Piano World Home Page Forums Our Most Popular Forums Digital Pianos - Electronic Pianos - Synths & Keyboards Kawai CA 95 makes an annoying electric hum sound

Last tuesday my new Satin Black Kawai CA 95 arrived. It was a heck of a job to get the 87 kg piano three stairs up to my studyroom, but it stands… It’s my first Kawai. After having some difficulties with another brand digital piano (inferior samples, noisy action with clicking keys, etc) I deceided to invest some real money in a new digital piano, hopefully for the ‘rest of my live’ I realy like the Kawai CA 95: fantastic pianosamples, great action, beautiful speakersystem and nice cabinet.

But now THE PROBLEM. The same evening I noticed an annoying electric hum sound coming from the piano. It makes me think of a transformator sound. The sound can be easily heard within a radius of 1.5 meters, if it is quiet in my room. In the shop I did not noticed this electric hum, because I was listening to the sound of the pianosamples and focused my attention to the action and sound of the speakers. But now, listening in my quiet studyroom to ‘the sound of silence’ when the piano is on, there it is: a very annoying constant electric hum sound.
Ofcourse I tried to locate the source of this electric hum. When I placed me ear directly on the wooden top of the piano, I can hear this hum coming from inside. The hum seams to sound stronger in the area of the topspeakers above the soundboard. But does not seem to be directly related. Because when I connect my headphones, wich disables the speakersystem, the electric hum stays the same. It also does not respond in getting louder of softer by changing the volumeslide of the piano, the hum stays the same.

This réaly disappoints me! Now my question to other owners of the Kawai CA 95. Do you also hear an electric hum around the piano, or coming from the inside of the piano? Please press your ear flat on the topshelf of the cabinet on the left or right side, near the topspeakers, to hear if IT is there.

Ofcourse there is a two years guarantee period for this piano, but I hate the idea to have to ask again some people to help me bring down the 87 kg piano, and so on back to the shop…

Do you think that a Kawai Technician is able to solve such a problem on the spot?

Please respond….

If it were my piano I'd open it up and look inside and see if I could dampen the hum which is probably coming from the power supply.

If you don't feel like doing this yourself call the dealer and let them deal with it.

I would definately not open the DP myself, because then you will void the guarantee ...
Call your shop and discuss it with them.

Mine doesnt hum. Ive seen inside.... scary stuff....

Disappointing, I know, but don't regret buying the Kawai.

I have used my CA75 for nearly five years, at least one hour a day. I still love it and it has never given a moment's trouble. I see no reason for the CA95 to be different.

But under no circumstances should you go "inside" the instrument. There is nothing you can do there and unless you are an advanced electronic engineer, you are unlikely to recognise anything there anyway. It's under guarantee - tell the seller of the problem and let him have the opportunity of putting it right.

But under no circumstances should you go "inside" the instrument. There is nothing you can do there and unless you are an advanced electronic engineer, you are unlikely to recognise anything there anyway.

You don't have to be an advanced electronic engineer to wedge a piece of foam to reduce or remove a sympathetic vibration if that alone can solve this issue. I think most folks could easily recognize a power supply.

I once completely dismantled the interior (dash, doors) of a Jeep Wagoner to eliminate rattles. I don't hold an advanced automotive engineering degree.

You are a very courageous guy Dave. I'am not. Especially not in matters of electronics. And I agree with others, I don't want to risk my two year guarantee on this brandnew Kawai. But thanks anyway.

Thank you Wumpletoad. My main concern now is: can they repair something like this on location? I realy don't want to take the piano three stairs down to bring it to the dealer. Has anyone (in Holland) experience with the Kawai service?

Where are you in Holland?

Well, the question I think is whether it's a defect or not.

Most electrical items with a transformer have a slight hum. It is possible with damping and shielding to reduce the hum so that it's almost not noticeable.

UKPaul's response suggests, either he cannot hear an existing hum , or your CA95 is louder than some others.

That's exactly why I would like to hear if other CA 95 owners, register such a hum or not. I would be realy disappointed when a Kawai technician comes to my home and say: "well sir this is a normal electrical sound". In my opinion a costly digital piano like the CA 95 should not produce such a hum.

I live near Castricum NH.

If you lived closer I'd offer to stop by and open up the unit to see if we could dampen the transformer.

I'm just outside of Den Bosch.

Thanks Dave, but I rather waite for a certified Kawai technician. As I said, I don't want to loose my two year guarantee.

It should be mentioned, perhaps, that if you decide to try to dampen the hum of the power supply with foam that you take care not to interfere with the unit's ability to cool itself.

As others have recommended, any concerns with your piano should be discussed with the dealer from whom the instrument was purchased. If there is a problem, a qualified technician should be able to diagnose the fault and offer a solution.

Please do not attempt to open-up the instrument to fix the issue yourself.

Kind regards,
James
x

I have to agree with the OP. You paid thousands for a brand new piano, with a warranty. Let the manufacturer deal with the problem.

Thank you James.
But what is your experience in this matter?
Did you ever noticed an electric hum around
the Kawai digital piano's, or a hum that can
be heard coming from the inside of the cabinet?
I mean is this an exception or a regular fenomena?

Dutch,

It is most likely a power supply transformer is humming. Out of any 100 of the same transformers from the same production line, a number of them are going to hum. It's a physical issue, the transformer is mechanically buzzing. It has a loose layer in its' winding somewhere, more than likely. Your dealer should identify the offending 'culprit' in the piano and replace it.

All manufacturers have this issue where a few of their products(of the same model) have the hum but most don't.

Kawai James(as usual) gave the correct instructions.

No, I do not recall hearing any humming sound when play-testing the CA95.

Again, if I was in your position I would contact the dealer to explain the situation.

Kind regards,
James
x

I own a CA95 and there is no hum noise ! So you should get yours replaced or fixed ; )

I would suggest to search for the source first, could turn out to be something very simple in the end (acoustic resonance, power supply that touches something and when separated/isolated the hum is gone). If your can't find , or fix it yourself - have someone take a look at it - must be an easy fixable problem and I would be very surprised if the whole unit needs to be replaced just for the hum noise. Especially if the rest of the DP is totally to our liking - keep it and have it fixed.

Spend $4000 on a defective unit, and then have to fix it yourself? Not me. That's what the warranty is for.

Sorry for my english is not good.
Sometimes other electric using equipments make electirical noise.(fans ,microwaves,some bulbs,elevators ).Fans with frekans invertor give electircal noise back to circuit and makes noise all sound systems.We are dealing with these systems on building automation systems.Ä°n a 5* hotel after putting a frekans invertor to a fan ,all anfi's started to make noise even 100 mt aways.When we closed invertor all noise disappears.After we installed high capacity filter (electrical) all sound problems solved.
You must check all your electic using equipments maybe your neigbours.
I'm also planning my first real digital piano and thinking CA 65.Now using Yamaha DGX 640.But your sound problem third in ca 65/95 series in these forum and up to these time no solution appears.I started going away from CA 's.But where I don't know

I spent €14,800 for my N3. The pedal harp was not correctly installed ... and the movers made the same error I might have made. I spent a few minutes under the piano, realized what I had to do, and did it. I could have called the dealer who was about an hour away but I did the work myself and mailed my suggestion to the Yamaha tech in Germany for future reference.

KAWAI Man....seems there's always some of US who get stuck...trying to fix our keyboards. I have the new Kurzweil SP4-88, marvelous sounds...had trouble twice and had to mail it back and forth to Mississippi(Memphis area...), as of two months ago---attention is directed to the Middle C area---the D # or E flat has dropped out! ....yes, can you imagine...if I open full the Volumne control...you can hear a distant 'muted' thud, have never taken it out on a gig, afraid too! ....so, we all get stuck...just about two years old. Will have to try and contact Kurzweil at Woodlawn Hills, CA or donate to a 50lC-3 for taX purposes; hopefully we can get it repaired...the Kurzweil People are not 'existent' at Waltham, Massachusetts ??...at least- I thought I'd make you feel good, if nothing else. Mr. Kawai was hired away to Yamaha many years ago...I guess, he was as good as Ray Kurzweil....dSav(Maine)

The Kawai CA 95 is realy a beautiful piano. Impressive pianosamples, very nice keyboard, great speakersystem and a good looking cabinet. Just try it, and judge for your self. It would be a pitty if you miss such a beautiful piano just because some problem stories, mine included I'am sure the problem with the electric hum will be solved by Kawai. I have spoken to the dealer already and he will come by at my house to listen to the hum. Then he will send a Kawai technician. Ofcourse I hope when a transformer has to be replaced, that it can be done on the spot.

Have worked on many humming problems in electronics. But not piano's. Transformers can have noise issues. Transformers are epoxied to stop noise and can break loose from there bond. The other parts can cause this is a leaky Capacitor and/or a regulator. Which will loosen the bond on the transformer after time. Post back on what the tech finds. You can put a small peace of wood up against the transformer (there might be more than one) with little pressure and listen to a change. Your tech will do this if he has the experience w PCB repair.

Cool, have it fixed. That's easier and more convenient than a replacement . Good luck, j

Hi Dutch Dhamma - has this been fixed now?

I also notice a hum from my new CA65 and would like to know your outcome. If it is fixable, I might mention this to my dealer.

I believe you are correct that it is a transformer noise; it comes from the right hand side of the piano - which is where the power cord plugs in - and is only present when it is turned on, and is still there if you plug headphones in.

Cheers

Alan

@Dutch Dhamma,

I have a CA95 and do not have the hum or sound you mention here, although it is unfortunate to see more owners (i.e., "DrAlan" on the previous page) coming forward to report the issue with their CA65's.

Looks like there may be a batch of CA65's that have this problem.

Perhaps Kawai should check this out now, before more are sold?

Hi Alan,
Coming friday the dealer is coming to my house. That seems to be the procedure. If the dealer acknowledge the complaint he will make contact with Kawai and then they will send a technician. The hum in my piano is good to hear on the left side as well on the right side. I realy like my Kawai CA 95, this is the only drawback. But I stay optimistic that everything will work out fine. I will keep you informed.

I agree. Digital piano's in this price range should not have 'humming transformators'. I don't understand how these piano's left the factory being unnoticed by people who perform quality checks. Maybe Kawai James can bring this subject under their attention

Hi . . Yes I've just checked an mine is also present left and right. It is also there a fraction of a second after you turn the power off, which suggest to me it isn't the transformer but rather mains hum amplified by the final stages of the power amplifier driving the speakers, which isn't picked up by the headphone amplifier. If it were mechanical hum from the transformer, it would stop the instant you cut the power.

It isn't a massive nuisance, but like others I feel it is disappointing and shouldn't be like that. My 15 year old hi fi amp has no hum whatsoever ......

Alan

I still think the problem is caused by the transformator. Because when I plug in my headphones, the main amplifier is not in function, or at least not in full power. When using headphones the Hum is still there. But I could be wrong. I'am sure a Kawai technician will come up with the right answer and solution.

No hum from my CA65. Only if I put my ear in contact with the DP can I hear the faint sound of the transformer.Definately not audible just sitting in front.

You could be right. I'd lay bets that the transformer is next to the power cord socket - there are two black screws on a diagonal there and it gets warm between them, and this is where the loudest hum is (press your ear up underneath the piano here!). Looks like this sound is resonating through the entire cabinet. Hope your engineer's visit results in a fix.

Cheers

Alan

Crack that sucker open and poke around in there yourself.

**LOL**

NOT!!

If it stays on after you turn-off the power switch then there is a good chance its the Transformer. It is made of a coil of wire making a magnetic field. Will take a second or two for the field to dissipate.

Last friday the Kawai dealer came to my house. He acknowledged the electric Hum and located the source of the Hum. It is coming from the transformator or closely connected device belonging to the transformator. In the CA 95 this thing stands on the interior bottom of the cabinet on the utter right side. Now he will make contact with Kawai in Germany. It is up to them to send a technician to repair the issue or to change the piano for a new one.
We also noticed that several keys of the GrandFeel keyboard are making more noise (landing on the bottom) then others. It is as if there is less damping or shock absorbing material under these keys.
With these two complaints I would not be surprised if Kawai decides to change this one for a new piano.

So spanishbuddha had it right ten days ago:You'll need a replacement transformer (or a replacement piano).

I hope replacing the transformer would do the trick. better than exchanging such a big bulky thing as a whole piano cabinet (+ boxes and everything else). Good luck !

What happened to your problem ?is it solved ?

Thanks for asking. This afternoon two Kawai Technicians from Germany visited my home. They acknowledged that this kind of electric hum of the transformator should not be there. The piano has to be quiet. Then they replaced the transformator for a new one. But this did not solved the problem. There was still an electric hum, to loud to be considered 'normal'. It seems the problem is caused by placing the transformator directly on the wooden bottom. I consider this as a flaw in the construction.
They will discuss this problem internally with Kawai. One of the technicians said that maybe it is an option that they try a new CA 95 in a absolutely quiet room. If this piano does not make the electric humming, it can be replaced with mine. Anyway next week he will make a telephone call to inform me of a possible solution. To be continued.....

Any updates on your humming issue? I think I have a similar problem on my CA95, but this is rather a rattling noise when the volumn is above 1/2, especially 3/4. The key that makes the most vibrating/rattling sound is the 3rd F key counting from the left hand side. This thing bothers me a lot. I don't think it's normal because my other DP doesn't have this problem even when you max the volumn. What should I do?

Kenboi2, if you have any concerns, please contact the dealer whom the CA95 was purchased, and/or the distributor in your region (e.g. Kawai UK).

Kind regards,
James
x

Hi Kenboi2 (and others from PW)! I, too, recently bought and received Kawai CA95 (I plan to write a short review, I am mostly very happy). But this thread and your post in particular really caught my attention, because:

1. My CA95 also makes audible electric humming noise after being turned on. It is not really disturbing during playing but when silent it is very clearly audible. In my opinion it's power source/transformator.

2. I spent several hours this weekend in search for audible resonance coming from the piano when playing F3 - rattling sound exactly as you describe it. There may be more than one "points of origin" but I strongly suspect the area around the power supply causes (or contributes to) the resonance/rattling. I am not very good and finding sound sources but it seemed to me the rattling (or part of it) comes from that place and when I held the power supply (it is in a special box kind of protruding from the bottom of the piano) firmly in my hand, the rattling diminished considerably.

3. There is another (perhaps related?) issue I have with my CA95 and I would like to hear your opinions on this one. Some keys (the F3 by far most of all) when played with the sustain pedal pressed make "more sound" that others. I do not mean only louder but kind of "more overwhelming", it is difficult to describe but it's like I am in the middle of a bubble made of one tone, like there is a piano tone with an envelope of loundess (if you now discard me as lunatic I can't blame you). Unfortunately I have the piano in a room with very poor acoustics (major reason why I have digital in the first place, to play with headphones) but it usually manifests itself as individual tones being louder, more "piercing" to the ears, not this overall "loudness bubble" enveloping a clear tone, but I don't know. It is present (to lesser degree) even in headphones, but it is more apparent when amplified by speakers, combined with the aforementioned rattling noise (and possibly poor room acoustics) - it then makes the overall experience quite unpleasant (especially as it is only one or two keys).

The key which behaves by far worst in this aspect is the discussed F3. I decided to record a little test and upload for your examination (link below). Let me know if you think this "sounds normal" or it's strange.

Test description:

1st half: I play F, then press sustain pedal. After pressing the pedal, the sound is amplified and kind of modified. I do this 3 times. Then I do 3 times the same thing with A (a third higher) - no similar thing happens. Then the infamous F again, 3 times.

2nd half: I press the sustain pedal and pres F repeatedly, the sound snowballs and becomes unpleasantly loud and "like in a bubble". I do the same thing with A (approximately similar velocity, as perceived), it is much quieter and without the unpleasant "envelope". Then F again. This recording is actually not really convincing, but when played on the piano it's crystal clear.

Link: https://soundcloud.com/hookxs/sets/f3-pedal.

I believe there is some error the sympathetic resonance computation, because this is not how accoustic piano behaves and even CA95 does this for a few keys (mainly F3). If so, it could and should be addressed by firmware update. Let me know your opinion. I am sorry for the lengthy and possibly comfusing explanation, describing sounds in foreign language is like trying to draw what apple tastes like. I'll be more than happy to clarify and case anyone is interested.

Hi Hookxs,

Thank you for your comprehensive review. I am glad there're more owners of Kawai CA95 stands out and unleashes their issues with the humming/rattling issue. Your sound clips wasn't as audible as when you hear it in person. But, of course, thank you for making the effort to put it up. I have emailed the digital technician from Kawai and waiting for his response.

As for your second issue, I believe it's the imperfection of samples taken off the Kawai Concert Grand. But, of course, I do hope there's a fireware fix. In order to see this fix in reality, we all need to participate. I would hope everyone of us who owns a CA95/CA65 with these issues email/call Kawai and tell them the truth. I've stopped playing because of the rattling sound. If not this issue, it's a very good digital piano. I love it!

To be clear: my sound clips do not demonstrate the rattling sound from the cabinet, these are straight-to-mp3 recordings while the rattling is mechanical, audible only when listening without headphones, most likely coming from the area of power source. It is not present in my sound sound clip.

On the other hand, the "second issue" (labeled 3 in my first post above) manifests mainly when pressing damper pedal, can this be sample imperfection? I believe string resonancies (of undamped strings) are computed based on which keys are played and which are held down, right? I believe this sympathetic resonance simulation is somehow flawed that it unrealistically amplifies (and modifies) the overall sound when F3 is played, thats why I hope this is firmware-fixable. Other keys don't do this, maybe one or two others to much lesser degree.

Hello Hookxs,

Thank you for your detailed description and for posting the example audio clip.

Regarding the transformer hum, I believe all transformers hum to some extent, however there can be a degree of variance from one transformer unit to the other.
The volume of the transformer may be a little more noticeable on the CA95 due to its position within the cabinet. However, if you have any concerns about the hum, I would raise this topic with your Kawai dealer.

Regarding the F-3 key rattling, this is not an issue I am familiar with, and again, is perhaps best dealt with by your dealer.

Finally, regarding the F-3 sound issue, I have listened to the recording and acknowledge (both aurally and visually) the increase in volume. To clarify, are you playing the key, then pressing the pedal, or pressing and holding the pedal, then playing the key?

I'm afraid I do not have an explanation for this phenomenon, and Kawai Japan is still currently on holiday for the Japanese new year. However I will try to look into this when we return to work on Monday morning. In the meantime, may I also recommend that you contact your dealer and the Kawai distributor in your country (Praha Music Centre?). It may also be worthwhile to send an email to Kawai Europe's technical support address.

Kind regards,
James
x

Hello James and thank you for your interest.

Yes, I play (and hold) the key and after a brief moment press the pedal, which boosts the volume. The order is irrelevant though, anytime the F3 key and sustain pedal happen to be pressed at the same time, the sound is boosted in volume and somewhat unpleasantly distorted. This boost even somehow adds up if you press the key repeatedly. While it may seem like a minor issue in the recording, when amplified by speakers (1/2 volume more than enough) it renders the piano almost unusable (I hate to say it out loud...). I must carefully watch for the presence of a particular key and pedal at the same time and compensate (or don't) - either way it damages the music and playing experience. Sometimes I get fooled by not playing F but E# instead, which doesn't raise the red flag but booom - there it is:-) I tried this on an acoustic piano and of course it does not exhibit this phenomenon. If nothing else than it is impossible from the point of energy conservation - you give the system nothing so you can't expect the volume to rise.

I plan to create and upload a MIDI file which demostrates the issue so other users can then play the MIDI and see is their piano works fine or not. I am kind of new to this MIDI world though, so at the moment I don't even now which editor to use that can handle pedals easily. I would like to have several keys played with the same velocity so that the volume boost can be compared and quantified. I also want to see if there are other keys that exhibit this behavior (to lesser degree perhaps).

I will contact my Kawai dealer (Music City Prague indeed), but should it be a software issue, I am afraid there is nothing they can do other than report higher up the chain. The other matters (rattling, transformator hum) don't really worry me since they are far less disturbing and I believe they are fixable easily. Once I have the "scientific" recording of the issue, I will contact Kawai Europe's support, like you suggested. I'll be happy if you discuss this issue with your colleagues, thank you.

Hookxs, may I ask you to create a recording with other notes in the same region, and different key/pedalling techniques.

e.g.

- Play E-3, hold key
- Play E-3, hold key, then press pedal
- Play F-3, hold key
- Play F-3, hold key, then press pedal
- Play F#3, hold key
- Play F#3, hold key, then press pedal
- Play G-3, hold key
- Play G-3, hold key, then press pedal

Also, may I ask if you have tried turning all the Virtual Technician parameters to 0 (Off)? This is of course an extreme measure, but it may help to isolate the cause of the problem.

Kind regards,
James
x

Ok, I will do it as soon as I get home. The short clip I uploaded yesterday is with Virtual technician settings as I had them adjusted for normal playing, definitely nonzero. I will try to set them to Off (damper resonance etc.). But I remember fiddling with it when I first discovered the issue (at that time I wasn't aware it is present even in headphones and was looking solely for outside sources of resonance/amplification) but setting resonances to Off didn't help (far as I remember) while setting to maximum values made the problem worse (subjectively?) - I will measure this as well.

Ok so I played with the settings a bit and indeed discovered that when I set the Damper resonance to Off the problem disappears (or at least diminishes considerably). Other settings (string resonance?) may have a little effect but probably not.

I recorded the test you asked for (up to G#3), each note is played first without pedal and then with pedal some time pressed after the key is pressed. I recorded this for damper resonance set to maximum value (10), default value (5) and Off. I would like to have all the notes in the recoring with same velocity and duration (as well as pedal) but I found no quick way how to edit the midi (advice welcome). Other settings are in their default values, Reverb is off.

Recordings:
Maximum resonance
Default resonance
Resonance Off

I believe this shows that the error is not in the samples but rather in the resonance algorithm and could be therefore fixable by firmware update. It may not be such a big deal for most users, especially with headphones, but when playing through speakers I find it extremely annoying.

Hi Hookxs and everyone else here. :-) Hope you get your issue resolved. I'm currently in the process of choosing my first DP and, being a complete rookie with quite the budget, the CA-95 really impressed me with its capabilities and sound. I'll keep an eye on this thread to see how this pans out. Good luck!

(I'll stop right there so as to not hijack this thread.)

I had a technician come over my house today to have my CA95 inspected. As soon as he and I moved the piano about 1 foot away from the wall, the vibration/rattle sound was almost completely vanished. He then checked inside the piano and found a few screws "slightly" loose. After he tightened them and put everything back in place, it sounded so much better. To me, the problem is caused by having my piano too close to the wall. I was told you need to separate your piano and the wall about 1 foot or more. In the past, I thought 6 inches away from the wall was enough, but now I guess it depends. I have this helps anyone with a similar problem.

BTW, I have looked inside the CA95 and I can tell you this is a very high quality built piano. He said it's a very very nice piano. I was very happy as soon as I heard he said that.

Kenboi2: did you push the piano back to its "original position", after the screws were tightened, and listen for the problem? Did it go away after the tech was finished? Was the vibration/rattle the wall or an interaction between the wall and piano? Please expound on your comments above. I am curious about this vibration/rattle you were hearing.

HwyStar,

I tried to push the piano back to its original position and the vibration/rattle sound wasn't there anymore. I find it very strange. I forgot to mention another thing. The technician also tightened a few sets of wires other than the screws. I guess it's a common problem in the CA95 series.

I have been away some time around this topic. But this is the latest news. Kawai delivered last thursday a brand new CA 95. Because of Christmas and New year it took some time, but this is the final outcome of the Humming sound topic. As mentioned before the replacement of a new transformer could not reduce the humming sound, that's why they decided to replace the entire instrument for a new one. This CA 95 is a lot quieter but still there is on the background the soft sound of the transformer, but in no way the same annoying sound as the first one. So I can live with it.
Now something really strange happened, that I cannot explain. This new Kawai CA 95 sounds a LOT BETTER then the first one (both instruments in factory setting). The difference is really amazing. It is as if the sound of the speakers and the soundboard of this one, is so much more dynamic, livelier, fresh and sparkling. And this not only concerns the sound through the speakersystem but also via the headphone set. I'am using a pair of Sennheiser HD 595 and it's a clear fact that the piano and other samples sounds much better then those of my first CA 95. I have no explanation. Even the dealer directly noticed the sound difference between the two when I came in his store to checkout the new piano. (It was his first Kawai CA 95 he sold to me, and he remembered the sound of the first one). But I became first really aware of this when the piano was standing in my study room. Is there somebody who has a reasonable explanation of this phenomena?
Anyhow, I'am very happy. I'am also very satisfied with the service of Kawai and my Kawai dealer: Aad Veldhuis in Amsterdam. I really love this instrument and I'am happy that I choose for Kawai. Amen

Dutch Dhamma, thank you for the update. I'm glad to read of this positive outcome.

I'm afraid I offer an explanation as to why your new CA95 should sound so much better than the first piano you received. However, I expect it may have been related to the humming transformer.

Kind regards,
James
x

tl;dr: You can fix this easily yourself with some silicone washers on the transformer

rambling narrative:

I had the hum. Very faint, but audible when I wasn't playing. I found that it was worse when I had the pedal support bolt down, and also that sometimes pressing the pedals or applying pressure to the casing above the pedals helped quell the hum.

The previous owner said he hadn't heard any hum, so it could be that I found it a problem due to my location being very quiet, and having sensitive hearing, or maybe there's something about my A/C power that causes it. I doubt the latter though, since hums are apparently often caused by poor earthing, but the CA95's power input is 2-pin, i.e. not earthed.

Removing the front panel decreased the volume a lot, and it seems that this was reverberating, amplifying the noise. (pics below)

I needed to find the hum's source, which I could hear faintly coming from somewhere, but very non-localized and hard to pinpoint. I disconnected the speakers (it wasn't those) and initially thought it was coming from the main circuit board on the left hand side, but eventually I discovered by putting my ear right onto the transformer, that that was the source. Unscrewing the transformer and lifting it up eliminated the hum completely. It wasn't really making any sound itself, just vibrating slightly at 100 Hz, and this was causing resonance in the CA95's wooden casing.

So, for a fix, I ordered an 8-pack of "Acousti Anti Vibration Silicone Washers", £2.02 inc delivery from Amazon. Maybe you can use something else like some felt or a piece of cardboard if you can't get hold of these.


They are 10 x 2 mm with a 2.5 mm hole, and proved to be a perfect fit. They're normally used for fixing fans to PC cases. I played around with various configurations, but found the most effective was to put two washers on each screw below the existing washers. Here the transformer is turned upside-down:



(I thought perhaps the existing metal washers were to earth the transformer, but in fact they are insulated by the existing rubber washer, so putting silicone washers below will not cause earthing problems.)



I then found that it was important not to screw the transformer down too tightly, else hum would follow. Essentially you want the screws just to just rest on top without providing additional downwards force over the weight of the transformer. With the screws loosened sufficiently, the hum was eliminated.


Removing panel:

1.



2.



3.

Nice problem solving, nice pictures.

Nice job Lolatu. When Kawai replaced my new CA 95 because of the humming transformer, it turned out that the second one also was not realy quiet. Less noisy then the first one, but still audible. The room in wich the piano is located is realy quiet and it seems that I have a very sensitive hearing. So after a few weeks, again it became a problem for me. I also could not accept the fact that a digital piano in this price range showed this kind of weakness. So I contacted Kawai Germany again. They said they would present this problem to their technicians in Japan. And they finally came up with the same solution you founded. Just four very soft silicone rings. After they placed the rings under the transformer it was absolutely silent. They even checked this with a real doctors stethoscope. The hum was gone. Patient cured I understand you bought the piano 'second hand' and did the job yourself. I was warned not trying to do it myself at the expense of losing my warranty. Anyway, placing four silicone rings under the transformer of the CA 95 seems absolutely necessary. Otherwise the vibrations of the transformer is lead through the wooden structure of the piano. However some people don't seem to bother, just as the previous owner of your piano did not notice the hum. I was told that Kawai from now on places those silicone rings under the transfomers of all the CA 95. A good thing. Well, I realy hope you will have as much fun with this piano as I'am having. I'am still learning to play, but I'am very happy to be able to do this on such a fine instrument.
Greetings,
Dhamma

Yes, nice fix lolatu, and great job documenting the steps too.

Cheers,
James
x

That's very interesting Dhamma! Glad yours was fixed too, and it seems I stumbled upon the right solution by chance.


That's unfortunate. It's like losing the warranty on your car for opening the bonnet! But I don't think that Kawai would really dishonour the warranty if you performed this simple fix yourself, so long as you don't break anything else. I fully intend to claim on the warranty if any other faults develop, but it would have been a lot more hassle to claim regarding this hum than it was to fix it myself.


Thanks - having a lot of fun so far! And it's encouraging me to practice more than I was before.