if you can get over the "shame hurdle" of sticking a Wal-Mart Casiotone in your rig, it may be the very best solution for the least money.  Don't mistake how they sound with the dual 5" on-board speakers for what they sound like through a real amp.  Those things can often sound surprisingly good if amped up right.

[iaresee]

Are you after something akin to the Pigtronix Attach Sustain pedal? For what it's worth you can find those used in the sub-$200 range. Sometimes in the sub-$150 range. And I'm not 100% certain but I think Pigtronix is using a Xilinx Spartan FPGA in there for the processing. I know Pigtronix is big on the Spartan for some of their other effects.

Like Mark already pointed out, any pedal solution you're going to apply is different from an ADSR filter you'd find in a synth. The synth version gets applied to each note pressed, the pedal to the output signal, which is a very different set of stimulus. For example if you set the attack to ramp up and hit a chord it'll fade in, but then if you add another note it will sound immediately with the pedal approach because you've already applied the attack portion of the filter to the signal. Whereas having this in the keyboard itself the additional note (if it's implemented correctly) should also fade in.

[Mick Bailey]

My Korg X9-11 guitar synth had good envelope shaping capability - only attack/release, but you could get some pretty good sounds out of it. Think the design could be lifted and developed to give ADSR

[A.S.P.]

I want TAP-TEMPO ADSR 

[bufftonz]

So getting back to the focus of the original topic, is there a way, or shall I say, could I just make a stand alone attack/decay/sustain-filter pedal unit that sits between organ and amp (just like the PigTronix or similar)? Is there a way to make something similar to the PigTronix much cheaper (assuming no paint and fanv knobs are involoved)??

[Rodgre]

Paia Gator.

They don't offer the kit at the present time, but I saw a project on some other SIY site for a modern version (without the 4136 op-amp).

It does swell effects, and can be triggered by an external source.

No decay control though.... I'm working on that.

Roger

[moritz]

So getting back to the focus of the original topic, is there a way, or shall I say, could I just make a stand alone attack/decay/sustain-filter pedal unit that sits between organ and amp (just like the PigTronix or similar)? Is there a way to make something similar to the PigTronix much cheaper (assuming no paint and fanv knobs are involoved)??

As others have mentioned The problem with a traditional style ADSR envelope generator is that they generally require some sort of cv/gate input to trigger the beginning of the envelope, and most of the ADSR projects you'll find on the net will reflect this. These projects are  intended more for monophonic, modular synths. You can't simply attach an instrument input at one end and an amp at the other, as the ADSR generator won't "know" that it must start the envelope from the beginning of a new note without something to trigger it at that "new" note (hope that makes sense?). Short of modifying your organ's keyboard to output a gate signal and then link this with an array of envelope generators (I think Mark was mentioning this), I don't think it's really possible to achieve a true ADSR effect. Maybe the effect could be approximated by passing the organ's entire output through a single ADSR generator (as you originally intended) and somehow adapting the ADSR to start the envelope from the beginning whenever a "new" signal appears at its input... however, I would assume that this way you'd only end up with a clumsy approximation of the effect.

Also, if it's a harpsichord sound you're after, I think there's more to that sound than just applying a particular amplitude envelope (ADSR) to a basic organ sound, which I think will leave you disappointed. Harpsichords have a sort of tinny resonance thing going on which the ADSR alone won't cover. As Mark mentioned, a basic Casiotone or a Yamaha Portasound I think would be a better bet in your situation. I confess I'm a bit of a lover/collector of old, cheesy keyboards, and you'd be quite surprised at the quality of harpsichord and electric piano sounds some of them produce. You can pick one up for a few dollars on ebay (also garage sales, goodwill stores, flea markets), and in my opinion, is a far better bet than a DIY solution.

As far as calculating costs go, beyond just a ballpark figure, it should be fairly straight forward once you've decided on a project: Make up a parts list, add up the basic component costs and from there see how much you want to spend on the "variable" cost components (eg: fancy hammond box versus a recycled container; milled aluminium knobs versus the most basic plastic jobs; primed, painted, water-slide decal-labelled, clear-coated box versus plain box with permanent marker labelling; that sort of thing...).

Hope that helps somewhat.

[bside2234]

Paia Gator.

They don't offer the kit at the present time, but I saw a project on some other SIY site for a modern version (without the 4136 op-amp).

It does swell effects, and can be triggered by an external source.

No decay control though.... I'm working on that.

Roger

I built the Paia Gator. It works really well with guitar/bass. I don't know about a keyboard though. I guess I could hook my sons keyboard up to my amp and give it a go.

[Gila_Crisis]

i'm planning about building a slow Gear clone.

[Mick Bailey]

My thoughts on this are as follows;

1. The triggering can be achieved via the audio source directly, as per the Sound Lab Mini-Synth Guitar Trigger based around U1-b and U1-c in that circuit

2. A simple 555 based A/D/S generator as per http://ralph-moseley.co.uk/blog/wp-content/uploads/2006/06/envgen.jpg could be fired off this.

3. If the starting point for the audio signal processing was the Tremulus Lune signal circuit (minus the LFO), the trigger signal could be tapped from the input of the first op-amp and fed to the trigger circuit of a Mini-synth type circuit. The output from this would then trigger the envelope generator. If you attached the LED driver circuit from the Tremulus Lune to the output of the envelope generator, which in turn modulated the LDR between the two tremulus op-amp stages, you would have an A/D/S envelope shaper with variable depth control.

I'm going to breadboard this as it's given me another idea to extend the possibilities of my modded Uglyface.

[Paul Perry (Frostwave)]

To get back to what the original poster Chris wanted, it is possible to make something if you are only playing monophonically. An envelope follower with independant attack/decay will get you most of the way there. But if you want it to be polypohonic, well no, there is nothing DIYable, and to my mind nothing commercial either that you can hang off an old combo organ to enable you to play shaped envelope notes.

[puretube]

Not exactly what Chris is looking for,
but an almost perfect solution...

[puretube]

Interesting link in 1st post of this thread...