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Replacing the atrocious sound system on a ,000 digital piano
Replacing the atrocious sound system on a ,000 digital piano
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Old 9th February 2019, 06:31 PM   #1
computerpro3 is offline computerpro3  United States
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Default Replacing the atrocious sound system on a $12,000 digital piano

Hi everyone,

I am a serious (but amateur) classical pianist that no longer has the ability to use an acoustic grand piano due to noise constraints, so I purchased the Kawai Novus NV10 digital piano. This is a hybrid instrument that uses a real acoustic grand action mated to optical sensors and a digital piano cabinet. So, you get all of the feel of a real acoustic without the noise.

There is just one problem - the built in audio is atrocious given the cost of the instrument. The only way I can get good sound out of it is to hook it up to my computer and use it as a midi controller with Pianoteq software and my Sennheiser HD650 headphones. But the speakers are horrendous, so I figured I would open it up and take a look.

Frankly, this sound system seems like a complete afterthought to me from both an architectural and quality standpoint. The woofers feel cheap, there is no real crossover network, there is point-to-point "fix it" wiring on the mainboard, and the system is generally underpowered.

Given the poor design and components of the system, I am wondering if I can simply take the audio output off of the mainboard, run it through something like a miniDSP and then directly to my own amplifiers and replacement drivers?

I spent some time today and drew up a schematic of the way the sound system currently works.

Click the image to open in full size.

Looking at it, I have several questions:

1. It seems that the mainboard has separate audio outputs for L/R channel and bass. I assume this means a digital crossover for the bass woofer? This is one issue that I may have to figure out that could impact driver selection.

2. I do not understand the pinouts or number of wires used on this system, it does not seem logical. For example, there are five wires coming off of the mainboard for the L/R channel output, which corresponds with five pins in the input of the Amp. But when the output of Amp 2 is daisy chained with the input of Amp 1, there are only three wires. Why?

3. Why does the bass signal need to be pre-amped, but the L/R channels do not?

4. Is there a way I can find out whether or not the signal coming off the mainboard is flat or processed to hell?

Here are some more pictures of the system. I would really appreciate any help!

View of the action with the cover off

Click the image to open in full size.

Amplifier Section

Click the image to open in full size.

Bass amp and Preamp

Click the image to open in full size.

"Crossover"

Click the image to open in full size.

How the drivers are mounted to the lid of the piano

Click the image to open in full size.

View with back cover removed

Click the image to open in full size.

Close up of L/R channel amps

Click the image to open in full size.

Mainboard

Click the image to open in full size.

Mainboard 2

Click the image to open in full size.

Mainboard output section

Click the image to open in full size.

Last edited by computerpro3; 9th February 2019 at 06:55 PM.
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Old 9th February 2019, 07:13 PM   #2
computerpro3 is offline computerpro3  United States
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Additionally, I just verified by unplugging the amps and then trying them just one at a time that each channel definitely has it's own amp.

With just the 8in woofer plugged in, I can hear even the top note on the keyboard coming out of it. So it appears that this may be a full-range signal passed through to the woofer.

With just the left channel amp plugged in, the entire left channel plays (tweeter and two woofers). I can push the 4in drivers to quite extreme xmax here; I am wondering if this is also a full range signal.

Would they really go through the hassle of having two separate outputs on the mainboard just to send two duplicate full-range signals? Seems like a waste?

Thanks
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Old 9th February 2019, 07:30 PM   #3
Mooly is offline Mooly  United Kingdom
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Replacing the atrocious sound system on a ,000 digital piano
Without proper documentation and circuit diagrams it all becomes guesswork... even if educated guesswork

The preamp board with the 4558 opamp looks to be more than just a gain block. The quantity and appearance of the passive parts suggests some kind of (probably) standard opamp type filter circuit. The transistors could be for muting to ensure silence when no keys are depressed.

The best way to gauge what the main board outputs are like could be to rig up an AC coupled feed to output to some external amplifier and see what the results sound like.
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Old 9th February 2019, 07:46 PM   #4
computerpro3 is offline computerpro3  United States
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Do can you think of any logical reasons they would use one 5 wire output and one 4 wire output instead of simply using two wires for stereo? I may start unplugging pins one at a time and see what impact it has.

One good thing about this piano is that it does have a line in, so I can play whatever test tones I wish through the speakers.
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Old 9th February 2019, 07:51 PM   #5
computerpro3 is offline computerpro3  United States
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Oh wow, I am an idiot! There is a pinout on the amps printed on the PCB! Pin 1: mute Pin 2: Hot Pin 3: Cold
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Old 9th February 2019, 08:46 PM   #6
silasmellor is online now silasmellor  Denmark
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Replacing the atrocious sound system on a ,000 digital piano
Interesting thread! Can I ask why you don’t simply take the output from the line out (at least the specs claim there is one) and run that to your own amp/speakers?

But I wonder if it really sounds better than some of the aftermarket grand piano samples like ivory? It is hard to gauge from the marketing material but i am curious what your impression is?
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Old 9th February 2019, 10:51 PM   #7
PRR is offline PRR  United States
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Your images come out thumb-size; I can't see much.

The one review of this model I found said it could be somewhat louder than a real baby grand next to it.

For $12K the dealer should come to your house and make it right. If he can't/won't make you happy, Kawai should back-up their product. Yamaha would do that, and Kawai is playing in Yama's league.

Maybe something is wrong in your piano, your power, or your room. (I concede that you probably know the room very well.)
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Old 9th February 2019, 11:26 PM   #8
indianajo is offline indianajo  United States
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I can't believe this doesn't have a headphone output: With silence feature when you have a plug in that socket.

Use that through a 1/8" stereo to dual 1/4 phone plugs or something to go to an external amp. Or if you are terribly interested in 28-54 hz, separate out a 3rd channel with a crossover for subwoofer amplifier .

I get very good sound out of my $699 ea new ( I bought them used.) SP2 speakers, on poles above and around my Hammond theatre organ. I play piano CD's all the time, it sounds very good. I use about 1/4 watt base level, (1.5 vpp 8 ohms) but for the peaks of hammer hit on ff passages I have 70 watts/ch. 200 w/ch would not be unrealistic on piano, with my 101 db 1w 1m speakers. The SP2 are +-3db 54 hz -14 khz. I don't have any hearing above 14 khz so I don't miss it. These speakers have a quoted distortion level at 1 w, look for that on any other product spec sheet. The CS800s sounds really good even though I use low wattage in my LR. Also it is available at the store.

My living room has plaster walls broken up by record racks bookcases the organ carpet and overstuffed couch, so I have no standing waves to mess up the sound. The sound bounces off the walls well enough that I don't need special monitors when I play. I use a digital effect box on the Hammond sometimes to simulate a huge rotary leslie speaker.

I have wood pianos to play in other rooms, but I live on a 1/3 acre lot in a separated house, so the neighbors don't complain if I play ff at 3 AM. This neighborhood isn't stylish, but it fits my music all the time lifestyle.

For other speakers than diyaudio posters think are worthy of hifi, see this thread: PA speakers for home HiFi use

Not everybody lives in the US south as I do. Nobody will demo Yamaha or JBL pro equipment, which are reputed to also sound good in the 15" woofer + 2" horn category. Don't waste time on 1" driver horn models, the midrange can be quite bumpy.
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Last edited by indianajo; 9th February 2019 at 11:36 PM.
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Old 10th February 2019, 01:34 AM   #9
abraxalito is offline abraxalito  United Kingdom
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From reading the blurb it sounds like the piano can output to USB (says 'USB to device') so I'd connect a USB DAC and work from there, bypassing everything from the D/A onwards.
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Old 10th February 2019, 08:54 AM   #10
Mooly is offline Mooly  United Kingdom
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Replacing the atrocious sound system on a ,000 digital piano
Quote:
Originally Posted by computerpro3 View Post
Oh wow, I am an idiot! There is a pinout on the amps printed on the PCB! Pin 1: mute Pin 2: Hot Pin 3: Cold
Not at all Its very difficult trying to figure out and reverse engineer stuff with no documentation. Its even more fraught when its such an expensive item.

Quote:
Originally Posted by PRR View Post
Your images come out thumb-size; I can't see much.
Try right clicking and opening the image in a new tab.

It is much better to attach images directly:

How to attach images to your posts.
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