Hi there all
working on a little project- ill try to be succinct to get to the actual issue...
jazz bass- TRS out.
neck pickup -> tip
bridge pickup -> ring
offboard is a module to process each pickup independently before blending them-
it will be high pass, low pass, both with variable resonance and freq, and then a parametric mid EQ/(switch)/bandpass section with Q, freq, and level for the eq.
**I will expand on this in the end**, but here is my current issue...
thats a LOT of knobs. I'm fine with amp-top or a pitcher's mound on the foor, but with this much tonal control, you would REALLY think presets would be necessary. Or at least a damn shame to do without...
my current thoughts
-arduino comes to mind, mainly because i've heard of it. Im not a programmer or really a huge 'computer guy' but I am clever and mathy, and i did well in the here-and-there programming in school.. Seems like an easy way to read and store whatever form of topology's information.
-digital pots- i dunno... seems like they don't get much love around here, and I'm not as good as some of you with overcoming frustrating parts... my naivete perhaps
-mechanized pots seem like something that i would... just @#$% up. im the type where the last 5% of a build is me stuffing wires in and slamming it shut like im trapping a mummy.
-vactrols :
THIS seems promising to me
... using digital pots to control vactrols, the latter acting in place of the original potentiometers.... eliminates the issues of catering the signal to the digipots' needs. are vactrols within a tight tolerance of eachother? will i be weeping trying to bias them all to a proper operating range? especially since i will A) have to configure some as voltage dividers instead of just rheostats, and B) implement dual-gangs for the fiters. in fact... i may be implementing dual-ganged voltage dividers in the bandpass... yikes
vactrols seem promising to me... arduino remembers the digipot setting, said resistance sets the LED, isolated controlled resistance badabing badaboom, albeit convoluted
Another thing to consider is that i will NEED (lol) dual ganged pots in a few spots, which complicated the idea of using
I suppose at this point, as presets are an issue of comfort and convenience, it comes to mind that to not stop short of a decent result, that i would need a few more features
: some sort of display.. preferably one that informs of the nature of the settings, not just a bank number. seems easy enough
: devise an algorithm to deal with adjusting presets RE: ''where does the pot pick up"
i'm not a believer in a preset that you cannot edit live, intuitively. I'll trust my mileage on that philosophy
It is ALSO worth noting that, because I have layed out such an exotic, and weirdly specific set of needs and goals that NO ONE GETS TO USE REASON with me and discourage this project in lieu of a readily-available project.
**the point of the project overall is, at least partially, to use different tonal characters imparted onto individual pickups via filters, BEFORE the pickups are blended. this could be used to get your sound
just right , or you could try to, say, emulate a Rickenbacker with your jazz bass. At its' most extreme you could have each pickup heavily affected by peaking resonance on both high and low pass filters, with a bump or scoop in the mids. At its simplest youd have 2 buffered pickups that you can blend together actively.
The mid section is interesting in that it is switchable between functioning as a parametric mid and as a Band pass, sharing the same state-variable filter.
The high and low pass are sallen-key 2nd-order types, with resonance (q?) from peaking to very sub-bessell. still working out how far in each direction.**
For some of these usages, might I suggest a FET as a voltage controlled resistor?
I don't understand why the vactrol is in there. I have a project on the bench which I hope to finish one day... Which has standard pot as encoder, into arduino and digital pot out, in my case the standard pot sets the rate of a wah pot curve which is output through the digital pot which lies in circuit.
If I ever get this one off th bench it may be the first in a few experiments with digi pots.
I bought the arduino mini or something with seperate USB board. Little bit cheaper but footprint is nice and small. In future I would buy just the chip and use the board I have to program that. Leaving the chip in circuit somewhere.
Two thoughts.
1. This is kinda what digipots are designed to do, so I think the vactrols will just lead you down the rabit hole - It's not easy to properly fake a potentiometer, as you have to have one resistance proportionally decrease while another increases.
Before we worry more about that,
2. Have you breadboard this (with all the pots) to get some idea of whether you actually need anywhere near all this control? You might be able to get away with a bunch of trimmers, and/or external switches.
Quote from: snarblinge on January 26, 2015, 02:51:09 AMI don't understand why vactrol is in.there
I had been getting the impression through initial research that digipots were a bit of a bummer for audio.. Finicky about signal level etc... Id be happy enough if the answer there is 'no' :)
To expand/ clarify, the become V.C. Resistors and no audio goes through the pots
Quote from: samhay on January 26, 2015, 04:45:31 AMTwo thoughts.
1. This is kinda what digipots are designed to do, so I think the vactrols will just lead you down the rabit hole - It's not easy to properly fake a potentiometer, as you have to have one resistance proportionally decrease while another increases.
Before we worry more about that,
2. Have you breadboard this (with all the pots) to get some idea of whether you actually need anywhere near all this control? You might be able to get away with a bunch of trimmers, and/or external switches.
1- it seems like a pain but it seems ... Understandable? Two vac biased to the same range being affected by the same (dc) signal of opposite phase
2- well I don't NEED any of the pots :p but really the flexibility is the whole point, and I'm just not the type to set a preset at home and assume that it will be perfect for my next gig .. Though i guess I'm 'pickup emulating' so it makes sense In a way. A few pots could be switches but that's the same problem anyway..
Quote from: Eddododo on January 26, 2015, 06:02:44 AM
I had been getting the impression through initial research that digipots were a bit of a bummer for audio.. Finicky about signal level etc... Id be happy enough if the answer there is 'no' :)
Fair point - the headroom will be limited to the digipots supply voltage and it looks like the through hole options are getting limited, so you might struggle to find parts that can take 9V. You could re-scale the circuit to run everything on e.g. +5V and use rail-to-rail op-amps.
Hmm that gets a little far off-message for me... Hell my basses all run at +18, and i was planning on +-12 or so in the 'unit' for noise floor and the headroom for peaking filters.. I disliked it at 9+ even.. But 5v??
I guess i didn't mention this but Im also eyeballing this to be able to drive my power amp without another pre.. So supply voltage is either important or more important
Have you considered using a multiplying DAC like a DAC0808 or DAC1208? The audio input becomes the reference voltage and the DAC multiplies by a fraction of 0/256 to 255/256 for a DAC08 or 0/4096 to 4095/4096 for a DAC1208. The digital inputs can be controlled by a binary counter or a PIC - you don't need anything as complicated as an Arduino although you could use it to calculate the multiplier as a decimal fraction. In fact, you could use ordinary 74HC192 up/down counters and a bit of random logic and avoid programming altogether.
The data sheet is here:
http://www.ti.com/lit/ds/symlink/dac1208.pdf
Edd:
1) You might consider using rotary encoders for your dials. Easy for a microcontroller to determine its position.
2) If you are still considering what microcontroller to use, research using PICs. The PIClist is a web site that has huge libraries of prewritten and pretested microcontroller code (written for PICs).
You could use Vactrols and have the LED's running from an Arduino's PWM outputs. Uno has 6 PWM outs. It also has 6 analog inputs to read 6 pots. Inside the Arduino is an eeprom to store presets in.
QuoteYou could use Vactrols and have the LED's running from an Arduino's PWM outputs.
Yep...
^ very cool...
i bit the bullet and just bought an arduino uno.....hence the old thread search..
but haven't a clue about using it at all, total utter noob with this stuff...but for a fiver i thought why not have a dabble :)..
should come in a few days,
any tips/links/cool audio/midi projects?....
the midi side of it interests me, especially building
midi drum stuff..ideally i'd like to make a basic midi drum brain for use in a DAW/triggering ezdrummer/percussion etc
and make my own piezo/pads/drums..
i'm guessing for the audio stuff you just need the usual buffer in/out setup with arduino between?...
as i said, total noob...so any advice is welcome.. 8)
Quote from: samhay on January 26, 2015, 06:53:35 AM
Quote from: Eddododo on January 26, 2015, 06:02:44 AM
I had been getting the impression through initial research that digipots were a bit of a bummer for audio.. Finicky about signal level etc... Id be happy enough if the answer there is 'no' :)
Fair point - the headroom will be limited to the digipots supply voltage and it looks like the through hole options are getting limited, so you might struggle to find parts that can take 9V. You could re-scale the circuit to run everything on e.g. +5V and use rail-to-rail op-amps.
I have a circuit layout I've been working on for an AVR controlled preset interface using Analog Digital digipots. Haven't procured the digipots yet to try out my design, but they have the broadest selection... although most are surface mount. However, the one I was most interested in (AD5242 dual channel 1Mohm resistance, i2c interface) only supports +5.5V supply. To get 16.5V supply support, we're limited to 200kohm. I'm sure opamps or companders could manage signal level, but that's a lot more circuitry.
There are high voltage digipots available:
http://nl.mouser.com/new/semiconductors/digital-potentiometer-ics/microchip-mcp41hvx1-potentiometers/n-4c498Z20ryhm
Quote from: ~arph on December 03, 2015, 08:02:44 AM
There are high voltage digipots available:
http://nl.mouser.com/new/semiconductors/digital-potentiometer-ics/microchip-mcp41hvx1-potentiometers/n-4c498Z20ryhm
Would be great if they came out with dual HV chips, i2c interface and 1Mohm range. I haven't experimented yet, but I suspect using a voltage divider to scale down signal before a 5V digipot may have undesireable effects for particular pedals/controls. Probably okay for LFOs but not sure about the added resistance for gain and tone controls.
Quote from: ~arph on December 03, 2015, 08:02:44 AM
There are high voltage digipots available:
http://nl.mouser.com/new/semiconductors/digital-potentiometer-ics/microchip-mcp41hvx1-potentiometers/n-4c498Z20ryhm
Those look very nice, but do not appear to be available through hole.
It's new.. I don't expect new products to be available in through hole anymore. I think we need to bite the bullet and find ways to handle these tiny packages
Quote from: ~arph on December 03, 2015, 03:42:07 PM
It's new.. I don't expect new products to be available in through hole anymore. I think we need to bite the bullet and find ways to handle these tiny packages
Adapter boards are a cool way to use SMD, and have them as modular plug-ins on a through hole board:
http://www.futurlec.com/SMD_Adapters.shtml
I plan on trying out some SMD soldering using a toaster oven:
http://www.freetronics.com.au/pages/surface-mount-soldering-with-a-toaster-oven#.VmCt3berTyM
Yeah, adapterboards are essential as we like to breadboard our stuff first ( I do ) but you still need the skill to solder the chip to the adapterboard. So there is no point in using adapter boards in final pcb designs
Quotei bit the bullet and just bought an arduino uno.....hence the old thread search..
[...]
any tips/links/cool audio/midi projects?....
http://wiki.openmusiclabs.com/wiki/StompShield (http://wiki.openmusiclabs.com/wiki/StompShield)
http://bleeplabs.com/store/nebulophone/ (http://bleeplabs.com/store/nebulophone/)
did this with some copper tape on the "fretboard" of an old
pipa I had and attached a metal bridge wired to the trigger, for a key-tar kind of thing
https://www.sparkfun.com/products/10587 (https://www.sparkfun.com/products/10587)
cheers gary, nice one,
i had midi notes out of it into my proteus 2000 last night...a good start.. 8)
i found a nice simple 6 pad/piezo trigger for midi drums (with velocity sensing)
and just got some piezos to play with...looks like fun..
the arduino mega looks really cool with 16 possible pads...excellent. 8)
i have a nanopad2 with 16 pads which is great , but i really want something i can whack/bigger pads etc.. :)
anyway, i'll have a crack at this today..(schematic @ 2:24.)
https://www.youtube.com/watch?v=vi-w_WqJjzQ
i also read that i could use a multiplexer 4051 to expand the inputs for more drums, so i have 2 of those handy now too..but i may just get the arduino mega for 16...hmmmm..
anyway, been looking at various projects, loads of possibilities, nifty stuff
but haven't a clue with the code lark , ( apart from tinkering with ready made values ;))
also got a LCD DISPLAY to write abusive stuff on too... ;D
>It's new.. I don't expect new products to be available in through hole anymore. I think we need to bite the bullet and find ways to handle these tiny packages
>Yeah, adapterboards are essential as we like to breadboard our stuff first ( I do ) ...
I don't expect many new chips to be through hole, but I thought I would mention it seeing as it may provide further difficulties for the OP (and others). In general I don't mind SMD, but it is a PITA to have to get the soldering iron out before you can play on the breadboard, so I tend to try to find TH alternatives when I can.
Quotebut it is a PITA to have to get the soldering iron out before you can play on the breadboard
that's really the only thing that scares me about SMDs. i imagine there will soon be many creative solutions:
(http://homepages.paradise.net.nz/bhabbott/smd_adapt/open.jpg) (http://homepages.paradise.net.nz/bhabbott/smd_adapt.html)
(http://homepages.paradise.net.nz/bhabbott/smd_adapt/closed.jpg) (http://homepages.paradise.net.nz/bhabbott/smd_adapt.html)
Very cool! reminds me of a pcb test jig
Apologies for pulling up this old thread, but best place I thought, also wouldn't mind an update on where anyone got to, mine is still on the bench
Considering having a play with one of these, I'm sure fun can be had
http://www.oddwires.com/pt2322-6-channel-audio-processor-ic/ (http://www.oddwires.com/pt2322-6-channel-audio-processor-ic/)
http://oddwires.blogspot.co.nz/2012/07/using-arduino-pt2322-library-for-audio.html (http://oddwires.blogspot.co.nz/2012/07/using-arduino-pt2322-library-for-audio.html)
If you want to use digitally controlled pots without driving yourself crazy with SMD smaller than SOICs,
the X9C104 is still available in 8-pin DIP and SOIC packages - you might have to hunt for the DIP ones, but a SOIC-packaged part is sold mounted on a 8-pin "DIP" pcb with a few onboard components (capacitors) from Sparkfun and on eBay. The only supply voltage is +5volts, but the signal range is +/- 5 volts (i.e., a 10 volt signal range if you bias it at Vcc/2). That is less than a 9 volt power supply, so they will work without vactrols or other workarounds.
In case you are wondering how Intersil got a +/- 5v signal range with a 5v power supply, they use an internal charge pump to bias the "wiper" switches.
mr coffee
There's another possibility which no-one mentioned originally, which is using CMOS switches controlled by a PWM waveform as a pot. There are plenty of PWM phaser designs around here that use a single switch as variable resistor, but it's just as possible to set up a pair of switches to make a complete potentiometer. The two switches are fed with inverted PWM signals.
This kind of thing used to be a pain to do (witness the hideous mess of LFO+PWM circuitry in PWM phaser pedals) but with AVRs/PIC/arduinos it becomes many times easier and uses far less parts.
Tom
Quote from: ElectricDruid on September 07, 2017, 04:54:13 PM
There's another possibility which no-one mentioned originally, which is using CMOS switches controlled by a PWM waveform as a pot. There are plenty of PWM phaser designs around here that use a single switch as variable resistor, but it's just as possible to set up a pair of switches to make a complete potentiometer. The two switches are fed with inverted PWM signals.
This kind of thing used to be a pain to do (witness the hideous mess of LFO+PWM circuitry in PWM phaser pedals) but with AVRs/PIC/arduinos it becomes many times easier and uses far less parts.
Tom
I like the sound of this, but I've never wrapped my head around PWM applications... I guess it's time I do
The basic principle is simple enough to understand. The switch has an on resistance and and an off resistance (which you'd often tweak with further external resistors) and varying the duty cycle gives you an "average" resistance which is between those two limits. So with a narrow 5% pulse wave, you're very close to off all the time, and you'll get only a shade less than the off resistance. With an 80% pulse wave, you're switched on 4/5ths of the time, so the resistance goes way down almost to the On resistance.
The "average" part requires that the PWM frequency is sufficiently higher than any signal that you might feed through the switch, otherwise you'd just have built an OTT chopper tremolo!
HTH,
Tom
PWM is more trouble than DPOTS because of the details of filtering the modulation frequency back out without turning into audible noise.
If you want to investigate PWM, search for INNOVONICS schematics. They did a compressor for radio stations around the world without any unobatanium parts that functioned very well.
mr coffee