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Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
hey, to one of you who has a bit of experience with midi controllers: what is the maximum safe number of channels to play on one drsstc(1kw if it helps). i know that it also depends on the song, but would you play three or four channels if it where a really deep song and one or two if it where a high pitched loud song?
Registered Member #1134
Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351
I have been playing with a MIDI arduino DRSSTC controller, I built back in 2009, so I have gotten to know the ins and outs quite well.
I regularly play 2 notes at any one time per coil, and consider this to be a safe maximum.
Ultimately the answer lies in pulse width.
The issue with 3 or more notes I have found, is that pulses of different frequency will at some point overlap (it is easier to see what I mean on an oscilloscope.), meaning, if your pulse width is set to say 50us, every now and then you may get a contiguous 150us on time. Of course if your pulse width is set to something a little more gutsy, say 200us, then suddenly you find yourself in a situation where the coil is on for 600us!
The solution is two notes or less per coil, and 2 coils or more, OR turn down the pulse width, and stick to lower notes.
I find a 2 coil, four note polyphony, to be very adequate for most midi tunes.
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
I have experienced that same problem as mentioned above, here is my solution.
So say you have your pulse width set at 100uS if one note is playing then it's pulse width will be 100uS. Now you want to play two notes I resize the pulse width so that both notes have a pulse width that is = original width / sqrt(number of notes playing)
So in this case 70.7uS = 100uS / sqrt(2) I have found that just dividing by number of notes playing doesn't work that well and tends to make the sparks smaller than they should be. Notes that overlap are ORed together, but with the equation mentioned above even overlapping notes don't result in massive pulses. On top of this I also scale back the pulse width as I go up in frequency using a square root equation.
The two things that will limit number of notes is power draw from the wall and heating of the driver transistors, peak current isn't as much of an issue. This is assuming a DR is the coil in question. I have done 3 and 4 notes before but any more than 3 just starts to sounds cluttered.
Here is an example of 3 note poly using this method on one of my smaller DRs
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
ah. i see. i don't have much experience in making music or using midi, so i have been trying to simplify midi files in fl studios down to the fewest possible channels. i guess i will have to try to build a controller that does as you say.
thanks, you where just the person i was hoping would answer too
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max drsstc midi channels
