Prophet 600 firmware upgrade revisited

While I intended to basically release the beta 2022 (2) and only do the smallest and most urgent fixes (hoping of course there would not be any) some very important code changes did came up which now lead up to the improved first release candidate v2022 RC1 ( download ). What happened and what is new?  Apart from those aforementioned small corrections (thanks to the contributors!) there are 2 new features and one really exciting major fix.  The 2 selected features that "sneaked in"were 1) vibrato has now the option to modulate only one of the two oscillators (parameter 222) and 2) the LFO can now be re-triggered when a new key is played (parameter 111) Now to the major fix "tuned pitch shift" : the poly-mod envelope pitch shift of OSC A as well as the LFO pitch shift of OSC A and B are now fully tuned and harmonic. Yes, that wasn't true before. In prior firmware versions tuning was not taken into account so that pitch shifts were detuned depending on how far the...

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...

The upgraded Prophet 600 offers two envelope shapes: exponential and linear. These are software generated and in versions 2.0 and 2.1 RC3 they are really exactly that: a pure exponential shape and a pure linear shape. Some users argue that a musical choice is somewhere in between. To the ear, the exponential shape drops very quickly at the beginning and then it tails off long. The linear shape on the other hand is thicker in the early decay phase but then it drops hard to zero. The human ear is stunningly sensitive to envelope shapes, even at very low volumes. In a recent nice YouTube video Starsky Carr directly compares the Prophet 5 (rev 4) envelopes to the Prophet 600 addressing exactly this finding:  Prophet 600 vs Prophet 5 // Is the 600 a better value option? - YouTube Now: the 2022 firmware has completely revised linear decay and release shapes, which are linear at the start but then tail off smoothly. To some degree the shape was inspired by the Prophet 5 rev 1/2 envel...