Prophet 600 firmware upgrade revisited

Based on the feedback on beta 2022 (1) there have now been some final additions, changes and fixes, most significantly: Typos and updates of the User Manual Fix for modulation delay glitches on new notes Documented MIDI specification for tool development Various small UI fixes Link to the beta 2022 (2) . If nothing unexpected happens, this will be the release in early July.  But there is one more thing.  Proof reading challenge : if you feel you have the time to read the beta 2022 (2) manuals with scrutiny I vow to donate 50 cents to medecins sans frontieres for every misspelling, typo or grammar mistake that is sent to me. This is not because I feel infallible, but rather that I'd like to see those typos gone and do something meaningful at the same time. Just drop me a message with list of findings. Thanks to all active contributors and also for the interest  from around the world  in this Prophet 600 blog. 

While the old Z80 based Prophet 600 has a software execution problem, the Teensy++ 2.0 based version has a hardware bottleneck: the multiplexers. Already during the alpha testing phase it was interesting to explore the software performance on different units. When performance tuned too hard you get effects of glitching, e.g. intermittent wrong voltages especially during fast pitch changes. Through structured testing we managed to pin it down to the multiplexers, which incidentally were different in all testing units. Now with the beta, there has been one case in which one voice never properly updated - and interestingly the same unit works fine with the 2015 GliGli version, but not with the (considerably tuned) 2022 beta. As that problem, too, was solved by replacing the multiplexers, I thought it is time to post something about the importance of the multiplexers in the Prophet 600 so other can benefit from it. In short: if you have CD4051BE multiplexers (from Texas Instruments), w...

The Prophet 600 has 2 envelope generators with 3 possible destinations: filter cut-off, amplitude and oscillator A pitch (as part of the poly-mod controls). So far the envelopes had fixed destinations. The amplitude envelope controlled the - well - amplitude. And the filter envelope controlled the filter cut-off (via envelope amount in the filter sub-panel) and the oscillator A pitch (via the envelope amount in the poly-mod section when oscillator A poly-mod destination is switched on).  The 2022 firmware comes with a new option to change the envelope routing. The options on offer are similar to the JX8P (yes, it's not all bad - there are good things inside the JX8P). The filter envelope continues to control the filter cut-off in all cases, but apart from the Standard routing (see above) you can now choose (using the menu parameter "555" - pressing 5 three times): Poly-Amp : The amplitude envelope continues to control the amplitude but it also controls the oscillator A p...

The problem is as old as the invention of patch storage: once you load a patch into the active synth parameters you run into a conflict with the panel controls. These become detached from the patch. Different solutions have been found over the years.  Jupiter 4 : the brute force approach means that if you store a patch you can never change it again. Yes, really! When a patch is selected, the panel controls have no effect whatsoever. I am sure there is more than one person who was close to a heart attack thinking that their Jupiter 4 was totally broken when first experiencing this... One parameter select : with the entry of the DX7 the single parameter editing UI concept became popular where you select parameter to see its value in a display and then use a universal dial or slider to change it. A nuisance, of course, but solving a lot of problems for synth designers, one of many being that the values can always be updated from memory without conflict... Endless dials : a more modern...

Dear all users of an upgraded Prophet 600, The beta release for the 2022 firmware upgrade is now available! You can download the code and new User Manual here:   Release v2022-beta.1 · image-et-son/p600fw (github.com) . *** NOTE: this is a beta release and it is therefore not the final release but rather very close to it ***  *** NOTE: the code and manuals come with no warranty whatsoever, you carry out updates at your own risk. Always secure patches before updating the firmware. ***  Note: in case you're totally new to the GliGli upgrade you would need to modify your Prophet 600. In this case you should consult the documentation provided by GliGli. GliGli's Prophet 600 blog ( My Synthesizer stuff: p600fw (gliglisynth.blogspot.com) ) contains the links to the technical manual. If you're already running version 2.0 or version 2.1 RC3 you should be familiar with the upgrade procedure either by USB or by MIDI. Please also refer to the User Manual. If you want to activel...

The GliGli upgraded firmware uses a patch parameter menu based on the number pad for changing things like vibrato, additional LFO options, envelope shapes etc. Most users find menu diving a nuisance. Since there are more than 10 parameters in the firmware upgrade and only 10 number buttons (0...9) the firmware even needed two "pages" of parameters. A double press of each number accesses an additional parameter. What's more, the location of parameters on the number pad was not completely systematic, e.g. pressing "2" would access the Vibrato Speed, but pressing "2" twice was accessing the LFO Range. A cheat sheet from Synthgraphics (list of parameters and their location) does help, as does the fact that the parameter name is scrolled through the display. Overall, not ideal but still not something one can't live with. The new 2022 firmware version to be published soon has even more parameters so that two pages are not enough. Therefore a different co...

The GliGli firmware (versions 2.0 and 2.1RC3) re-designated the original "Mixer" and "Glide" of the Prophet 600 knobs to control the volumes of oscillators A and B separately. This has the disadvantage that the glide amount needed to go into the - not very user friendly - parameter menu. On the other hand with the GliGli layout, one could (over-)drive both oscillator A and B amps. Personally, I also appreciate the clarity of controlling the two volumes with the two knobs, conveniently positioned next the oscillator sections. There are obviously good reasons for either choice of layout. Now, I have had requests from several users that the original Sequential Circuits layout be brought back. I even had one collector who said he refused the GliGli upgrade because he didn't like the fact the panel control descriptions don't match the control function. And he has a point - not many people got hold of a synth graphics panel overlay to match the GliGli upgrade and ...