So far, we've bee concentrating on reading the neck of our MIDI bass, by running a resistor ladder up the fingerboard, and shorting one end to ground to read which string is pressing against which fret.
This video popped up on Google+ this morning - it's a follow-up to Jeri Ellsworth's C64 bass video taken at the MakerFaire earlier this year.
https://www.youtube.com/watch?v=_kDhpFaf4EY
We haven't really invested a lot of time into reading when each string is actually plucked, but this video has a great idea in it - simply put a custom shaped piezo in contact between each string and the bridge. It's so simple, it's genius!
Showing posts with label bass. Show all posts
Showing posts with label bass. Show all posts
Monday, July 9, 2012
Thursday, June 21, 2012
MIDI bass frets
There's something not quite right with our laser printer.
It seems to be printing bitmaps at about 95% of full size.
We made up a couple of frets for our MIDI bass and allowed a generous border around each piece (so it can be cut/sanded/filed to an exact fit after being mounted onto the guitar neck)
The only thing is, that even allowing for this relatively large border around each piece, they are only just the right size to go on the fingerboard.
Here are some surface-mount resistors connected onto each section of fingerboard. These boards will be mounted face down onto the neck. The pads on the edges of each board will be connected by strips of copper tape, running under one, over the top of the (plastic, non-conductive) fret between the two, and joining the pads on the next section of fingerboard. By doing this, we can create a resistor ladder for each string along the length of the guitar neck.
It seems to be printing bitmaps at about 95% of full size.
We made up a couple of frets for our MIDI bass and allowed a generous border around each piece (so it can be cut/sanded/filed to an exact fit after being mounted onto the guitar neck)
The only thing is, that even allowing for this relatively large border around each piece, they are only just the right size to go on the fingerboard.
Here are some surface-mount resistors connected onto each section of fingerboard. These boards will be mounted face down onto the neck. The pads on the edges of each board will be connected by strips of copper tape, running under one, over the top of the (plastic, non-conductive) fret between the two, and joining the pads on the next section of fingerboard. By doing this, we can create a resistor ladder for each string along the length of the guitar neck.
Monday, June 11, 2012
MIDI bass frets - exploded view
Here's a quick diagram showing how our MIDI bass fret system works.
We've already removed the fingerboard off our bass guitar, and plan to replace it entirely with home-made circuit boards (each section between two frets is a separate PCB).
The pcbs are fixed to the guitar neck, screwed down on top of some sections of rubber padding. This serves two purposes. The first thing it does is create a "pocket" for the surface-mount electronics on the PCB to comfortably fit without getting damaged. Secondly, it pushes back against the board mounted upon it.
This allows us to use copper table, placed over the fret (each fret is a piece of laser-cut acrylic) to create a single, continuous circuit up the entire length of the neck.
For each guitar string, the circuit is simply a resistor and LED, so each PCB has four resistors and four LEDs (one for each string)
We've already removed the fingerboard off our bass guitar, and plan to replace it entirely with home-made circuit boards (each section between two frets is a separate PCB).
The pcbs are fixed to the guitar neck, screwed down on top of some sections of rubber padding. This serves two purposes. The first thing it does is create a "pocket" for the surface-mount electronics on the PCB to comfortably fit without getting damaged. Secondly, it pushes back against the board mounted upon it.
This allows us to use copper table, placed over the fret (each fret is a piece of laser-cut acrylic) to create a single, continuous circuit up the entire length of the neck.
For each guitar string, the circuit is simply a resistor and LED, so each PCB has four resistors and four LEDs (one for each string)
Saturday, June 9, 2012
MIDI bass fret setup
We're replacing the entire fingerboard for our MIDI bass, and replacing it with a number of PCB sections. We're basically creating a resistor ladder on the underside of the fingerboard, for each string on the guitar. The idea is that the resistor ladder creates a voltage divider and we take an analogue input from the resistor network into the PIC microcontroller
If all the strings are connected to ground, and all the frets on the fingerboard are connected at different points along the resistor ladder, we should be able to tell which fret the string is being pressed against, and therefore which note to play.
In the example above, if the (grounded) string was held on the second fret, the total resistance between the nut end of the board and the input pin would be quite high - so the voltage divider creates a high voltage on the input pin.
But if the player holds the (grounded) string on, say, the 18th fret, the 5v going through the resistor network goes through fewer resistors between the input pin and ground, causing the voltage on the input pin to drop. With clever use of resistor values, we should be able to create a look-up table in firmware such that we know instantly which string is being held against which fret. No more latency issues trying to sample and decode the frequencies that the strings are vibrating at!
If all the strings are connected to ground, and all the frets on the fingerboard are connected at different points along the resistor ladder, we should be able to tell which fret the string is being pressed against, and therefore which note to play.
In the example above, if the (grounded) string was held on the second fret, the total resistance between the nut end of the board and the input pin would be quite high - so the voltage divider creates a high voltage on the input pin.
But if the player holds the (grounded) string on, say, the 18th fret, the 5v going through the resistor network goes through fewer resistors between the input pin and ground, causing the voltage on the input pin to drop. With clever use of resistor values, we should be able to create a look-up table in firmware such that we know instantly which string is being held against which fret. No more latency issues trying to sample and decode the frequencies that the strings are vibrating at!
Friday, June 8, 2012
MIDI bass instrument
As we haven't got everything quite to hand to finish off our multi-effect pedal circuit, and with Thursday being the regular BuildBrighton meet-up, we needed something else to work on. And, having access to a full equipped workshop with some really cool tools, it wasn't time to play about with resistors and microchips - we needed to do something BIG!
As we're working on some MIDI Arduino shields for an up-and-coming MIDI workshop, it made sense to work on a MIDI instrument. But exactly what?
We've already spent some time considering making a midi guitar - where the input from the strings against the frets is converted into a midi signal and fed into a synth. A few years we tried this, taking the audio output from the jack socket on the instrument, and analysing it to try to work out which note(s) were being played.
It turns out that this is very difficult.
To try to simplify things, we looked into making individual string pickups (so each string has it's own signal to analyse instead of trying to work out which chord is being played across all six strings!). This is exactly how the Roland's GK-3 "divided pickup" works. The signal from each string is sampled and an output value given to a different channel. The only problem with this approach is that there's a noticeable delay between plucking the string and the sound being played. It gets worse with lower notes and makes a bass guitar almost unplayable!
So we're back to using the contact of the strings against the frets as our signal, which removes the need to analyse the audio output. We started by:
Removing the traditional fingerboard from a bass guitar. This was quite easy (once we decided we'd never want to reuse the original fingerboard). Just plenty of heat from a hot gun, and some levering with a couple of screwdrivers.
It actually took three of us to do this! The neck was removed from the body and one person held it with one hand while hacking at it with a screwdriver with the other hand. The second person also levered away with a screwdriver, while the third waved the hot gun up and down the neck of the guitar. It took less than 10 minutes to remove the fingerboard!
(the scorch marks on the neck will be sanded out when we come to finish the instrument!)
With the fingerboard removed, it was time to design a replacement.
We're going to be making the replacement fingerboard from copper clad board, cut into sections, with an acrylic fret (3mm) between each one.
The first fret of the bass was measured as 46.5mm long.
Given that the length of a guitar string is exactly half one octave higher (i.e. the string length when the 12th fret is played is exactly half the string length of the open low E string) we came up with the following formula:
Length of next fret = length of previous fret / (2^ 1/12)
where 2^(1/12) is two to the power of one over twelve.
We made a cardboard template to try the idea out:
By the time we'd reached the end of the neck, we had 23 frets.
The original bass had only 22 so it looks like our original measurement on the first fret was a little out. However, it's still within a reasonable distance to recreate the original bass "feel" when playing.
Exact length isn't critical because we're never going to be playing the bass "acoustically" - our replacement frets will actually be switches, activated by the string being pressed against them. More details in the following post(s).....
As we're working on some MIDI Arduino shields for an up-and-coming MIDI workshop, it made sense to work on a MIDI instrument. But exactly what?
We've already spent some time considering making a midi guitar - where the input from the strings against the frets is converted into a midi signal and fed into a synth. A few years we tried this, taking the audio output from the jack socket on the instrument, and analysing it to try to work out which note(s) were being played.
It turns out that this is very difficult.
To try to simplify things, we looked into making individual string pickups (so each string has it's own signal to analyse instead of trying to work out which chord is being played across all six strings!). This is exactly how the Roland's GK-3 "divided pickup" works. The signal from each string is sampled and an output value given to a different channel. The only problem with this approach is that there's a noticeable delay between plucking the string and the sound being played. It gets worse with lower notes and makes a bass guitar almost unplayable!
So we're back to using the contact of the strings against the frets as our signal, which removes the need to analyse the audio output. We started by:
Removing the traditional fingerboard from a bass guitar. This was quite easy (once we decided we'd never want to reuse the original fingerboard). Just plenty of heat from a hot gun, and some levering with a couple of screwdrivers.
It actually took three of us to do this! The neck was removed from the body and one person held it with one hand while hacking at it with a screwdriver with the other hand. The second person also levered away with a screwdriver, while the third waved the hot gun up and down the neck of the guitar. It took less than 10 minutes to remove the fingerboard!
(the scorch marks on the neck will be sanded out when we come to finish the instrument!)
With the fingerboard removed, it was time to design a replacement.
We're going to be making the replacement fingerboard from copper clad board, cut into sections, with an acrylic fret (3mm) between each one.
The first fret of the bass was measured as 46.5mm long.
Given that the length of a guitar string is exactly half one octave higher (i.e. the string length when the 12th fret is played is exactly half the string length of the open low E string) we came up with the following formula:
Length of next fret = length of previous fret / (2^ 1/12)
where 2^(1/12) is two to the power of one over twelve.
We made a cardboard template to try the idea out:
By the time we'd reached the end of the neck, we had 23 frets.
The original bass had only 22 so it looks like our original measurement on the first fret was a little out. However, it's still within a reasonable distance to recreate the original bass "feel" when playing.
Exact length isn't critical because we're never going to be playing the bass "acoustically" - our replacement frets will actually be switches, activated by the string being pressed against them. More details in the following post(s).....
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