Looking for user manual for Technics SA-AX720 receiver

check here....

https://www.manualslib.com/manual/1010383/Technics-Sa-5250.html#manual

If the Amplifier has more Output Power and Better Quality Sound then it is worthwhile to do so -Yes you can connect Amp to Technics Receiver you have mentioned

try http://www.chung-sim.com/panasonic.sa-gx370.html

Connect the 6-channel analog outputs of the AC500 to the 6-channel analog inputs on the AX720 using 3 RCA cable pairs.

http://archiwumallegro.pl/technics_shac500d_procesor_surround_ddigital_dts-1215399983.html

Digital sources will enter the AC500 and be converted to 5.1 analog output.

Be advised, that input on the receiver will not allow any internal DSP manipulation. WYSIWYG.

According to my Technics SA-R210 manual to UNMUTE without the remote....do the following......PRESS BOTH THE VOL UP & DOWN CONTROLS & THE LOUDNESS SWITCH ON THE UNIT AT THE SAME TIME......Not sure it will work for your model but that is what it shows for The Technics SA-R210 model, so it should be pretty much the same

I too have a Technics SA-GX100 and it's rated at 2 x 40W @ 8 Ohms. I have the Technics SB-2840 floor model speakers hooked to it, which are rated at 200W Music Input - 8 ohms. It sounds very nice just to be a 40W receiver.

try emailing them.

[email protected]

THIS UNIT HAS NO SUB WOOFER AMP IN IT. THE ONLY WAY TO OVER COME THIS IS TO HOOK THE LEFT AND RIGHT FRONT SPEAKERS STRAIGHT TO THE SUB WOOFER AND THEN GO FROM THE SUB WOOFER BACK TO THE INPUTS ON THE BACK OF THE UNIT FOR THE FRONT SPEAKERS. THE SUB WOOFER THIS WAY WILL EXTRACT THE BASS AND THE FRONT WILL RECEIVE THEIR PART. THIS SOUNDS CRAZY AS HELL I KNOW BUT THAT'S HOW I GOT MINE TO WORK. THE OUTPUT FOR THE SUBWOOFER IS USELESS AND PUT THERE FOR YOU TO HOOK UP AN AMP FOR A SUB WOOFER. EVERYTHING HAS SHORT COMINGS, AND THAT'S THE ONE FOR THE AX-720.

The audio amplifier IC of your device are damaged you need to replace it.

Look for lossing solders points or bad conections. Start to look on those components of hi wattage and components to get hot alot, those are the most common to have weak solders spots.
Also some equipment need to be clean because the dust can make problems.
good luk.