Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.

Messages - Xavier

Pages: 1 [2] 3 4 ... 83
PreenFM2 / Re: PreenFM2 SMD version
« on: November 19, 2017, 11:47:35 AM »
I don't get exactly how the firmwares flashing will work.

Is there still the JMP3 to flash the STM32F4 through USB ?
Will the STM32F1 flashing require the ST-LINK programmer ?

Would be great to have also a led for the STM32F1, so that we can make it blink a little when the board is switched on to check it's correctly flashed and working.

PreenFM2 / Re: Vishay OLED brightness
« on: November 18, 2017, 05:07:22 PM »
The white Raystar i just received is also much darker than the other colors.
Its brightness is very sensitive to voltage. You need a strong 5V.
I quite like anyway it and it's very quiet :)

The green one is very nice but same nois as the yellow one.

PreenFM2 / Re: TX81z W1-W8 + Feedback Waveforms .txt
« on: November 18, 2017, 03:56:10 PM »

Great work !  :)

PreenFM2 / Re: PreenFM2 SMD version
« on: November 18, 2017, 12:13:29 PM »
You can have both. The encoder changes the volume globally  and the software per channel / instrument. The MCP42010 can jump instantly to any set value. These will have to be bit-banged though because all the SPI/I2S interfaces are used.
I have started changing the schematic for 4 audio channels and I've ordered some more components. I will probably also put a TDA2822M as a headphones stereo amplifier. This is linear rather than class D because I don't want the extra switching noise and 500mW per channel is plenty for headphones.

Better DACs to allow 4 independants output is for me the most interesting part.
Is a headphones jack really usefull on the preenfm2 ?
I understand it is for sound modules with sequencer, but i wonder here if it's worth the effort here.
Where the jack will be ?

I've changed all MIDI headers to 3 pins. The new encoder has a separate push switch connected. I will probably have to chose between separating the switches of all the other encoders and the P3 analog input header because I've started to run low on pins. Which one is better? Also is it worth having 4 separate LEDs  or more LEDs? If so maybe it's worth dropping a second MCP23S17 to handle the extra switches and LED outputs.

Must be on the midi out only. If plugged on the midi in, there will be a shared ground with the midi device that sends midi.
Would be great to be mistake proof and having it just on the midi output.

Separate Leds or more leds are not usefull. The current ones are not even visible on all preenfm2 with metal case (the majority).
The 20x4 LCD is big enough to contain all usefull info.

I would prefer P3 than separated encoder switches. There might be a Eurorack version using them in the future (not from me).

An even better option would be to replace the port expanders with a STM32F103 (only $1.20) running at 8MHz (internal RC clock) which can handle all the encoders, switches and LEDs independently and free a lot of extra pins in the STM32F4 and it can also keep track of the encoder values.

Ouch... another firmware to write/maintain/flash... That would make the development and upgrade process much more complicated.
I think we should avoid that.

PreenFM2 / Re: PreenFM2 SMD version
« on: November 17, 2017, 12:04:46 PM »
Anyone else thinks that having more audio outputs is a good idea? What other changes would you like to see in PreenFM2?

More audio outputs is something many people asked.  Two 6.3mm stereo sockets sounds good to me.
If you change the pot to an encoder, would be great to have it clickable.
The preenfm2 has not enough buttons, so having a dedicated STM32 input for each of the 5 encoder clicks woud be usefull.

Also a Ground pins is missing near the Midi output header. Midi output cable are supposed to be shielded. Never had any problem with that but it cannot hurt adding that.

Pins available for a graphical display would be great. Parallel, i2c, spi something else ? I don't know much in graphical display.

I don't know if you modified the Connectors. P3 is important for the vcIn firmware.
The jumper JMP1 is totally useless. Must be connected in all situation.

PreenFM2 / Re: PreenFM2 SMD version
« on: November 17, 2017, 12:03:29 AM »
The target are hobbyists who want a PreenFM2. After I proof the design someone else or a small company can manufacture the PCB with all the SMD components soldered and sell that as a kit. The end user will only have to solder the encoders, LCD, switches and sockets. With a stencil and a soldering oven and even a manual component place these PCBs can be manufactured very fast and cheap. Small companies who have automated pick and place machines can churn these boards in tens per hour.

The strength of this project is the firmware and the hundreds of man-hours you guys put in to develop it. So any derivative design should be able to reuse this firmware without too many modifications.

Keep in mind that a new Korg Volca FM can be bought for 150$. It can also load DX7 patches, has a case, MIDI and a sequencer. It doesn't have the same flexibility as the PreenFM2 though. The out of stock PreenFM2 kit and a metal case is 212E + 70E (approximately 330$) and this is one reason the Volca FM is selling so well.

I will build these SMD versions PreenFM2 mostly for myself and I'll solder them by hand. I do have a powerful stereo microscope and a steady hand so the only drawback is that it will probably take me an hour per board.

So I think you can use my build to proof a cheaper design, add a few new developments if you want and make the PreenFM2 more accessible and popular.

I was hopping you were not going to write that.
I really like the preenfm2 like it is today.  I would like it to remain a DIY project.

If like you say a small company manufacture the PCB, i would really feel robed.

PreenFM2 / Re: Subtle distortion on one channel
« on: November 15, 2017, 11:01:05 PM »
Each channel is the sum of 2 Dac outputs (12 bits + 6 bits).
The resistors pair 115K and 1.8K have a ratio of 63.88 (6 bits = 64) which is what is used in the sum.

You can verify with a multimetter that you mesure the same value on the 2 115K and the same on the 2 1.8K.
You'll get a lower value for the 115 because of the other components in the circuit.

(You can verify the same thing for all the paired resistors around the op amp, they are all part of the output audio.)

PreenFM2 / Re: PreenFM2 SMD version
« on: November 15, 2017, 10:41:35 PM »
Xavier, do you think the design I'm doing will be of any interest?

This is a great project. But i'm not sure who the target is...

PreenFM2 / Re: Vishay OLED brightness
« on: November 13, 2017, 09:34:06 AM »

Thanks a lot for the screenshots.  :)
That's very usefull and interesting.

All people who were annoyed by the high frequency peak reported it's not audible anymore after the shield + OLED resistor modification.
If you haven't done it before, look at the spectrum while trying to find the best place for your shield. 5mm can make a difference.
Also, verify what you hear is not directly the display (put the preenfm2 far away from you) and not a peak in the audio. (That happened to someone);.

I've just ordered a white and a green OLED display (Raystar). I'll report what result i got from them.

PreenFM2 / Re: November 5th 2017 -> 2.08
« on: November 10, 2017, 08:38:44 PM »

I think i remember there's 60Ko of RAM free on the preenfm2.
That's 30Ko per channel (stereo).
Each float takes 4 bytes to store so that's 7500 samples, at 40.000Hz your delay can be 0.18 second long... Could be a chorus maybe.

I don't know to much how a reverb algo works, but i assume the CPU usage will be big.

PreenFM2 / Re: November 5th 2017 -> 2.08
« on: November 08, 2017, 02:08:53 PM »
but how high can the ui go? do i loose resolution if i choose higher frequency range? or can the ui display values above 99.9? can the preset save values to 600.0?

The display maybe a bit weird after 100.0, but everything should work.
The UI also uses the same define.

The only thing is that your midi clock synchronised value will be after the last available frequency. it means that if you save presets with "MC" (or MC/2 or MC*2 etc....) frequency, they won't be "MC" anymore after the change.

PreenFM2 / Re: November 5th 2017 -> 2.08
« on: November 08, 2017, 09:20:08 AM »
just curious, where did the extra cpu come from that we can now have such fast lfos?

That does not use more CPU.
What ever the LFO frequency is, LFOs are updated every 32 samples : ~1200 times per seconds.

In theory with 1200 update per seconds, you should be able to go up to 600Hz.
If semeone wants to experience, it's now a simple constant to modify in the code :

PreenFM2 / Re: Midi CC Bug?
« on: November 07, 2017, 11:25:23 PM »
I forgot to "publish" the release, it should be visible now in the link above.

PreenFM2 / Re: Midi CC Bug?
« on: November 07, 2017, 10:54:17 PM »

Firmware 2.08a will make your octatrack happy :)

PreenFM2 / Re: Windows & macOS editor 2.08.2 : standalone & VST
« on: November 07, 2017, 10:07:03 PM »
I've checked in the 2 Makefile i used under Linux.
I think it's the best way to be sure binaries are linked correctly against the libs of your distro.

I have 2 linux distros, I could not have it compiling under the older one. It compiles fines under ubuntu Mate 16.04.

Go in Host/Builds/Linux and type make to build the standalone version.
The standalone version works fine.

Go in Plugin/Builds/Linux and type make to build the VST version.

I never tried VST plugin under linux before. I quickly downloaded the free Tracktion 6 for linux, but it complained not being able to inialiaze the VST.
What host do you use ?

Pages: 1 [2] 3 4 ... 83