|
|
Post by feijai on Oct 22, 2023 15:28:40 GMT
I have three sources of quantized CV for notes: CV out from my Akai MPK Plus when playing notes, CV from the MASTER via MIDI, and output from the QUANTIZER. And all three of them have different CV tracking.
Here's hoping it's just a linear difference!
I cannot adjust the CV out on the MPK. But the quantizer and the master have trimpots in the back. Unfortunately I have no idea what they do. Does anyone know? Lacking an oscilloscope I am hesitant to start screwing with them, especially when one of the master trimpots says "5V Adj".
Any help? Frustrated.
|
|
|
|
Post by feijai on Oct 22, 2023 17:05:59 GMT
Some more experimentation. It looks like the Quantizer and the external CV are more or less matching. So I will assume that the external CV from the MPK Plus is accurate. (Note: I have a MASTER I/O R2). So: - The MIDI CV doesn't quite track with the Quantizer and external CV. It's close enough for government work, but not amazing.
- The MIDI CV stops about halfway through the final octave, whereas the external CV goes clear through the octave. I can imagine two possibilities. (a) There is a bug/misfeature in the MIDI CV code which stops at about 4.5 octaves rather than going the full 5. (b) The MASTER isn't tuned to reach 5V.
- I've noted before that the Quantizer unfortunately appears to only have a 0-4V range. But my Quantizer doesn't go to the end of 4V: it stops one semitone before 4V. I can imagine to possibilities here too. (a) The Quantizer isn't trimmed to reach 4V or (b) The code just goes there and stops.
The problem is that there are more parameters here than there are trimpots to toy with. :-( The Master has two tripots, one labelled "5V Adj" and the other labeled "CV Adj". The Quantizer has one unlabelled. What I don't know is whether these trimpots *stretch* (multiply) values, *transpose* (add to) them, or *limit* them. And what 5V Adj does I don't know exactly... Really wish this information was in the wiki. Time to get out the multimeter.
|
|
|
|
Post by feijai on Oct 22, 2023 18:10:00 GMT
Also this is to be expected I guess given 5V but:
- 0V CV output from the MPK is (of course) MIDI note 0 (C0). But 0V CV output on the MASTER I/O is MIDI Note 24 (C2). Argh.
|
|
|
|
Post by solipsistnation on Oct 22, 2023 18:59:35 GMT
The problem is that there are more parameters here than there are trimpots to toy with. :-( The Master has two tripots, one labelled "5V Adj" and the other labeled "CV Adj". The Quantizer has one unlabelled. What I don't know is whether these trimpots *stretch* (multiply) values, *transpose* (add to) them, or *limit* them. And what 5V Adj does I don't know exactly... Really wish this information was in the wiki. Time to get out the multimeter.
I believe the 5V trimmer lets you adjust the 5V out to be actually 5V. I am also pretty sure there were significant updates to the MIDI code in the newer master modules. |
|
|
|
Post by feijai on Oct 22, 2023 19:12:24 GMT
So if the 5V adjust just tweaks what 5V is on the ribbon, I presume you can (but shouldn't) push it to higher values?
Does anyone know what the CV Adj trimmer is? Does it stretch (multiply) the CV values for MIDI notes?
|
|
|
|
Post by robertlanger on Oct 22, 2023 19:47:18 GMT
So if the 5V adjust just tweaks what 5V is on the ribbon, I presume you can (but shouldn't) push it to higher values?
Does anyone know what the CV Adj trimmer is? Does it stretch (multiply) the CV values for MIDI notes?
Yes, 5V should be roughly precise. The CV Adj. trimmer on MASTER adjusts the tracking, yes. The MASTER starts at MIDI note 24 for 0V and then upwards; and, yes, it cannot reach full 5V because this is the supply voltage. Electronic circuitry usually needs some headroom between signals and supply lines (although this has improved a lot with the modern rail-to-rail opamps, that go almost the full supply range. |
|
|
|
Post by feijai on Oct 22, 2023 20:07:29 GMT
Yes, 5V should be roughly precise I'll check tomorrow with a multimeter. If it's not at 5V, I presume I can adjust the 5V Adj trimmer? Okay, I'll try to get that to match the incoming CV and Quantizer results more closely. Okay, so we'll chalk that down as a necessary feature. |
|
|
|
Post by feijai on Oct 23, 2023 11:25:03 GMT
Checking with the multimeter, my R2 MASTER read 5.01V, very occasionally dropping to 5.00V. A quarter turn counterclockwise on the 5V ADJ trimmer pulled it firmly to 5.00V.
Question: should I have kept it at 5.01V? Would it be pulled to 5.00V under load, and so now it'll get pulled to, I dunno, 4.98? Or does it not really matter?
Will check the quantization of the MASTER in a while.
|
|
|
|
Post by robertlanger on Oct 23, 2023 14:50:18 GMT
Checking with the multimeter, my R2 MASTER read 5.01V, very occasionally dropping to 5.00V. A quarter turn counterclockwise on the 5V ADJ trimmer pulled it firmly to 5.00V.
Question: should I have kept it at 5.01V? Would it be pulled to 5.00V under load, and so now it'll get pulled to, I dunno, 4.98? Or does it not really matter?
Will check the quantization of the MASTER in a while.
This high precision is not necessary vor the supply voltage; as long it is between 4.8 and 5.2 volts, everything is fine! This is still a legacy from the early days, where some functionality relied on a more precise supply voltage, but this is of no concern now, |
|
|
|
Post by feijai on Oct 23, 2023 19:00:31 GMT
Some more analysis tonight.
The minimum (notionally 0V) position of the quantizer, Master I/O over MIDI, and external CV from the Akai MPK Mini Plus, are all a bit different. I'd say that the Quantizer and Akai differ by about 4 cents, and the Master I/O deviates by about 15 cents. This isn't a major issue if you can tune your VCO, but for modules with fixed tunings it could be annoying. Additionally in the top octave the Master I/O starts deviating and going flat ultimately by about 24 cents at the top C. [Can't tell what the Quantizer would do since it's 4 octaves].
Mind you, I have an R2, and as I understand it the R4 has better MIDI.
|
|
