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Music Easel touchplate logic errors
MUFF WIGGLER Forum Index -> Buchla, EMS & Serge Goto page 1, 2, 3, 4  Next [all]
Author Music Easel touchplate logic errors
slow_riot
I offered to help someone get to the bottom of this and my solution came up short. So I thought I would create a dedicated thread and see if anyone has any ideas.

The error has been reported as jumping octaves and other incorrect behaviour from the touchplate, which is allegedly cured by touching the body to the 0V common ("ground") pin.

My belief was that there was some kind of floating ground issue with the class II power, and with the body being at earth potential this would cause any logic referenced to 0V to give erroneous values. However my solution of earthing the Easel did not work. My next idea is that there is some kind of EMI susceptibility. The person who I had offered to help said that the issue was made better at home by removing dimmer circuits for lighting in their studio.

My concern with the make shift solution of an antistatic wrist strap is that if there is a fault on the 0V line in the soundsystem there is an unacceptable lethal danger. (Legally in a Class II non earthed device it is required that live voltage has at least 2 full insulations away from anything the user can be connected to, and with the makeshift solution this condition is absolutely not satisfied)
trax
Can you duplicate the problem at multiple locations under multiple power sources or does the issue just manifest itself at one location?
slow_riot
Multiple locations.

I think EMI might not be right, more likely noise on AC power lines?
Oxix52
I have always had this kind of issue with any kind of touch surface. I have used a Buchla 222e, Easel keyboards(2), Make Noise Rene, and 2 Make Noise Pressure Points. In my case, it happens when my Mitsubishi mini split air conditioner kicks in with heating or cooling. This doesn't happen in my house, only in my studio, which is a converted one-car garage. The solution for me, is to either hold on to a metal part on the system, or plug a cable in to the ground jack and hold on to the other end.
slow_riot
Oxix52 wrote:
I have always had this kind of issue with any kind of touch surface. I have used a Buchla 222e, Easel keyboards(2), Make Noise Rene, and 2 Make Noise Pressure Points. In my case, it happens when my Mitsubishi mini split air conditioner kicks in with heating or cooling. This doesn't happen in my house, only in my studio, which is a converted one-car garage. The solution for me, is to either hold on to a metal part on the system, or plug a cable in to the ground jack and hold on to the other end.


In that case it sounds like my initial belief about the cause of the issue was not so misplaced, maybe poor/non-existant earth is why my proposed solution of connecting "ground" banana connector to mains earth didn't work?

Or maybe some other equipment is messing with the Easel's 0V ?

Sorry, kinda talking out loud here, but hopefully can come up with a working solution that might benefit others...
shellfritsch
we've had this problem quite a bit with our easel. we often have to ground to the unit to get good accurate behavior. my wife has been shocked by it twice. scary.
Oxix52
shellfritsch wrote:
we've had this problem quite a bit with our easel. we often have to ground to the unit to get good accurate behavior. my wife has been shocked by it twice. scary.


That is really scary. I have never been shocked by anything. I have read of people with mixing boards that have touch-sensitive faders having similar problems. They seem to think it has something to do with being on a carpet or the kind of shoes one wears. I don't really know of such things. I just either hold the tip of a cable that is connected to the system or turn of my air conditioning to make my touch controllers work reliably. seriously, i just don't get it
Umcorps
No issues to report here. It's always worked as expected.

Since the start of the year, my Easel has been grounded permanently to a small Euro skiff via a banana cable to a CVGT1 converter. Ironically, this was to resolve bad earth issues arising from the skiffs uZeus power supply. Both units play nicely together when linked.

@ shellfritsch Being shocked by an instrument is not something that should ever happen. You need to unplug that sucker and get it out of your studio and into a repair shop asap before it kills someone.
slow_riot
Thanks for relating your experiences people.

Mark, it's quite likely that the Easel that shocked the user is the same as the one you are using. The fault is in the subtleties of the power supply in different working set ups. I would recommend providing a direct connection to earth.

I was given a link to this thread:

https://www.muffwiggler.com/forum/viewtopic.php?p=1727571&highlight=#1 727571

Which makes it sound like there are 2 mechanisms for erroneous behaviour, apart from needing earthing it sounds like the Easel is sensitive to voltage fluctuations on the AC power lines.
gddfp
slow_riot wrote:
Oxix52 wrote:
I have always had this kind of issue with any kind of touch surface. I have used a Buchla 222e, Easel keyboards(2), Make Noise Rene, and 2 Make Noise Pressure Points. In my case, it happens when my Mitsubishi mini split air conditioner kicks in with heating or cooling. This doesn't happen in my house, only in my studio, which is a converted one-car garage. The solution for me, is to either hold on to a metal part on the system, or plug a cable in to the ground jack and hold on to the other end.


In that case it sounds like my initial belief about the cause of the issue was not so misplaced, maybe poor/non-existant earth is why my proposed solution of connecting "ground" banana connector to mains earth didn't work?

Or maybe some other equipment is messing with the Easel's 0V ?

Sorry, kinda talking out loud here, but hopefully can come up with a working solution that might benefit others...


Mains "earth" and the Easel's "GND" have no business with each other. They are not connected, and they really shouldn't be. Mains earth is a safety thing, whilst "ground" in any electrical circuit is a reference potential.

Most problems with the Easel's keyboard (as I stated in the other thread) come from either fluorescent lighting devices [nearby], or mains voltage dimmers [on the same supply line], or a combination of both (and potentially also other appliances which "disturb" mains voltage: fridges, aircons, etc.).

The "shock" some people get when touching [the metal casing of] electronic devices is often just an electrostatic discharge, which is yet another possible cause for erratic behaviour of the Easel's keyboard, and really should be looked into (the reason why your body gets charged, that is)... floor carpets et all.

If none of the above applies, then look into how all of the studio equipment is connected to each other. For example, the GND reference of one device is likely "carried over" to another device when they are connected with a shielded cable (Line Out cable from a synth to a mixing board is the obvious candidate here), which is then in turn connected to any other device connected to this mixer, etcetera. This can get real messy real quickly. If, in this instance, you then connect the Easel's GND to "something else" (e.g. your body), the Easel loses its single reference (its own PSU GND) and might get confused, so to speak, and thusly goes into unpredictable behaviour mode.
In these situations, I find it helpful to meticulously draw out a diagram of all of the studio's connections -- including their GNDs and mains earthing -- so to see where and what is connected to what else. Also, include light sources and anything else in the studio connected to mains. Then start disconnecting stuff one by one, and check what happens at each step.
In many, if not most cases, star grounding is the best solution, and in many studios, the mixing board is the "center of the star"...

Not sure if this helps... it's a darn tricky & complicated subject.

_g
slow_riot
^^^

Thanks for your insights, although I would disagree on 2 points.

The Easel is sold as class II device through using a double insulated power brick for mains entry, thus not requiring earth for safety. However mixing of class II and class I devices in most audio systems defeats the safety criteria in Class II products as the shared 0V needs to always be 2 insulations away from live potential (not likely), thus earthing of 0V is recommended.

I think it is dangerous to suggest shocks from non earthed equipment are static discharge related, I know I can feel the difference between 115VAC from a non earthed floating ground and a simple static discharge.

After studying the 218 schematic today I am convinced I understand the nature of the fault. The body is a receiver and transmitter for a multitude of electromagnetic fields (50/60hz mains hum, and any radio frequencies such as flourescant lighting), and the use of a capacitive touchplate circuit assumes the body is at a fixed potential which is absolutely not the case.

By touching your body to the Easel 0V through a connector you introduce this picked up EM interference onto the negative reference that the touchplate logic circuitry is "reading", and through sheer luck, the interference, being also introduced positively to the capacitive sensors, is cancelled out. But, there is no practical way to implement this "fix" and also satisfy the criterea of having a non lethal musical instrument.

My conclusion is that these faults are inherent in this kind of crude capacitive sensor design. Circuitry taking into account EM signals on the body needs to be designed, which would not be something that could be added as an afterthought.
gddfp
slow_riot wrote:
^^^

Thanks for your insights, although I would disagree on 2 points.

The Easel is sold as class II device through using a double insulated power brick for mains entry, thus not requiring earth for safety. However mixing of class II and class I devices in most audio systems defeats the safety criteria in Class II products as the shared 0V needs to always be 2 insulations away from live potential (not likely), thus earthing of 0V is recommended.

That is correct, yes. And it's particularly the mixing (no pun) of both classes which often cause unexpected problems. As you know. :-)

slow_riot wrote:
I think it is dangerous to suggest shocks from non earthed equipment are static discharge related, I know I can feel the difference between 115VAC from a non earthed floating ground and a simple static discharge.

I'm not so sure of that. Static discharges are in the +20K V realm (though obviously with much lower current, otherwise there wouldn't be any e-musicians alive anymore today)...
In any case, static electricity makes a lot of electrons flow back & forth in a rather unstable manner, so I wouldn't rule it out as a possible source of problems; not insomuch the discharge itself, but rather the cause of static electricity building up.

slow_riot wrote:
After studying the 218 schematic today I am convinced I understand the nature of the fault. The body is a receiver and transmitter for a multitude of electromagnetic fields (50/60hz mains hum, and any radio frequencies such as flourescant lighting), and the use of a capacitive touchplate circuit assumes the body is at a fixed potential which is absolutely not the case.

Yes.

slow_riot wrote:
By touching your body to the Easel 0V through a connector you introduce this picked up EM interference onto the negative reference that the touchplate logic circuitry is "reading", and through sheer luck, the interference, being also introduced positively to the capacitive sensors, is cancelled out. But, there is no practical way to implement this "fix" and also satisfy the criterea of having a non lethal musical instrument.

My conclusion is that these faults are inherent in this kind of crude capacitive sensor design. Circuitry taking into account EM signals on the body needs to be designed, which would not be something that could be added as an afterthought.

I totally agree... "crude... design" being the operative word here.
Capacitive keyboards are fickle designs... but at the time being, it's the best we can get for a reasonable price. Everything needs to be aligned properly in order for them to operate in a predictable manner. Which isn't always easy or even feasible... but I guess that comes with the territory.

_g <still not offering any direct solution to the problem, but hey...>
BooleanYulian
I have had a similar problem since I got my Easel last summer. The resulting error is that not all key pads trigger.. and not always the same ones.. one "floating" key will not trigger.

After speaking to Alex at BEMI, I was told that the Easel is "picky" about its power source and that it "prefers" to be on its own on the electric circuit (I verified this behaviour and, so far, the workaround has been to hold on to the Easel's ground lug while powering up).

I said that its completely absurd since it needs to be connected in a studio and that I expect to be able to bring it with me to gigs and other studios as it is a portable performance instrument d'oh! ..

I obviously expressed my deep disappointment at having them ship out a faulty design (and questionable QA) that they charge 4k for and made me wait for a year.

Long story short, after insisting on a solution, I was told that they had pinned the problem to the touch plate's DC-DC converter and were in the process of redesigning the converter PCB.. I was assured that they would ship me the new converter board (for me to install at my cost !!!) as soon as it became available (ETA Oct 2014).. It showed up yesterday after several reminders
not this shit again

.. I have yet to install it.. I can report back as soon as its done

Y.
slow_riot
It would be great to hear about that when you are ready. Power supply is one thing I've looked at, but the the main thing that leads me into thinking that's a dead end is, why does touching the easel ground solve the problem ? That strongly implies the mode of the fault is through electromagnetic interference on the body and not through the power supply.
BooleanYulian
For sure, I'll let everyone know as soon as I pop-in the new converter board.

As far as to WHY the grounding workaround works?.. never really gave it much thought since this was to be temporary...

if it is an EMI issue, perhaps the new converter adresses it with better shielding or something.. It was never a question of being a PSU issue afaik.

regardless, I will be in a better position to comment once I can compare the old/new converter boards side by side.. if there are any physical differences (like if its encased in lead hihi ), I'll put up some pix..

keep ya posted
Y.
papz
It might help...

I use a early 218 BEMI with my 208r rev2, it works fine without any of the problems commonly described.
Both share the same PSU (Meanwell PD2515 + 7805 + 7812) mounted to the 218's boat, which is the 218's original BEMI boat (with the large hole).
ttown23
Also, I use my 218 BEMI with a 208r rev. 1 and have never had such problems. They are both mounted in a custom 12U rack that I built out of BEMI 6U boats and custom side panels.
BooleanYulian
hey foks.. I finally got around to installing the new power distribution board with the new DC-DC converter.. the old/new look radically different. see pics (old on left and new on right)

regardless to say it seems to have resolved my grounding issue. hopefully it will resolve other's issues as well.

If you contact Alex he should be able to send you one.

Installation is pretty straight forward: remove the keyboard, disconnect all cables, 4 screws and 2 external plastic nuts holding the TRS output jacks in place (careful will these, i was a bit clutzy and they fell into an open space just below the IO panel and ended up inside the case, between the plastic and the boats so I had to disassemble the whole unit to get them out. My mistake, I wasn't paying attention smile )


[/img]
slow_riot
Thanks for letting us know, great to hear that you found a solution and I'm very happy if I'm proved wrong! smile
Jonatilj
Just got my Easel and it suffers from the similar erratic touchplate behavior. If I hold a note it runs though random pulses of notes and if I touch the body of the instrument it works fine. I am a newbie and not very skilled in electronics so I am not sure if I dare change the converter myself but I have contacted the seller as a first step. I was hoping this new batch of Easels would be improved but no. Everything else seems fine though.
BooleanYulian
It is quite a frustrating bug indeed.

Fwiw, you do not need any real knowledge in electronics to change the board. There is no soldering required.

Should you want to try it, I am certain Alex can provide you with step-by-step instructions on how to do it. However, any tech or friend of yours with minimal understanding of electronics could do it in about 30min.

In your case, I would probably contact BEMI myself and push to have the replacement converter board sent directly to me asap, then go see my dealer with the board and have them replace it. In my experience, this would be faster.

my 2 cents
Y.
Jonatilj
Thanks for the advice, much appreciated! I have emailed Analogue Zone from where I got the Easel and I guess either them or me will contact Alex. I think I will try to change it myself but perhaps together with a friend who is more experienced in electronics. I wouldn't want to send it back to Budapest. Until it is fixed I'd stick to short notes on the keyboard wink
slow_riot
You don't need to send the unit anywhere for a replacement like this, swapping out a board is just a manner of remembering everything you did to do it in reverse. Ask for notes from BEMI, it's just going to be a matter of using a screwdriver and gently easing out the DC-DC converter card, then putting the new one in. No soldering or other skills necessary.
Jonatilj
Thanks, I will do that.
ghostcode
glad to hear they are aware and have a fix.

been trying to email about it and have yet to get a response. hope they get back to me soon.
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