Hi Guys. This is my first post on the darkside although I'm a regular on the 'Building Your Own Stomp' side of things
Anyway, I'm a big Brian May fan and have many pedal builds in that area and was thinking about building a digital delay to do the Brighton Rock thing. For those not aware, its Brian Mays concert showpiece where he uses a delay effect with 2 repeats (one at 800ms and the other at 1600ms) to build layers and harmonise etc.
So I'm thinking of trying to make a digital pedal with just that, 2 repeats 800ms apart.
The thing is, even though I am a software developer by trade, I've never done any DSP and dont know where to start with processors, loaders etc?
I've googled a little bit and got lost but I trust the guys on this forum. So a point in the right direction would be great.
So can anyone advise on what processor I should be using and what other equipment do I need to get up and running?
Thanks
Quote from: nickbungus on June 28, 2019, 06:17:57 AM
Hi Guys. This is my first post on the darkside although I'm a regular on the 'Building Your Own Stomp' side of things
Anyway, I'm a big Brian May fan and have many pedal builds in that area and was thinking about building a digital delay to do the Brighton Rock thing. For those not aware, its Brian Mays concert showpiece where he uses a delay effect with 2 repeats (one at 800ms and the other at 1600ms) to build layers and harmonise etc.
So I'm thinking of trying to make a digital pedal with just that, 2 repeats 800ms apart.
The thing is, even though I am a software developer by trade, I've never done any DSP and dont know where to start with processors, loaders etc?
I've googled a little bit and got lost but I trust the guys on this forum. So a point in the right direction would be great.
So can anyone advise on what processor I should be using and what other equipment do I need to get up and running?
Thanks
If you're a DIYer and like to make your own enclosures, you can check out my TGA Pro (https://www.tindie.com/products/Blackaddr/arduino-teensy-guitar-audio-shield/) audio shield for the Arduino Teensy. You can see some custom enclosure projects with it here (http://blackaddr.com/products/) at the bottom of the page.
The Arduino Teensy boards provide a great audio library to handle all the hard stuff around realtime audio letting you focus on the DSP stuff. The code examples in my software library (https://github.com/Blackaddr/BALibrary)include a few delay based demos (https://github.com/Blackaddr/BALibrary/tree/master/examples/Delay) for digital delay, analog delay and sound-on-sound. Of course you can make your own from scratch.
If you're looking for something already in an enclosure Mark Seel (a member here) makes the C99 (https://www.indiegogo.com/projects/c99-digital-multi-effects-pedal#/).
Starting to get a little pricey but you could also search for the Owl pedal.
A good option to start DSP is any platform using FV-1. But for your specific project it's not the best fit due to the long delay you need.
Thanks.
I have looked at the Fv1.Is it not capable of the 800, 1600ms delay times?
Quote from: nickbungus on July 03, 2019, 02:54:33 AM
Thanks.
I have looked at the Fv1.Is it not capable of the 800, 1600ms delay times?
Due to the available RAM, by default it gets to 1 second. If you need more, you need to compromise bandwidth. If you lower the sampling rate you can get to longer delays. Some commercial pedals are using an external tweakable clock to drive the FV1 and achieve longer delays.
Mat
There's also an "8 second delay" patch floating around for the FV-1 that does sub sampling in the algorithm. This could probably be adapted to give a 2 second delay and then you could add some low pass filtering ahead of it to suppress any aliasing if it's a problem.
I have a 2 seconds version of the 8 seconds algorithm, if someone is interested
Brilliant
Thanks guys. I'll try the FV-1 then!!!
You will be further limited in delay time if you need stereo, or high-ish fidelity. Just a heads up.
The FV-1 is definitely best bang for buck. But unfortunately you can't really expand apon the limitations of the chip. Sacrifices (sound quality for delay time) have to be made one way or another. It's also in assembly, so not the most straightforward of programming languages. There's a visual tool out there that may help in developing algorithms, SpinCad it's called.
The other way is using a dedicated microcontroller like ARM or PIC, which is the way I like to use. It's more work to get the chip up and running, it's not audio-centric so you have to build a program foundation to configure the chip's peripherals before you can think of passing audio through. But has much more flexibility in delay time by adding external memory, more control inputs, displays, that sort of stuff.
An in-between would be teensy, which is Arduino-based. Easier to get started with the excellent visual editor and large community. Only downside is you have to use their stamps or their bootloader chip, which slows you down a little if you like making custom PCBs. Still a great product!
Well you could always use 2 X FV-1 chips to get both delays with up to 2 seconds on high quality delay. I would consider using two chips in series with a delay of 800ms on the first FV-1 for the first delay which feeds into the second FV-1 for the longer 1.6 second delay.
You could even use the FV-1's in this setup to generate the Harmonies.
ie. You can have 800ms of delay on the first FV-1 going to the left DAC feeding the second FV-1 and the output of the right DAC having the 800ms plus whatever harmony you need. The second FV-1 can have another 800ms delay (1.6S total) plus the second harmony added.
Maybe a little more info on what exactly Brian May is doing for this effect would help my work out how to do it properly
I was doing a similar thing for the Steve Vai song 'Ballerina 12/24 which can be done on a single FV-1 as the delays are much shorter.
major sixth 9 semitones up delay 180ms, and a perfect fourth 5 semitones up delay set at 360ms.if I remember correctly.
I hope I am making sense here.
EDIT- Ok so ignore my harmonies idea above as after listening to Brian Mays solo the harmoines are not part of the effect they are accumulated through the overlapping delays, which I had not realized before, so this is easier to do than I thought.
Ice-9, you're in Newcastle!! I live in Birtley
I'm struggling to find a supplier of the FV-1 chips. Cant find them from the recommended distributors.
Also, would it be cheaper/easier to add ram rather than use 2 FV-1s?
Quote from: nickbungus on July 04, 2019, 08:52:38 AM
I'm struggling to find a supplier of the FV-1 chips. Cant find them from the recommended distributors.
I found them here: https://www.profusionplc.com/parts/spn1001-fv1
Quote from: nickbungus on July 04, 2019, 10:09:11 AM
Also, would it be cheaper/easier to add ram rather than use 2 FV-1s?
Be great if you could but they are not expandable.
Quote from: nickbungus on July 04, 2019, 08:52:38 AM
Ice-9, you're in Newcastle!! I live in Birtley
I'm struggling to find a supplier of the FV-1 chips. Cant find them from the recommended distributors.
Birtley Eh ! I'm just along the road at Leam lane.
As Bluebunny posted above the UK supplier is Profusion PLC and they have quick delivery. I usually get a delivery every week but I only order as many as I need for the week
You can't add ram to the FV-1.
QuoteBirtley Eh !
Posh end mind, Northside!! Also, if you see the band DirtMonkey advertised - thats us!
Right - chips are ordered. My degree is in Computing for Industry and I've done a bit of pIC. Do I need anything to order anything to program and load or can I knock something up myself?
Quote from: nickbungus on July 04, 2019, 11:39:47 AM
QuoteBirtley Eh !
Posh end mind, Northside!! Also, if you see the band DirtMonkey advertised - thats us!
Right - chips are ordered. My degree is in Computing for Industry and I've done a bit of pIC. Do I need anything to order anything to program and load or can I knock something up myself?
I checked oot the band and I see you will be playing the 'Three Tons' in a bit (November?), see if I can get there for that as it's one of my locals.
For writing your own programs you will need to have an EEPROM programmer, My choice is the Pickit2 but you could build your own cheaper. If you go for a Pickit programmer note that you need the Version2 not the Version 3.
If you need any help regarding working a schematic for a 2 chip FV-1 I can chip in ;D
Excellent. I've ordered one of these https://www.ebay.co.uk/itm/Microcontrollers-PICkit2-PIC-KIT2-Debugger-Programmer-For-PIC-DsPIC-PIC32-PIC24/192905065375?hash=item2cea09b39f:g:3zEAAOSw6y5cjX2R (https://www.ebay.co.uk/itm/Microcontrollers-PICkit2-PIC-KIT2-Debugger-Programmer-For-PIC-DsPIC-PIC32-PIC24/192905065375?hash=item2cea09b39f:g:3zEAAOSw6y5cjX2R)
I need all the help I can get as I'm flying pretty blind here and I cant seem to find the info to get me up and running.
I'll mock up a pseudo schematic/diagram of what I am trying to achieve.
Thanks again
QuoteIf you need any help regarding working a schematic for a 2 chip FV-1 I can chip in
:icon_rolleyes:
(https://docs.google.com/uc?id=17d2tLUFkYVIoRKjRE9ZpNFVow0E01Lfv)
Ok, its very crude and I've omitted a few bits that I hope are implicit. The image below May (intentional pun) help! I think the main thing to note is the three outputs. I will also make the outputs switched so that when there isnt a jack inserted on the left and/or right channel the signal is routed to the Main Output. So I will need some splitting/buffering circuitry somewhere in the line.
The footswitch is there to indicate that the effect is switched and when not engaged each output still receives signal.
I suppose having up to One second delay I may as well add a pot for delay time. At a low setting this could probably produce a nice doubling (tripling) effect. Would I need a dual gang pot?
(https://skypeguitarlessonsonline.com/wp-content/uploads/Brian-May-Stage-Rig-and-Pedal-setup-696x522.jpg)
For the delay time I would probably set the limit to 800ms each so that when the delay pot is set at max you will get your magic number of 800ms+1600ms. A single pot can control both FV-1 chips without the need for a dual gang. This way the delay taps will keep the time with each other, ie the second delay will always be double the first.
For the multi jack outs you will have to think that one through carefully for how it is switched and mixed. The DSP chips will each need an EEprom for your program but I expect you already knew that.
QuoteFor the delay time I would probably set the limit to 800ms each so that when the delay pot is set at max you will get your magic number of 800ms+1600ms. A single pot can control both FV-1 chips without the need for a dual gang. This way the delay taps will keep the time with each other, ie the second delay will always be double the first.
Sound Great
QuoteFor the multi jack outs you will have to think that one through carefully for how it is switched and mixed.
Switching: perhaps having a 0ms delay time when the effect is not engaged might be an easy hack.
Mixing is a bit trickier. I was thinking using the stereo outs from the first chip, have left going to 1 output and right going to the 2nd chip, but this will need some thought in implementation.
QuoteThe DSP chips will each need an EEprom for your program but I expect you already knew that.
Looking at the datasheet, there's a schematic in there using a 24LC32A. Will these (https://uk.rs-online.com/web/p/eeprom-memory-chips/0454416/?cm_mmc=UK-PPC-DS3A-_-google-_-DSA_UK_EN_Semiconductors-_-EEPROM+Memory+Chips-_-DYNAMIC+SEARCH+ADS&matchtype=b&aud-359023897639:dsa-611842914139&s_kwcid=AL!7457!3!230837186532!b!!g!!&gclid=CjwKCAjw6vvoBRBtEiwAZq-T1QE9QMpG5PMeblT0l5nFaWyTfY72ffZ-dxPMRjDs0UzV_jvUH_ECORoCXdwQAvD_BwE&gclsrc=aw.ds) cut it? I've added them to my RS Components basket but yet to order.
This is how I would consider connecting the two DSP's together, I have used the datasheet to get an idea of the signal flow, I have just used a simple buffer as the input, you might want to use a more complex preamp section possibly.
Connecting one output of the FV-1 to the input of the second FV-1 is done using the standard filtering from the datasheet.
This might give you a head start on the basic DSP part. A pot is connected to both FV-1 pot0 inputs which can be used to control the delay time and I would think about using 2 more pots to control the delay level of each FV-1 chip separately if that's what you require.
You will need to look at adding the outputs from the FV-1's to the mixing section etc.
(https://i.imgur.com/Zth5hNh.png)
Thank you Mick - thats amazing. Any chance I can get a higher res version of the schematic
I'm reading up on SpinASM now.
Here is a larger drawing, note that this is just a small building block and idea of how the 2 FV-1 chips could be used, there will still be a lot of stuff to add to make a complete effect.
1st FV-1- left output will carry 800ms delay to output mixing
1st FV-1- Right output will pass 800ms delay to the 2nd FV-1
2nd FV- 1 left output will carry 1.6 second delay to output mixing
2nd FV-1 Right output not used (possibly use to add feedback)
The Eeproms you linked to are the correct ones.
I hope this gets you started with your plan. I suppose there are many other ways to build what you are looking for and this is just one option.
(https://i.imgur.com/1ogjOee.png)
Quotenote that this is just a small building block and idea of how the 2 FV-1 chips could be used, there will still be a lot of stuff to add to make a complete effect.
Thanks, I appreciate that but I didnt have a clue so this is such a massive help. My plan is to etch your schematic and then breadboard the mixing stage. Looking at how Electric Driuid (https://electricdruid.net/diy-digital-delay/) did his for inspiration.
Thank you so much for your help and time Ice-9. It is truly appreciated.
Quote from: nickbungus on July 06, 2019, 05:14:31 AM
Quotenote that this is just a small building block and idea of how the 2 FV-1 chips could be used, there will still be a lot of stuff to add to make a complete effect.
Thanks, I appreciate that but I didnt have a clue so this is such a massive help. My plan is to etch your schematic and then breadboard the mixing stage. Looking at how Electric Driuid (https://electricdruid.net/diy-digital-delay/) did his for inspiration.
Thank you so much for your help and time Ice-9. It is truly appreciated.
Yes, Electric Druids Digi delay is also a very good echo to look at as it has up to 4 seconds of delay there may also be a way to tap the delay for the two separate echo divisions, worth having a word with Tom as it might be possible to alter the code to allow this.
You might also want to check out the fV-1 project thread here, it is the first FV-1 project I brought to this forum and there have been hundreds of that pedal built but be warned it is a HUGE thread. Lots of info on many things as well as how to program the eeproms etc.
Exciting times!! Orders are starting to arrive. My schematic is nearly finished for my prototype. Just trying to figure stuff out!
Its hard to follow the original FV-1 from Mick as its old and a lot of the image links are dead.
I take it this is how to connect my Pickit 2 programmer to the EEPROM?
Connections for 24LC devices
---------------------------------------
PICkit 2 Pin 24LC Device Pin (DIP)
(2) Vdd ! 8 Vcc
(3) GND 4 Vss
(5) PGC 6 SCL (driven as push-pull)
(6) AUX 5 SDA (requires pullup)
7 WP - disabled (GND)
1, 2, 3 Ax pins
Connect to Vdd or GND per
datasheet and to set address
! 24LC devices may not program properly below 3.6V VDD.
This is a limitation of the PICkit 2 AUX IO pin.
If you fit sockets for the EEproms then you can program them off board, the pin connections you have listed look good.
QuoteIf you fit sockets for the EEproms then you can program them off board, the pin connections you have listed look good.
Really?? That sounds great.
Is it as simple as just putting the EEPROM on a bread board, match the pins to the Pickit2 device and then load from the configured Development Programmer?
No other circuitry required? Then plug it into my main board?
Quote from: nickbungus on July 10, 2019, 10:23:26 AM
QuoteIf you fit sockets for the EEproms then you can program them off board, the pin connections you have listed look good.
Really?? That sounds great.
Is it as simple as just putting the EEPROM on a bread board, match the pins to the Pickit2 device and then load from the configured Development Programmer?
No other circuitry required? Then plug it into my main board?
Sort of,
You can use the Spin development program to build your effects program and save as a HEX file. You then use that HEX file with the Pickit2/software to program the EEprom.
Yes you can just wire up the pickit2 and eeprom to breadboard.
QuoteSort of,
You can use the Spin development program to build your effects program and save as a HEX file. You then use that HEX file with the Pickit2/software to program the EEprom.
Sorry, I knew that. Had read it a few times in the posts but I had a brain fart when writing my post.
Trying to lay my hands on SpinCad but I havent had confirmation from the HolyCity forum. If anyone can send me a link, that would be most appreciated.
QuoteTrying to lay my hands on SpinCad but I havent had confirmation from the HolyCity forum. If anyone can send me a link, that would be most appreciated.
Its ok, Larrys let me into his Digital world and I am a digital girl! I thought I was analog only but times are achanging!!
Quote from: nickbungus on July 10, 2019, 03:44:46 PM
Its ok, Larrys let me into his Digital world and I am a digital girl! I thought I was analog only but times are achanging!!
Glad we were able to work that out. Now come to grips with the fact that most people want their digital delay to sound "more analog".
Hint - high pass and low pass filter before the delay.
Extra credit - push the high pass farther up in frequency than you might think. I love this sound! It keeps an element of "delay-ness" and yet keeps a lot of spectral clutter out of the sound.
Whether DSP emulates some piece of analog gear is almost completely unimportant to me. Whether it sounds great is quite important!
Loving the SpinCad!! Still finishing off my schematic but I'm looking at SpinCad trying to work everything out.
My question is to do with the switches on the FV-1. I cant seem to find any reference to them in SpinCad and on the datasheet apart from the schematic.
I was hoping they could be used as controls but I'm now starting to suspect they are solely for toggling between patches. Is that true?
If you are meaning the S0-S2 switches, then yes they are for selecting which one of the 8 effects programs are selected from either the internal or external EEprom locations.
Thanks Mick, thats somewhat scuppered my design!!
SpinCAD lets you work on 8 patches in a "bank". It is possible to think of a switch as a control, e.g. long/short delay times but then you have to start with a patch (e.g. patch 0, all bits are low) and make copies of it and then edit those things in 3 dimensions so to speak, so that patches where bit 0 is high are all short delay, and when bit 1 is low, are long delay, etc.
Requires a bit of planning but actually can be done. The only real downside is a bit of a glitch is possible when switching. You can also be tricky if you like and add extra differences not strictly associated with what you said the switch is supposed to control. A switch could be chorus/phase which makes major differences in the algorithm.
I Just noticed a typo on the basic buffer input C8 should be 100n not 1n
I'm just finishing off the schematic and then I'm going to tidy it up. I've got 2 isolated outputs for the 3 amp setup that route the signal back to the main output if a Jack isnt present to avoid ground hum. Not sure if I need to add opamps to mix the signal back into the main output if there isnt a conncetion?
Also, I think I'll add 3 external level pots. Should help get the mixing if required.
(https://docs.google.com/uc?id=1x4n3N1NGBEUMv-7Ph0yMBU9zPD88UzOl)
Quote from: nickbungus on July 04, 2019, 08:52:38 AM
Ice-9, you're in Newcastle!! I live in Birtley
I'm struggling to find a supplier of the FV-1 chips. Cant find them from the recommended distributors.
I'm in Sunderland!
The North East Solder Sniffers!!
Going to repost this so its not lost on the bottom of the page :icon_lol:
I'm just finishing off the schematic and then I'm going to tidy it up. I've got 2 isolated outputs for the 3 amp setup that route the signal back to the main output if a Jack isnt present to avoid ground hum. Not sure if I need to add opamps to mix the signal back into the main output if there isnt a connection?
Also, I think I'll add 3 external level pots. Should help get the mixing if required. (Also I've put the opamp as a LM324 but thats to be decided - I just put a quad on just in case I needed some to mix signals).
Also I've made a mistake with the switched Jacks and connected the switched signal to ground - sorry/
(https://docs.google.com/uc?id=1x4n3N1NGBEUMv-7Ph0yMBU9zPD88UzOl)
I think Frank (one of the FV-1 designers) talks about using an anti-aliasing low pass filter between 2 chips if daisy chaining them, or in the feedback loop if it is external to the chip. Something about preventing aliasing of out of band signals due to delta-sigma or sigma-delta or pi beta theta epsilon or one of those other fraternities. I've never daisy chained my FV-1s so I'm not sure about it, but it would be good to know that this is not a problem before committing to build such a complicated beast.
Might be worth inquiring over at the Spin forum.
Quote from: Digital Larry on July 18, 2019, 11:31:10 AM
I think Frank (one of the FV-1 designers) talks about using an anti-aliasing low pass filter between 2 chips if daisy chaining them, or in the feedback loop if it is external to the chip. Something about preventing aliasing of out of band signals due to delta-sigma or sigma-delta or pi beta theta epsilon or one of those other fraternities. I've never daisy chained my FV-1s so I'm not sure about it, but it would be good to know that this is not a problem before committing to build such a complicated beast.
Might be worth inquiring over at the Spin forum.
Larry, The schematic snippet I drew has the anti aliasing filtering in the schematic as per datasheet so should work fine.
Cheers guys.
Quote from: Leetut on July 18, 2019, 06:38:03 AM
Quote from: nickbungus on July 04, 2019, 08:52:38 AM
Ice-9, you're in Newcastle!! I live in Birtley
I'm struggling to find a supplier of the FV-1 chips. Cant find them from the recommended distributors.
I'm in Sunderland!
What' s the odds eh! three of us all just round the corner from each other.