EEVblog #1108 - Casio CT-X700 Keyboard Teardown - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: July 21, 2018, 11:23:29 pm
content: How do Casio make a full size velocity sensitive electronic keyboard for US$175?

author: Jr460
author_rank: Regular Contributor
timestamp: July 22, 2018, 01:00:49 am
content: I was talking to the screen before you even opened the thing, two contacts per key, timing difference.I had to laugh at part when you said it was directly going into your camera, that's why it sounds so good. No, it doesn't sound good. I guess for the low-end market they are aiming for it sounds OK.You need to do a teardown of a Fatar keybed.A lot of the higher end keyboards get the keybed from Fatar. I think Yamaha makes their own. Fatar has models that have a real feel and in some cases even a small hammer system so you feel the break when playing. I'd like to see how they do things like polyphonic aftertouch.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 22, 2018, 02:16:43 am
content: I'm surprised it doesn't use a class D amplifier when it has provision for running on batteries.

author: helius
author_rank: Super Contributor
timestamp: July 22, 2018, 02:59:17 am
content: Quote from: Jr460 on July 22, 2018, 01:00:49 amKey pressure is generally either electro-optical (Fatar system) or capacitive (Ensoniq system). Kurzweil used a unique resistive system that sends pressure in proportion to contact area on a rounded rubber bumper:http://www.jefflaity.com/midiboard/All of these are rare, only about 10 models of keyboard or synth have had key pressure out of thousands that were made. Boards that can only send channel pressure usually use an elastomeric strip with a rubber conductive inner layer. As the keybed is depressed against the strip, its resistance decreases.

author: Towger
author_rank: Super Contributor
timestamp: July 22, 2018, 07:52:30 am
content: Quote from: NiHaoMike on July 22, 2018, 02:16:43 amThe have been regurgitating the same design for ~30 years.

author: Muttley Snickers
author_rank: Unknown
timestamp: July 22, 2018, 08:28:36 am
content: I bought one of their "high end" arranger keyboards about ten years ago and after unboxing it I heard something rattling around inside, I opened it up and it turned out to be a screw and mounting plate floating around and it was then that I discovered some of the worst attempts at soldering that I had ever seen in any product, just big ugly blobs of dry solder on every ribbon cable connection, it looks at least like they have improved their skills somewhat since then.Up until then I only had good things to say about Casio products so this was certainly a disappointment, out of disgust I returned it the following day to Allans Music and exchanged it for a Roland which I still have to this day. I can't play music for peanuts but at least I have more buttons to press and knobs to twirl in the lab, I also claimed it on tax as a tone generator.

author: woox2k
author_rank: Regular Contributor
timestamp: July 22, 2018, 08:57:40 am
content: It's always fascinating to see how complex things can be achieved so easily. When someone would ask me to design a velocity-sensitive key, 2 membrane system and using software to measure timing to achieve that wouldn't be my first idea.Now i'm tempted to take apart my m-audio axiom keyboard. It probably has the same system for velocity but it also has a 128 step aftertouch...

author: Grapsus
author_rank: Regular Contributor
timestamp: July 22, 2018, 12:08:32 pm
content: If we take into account the huge case, the sample playing circuit, the amplifier, the speaker, the LCD, etc., the bill of materials amounts to probably less than one dollar per keyLike others said, it's the same mechanism that all every cheap keyboard has been using for 30 years. It does the job, but I've read the this rubber dome system has a lot of jitter to it. MIDI codes 128 levels of velocity, and let's say you drop a 100g mass from 10cm on a key several times, the results may be scattered between like 50 and 120. Dave, if you're curious to test this, just plug the USB port into a Linux computer and use the command "aseqdump" which is standard and will print all the MIDI events like "Key On" with the velocity.Also I agree that the plastic bending every time you press a key looks not very durable. I have a very cheap MIDI keyboard (it just sends the keys, does not play sounds on its own like this Casio) and at least they've used one spring per key. But hey, people seem to love this CT-X700, on Thomann (biggest european music gear shop) it has hundreds of reviews and almost 5/5 stars.

author: aqarwaen
author_rank: Regular Contributor
timestamp: July 22, 2018, 03:07:35 pm
content: i wonder does this keyboard come with any psu ,what you can plugin in there.i mean sing shop batteries only ,sound like very expensive solution longterm....

author: Jr460
author_rank: Regular Contributor
timestamp: July 22, 2018, 03:58:33 pm
content: Quote from: helius on July 22, 2018, 02:59:17 amLooks like that video was talking about an older Kurz. I had the understanding that all the newer ones used a Fatar. I think my PC3x is Fatar based. Could be wrong. Used to be a real good Kurz forum that the PC3 product manager and several of the engineers watched and posted in. That would have ben the place to ask for sure.Yep, I saw the mono pressure setup back in the original DX7.The M-audio stuff has the same thing. Had a Keystation88 for a while and C4 broke in a an odd way, had to get the part and instructions on fixing it. You had to really rip the thing almost completely apart to get that one key out and put in a new one. Just like the Casio it had 2 tabs on the bottom of the keys that hit the switches. The tabs were not reenforced well, the Casio seems to have done the right thing. One of the tabs partly broke off and jammed things up. The plastic modeling of the new key was a new rev and added plastic in that weak area. The mono aftertouch on M-audio from what I saw was nothing special.

author: helius
author_rank: Super Contributor
timestamp: July 22, 2018, 05:02:45 pm
content: In fact, you cannot buy a new keyboard with polyphonic aftertouch today. The Fatar and Ensoniq key pressure boards ended production in the 1990s.The only boards this century with key pressure were the Rhodes RPC-1 and the VAX77, and both companies are defunct.

author: bigsky
author_rank: Regular Contributor
timestamp: July 22, 2018, 07:58:58 pm
content: One point that Dave didn't mention is the keyboard contact arrangement. 61 x 2 = 122 contacts. I wonder how it is implemented? From the PCB layout, perhaps 8 drive lines and 16 sense lines - that would explain the dual diode package on each key, and it would suit the velocity sensing. It would be an interesting exercise to see if any signals could be detected on the wires, perhaps try to work out the scanning frequency, which must be pretty fast in order to measure the velocities.I wonder what the design life of the keys is? Not long, I suspect

author: Mike Warren
author_rank: Unknown
timestamp: July 23, 2018, 12:16:16 am
content: Quote from: Jr460 on July 22, 2018, 03:58:33 pmYes, Fatar TP40L. I used to own a PC3x. I now have a Forte which uses a variant of the same keyboard. Fatar uses the same basic idea of membrane switches for velocity sensing in many of their keybeds.QuoteThere is still one. Not sure if Dave Weiser posts there (but he no longer works for Kurzweil), but at least one of the R&D engineers regularly post there.http://forums.godlike.com.au/

author: Mike Warren
author_rank: Unknown
timestamp: July 23, 2018, 12:21:46 am
content: Quote from: bigsky on July 22, 2018, 07:58:58 pmThat idea is used in a lot of quite expensive keyboards and they are generally quite reliable for many years. My last keyboard, which I owned for 7 years, had the same type of keyswitches and wasn't showing any signs of problems after being played for an average of about 18 hours per week.

author: Brumby
author_rank: Unknown
timestamp: July 23, 2018, 01:45:11 am
content: Quote from: Mike Warren on July 23, 2018, 12:21:46 amI'm not at all surprised. The actual flex of the plastic isn't all that much at the hinge point and if that flex is kept within the elastic range, then the keys aren't going to fail because of bending. The elastic range may change over time as the plastic ages - and that could bring the movement into the destructive range.As such, it is my expectation that playing 18 hours per week over 7 years is going to be a lot less likely to encounter a failure than playing 6 hours per week over 21 years.

author: Mike Warren
author_rank: Unknown
timestamp: July 23, 2018, 02:58:36 am
content: Quote from: Brumby on July 23, 2018, 01:45:11 amI wasn't referring to the hinge. That is quite a bad idea for longevity and I've seen many of those broken over the years. I was referring to the membrane switches.I had a Roland RD1000 many years ago (AU$6000 in the late 80s). That had rather expensive leaf switches and I had to go into it and clean them after a few years.

author: Brumby
author_rank: Unknown
timestamp: July 23, 2018, 05:11:37 am
content: Ah. My apologies.

author: Mike Warren
author_rank: Unknown
timestamp: July 23, 2018, 05:18:14 am
content: Quote from: Brumby on July 23, 2018, 05:11:37 amMy apologies. I now see I misread your post as referring the the switches, but I see now you were talking about the keys themselves.

author: Fungus
author_rank: Super Contributor
timestamp: July 23, 2018, 09:22:30 am
content: Add me to the "knew the answer before it even started" list.I'm more interested in how they multiplex all that together in so few wires going to the keyboard. Maybe an investigation there, get an oscilloscope on the wires and look at the signals. I imagine it's quite a high scan rate. Musicians are fussy, they can feel a millisecond delay in the key response.Dave: The keys go in groups called "octaves" (they repeat every eigth notes). The black ones are called the "the black notes".All the white keys in an octave are a slightly different shape. I never thought about how the extra white key at the top must be a complete pain for the people who make those. It totally wrecks things from a design point of view.I'm slightly shocked that the "spring" and "hinge" in each keys is just the plastic of the key, flexing. If they've cut any corners on this model to get the price down, that's where they cut them (are there any other keyboards that do that?)

author: tooki
author_rank: Super Contributor
timestamp: July 23, 2018, 05:00:06 pm
content: Quote from: Jr460 on July 22, 2018, 01:00:49 amAll the major manufacturers (Yamaha, Casio, Kawai, etc) make hybrid digital pianos that contain a full hammer action, just without strings. I know the Yamaha ones (the AvantGrand series) use multiple fiber optic optocouplers per key (in some, there are sensors on both the key and the hammer). They look neat inside, with little red lights but no wires in the mechanism.I haven’t had a chance to look at one in great detail, but I think I read that some use a graduated transparent barrier that provides analog response, not just binary. (Others supposedly use Gray code.)They also make simpler, smaller actions for cheaper digital piano models.

author: hwj-d
author_rank: Frequent Contributor
timestamp: July 24, 2018, 06:21:34 am
content: Yes, there is a large global manufacturer of such keyboards that almost all well-known manufacturers such as Clavia Nord, Roland, Yamaha(?), and as they all are called, insofar as they actually doesn't develop such things themselves. And this isFatar, an Italian company that specializes in such keyboards.http://www.fatar.com/Pages/Intro_production.htmI wouldn't be surprised if the branding could be seen somewhere.﻿Edit: These rubber hats and two flat cables are typical. The difference in quality is in the mechanics around it. There should be somewhere an external midi interface electronics for that.

author: Mike Warren
author_rank: Unknown
timestamp: July 24, 2018, 06:37:48 am
content: Quote from: hwj-d on July 24, 2018, 06:21:34 amCasio, Roland, Yamaha, Korg and Kawai all make their own keybeds. Pretty much everyone else uses Fatar.

author: tooki
author_rank: Super Contributor
timestamp: July 24, 2018, 06:59:17 am
content: Quote from: hwj-d on July 24, 2018, 06:21:34 am1. I think you totally missed the point I was making:hybriddigital pianos. Those Fatar mechanisms aren’t evenclose. The hybrid actions include thefullhammer mechanism of a real piano, except that the hammers have no strings to strike. Hence a hybrid between an acoustic piano action and a digital instrument. Look at this:https://youtu.be/omK58tFQTLchttps://youtu.be/dhkGTWDcqBk(A pianist friend of mine was here visiting a few years ago and had a chance to try the Yamaha AvantGrand pianos at a big music store. He loved it so much he spent over 3 hours there playing it and talking with the salesman (who knew he was a tourist and wouldn’t result in a sale!!). He said it was the first digital piano he’d tried thatfeltlike a real piano, and a good one at that. But being digital, you can adjust the volume or use headphones, making it suitable to apartment life. He’s delighted with it.)2. Do you honestly believe that Yamaha, a respected maker ofacousticpianos, would outsource its keyboard beds?! Musical instruments are Yamaha’s oldest business, that’s why their logo is tuning forks...

author: hwj-d
author_rank: Frequent Contributor
timestamp: July 24, 2018, 09:55:45 am
content: @tooki:My post was not an answer to your post and your hybrid pianos.That was my thoughts to the OP!Look at the context of my post. I didn't speak to, or criticize you.I've explicitly pointed out that otherswho do not make these keyboards themselvesusemostlythose from Fatar. At Clavia Nord electro, Hammond (SKx), both "waterfall" style keyboards, I assume that all are fatar keyboards inside. But I also like to be convinced of the opposite, if that isn't true. Depending on their needs, Fatar produces no-hammer keyboards, middle-weighted (Clavia Nord stage), and weighted keyboards with (heavy, "Fatar Grand Touch" >35kg), or without internal wood clappers.Whether a manufacturer of stage pianos actually uses custom, fully weighted keyboards in their respective models, is a matter of their intended use, price, and, most importantly, weight.