Anybody Manufacturing Top Octave Synthesizers - Page 1
Forum section: electronics / general

author: jonovid
author_rank: Super Contributor
timestamp: December 19, 2021, 02:31:17 am
content: a top octave synthesizer icis made up of 400 or more flip-flop's end-to-end to get all 12 notes from one clock inputdividedTOS chips require only one oscillator frequency, usually 1 MHz to 2 MHz. this high frequency signal supplies theclock frequency which is then divided by the TOS chips into the twelve equally tempered top octave musical notes of the scale. The twelve divisor ratios are multiples of the twelfth root of two which is 1.05946.used in 1960s retro combo organs and eurorack modular retro synthesizersbut were do you buy them today? or is anybody manufacturing top octave synthesizer ic'shttp://www.armory.com/~rstevew/Public/SoundSynth/TopOctave/topdividers.html

author: retiredfeline
author_rank: Frequent Contributor
timestamp: December 19, 2021, 03:12:21 am
content: I remember those, but never used one myself. I could only afford resistors for my stylophone.I have wondered if it could be done with a MCU. A search shows that somebody has indeed written firmware to do this:https://community.atmel.com/projects/emulate-top-octave-generator-ic-eg-mk50242

author: Brumby
author_rank: Unknown
timestamp: December 19, 2021, 04:25:54 am
content: Quote from: retiredfeline on December 19, 2021, 03:12:21 amSame.

author: Cerebus
author_rank: Super Contributor
timestamp: December 19, 2021, 05:25:40 am
content: It would be trivial to do with even a small FPGA or CPLD, it's basically 12 off 10 bit counters.In fact it's so trivial that I've written (off the cuff) a 1 note version of it, building it out to the full octave is just cut and paste scut work. It synthesises to 18 LCs on a lattice iCE40, so would be 12*18 LCs = 216 LCs which puts it into the territory where the smallest devices made would accept the whole thing - it'd fit into a 256 LC MachXO2 which are only £3 a piece in 1 off quantities.Here's the Verilog code:Code:`timescale 1ns / 100psmodule TopOctave (input wire clk,input wire reset,output reg C5);parameterC5_divider = 478;// 1st note, repeat 12 times for the others ========================================reg [9:0] C5_counter;always @(posedge clk)beginif (reset)beginC5 <= 0;C5_counter <= (C5_divider - 1); // Probably being hit around the head with a fencepost here.// probably better to run at a much higher clock to minimise the off by one errorendelse if (C5_counter == 0)beginC5_counter <= (C5_divider - 1);C5 <= ~C5;endelseC5_counter <= C5_counter - 1;end// =================================================================================endmodule`ifndef SYNTHESISmodule TestBench();parameterclock_period = 250, // 4MHz clockclock_pulse_width = clock_period/2;reg clk;reg reset;always #(clock_pulse_width) clk = ~clk;initial begin$dumpfile ("TopOctave.lxt");$dumpvars (0, TestBench);clk = 0;reset = 0;#(clock_period) reset = 1;#(clock_period) reset = 0;#10000000 $finish; // 10msendwire C5;TopOctave DUT (clk, reset, C5);endmodule`endif

author: Synthtech
author_rank: Regular Contributor
timestamp: December 19, 2021, 11:03:10 am
content: Flatkeys in England manufacture TOG modules as well as octave dividends for a lot of vintage organs and synths. A few of them even use FPGAs.

author: Bassman59
author_rank: Super Contributor
timestamp: December 20, 2021, 11:26:27 pm
content: Quote from: Cerebus on December 19, 2021, 05:25:40 amAges ago, I belonged to this listserv that was all about various combo organs (Vox, Farfisa, Yamaha) and there was some interest in an open-source project to recreate one. Everyone seemed to get hung up on the top-octave generator and I thought about it for a bit and came up with basically what Cerebus did.A few of the people on the listserv were upset by the fact that you'd have to buy a programming dongle (I think I targeted Spartan 3A) and use non-open-source tools and all of the usual, and that was when I bowed out.

author: Cerebus
author_rank: Super Contributor
timestamp: December 21, 2021, 12:25:31 am
content: Quote from: Bassman59 on December 20, 2021, 11:26:27 pmSpartan 3A dates it. If someone was really fussed about open source they could use the Lattice iCE40 series which has a fully open source tool chain and needs nothing more exotic to program it than a $5 flash programmer, but has the disadvantage that the parts are one time programmable (you can use an external SPI flash for development or for reprogrammability in the field). Personally I'd probably be looking at MachX02 (internal reprogrammable flash, you can make an effective standalone 'chip') if 3V3 was acceptable. For 5V compatibility, which I can see as an issue if you needed to support older (musically) instruments, then you're looking at older families of devices and are probably stuck with proprietary development software, external bitstream memories and all the general inconveniences that went with old generations of FPGAs/CPLDs.The thing about people who get a bee in their bonnets about open source in this sort of context is that it makes no sense. They want to replace a part that required serious proprietary resources to create, and would be happy to use salvaged or NOS, but balk if you need the odd proprietary tool to recreate them as FPGAs? Even if you require proprietary tools to create the bitstreams there's nothing that stops the bitstream from being freely redistributed, and if someone has problems with shelling out for a $5 third party programming cable then they've picked the wrong hobby trying to fix up old electronics.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 21, 2021, 02:43:28 am
content: Quote from: Cerebus on December 21, 2021, 12:25:31 amWell, the "open source" thing is one thing, and only part of the problem for those people IMHO. Many are just looking for a ready-to-use solution, but fully open-source. Meaning they don't want to do any effort, or are just not qualified to do so (but they seem to think they are for judging they absolutely need something open-source). What that means is, basically something like this can be implemented in a few lines of HDL (say a few tens for a complete solution with all the boilerplate code), and portable enough that it can be synthesized on any FPGA you like. And now some of them are supported by open-source tools, actually, like yosys. But if you don't provide a ready-to-use solution using yosys yourself, many people will whine. Granted, at the time Bassman59 did it, there probably was absolutely no open-source tool for FPGAs, but this is just a minor concern IMO. I'd be willing to bet that if you release something like this today, you'll get a lot of the same reactions.And it opens the can of worms question, what is open source anyway, when hardware is involved? If you use discrete logic gates, do those guys think it will make it more open source? Are the off-the-shelf logic gates you use open source? They aren't. The line is fuzzy, and people will put it wherever they feel like. It's always going to be pretty subjective, because *100%* open source hardware, if you're considering it on a strict level, does not exist.

author: Cerebus
author_rank: Super Contributor
timestamp: December 21, 2021, 01:16:04 pm
content: Quote from: SiliconWizard on December 21, 2021, 02:43:28 amWell, some hobbyists have made their own transistors or valves. Once you've got to that stage, making your own passives is a walk in the park. Then it's just a question of deciding whether you have to blacksmith your own wire drawing tools to make ittrulyopen source.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 21, 2021, 07:13:27 pm
content: Quote from: Cerebus on December 21, 2021, 01:16:04 pmYep. Now that would seriously start looking open source.But, what about all the tools and products you used for making your own components, to begin with?

author: Cerebus
author_rank: Super Contributor
timestamp: December 21, 2021, 08:46:11 pm
content: Quote from: SiliconWizard on December 21, 2021, 07:13:27 pmThat's why I picked on Blacksmithing, it's one of the few activities where you can start with materials dug out of the ground, fire and banging things with rocks. As you progress the tools get made, then more refined. Metalurgy and glass making are truly ancient arts that rely on no prior technology other than fire lighting. However, if you start from scratch you'd probably get to the stage of high vacuum pumps (which you need for making both vacuum tubes and single crystal silicon) just around about the time where your descendants will have to take up the torch from you.

author: jonovid
author_rank: Super Contributor
timestamp: January 10, 2022, 01:11:21 pm
content: if anyone is interested in building an electronic piano or organ from scratchor synthesizer based on 1970s 1980s electronicsthat can beTMS3615NSnew old stock data sheethttps://amigan.yatho.com/TMS3615NS.pdfI found this ic the TMS3615NSTMS3615NS Octave Multiple Tone Synthesizer circuit design electronic organhere is a complete piano / organ circuit with multiple TMS3615NS usedhttps://electro-music.com/forum/phpbb-files/jen_piano_73_104.png

author: MIS42N
author_rank: Frequent Contributor
timestamp: January 30, 2024, 10:45:14 am
content: In case anyone is looking, it was I who posted the emulation in the ATmel community, but it appears to have been deleted.I resurrected the code recently, and modified it to produce more accurate notes. It is public domain, and is here:https://sourceforge.net/projects/top-octave-generator/