Guitar string processor?
Mickster
Posts: 2,693
in Propeller 2
Hex pickup (one sensor per string).
Sampling: 8KHz
I need to sample the frequency, modify it and output the modified signal with minimal latency.
Would the P2 be up to this?
Sampling: 8KHz
I need to sample the frequency, modify it and output the modified signal with minimal latency.
Would the P2 be up to this?
Comments
https://www.roland.com/us/products/gk-3/
I had a Godin with that kind of pickup, but I hated the 13 pin interface.
Jon,
What MIDI connector was Cavin using? 5 or 13 pin.
I just sold my Casio MG-510 recently that had the only 5 pin standard MIDI connector that I know of.
https://www.ebay.com/itm/352887871058
> Would the P2 be up to this?
Without a doubt... 6 strings @ 8 kHz and realtime MIDI out shouldn't make the P2 sweet using a single cog in PASM . Goertzel, asynchronous UART, and ADC on every pin is available in hardware. This would actually be a very good demonstration of what the P2 can do using a single cog. I think you could go a lot higher than 8 kHz for better precision.
As I recall, 13. I don't think Kiesel Guitars makes those anymore.
That horrible Auto tune that we hear on every new pop song? Well the big name is Antares.
Well they did the same for guitar. I have 3 of these things and absolutely love them.
The problem is that the one developer retired and so they killed the product.
The strings might be perfectly tuned but any pressure on the fret and the note goes slightly sharp. The processor figures what the frequency is supposed to be and corrects it.
I can also strum all strings open, followed by a button press and the processor compensates for any out-of-tune strings.
The possibilities are endless; one can be playing in standard tuning and part way through the song, switch to an open tuning and kick-in with the slide.
I didn't think for a minute that I had a critical ear for this stuff but it's almost painful to go back to a regular guitar because perfect intonation is next to impossible to achieve at any price.
So, analog in, analog out.
I download it years ago.
Must research the source.
The 8KHz was a starting point because this is the sampling rate of the Antares.
But if I understand correctly, 44.1KHz is required to cover the full range of human hearing but a guitar? Aren't we talking more like 1.2KHz and therefore a Nyquist of ~2.5KHz?
For acoustic, 12 to 16khz minimums, for that "open sound", scrapes, touches, knocks on the body and strings.
Just the range of fundamental sounds can hit 2khz, fwiw.
Frequency, not sample rates.
Isn't that more for synthetic reproduction of string plucking (I had to go read-up)
This is the Peavey guitar with the integrated Antares Auto-tune.
Yeah, Tronical. I might stick one on my Telecaster. Not as good as Auto-tune though because you can't switch on-the-fly during a song and it does nothing for bad intonation or correct for finger pressure making the notes sharp. Nor does it do the other cool stuff like virtual-capo, string doubling, pickup emulation, etc.
"Daisy is an embedded platform for music. It features everything you need for creating high fidelity audio hardware devices. Just plug in a USB cable and start making sound! No soldering required.
Daisy features two channels of line level audio IO on-board, thanks to its high fidelity stereo audio codec(AKM) with up to 24-bit, 192kHz. Adding additional channels of audio is easy using standard digital audio protocols such as TDM, I2S, PDM, and S/PDIF which are broken out to the pin headers.
There is full support for USB MIDI IN and OUT through its onboard micro USB port and the USB pins on the header bank. It also features UART pins for connecting MIDI through 5 pin DIN, or TRS cables.
USB and Connectivity
With full OTG-support as host and device on the built-in micro USB port, along with additional pins for a second port, the Daisy can become any USB device your heart desires. Build an audio interface, MIDI controller, or sample player! On top of that, the built-in micro USB can also be used for powering, programming and debugging the Daisy.
There are 32 total GPIO pins which can be configured as standard GPIO or one of several alternate functions including 16-bit Analog to Digital Converters(x12), 12-bit Digital to Analog Converters(x2), SD Card interfaces, PWM outputs, and various serial protocols for connecting to external sensors and devices including SPI, UART, I2S, and I2C.
In addition to being powered through the onboard micro USB port, Daisy can be powered through a dedicated VIN pin on the header bank. It has an extremely wide input range of 4V to 17V and current consumption is low enough that you can even power it from a battery!"
https://www.kickstarter.com/projects/electro-smith/daisy-an-embedded-platform-for-music/description
How many features of this Daisy module can the P2 do? It has a C++ library
If the P2 can't do it you can also just interface a p2 to a Daisy
I'll check it out, always interested in digital audio. I have lots of this stuff and in fact I liked one particular processor so much that I now have six identical units.
But this is not what I'm Prop-osing
Guitar players are constantly having to re-tune the instrument....it can be a pain during a performance. Furthermore, not all tunes are played in standard tuning. If I want to sound like Keith Richards when playing Brown Sugar, for example, I need to tune to "open G" tuning.
Many performers carry multiple guitars for this reason.
The horrible Auto-tune that we hear way too much of on modern music vocals? Well the big name is Antares. Antares got together with Peavey and built a guitar using similar technology. There is a piezo pick up for each string. The string tension (tuning) can be way off but the MCU compensates for this and outputs the corrected frequency. This is not pitch-to-MIDI conversion.
This also means that I can instantly switch to an alternate tuning.
The developer retired and so the product was discontinued....very few guitarists were even aware of its existence.
This a very interesting project. I think the P2 can shine here, because it should be possible to connect 6 independent 24bit adcs.
I think, that the pitch shifting is not the most difficult part. It could be done using different sample rates for writing and reading of a short buffer together with some interpolation.
Finding the 6channel piezo hardware, doing a really good tuner to find the deviation will be more difficult.
The most difficult part will be to get a real fine magnetic pickup sound from the corrected piezo signal. Together with the frequency response there is completely different dynamic behavior. I had to learn, that the pickup is the really important part to make the specific sound of a guitar. (forget "tone wood")
Are there single string magnetic pickups somewhere?
https://www.lrbaggs.com/pickups/electric-guitar-acoustic-pickup
On the pickup subject... I would point out that Chip's 'Fun with Goertzel' looks like it runs at a 1 khz sample rate, and that appears to be randomly chosen. I have done no math on this, and it is still half-baked.. but the sample rate can probably run MUCH faster... The strings are metal, why not try to do a pickup that can be etched on a PC board? Maybe even end up with something superior... You would only need 1/2 of the demo per string.
The tech docs show a connection from a summing board to one output. I guess you could pull a signal from each pickup since they show 6 wires.
Welcome to the forum!
There are quite a few available from Japan for ridiculous money but occasionally, they come up locally.
Simply remove the existing controller board and replace it with the P2 development unit.
If the project is a non-starter, replace the original board and it can be re-sold.
Here's what happened: The base model has limited firmware and the guitar itself is nothing fancy (Peavey Predator).
Included with the base firmware
Auto-tune (for me, this alone is worth the cost).
Another cool feature is "solid tune", meaning that any note played anywhere on the fretboard is perfect. This is impossible to achieve with standard guitars, no matter the price. Even with the best intonation calibration, the fact that one exerts pressure on the string/fret, causes the note to go sharp. Not with this system.
Some of the more common alternate tunings (open-G, open-D, Drop-D, DADGAD and more)
Optional firmware expansion packs
Acoustic emulation
12-string emulation
Various pick up emulation
Virtual capo up (no capo required)
Virtual capo down (impossible on conventional guitar)
Any tuning whatsoever
..... And many other possibilities.
Unfortunately the expansion packs were pretty pricey when at the end of the day, the physical guitar is only a cheap Peavey Raptor or Predator or something.
This wasn't received too well.
https://www.ebay.com/itm/Peavey-AT-200-Auto-Tune-Guitar-Auto-Tune-Standard-Alternate-Tuning/164111033080?hash=item2635c7a2f8:g:dZIAAOSwnm1eYEw1
Edit: Note: To avoid confusion; this guitar is also equipped with regular humbucker pick ups. The piezos are part of the bridge. Therefore it can be used as a conventional electric, albeit without Auto-tune.
Another possibility is the Line6 Variax.
These also have the built-in piezo sensors and their own electronics. The Variax processor is more about emulating other guitars and does a very good job but doesn't do Auto-tune.
The Variax 300 should be available on ebay for a couple of hundred.