muddy sounding electric piano

[dolcemusik]

I'm starting to learn piano again and this is one of those things where I really am putting aside time every weekend now to play for a couple of hours.

My question is, I have a digital piano, its a technic and it looks lovely, it has a wooden finish. I bought it about 9 years ago and it hasn't seen much use..

But now I've started playing again, everything in the left hand sounds really muddy,  I have taken the sustain off (which is automatically on when you power it on) but it still sounds muddy.  As far as I can understand, if it is electric, the sound will either work or it won't, I'm guessing it must be the voiceings I'm playing?  Can anyone help me on this?

I can't afford to have lessons, really can't, and ages ago I bought myself a couple of books on jazz piano as that's what I want to play (I play jazz on my saxophone) but I can't find anything in there about voicings, or not anything helpful.

Does anyone have any advice or can you point me to any good sites on the web?

[iansinclair]

do you still have the manual for it?  That would be the place to start.  If not, the manual may be available on the web -- although you might have to pay for the download.  Try https://www.know-your-keyboard-piano.com/technics-keyboard-manual.html

[indianajo]

Electric music equipment finds the piano a demanding sound to reproduce due to the high power demands of the attack at the beginning of the note, and the wide frequency content of the proper sound. 
If your "piano" sounded good when you bought it, and not 5 ,10,15, or 20 years later, it is possible the power supply has deteriorated.  There are energy storage devices called "electrolytic capacitors" in the power supply that can leak the water out past aged rubber seals.  If your power amp doesn't have enough energy, the power transistors can't faithfully reproduce the signal presented to them. furthermore, there are other electrolytic capacitors used in blocking DC voltage and allowing AC through, which if dried up they can change the frequency response of the AC signal going through. 
Very cheap capacitors in computer boards and remote controls frequently deteriorate in 3-5 years.  More expensive ones used in quality gear can last twenty, but it was up to the production engineering department how much money they spent making your instrument sound good 5, 10, 20 years out.  They still sell lots of 500 hour life caps to repair shops, just check out the websites the distributors.  They also sell 10000 hour caps for about 1/3 more, using different rubber.  It is up to the purchaser. 
I make a hobby of buying old hifi and organ equipment, and changing the capacitors to make them sound good again.  Some of the basic instructions are on post #2 of this thread: https://www.organforum.com/forums/showthread.php?22133-Magnus-Electronic-Organ-Model-3051
A post 1990 product may have surface mount capacitors, which it takes a $700 tool to unsolder.  So in that case I wouldn't have them all done, maybe just the two big ones in the power supply. Not the line voltage rated ones before the transformer in a switcher supply, the two rated 50 volts or less feeding the amp stage. 
If you don't want to learn to do this, change them all out, you should carry your "piano" to a shop, or buy a new one. It is hard to get a shop to replace more than "the one that was bad", which leaves your instrument full of bottles full of slime sealed with 10 year old rubber.  It is also hard to get a shop to spend the money and time to sort out the 500 hour replacement parts from the 10000 hour parts, and use the latter.  Usually the tech just calls the supply house on the phone and gets a part that "works".  Yeah, a year or five, anyway. Like a PC or a cell phone.   When I do an instrument that sounds stupid, I replace all the electrolytic caps, and with long life parts.  part of boing an amateur I suppose, not a professional. 
 My objection to products from a certain continent is partly that they build to last five or ten years, not the 20 to 40 years a real musical instrument should work.  It takes 10 years just to get good on a piano, what use is one that wears out in five years.  Yet I look at bands on the television, they all have shiny new gear from famous manufacturers, not what they bought at the start of the digital revolution.  The only electric survivors on stage  seem to be the hammond tonewheel organs built 1955-1970, of which I own a collection. 
Good luck. 

[oxy60]

That the sustain comes on with the power indicates that you need to read the manual. There  is no substitute for consulting instructions.

[grasoon]

Not sure if there is anything to do with your room acoustic, mine have the same  problem too but solved it with room treatment. Have you tried them with the headphone?

[oxy60]

Most electronic keyboards have far more options that most players will ever use. The poster needs to restore/reset the instrument to factory fresh out of the box and only select the options needed. The instructions hold the key.