Millenium MPS-750

[anwe79]

Hi all

I got a Megadrum a few years back, with plans on making a DYI kit, but haven't had the time to follow through on that.
I did make a 3D printed mesh head that works quite well, but it's still just a prototype...
(Openscad code here if anyone has a 3d printer and wants to test:
https://github.com/anwe79/Pdrum.
Note: PLA will slowly creep under tension and deform, ABS works better.
I learned this the hard way...)

Anyhow, I really wanted to get back to drumming, so I just got a Millenium MPS-750 kit instead, and have started testing it with Megadrum.

Since technical information on this kit seems very scarce, I thought I would share what I have found out so far to help any fellow owners.

Overview:
4 dual piezo mesh heads.
Heads are side triggered, rim sensor is mounted in the center of the body below the head.
1 Piezo/switch/switch 3 zone ride (with choke).
2 Piezo/switch dual zone crashes (with choke).
1 single Piezo Hi Hat (no edge/choke).
1 rubber on metal single Piezo kick pad.
1 optical Hi Hat foot controller.
All parts have de-facto standard 1/4 inch "phone" sockets/jacks.
The supplied cable snake is quite short.
The module end is a DB-25 male (pin-out coming later).

Mesh heads:
Nothing special, but quite ok mesh heads.
Tip is head, ring is rim.
It would seem that it might be possible to make some modifications to swap the sensor functions,
to convert the heads to positional sensing, since the rim sensor is dead centered under the mesh head.
This is just speculation though...
The heads have an undocumented sensitivity trim pot, underneath on one of the body arms.

Cymbals:
"Yamaha-style", but with a catch. The resistor is 4.7 k, and on the bell, not the edge.
The crashes and ride have the same connector board internally, the crashes just leave the bell connector unconnected.
I haven't opened the hat yet, but I wouldn't be surprised if it used the same board with just the piezo connected.
They even have the 4.7 k resistor populated, so you might be able to hack a makeshift third zone into them.
I haven't got the bell working in Megadrum just yet, still need to figure out the proper settings.
Bow and edge works well. Having some issues with chokes getting stuck, but I suspect it's just a settings issue.
All cymbals have an undocumented sensitivity trim pot close to the jack.

Kick:
Nothing special, but quite acoustically noisy, and very rigid, so it transports the vibrations well down to the floor

Hi hat controller:
Optical controller based on ITR8307 sensor with a moving "mirror" (dull aluminum tape) mounted to the pedal..
Does give a continuosly variable current out, but I haven't yet got it to work well with Megadrum,
I only get any real response at the very end of travel after the pedal hits the stopping rubber.
Might be a settings issue, but I think the pedal may have been designed to work more as a switch, since the response is very nonlinear.
Physical or electrical hacking may be able to fix that though, to be investigated...
I made a rough reverse engineering of the circuit, the ITR8307 is basically used as the first stage of a darlington pair, can post a schematic if anyone is interested.

I'll get back later with a cable snake pin-out, and maybe some rough settings for Megadrum / Superior Drummer 2.
I hope this info might be useful for someone considering this kit.
Over all it's pretty good considering the low price.
The rack is fairly sturdy, even if the connecting parts are plastic they seem pretty durable.

If there are any more details you would like to find out, let me know, I'm not afraid to take things apart.

PS. I haven't tried the supplied module as a Midi controller yet. It seems ok for practice, sounds are what you'd expect in this price range, a bit drum-machiney, and triggering is ok but not stellar out of the box.

/Andreas

[airflamesred]

I'm sure some settings would be very useful; good post.

[anwe79]

Thanks for the encouragement,
I've got all 3 zones of the ride working fairly well tonight.
Since the resistor is swapped compared to a Yamaha, I had to swap Bell/Edge note locations in Megadrum.
(I tried just swapping thresholds, but i guess the code doesn't work that way)

However, the settings are a bit extreme at the moment (gain 8 with 145 high level on bow).
It just dawned on me that I think I forgot to replace the PS power jumper while leaving the PS board connected
(was verifying wiring and experimenting by bypassing the PS board),
which would probably pull the signals on the PS enabled inputs down extremely low (not sure).
Hope I haven't boogered anything on the PS board, but things seem to still work, so I'm not too worried.

Will get back with ride settings once I've reconnected the PS power and verified the settings still work (or I have readjusted them).

In the meantime, here is the pinout for the DB-25 connector on the MPS-750 module, and what I have it connected to on the MD ribbon cable:
(Pin numbers as seen from the solder side of a female connector, I think they are the same from both directions though)

1. Hi Hat tip, MD pin 35
2. Kick tip, MD pin 37
3. Hi Hat Controller tip, MD pin 38
4. Hi Hat Controller sleeve, MD pin 15/16 (ground)
5. Ride ring, MD pin 32
6. Crash 1 tip, MD pin 29
7. Crash 1 sleeve, MD pin 15/16 (ground)
8. Snare ring, MD pin 34
9. Tom 3 tip, MD pin 23
10. Tom 3 sleeve, MD pin 15/16 (ground)
11. Tom 2 ring, MD pin 26
12. Tom 1 tip, MD pin 27
13. Tom 1 sleeve, MD pin 15/16 (ground)
14. Hi Hat sleeve, MD pin 15/16 (ground)
15. Kick sleeve, MD pin 15/16 (ground)
16. Hi Hat Controller ring, MD pin 40
17. Ride tip, MD pin 31
18. Ride sleeve, MD pin 15/16 (ground)
19. Crash 1 ring, MD pin 30
20. Snare tip, MD pin 33
21. Snare sleeve, MD pin 15/16 (ground)
22. Tom 3 ring, MD pin 24
23. Tom 2 tip, MD pin 25
24. Tom 2 sleeve, MD pin 15/16 (ground)
25. Tom 1 ring, MD pin 28

Crash 2 is on a separate TRS cable, T=Bow, R=Edge, S=ground.

/Andreas

[airflamesred]

Thanks for the encouragement,
I've got all 3 zones of the ride working fairly well tonight.

Well, congratulations, I am impressed. Is/was it easy enough to do? I ask because A lot of people seem to struggle and I often wonder whether it's just, lazyness, not RTFM, or maybe the not plug and play is daunting?
Anyhow if you would like to share your settings or, better stil,l a procedure I suspect this will be very useful.

[stefan1982]

Thanks for the encouragement,
I've got all 3 zones of the ride working fairly well tonight.

Well, congratulations, I am impressed. Is/was it easy enough to do? I ask because A lot of people seem to struggle and I often wonder whether it's just, lazyness, not RTFM, or maybe the not plug and play is daunting?
Anyhow if you would like to share your settings or, better stil,l a procedure I suspect this will be very useful.

I don't think it's laziness.. To be honest, I think MDM is usability-wise a nightmare (don't get me wrong, I love MDM and respect Dmitri's work very much). Nothing is easy to grasp, or seems logical to understand.

I'm trying to get some configuration flowdiagrams together, for configuration of pads and cymbals. Which I hope, in the future could be converted into some new version of MDM with has some kind of configuration wizard for pads and cymbals.
Something like this would bring MegaDrum to a higher level usability-wise and could open up to a complete new audience.

[anwe79]

Well, I do have prior experience with similar stuff (audio electronics, programming, server configuration, that sort of stuff),
so I guess I may have a head start from the average user. That, and I spent most of the easter weekend trying to figure stuff out .

Configuration flow charts are a very good idea!
I've put together dot-file charts before, I'll see if I can make some for this as well.
I likely will have to start over with new values anyway, so putting together a guide from start to finish is not going to be a lot more extra work.
Some of the threshold stuff is tricky to get a grip on just from the text.
The documentation is pretty good and detailed, but you need to either read every detail, or know exactly what you can skip without missing something crucial.

Edit: Had to run to a meeting before.

There are also good bits of information that help a lot scattered around the forum, in videos, et.c.
But it takes a while to find it all and piece it together to get a good understanding of what's important, and what order is good to get going.

I've just repowered the PS board now, I'll see how I get along and post again later tonight.

Edit2: Sorry, scratch that, I got sidetracked with weird session management issues, will pick this up tomorrow instead.
BTW, PS power on or off doesn't seem to have affected ride signal strength at all. Maybe I misunderstood, and it's not on one of those inputs.

/Andreas

[anwe79]

I've played around some more tonight, but I can't quite get the hang of how to go back to "default" settings, to make a walk through for a complete setup.
Holding the right button down while powering on as suggested in a few posts I've seen only seems to get me into firmware update mode.
Loading from a slot that I haven't touched yet fails (seems fair, it might be garbage data).
Maybe it's as simple as turning off autoload config? Just thought of this, while posting, will try that next.
I'd prefer to have all defaults on every setting to make the walk through as accurate as possible.

Meanwhile, I've been playing with the HH controller to see if it can be used properly, but I think that's the first bad news so far.
The physical range of the controller seems to be way too small.
It's just the very last 7 or so mm of throw (inside the controller box) after the rubber stop is hit that gives any reading.
Looking at the data sheet of the sensor (http://www.everlight.com/file/ProductFi ... 24-TR8.pdf) this seems to make sense.

I can get a full dynamic range in that very small movement range after following these instructions:
viewtopic.php?f=4&t=1986#p21730

But since there is nut much response until you really lean on the pedal, it's pretty useless.
It's like having the full control range between sloppily closed and really tight on a physical Hi Hat.
I tried experimenting a bit with some shinier aluminum foil, and there was some slight improvement,
but not enough to make it usable as anything but an on/off switch.

Making the existing sensor give a usable throw by hacking the pedal mechanically is probably too complicated,
so I think I'm going to hack it with a hall sensor and magnet instead.
I'm just going to take some measurements first, to make sure I'm not missing something.
Perhaps I might get away with something as simple as putting a resistor across the output for an I/V stage.
If my reverse engineering attempt is accurate, I think the output is straight from a bjt, so it would be a current, not a voltage.

Anyhow, I'll try some more stuff and get back again when I get any results that are worth posting.

/Andreas

[dmitri]

Maybe it's as simple as turning off autoload config? Just thought of this, while posting, will try that next.

Yes, setting Autoload Conf to No will force it to load default settings on power up.

[airflamesred]

Good stuff Andreas, With regard to the default I'd just perhaps start from zero (Dmitri will probably know what the shipped default is) or there abouts. I think the important thing is how to get the value of 'B' rather than what 'A' was.
It would be great just to be able to load a preset for the pad/cymbal but both threshold and, more importantly, high level are also affected by playing style.

[anwe79]

Maybe it's as simple as turning off autoload config? Just thought of this, while posting, will try that next.

Yes, setting Autoload Conf to No will force it to load default settings on power up.

Thanks! That did the trick, one should always try the simplest things first of course .

I think the important thing is how to get the value of 'B' rather than what 'A' was.
It would be great just to be able to load a preset for the pad/cymbal but both threshold and, more importantly, high level are also affected by playing style.

Agreed, the exact settings will vary depending on lots of variables. Playing style and hardware is probably most important, but lots of other stuff as well, like mechanical setup, electrical noise, trim pot settings, part value variations, the list goes on and on. A preset will probably work fairly well for most with the exact same hardware, but may need some tweaking to get just right..

I'm trying to get some configuration flowdiagrams together, for configuration of pads and cymbals. Which I hope, in the future could be converted into some new version of MDM with has some kind of configuration wizard for pads and cymbals.
Something like this would bring MegaDrum to a higher level usability-wise and could open up to a complete new audience.

Agreed.
I don't want to steal your idea, but maybe we can start a new thread about this and collaborate?
I could start on something on my own, but it would be limited to the hardware I have available and my limited experience with Megadrum.
If we could collaborate I think the resulting guide would be so much better in the end.
Then, when we hopefully have a general "best practice" work flow nailed, this could possibly be turned into a configuration wizard.

It may need to be coupled with some in depth explanations about gains, thresholds, and similar concepts.
I would prefer to take the approach to assume as little as possible about the users prior knowledge.
If they already know the details, they can always skip ahead to the more interesting parts.

I've included a super simple mockup dot-file as an example and the svg graph it generates.
The language is pretty simple (although I always feel a bit intimidated by language grammars, they are just plain hard to read in my eyes );
http://www.graphviz.org/content/dot-language.

On linux with Graphviz installed, generating the svg is a simple as:

Code: Select all

dot -Tsvg Setup_overview.dot > Setup_overview.svg

I assume it's similar on other platforms, but as always YMMV.

The main advantage with dot files are that they are pretty easy to understand and only require a basic text editor + Graphviz,
and being text we can use a VCS to keep track of changes..
They can include hyperlinks, so the main graph could drill down into specific subgraphs, for example the routine to configure a specific pad type.
The downside is that the layout is auto-generated, so the output may not always be exactly what you expect or pretty.

Dmitri: I hope we are not stepping on your toes here.
The existing documentation is in my opinion pretty good already, it's just that it requires quite a bit of the reader to get started.
I think what we would try to achieve is to give the user some more "hand holding" to speed the process up a bit.

Let me know what you think.

Back to business, I have drums to (re)configure

Edit: SVGs aren't allowed, trying PNG instead.
/Andreas