Casio GP-510 Sound Engine Malfunction

[GGGeoff]

Well it was a brief honeymoon. My nearly new GP-510 has gone off the deep end. The sound engine or effects processor has somehow corrupted its internal parameters. This is the second time it has happened. The previous time, I gave up and went to bed. The piano was back to normal by morning as if nothing had happened.

 

The problem starts with the grand piano sounds: loss of stereo separation, loss of depth/volume, and certain notes (F#3, G3, G#3, and a cluster in the bass as well) sound quiet and thin. If you've ever heard an acoustic piano with two of three strings muted on a note during tuning, it's not unlike that.

 

Selecting different tones, such as Harpsichord, or Electric Bass, provide stranger sounds... like you are standing at the very back of an enormous hall and hearing only reverberated sound.

 

I managed to record some of the weird sounds onto a USB stick. When played back, they either sound just as weird, or different, but still not right.

 

Playing a Concert Play piece, such as Raindrop, results in the provided piano track sounding incredibly distant, while the orchestra sounds almost normal, but not quite right.

 

I have tried:

• Factory Reset in the menu, which does reset all settings, but is not a cure for this behavior.
• Adjusting hall reverb and position, as well as toggling through various scenes.
• Adjusting EQ, etc.
• Power off and unplug the DC Power supply, let the piano sit for a few minutes.

 

Nothing has helped, other than last time of leaving it overnight, unplugged.

 

Anyone experience this and know of a fix, like a true hard reset? Is this a usual bug? I'm thinking a call to my dealer is in order.

[Brad Saucier]

Hi Geoff.  I would definitely call the dealer.  Unfortunately that does not sound normal.  They should be able to sort everything out for you and make things right.  Please keep us updated. 

[GGGeoff]

Hi Brad,

 

Thanks for the reply. I'll be contacting my dealer today. As expected, the piano was completely back to normal in the morning, as if nothing at all had happened. Curiously, the WAV files that I recorded onto a USB thumb drive in the piano, when played back on my computer, sound perfectly normal. I don't know the architecture of the CASIO sound engine and amplifier chain, so I can only make educated guesses based on careful listening.

 

Next time this happens, I'll record it with my iPhone.

[mike71]

Not having a schematic diagram of the piano I could only make an educated guess. If the digital recordin it's OK, the problem lies in the DAC and analog parts.

On 12/7/2021 at 6:59 AM, GGGeoff said:

Selecting different tones, such as Harpsichord, or Electric Bass, provide stranger sounds... like you are standing at the very back of an enormous hall and hearing only reverberated sound.

 

 

 

It could be you're hearing the difference of left and right channel. The piano sounds weird even if listened with headphones or using the line outs to an external amplifier?

 

If the audio amplifier board  is on a separate board and the audio signal is on a loose connector the effect will be you're going to hear the differential signal. GP-510 doesn't have hex layers so I suppose you can't make a tone with a simple mono triangle wave. Using a simple mono signal makes the differential signal null.

 

 

[GGGeoff]

3 hours ago, mike71 said:

Not having a schematic diagram of the piano I could only make an educated guess. If the digital recordin it's OK, the problem lies in the DAC and analog parts.

 

It could be you're hearing the difference of left and right channel. The piano sounds weird even if listened with headphones or using the line outs to an external amplifier?

 

If the audio amplifier board  is on a separate board and the audio signal is on a loose connector the effect will be you're going to hear the differential signal. GP-510 doesn't have hex layers so I suppose you can't make a tone with a simple mono triangle wave. Using a simple mono signal makes the differential signal null.

 

 

 

Interesting thought. Left minus Right would be all the out-of-phase stuff like hearing only reverberations, plus it would be mono. The first time this happened it was while trying out different headphones, and it affected the main speakers as well once I unplugged the headphones.

 

The second time it happened was also while wearing headphones (Philips SHP-9600 wired open backs). Could be coincidence, or not.

 

That it survives a Factory Reset and fixes itself by morning tells me it may be physical - like heat related. Could indeed be a dodgy connector.

 

Oh, and the most affected sound was the Electric Bass... which if I remember right is about as close to a simple mono triangle tone as you can get. The Harpsichord sound was also strongly affected. Either one you couldn't hear the direct sound, but only the hall reverberation. Recordings were fine.

 

The other unfortunate symptom is a pulsing digital whining if I connect both the USB Host and Audio Line Input to the same device (like an iPad or USB-C Hub). In fact, just connecting the shields of those two inputs together on my GP-510 results in the sounds. It's like the noises you used to get if you held an early LED calculator near an AM radio (yes, I just dated myself). If that noise is typical of these pianos, I figure I'll have to add up an isolator transformer on the line input from my iPad. Likely unrelated to the problem I started the thread, but curious if it's typical for this brand.

Edited December 9, 2021 by GGGeoff

[Joe Muscara]

USB noise is an unfortunate problem a lot of keyboards have. I would believe that's unrelated to your initial issue.

 

As far as the initial issue, I wonder if it's the headphone jack. I've seen times where working the jack by inserting/removing the plug a couple of times fixes problems. There is a physical switch in there that tells the unit that headphones are plugged in so it knows to shut off the internal speakers and sometimes that switch gets stuck.

 

What I might suggest is that if the sound is okay through the speakers, try not using headphones for a while and see if the problem returns. If it only happens after you insert headphones we might have a culprit.

[GGGeoff]

Just an update on this. The amplifier sound distortion problem hasn't happened again, even when switching several times between the built-in speakers and headphones.

 

I have, however, found a solution for the USB noise when connecting both USB and Audio Line In to the same device. The item that finally solved it is a USB Isolator. There are many kinds available, but I chose to go with the bare board from Adafruit, as I've had good luck with their products and appreciated their video explanation. The board must be switched to High-Speed for the CASIO to talk to my iPad. Basically it's an opto-isolator for the USB data lines, and power pass-through via a tiny on-board transformer, up to 100mA. That tiny board is plugged in using a small USB-A to USB-B adapter rather than a cable, thus keeping it tucked away under the piano out of harm's way. Between my iPad and my USB-C hub, I have a quality 4' USB-A to micro-USB right-angle plug into the isolator board.

 

Adafruit USB Isolator

 

Alternatively, I tried a line-level audio isolator, which also eliminated the USB whine, but then picked up some different environmental EMI noise itself from room lighting (though nowhere near as obnoxious as the USB whine was). The USB isolator ended up the winner since it doesn't introduce anything into the audio feed and accomplishes the goal of isolating the grounds of the two signal paths.

 

I suppose I should put together a separate thread detailing my setup. Once I receive the final USB-C cable that will clean up the connection path from my USB-C hub to my iPad Pro, I'll take some photos. I may yet design and 3D-print an enclosure for both the USB isolator and the USB-C hub.