From SCSTRAUS@teletechusa.com Tue Dec 12 17:28:59 1995 Date: Tue, 12 Dec 1995 15:22:38 -0700 From: SEAN STRAUS To: scstraus@wonderland.teletechusa.com Subject: Re: MIDIizing analog effects units -Forwarded Received: from gE???/E ([157.242.65.187]) by ux1.lmu.edu (8.6.12/8.6.9) with SMTP id OAA06996 for ; Tue, 12 Dec 1995 14:20:58 -0800 Message-Id: <199512122220.OAA06996@ux1.lmu.edu> Date: Tue, 12 Dec 95 14:21:39 -0800 From: Peter Mosinskis Organization: LMU X-Mailer: Mozilla 1.22 (Windows; I; 16bit) MIME-Version: 1.0 Newsgroups: rec.audio.pro,rec.audio.tech To: scstraus@teletechusa.com Subject: Re: MIDIizing analog effects units References: <30CCBF62.5B0F8185@teletechusa.com> Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii Sean Straus wrote: >I have a classic Electro-Harmonix Bass Micro Synth which has about 10 >changable parameters, and I can get alot of sounds out of it when I play >with it long enough, but it's quite impractical to change sounds in the >middle of a show (it just takes too much tweaking.) So what I want to do >is MIDIize the control of the parameters and the bypass switch, so I can >have some sort of memory of different configurations which I can switch >between with a footswitch. I don't know the exact method to employ, but >I'm pretty sure I just need some sort of digital potentiometer, and some >kind of MIDI controller which will interpret the MIDI and remember the >different configurations of the potentiometers. Does anyone know of the >exact sort of hardware available for this kind of project, and where it >is available? Your help is greatly appreciated, and I'll keep everyone >updated on how it's going (I have a feeling this is something that a lot >of people might want to do, and it could be useful to have a FAQ on it.) Sean, Your request is very thought provoking. Lately, I've been trying to figure out how to do similar stuff--I am interested in building a standalone MIDI controller (like a stand-alone pitch wheel) which could be used to send MIDI information to an effects processor, etc. Unfortunately, I haven't gotten any really good replies about how exactly to accomplish this kind of stuff. A good place to start: The International MIDI Association 5316 West 57th Street Los Angeles, CA 90056 USA (213)649-6434 (Note: This may be an old number/address. I'm not sure if the company is correct. I think the info below is more applicable). You can buy the spec, which should cover just about everything. It's published by the MIDI Manufacturers Assoc. (MMA), and costs around $50 I think. They do release some of the documentation to distribute over the net though. You can get those documents and a link to the MMA's web site with more info about ordering the spec at http://harmony-central.mit.edu/MIDI/doc.html. Use Harmony Central to find some other sites with MIDI stuff. As my knowledge of electronics is fairly limited (and my knowledge of digital electronics is close to zero), I think the MIDI spec book will be the best place for you to start. As far as the "digital potentiometer" idea, that's a matter of probably something like using an A/D converter to convert a voltage/current into digital/MIDI information, a microcontroller to process it and send it into a storage device (RAM?), and a D/A converter to change the stored digital message back to a voltage, which could control something like an analog optoisolator, a JFET, or a transconductance op amp which would act as a voltage- or current-controlled resistor equivalent to a pot. Like I said, my knowledge of digital electronics is very limited, and this design is not exactly straightforward, textbook stuff. Let me know if you find out any interesting stuff. I'll keep my ears open as well. Regards, Peter.