Integrated Amplifier - Volume Control Problem

A number if things can be wrong with it, from the audil preamp to the the audio amplifier. Even as simple as a bad volume control. Does the actual noise change patterns when you move the volume?

If it's an old type control then you can spray it with Servisol switch cleaner. You might have to take the top cover off to get better access.

No fear.
Try to reachinternal side of front panel with volume controls. Put some paper towels under the front panel. Pour lighter fuel into every dirty volume control turning knob around several times.- It will rinse out all dirt from carbon track or contacts. (I don't know what kind was used).- This is only temporary solution, good for one year or so. Proper solution-> unsolder volume control, open it up , inspect and clean or replace for a new one. It will work, I did it hundreds of times...always with positive results.

It's probably dust in the volume control. It gets in between the carbon track and the wiper that rotates on the track, or the resistive / carbon track inside the control is wearing out. As yours is stereo there will be 2 tracks and 2 wipers, one could be worn more than the other.
This should give you an idea. Inside Pot

I reckon this could be an older type of volume control, which if it is a spray of Servisol Video 40 on the workings of the control (inside the unit if you can) should correct it. Otherwise it's an IC that controls it and needs to be replaced.

Well it sounds like your amplifier IC's are working correctly since you are hearing that pop. I have the same amplifier and every 10db increment it pops. Have you tried every input? Possibly try starting at a low volume, plug an RCA plug into CD or any other input, and touch the center prong of the other end of the cable. You should get a 60hz hum if your in the USA, otherwise it will be 50-55hz. Regardless it should make noise.

there is dust inside the switch try blowing some air into it,

I have a Korg C-15s and also experiencing loud crackling sounds when I turn it on. The problems seems to be either the sliding volume control or the amplifier itself. Honestly though, I believe the issue is the volume control. I opened my piano to get a closer look and attempted to clean the contacts on the volume. Unfortunately after cleaning the contacts, the crackling sounds became somewhat worse. After I turn the piano on, the volume control is generally rendered useless......volume set to low volume and the noise is quite loud and other times the volume control is set high and get very low volume crackling noise. No real consistency. The noise does diminish after a few minutes but so does the piano sounds to an inaudible level. There were a couple of instances where I turned it on and surprising enough, no no noise and perfect sound. For these reasons I believe the issue is within the volume control and not so much the amplifier. I have an electronics background and noticed that the volume control is very unique in design and is not something that can be substituted with another volume control from other sources.

My recommendation is to check the sound quality of the audio from the RCA L/R audio outs on rear of the piano by connecting to a stereo receiver. If it sounds fine you're in luck. If the crackling sound does not diminish after a few minutes like mine does, I would suggest disconnecting the internal speakers and using the audio out only. You can connect a pair of studio monitors or high quality computer speakers, preferably with a small subwoofer to deliver the full audio range and deeper tone of a real piano. I'm currently using a basic pair of Logitech computer speakers and is quite acceptable until I can afford a high quality set of monitors or relocate my piano closer to my high quality Yamaha receiver.

I hope this info helps a bit.

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Kenwood 54 Manual Stereo Integrated Amplifier HiFi Engine

Set your SAT receiver to full volume and use your Sony TV volume control as the master volume control. If you use an external surround sound amplifier do the same thing using the amplifiers volume control as the master volume control.

Consider that all source devices that have the ability to control their output volume will output what they call line level 0dB when the source device is set for maximum volume. If you set the source device to 1/4 volume your output to the amplifier may be around -25dB or lower. Introduce that low of an audio level to the amp and you will have to turn the amp up to half way or better causing the amp to amplify noise too.