{"id":596,"date":"2019-06-05T17:41:50","date_gmt":"2019-06-06T00:41:50","guid":{"rendered":"https:\/\/synthfool.com\/kevin\/?p=596"},"modified":"2019-06-05T17:41:50","modified_gmt":"2019-06-06T00:41:50","slug":"apple-ii-sequencer","status":"publish","type":"post","link":"https:\/\/synthfool.com\/kevin\/apple-ii-sequencer\/","title":{"rendered":"Apple II Sequencer"},"content":{"rendered":"\n

Made a analog style sequencer using an Apple II.<\/p>

It’s equipped with a Mountain Computer ADC \/ DAC board.<\/p>

The board can read in 16 channels of voltages.<\/p>

It can also output 16 channels\u00a0 of voltages.<\/p>

Voltage ranges are -5 volts to +5 volts.\u00a0<\/p>

Resolution is 8 bit whether reading or writing.<\/p>

Using a blank piece of aluminum panel here, 16 NOS Moog 100K linear pots and some new Cosmo (Moog) knobs, I built a crude 16 stage sequencer within 2 hours.<\/p>

I also included 16 capacitors that cured a small problem with channel to channel interactivity.<\/p>

I then programmed a traveling bar graph displaying notes as vertical bars of varying height.<\/p>

The top of each bar would flash as that particular note played.<\/p>

All software is written in Applesoft BASIC.\u00a0<\/p>

The code was very short.<\/p>

Making a change such as the choice between V-trig and S-trig outs was one line of code.<\/p>

Using one of the game paddle inputs, I added a pot for use as tempo.<\/p>

I also added a gate output jack, along with both a positive CV out channel as well as an inverted CV output jack.\u00a0<\/p>

Again, inversion was as easy as adding one line of code.<\/p>

The sequencer can be run forwards or backwards.<\/p>

It could be a single channel 16 stage analog sequencer.<\/p>

Or an 8 stage with variable duration per stage via the second row of 8 pots.<\/p>

The Apple’s stock cassette jacks could also be programmed to allow syncing the sequencer either to or from an external source, change the direction of the sequence, etc.<\/p>

In hardware, I plan on adding some opamps to offset the CV out(s) to 0 – 10v instead of -5 to +5 and additional drive capability.<\/p>

I may also add a gate LED and driver.\u00a0<\/p>

In software, I plan on adding variable stage length, duration (as an 8 stage) and a quantizer.<\/p>

Also a preference page allowing choice of colors for the display and other settings.<\/p>

A method of changing direction on the fly would be desirable also.<\/p>

One problem: The bar graph display does not update the note heights until the next cycle of the sequencer. Therefore, changing stages while playing does not show the changes graphically without a considerable delay.<\/p>

This is me testing out a quickly built 16 stage sequencer using an Apple \/\/e computer.<\/p>

It only took about 3 hrs to build the panel and write the (pretty crude) software.<\/p>

LOTS of possibilities to explore in the future though.<\/p>

The Apple has a Mountain Computer 16 chan ADC \/ 16 chan DAC.<\/p>

Everything written in Applesoft BASIC.<\/p>

The synth is a Moog 55A that’s here for service.\u00a0<\/p>

Nothing serious going on here.<\/p>

Building the sequencer and taking the video were just for fun.\u00a0<\/p>

Short story: http:\/\/www.youtube.com\/watch?v=mRFRFnrNni0<\/p>

Long story:<\/p>

I (very quickly) hacked together an analog style sequencer using an Apple II computer equipped with an old Mountain Computer ADC \/ DAC board.<\/p>

This board can read in or output 16 channels of analog voltages.<\/p>

Voltage ranges are -5 volts to +5 volts (though I can change this.)<\/p>

Resolution is 8 bit, but it’s still fairly accurate hitting note CVs closely.<\/p>

I made the panel from a piece of scrap aluminum I found here<\/p>

Used 16 100K linear pots (NOS Moog) and some new Cosmo (Moog style) knobs.<\/p>

Built and wired it up along with some vinyl lettering in around 2 hrs.\u00a0<\/p>

For software, I programmed a traveling bar graph that displays notes as vertical bars of varying height.<\/p>

The top of each bar would flash as that particular note plays.<\/p>

One CV out jack is the “normal” mono out.\u00a0<\/p>

A 2nd CV out jack is right now programmed as being the same notes, but inverted.<\/p>

The gate out jack can be whatever- V-trig, S-trig, pulse.\u00a0<\/p>

In the video it’s making S-trigs for the Moog 911 envelope generator.<\/p>

Software is written in Applesoft BASIC.\u00a0<\/p>

(Comes built-in on the Apple.)<\/p>

The code was incredibly short. I couldn’t believe how little it takes to write something like this.<\/p>

Making any change such as adding a quantizer, variable note durations or sequence length takes about 1 or 2 lines of code.<\/p>

Right now it’s programmed as a single channel 16 stage analog sequencer with mono CV out.<\/p>

But I might make it be an 8 stage with the second row of 8 pots changing the duration of the first 8 stages.<\/p>

A 30+ year old computer driving a 30+ year old synth can still be a lot of fun.<\/p>

This critter could also be programmed to allow syncing it to or from an external source.<\/p>

You could even make it go backwards or write a “performance” to disk without too much work.<\/p>File date: 12\/21\/2010<\/cite><\/blockquote>\n\n\n\n

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Made a analog style sequencer using an Apple II. It’s equipped with a Mountain Computer ADC \/ DAC board. The board can read in 16 channels of voltages. It can also output 16 channels\u00a0 of voltages. Voltage ranges are -5 volts to +5 volts.\u00a0 Resolution is 8 bit whether reading or writing. Using a blank […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[74,11,58,75],"class_list":["post-596","post","type-post","status-publish","format-standard","hentry","category-ideas","tag-appleii","tag-moog","tag-projects","tag-sequencer"],"_links":{"self":[{"href":"https:\/\/synthfool.com\/kevin\/wp-json\/wp\/v2\/posts\/596","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/synthfool.com\/kevin\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/synthfool.com\/kevin\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/synthfool.com\/kevin\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/synthfool.com\/kevin\/wp-json\/wp\/v2\/comments?post=596"}],"version-history":[{"count":1,"href":"https:\/\/synthfool.com\/kevin\/wp-json\/wp\/v2\/posts\/596\/revisions"}],"predecessor-version":[{"id":599,"href":"https:\/\/synthfool.com\/kevin\/wp-json\/wp\/v2\/posts\/596\/revisions\/599"}],"wp:attachment":[{"href":"https:\/\/synthfool.com\/kevin\/wp-json\/wp\/v2\/media?parent=596"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/synthfool.com\/kevin\/wp-json\/wp\/v2\/categories?post=596"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/synthfool.com\/kevin\/wp-json\/wp\/v2\/tags?post=596"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}