Author Topic: Audio Effects DSP Board  (Read 46836 times)

markseel

Re: Audio Effects DSP Board
« Reply #320 on: October 01, 2018, 12:37:33 PM »
Yep the video sucks!   :o

The ToneCore thing sort of baffled me.  DSP is hard without having to learn a new programming environment, user libraries, software architecture, and assembly language.  That's why my goes with this was to try to distill the learning curve to just DSP - assuming you already know some 'C'.  But the ToneCore, Owl, MiniDSP, and Blackaddr/Teensy do have hardware for you to get up and running quickly.

The FlexFX boards are intended to scale in production and are minimal in design so that little is assumed about the end application.  Scaled to 1000 the board costs about $22 to make (at 100 cost is $38) - including BOM cost, assembly in China, and shipping back to the states.  So the cost does scale nicely.  Much of that cost is the XUF216 as its price bottoms out quickly - but that's when getting them from other distributors.  I used to work for XMOS and it's possible to work directly with XMOS sales to negotiate a direct cost.  If there's volume to make XMOS interested then that'd perhaps get the module down to $18 to $20 at 1000.  I'd have to sell them for a modest markup so that I can pay bills.  So maybe $30?

Seems that a boutique pedal would absorb this module cost OK.  A pedal BOM would still have to add the audio converters, analog circuitry, knobs, jacks, a 'mother-board' for the FlexFX to plug into, a case, etc.  But with the guitar interface board that I just played out (fits on top or below the FlexFX board) you'd only need to add the hardware (knobs, jacks, case).  That board is much cheaper to make than the FlexFX board.  So the BOM for the brains of a pedal is still well below $50.  You could actually just solder those two boards together, stuff it in a case, and manually point-to-point wire in the jacks and knobs.

I'll look at Tindie.  I emailed my PCB house on pricing for lower volume in case I can get this going with those who are already interested.  And if not I'll carve out some time to assemble them myself (takes me about 2 hours per board). 

audioartillery

Re: Audio Effects DSP Board
« Reply #321 on: October 01, 2018, 12:56:40 PM »
Have you thought of a doing a single-board solution?  Xmos and codec on same board, and a bunch of inputs exposed for hooking up pots and switches.  Might be more cost effective than making two separate boards.  And could be more compact.

I agree what you have is totally tolerable for boutique pedals.

markseel

Re: Audio Effects DSP Board
« Reply #322 on: October 01, 2018, 01:06:59 PM »
Yeah I did consider that and I sort of go back and forth.

As soon as I design a board for the pedal application I have to choose the converters and analog circuitry and these decisions are influenced by cost/performance/feature tradeoffs.  If I add jacks and pots then the pedal dimensions get thrown into the mix.  I also then don't scale the XMOS USB/DSP module production as well.  So it's a tough call!  I think I'd rather stick with the module approach. 

The USB audio/midi DJ collaboration product (the Collaborative Audio Interface by Bitstream Audio) uses four of these modules per product.  The module was a good way to get that product (prototypes have been built) off the ground and works for low volume.  But when that product scales up in production no doubt Bitstream will want to eliminate the modules and put all of the stuff on one PCB to lower production cost.  But having the modules being minimal and flexible allowed that initial work to move quickly.

For my C99 pedals I designed an all-in-one board to eliminate the modules.  Then after reviewing the layout for noise and running out of room here and there I went back to using the modules!

So I still want to stick with this being a minimal USB/DSP module with I/O's and no hard assumptions on analog interfaces.

markseel

Re: Audio Effects DSP Board
« Reply #323 on: October 01, 2018, 02:55:15 PM »
I'm going to try this within a few weeks ... The USB/DSP board with the guitar/analog interface board (same one as offered on KickStarter), and power converter / pot interface board.  All three boards stacked.  This would have a 1.0"x1.5" footprint and a thickness of just more than a USB jack.

The analog board has the guitar input, line output, and connections for 3 high-speed high resolution analog inputs (pots, wah pedal, etc).  The power board has a 9V input and auto-switches between the external 9V supply and the USB 5V supply.  It also has 4 low-speed analog inputs for pots.

This would allow you to just hook up pots, jacks and power and place the stack in your case to make your own programmable digital effects pedal.  You wouldn't necessarily need the USB jack if you used JTAG to update the firmware.  But you could leave the jack on and update firmware by opening the case and plugging in a USB cable.

« Last Edit: October 01, 2018, 03:01:01 PM by markseel »

audioartillery

Re: Audio Effects DSP Board
« Reply #324 on: October 01, 2018, 04:05:11 PM »
Any chance you can do more inputs?  4 pots, 2 switches (still analog input, in case it's 3+ position), and a footswitch is kind of my minimum pedal board criteria.  Otherwise I need to add an analog mux (which is what I'm doing on the Blackaddr board).

Auto switching between pedal supply and USB is really nice.

markseel

Re: Audio Effects DSP Board
« Reply #325 on: October 01, 2018, 04:15:57 PM »
That stackup supports 7 knobs (4 on the power board, 3 on the guitar interface board), guitar in, line out, 9V in.  Want more?  That power-board could change a little.  It has a 10-pin header with ground, 9V, and 8 connection for the pot - I was thinking that two connections per pot would make wiring up easier.  But ... that 4-channel I2C ADC comes in an 8-channel version.  So we could them just have one ground, 9V, and eight pot inputs.  That'd be 11 total pot/switch inputs.  But you'd have to wire your pots/jacks to a single ground somehow.  Sound better?  Hmm, or extend the board for another row of headers for two connections (ground and ADC input) per pot.  I guess that would be an 18 or 20-pin dual row header.  Board would then grow to 1.6" - no biggie.
« Last Edit: October 01, 2018, 04:17:57 PM by markseel »

audioartillery

Re: Audio Effects DSP Board
« Reply #326 on: October 01, 2018, 11:17:50 PM »
7 analog inputs should be plenty. Nice if they all wire to one board, but not super critical.

How would this all mount in a stompbox enclosure? Standoffs attaches to the floor plate?

Oh, I may have missed it above but what about outputs? Need at least an indicator LED. Iíve been using 5mm hat form factor Neopixel RGB LEDís and itís really nice to be able to put out different colors from the same light. And you can chain them. Instead of on/off you can do bright/faint which is a nice touch. So you need an output line, possibly level shifted up to 5v (mine are working at 3.3v). And on the Teensy thereís a DMA library for them so you donít need to lock interrupts while bit banging the output pin. On the Xmos I guess you could have one core deal with that.

markseel

Re: Audio Effects DSP Board
« Reply #327 on: October 02, 2018, 10:57:04 AM »
Yeah those LED's are cool.  So here's a couple of options for additions to that power board:

1) Add a couple of 3.3V / 5V level shifters to condition two XMOS GPIO's for LEDs/switches, the one wire LED protocol, etc.

2) Add a I2C controlled LED drivers with PWM and input features.  The PCA9670 has 8 ports that are 5V tolerant, can be input or output, can drive LED's via PWM (brightness), and has blinking functions.

Thoughts?
« Last Edit: October 02, 2018, 11:01:48 AM by markseel »

markseel

Re: Audio Effects DSP Board
« Reply #328 on: October 02, 2018, 01:29:22 PM »
Here's the power and I/O board.  9V input for powering from 9V source, auto switching between 5V and 9V sources, 8 analog inputs (for pots), 8 digital I/O's for LED's and/or switches.  The digital outputs also support PWM for LED brightness control.



audioartillery

Re: Audio Effects DSP Board
« Reply #329 on: October 03, 2018, 11:54:49 AM »
Personally I like the one wire LED option.

markseel

Re: Audio Effects DSP Board
« Reply #330 on: October 03, 2018, 05:54:22 PM »
Yeah the 1-wire LED's are simpler :-)

Looks like the FlexFX USB/DSP module KickStarter will fail.

I'll try again but this time it will only require 20 backers.  At 20 the FlexFX board PCB+parts+assembly+shipping jumps to $80 per board.  But if I assemble the companion audio/power/IO board myself I could keep the price down.

I'm started a PCB design that has four pots, a landing spot for the FlexFX module, the analog circuitry and ADC/DAC, and connections for 9V and LED's and switches.  It's dimensioned to fit inside of a Hammond 1590BS case.  The board is secured by the pots being mounted to the case.

Dimensions and pots/jacks placement would look like this: https://www.kickstarter.com/projects/vfepedals/vfe-pedals-new-pedal-line-educational-kit

Those are some nice looking pedals!

So next KickStarter will be a 1590BS sized kit (case not included) that has the 1590BS PCB and FlexFX board, surface mount parts, FlexFX module, and pots soldered in.  The kit would include two 1/4" audio jacks, a 3PDT foot switch, and 2.1mm power jack - these are not part of the PCB and have to be wired/soldered during pedal assembly.

Making a pedal with this kit would require people to supply a 1590BS case, drill holes (for the pots, audio jacks, and power jack), drill more holes for your own LED's and toggle switches, and do the final assembly.

It looks like I could offer this Digital Effects Pedal Kit together for $110 + shipping (shipping in US is maybe $10?) if I do the pedal PCB assembly myself (pretty easy to do) and only outsource the FlexFX module assembly (China).  To cover any mistakes I'll set a KickStarter reward cost $125.

If folks here think that this is viable I'll lay out the PCB board for the Hammond case - won't take more than a couple of days - and do a test run with some prototype boards.

Feedback welcome!
« Last Edit: October 03, 2018, 06:06:52 PM by markseel »

audioartillery

Re: Audio Effects DSP Board
« Reply #331 on: October 03, 2018, 06:51:36 PM »
I think $125 shipped is viable.  I'll kick down for one unit -- may be able to interest another friend or two.  But you'll want to have some photos of what this looks like in the kickstarter this time in order to draw a few more people in.  If you don't have units to photograph before putting the kickstarter up PM me and I'll do a mechanical model of if so you can at least have some plausible renderings.

markseel

Re: Audio Effects DSP Board
« Reply #332 on: October 03, 2018, 07:00:52 PM »
OK cool.  Yeah I'll video the assembly of a unit to show the steps and internals and such.

markseel

Re: Audio Effects DSP Board
« Reply #333 on: October 10, 2018, 01:11:42 PM »
Here's the FlexFX mother board for Hammond 125B cases that I'll make.  It has no electronics on it so you can fabricate these PCB boards yourself (PCB Gerbers will be public) if you want to.  Or you can design your own PCB from scratch without much fuss as long as the FlexFX landings (the four 10-pin headers) are wired up correctly (just copy the connection on this board).

The 125B mother board has landing spots for potentiometers, 3-way toggles, and LED's, and has connections for foot-switches. Since this is fitted for a 125B case - that has some depth to it - the 9V power jack and the two audio jacks would fit underneath this board.

It also has landings for the FlexFX boards for one or two! USB/DSP module(s), a power and I/O (8 pot inputs, 8 digital I/Os) module, and an analog (guitar in, line out) module.  The modules stack up and can be placed on either of the two landings in any order.

The pic shows some possible control layouts.  Blue circles show one potentiometer/knob arrangement while the green circles show the other.  Any number of pots can be populated as long as they don't physically collide.  Same for the toggles ... red shows one arrangement and yellow shows another.  The red circles show LED's (up to five).

Labels P0 - P5 are for the (up to) six pots.  Labels T0 - T7 are for the (up to) 8 toggle, although physical collision will limit actual use.  Labels S0 - S1 are for the one or two foot switches, and L0 - L4 are for the (up to) 5 LED's.  There's also a two 4-pin headers to attach one of those USB to 4-pin cables - for downloading firmware and testing.

So basically choose your part locations, drill the case holes, and assemble for a custom digital affects pedal.  The board cost, two-layers with no electronics on it, should cost very little.  A set of FlexFX boards to put on the motherboard (one USB/DSP, one power/IO, and one analog) should then come in at around $100 with discounts for higher volumes.

« Last Edit: October 10, 2018, 01:56:02 PM by markseel »

audioartillery

Re: Audio Effects DSP Board
« Reply #334 on: October 11, 2018, 11:52:24 PM »
Looks pretty reasonable Mark.  You make a good point -- it's trivial to spin an interface board as long as we keep the module pinout the same.

Looking forward to the next kickstarter (or whatever).