Hum I've got a bad hum in my system. I have a yamaha m-4 amp, pmx-9000 preamp/mixer, and klipsh lascala speakers (yea, they're a little old and I just brought them out of storage). I have the componenets grounded (to a ground rod), it didn't help. When I looped an equalizer/reverb unit thru the preamp, it made it much worse. Any ideas Dorsey

The cracking and humming sound is because of the improper earthing

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You have a short. This is either from a bad cable or a faulty price of gear.

to find the problem do you want to isolate pieces of the system. Turn on just your speakers (if they're powered) or amps (if the speakers are not powered). With the mixer off, if you were getting a pause the short exists after the mixer. No buzz? Great! Turn the amps or speakers off to prevent popping. Turn on the mixer, and then turn on the speakers or amps. If you have a bus now with all channels on the mixer down it is likely your mixer. If there is no buzz, Bring the channels up one at a time. Once you find the buzz, turn the channel back down and plug unknown working microphone and cable into its channel. If the Mike buzzes when you bring the channel up it's the channel on the mixer. If it does not then the issue exists before the mixer. This is most likely and also the least expensive to resolve. Check the snake if you have one and all cables in line in a similar fashion. Most likely a snake channel has failed, you have a bad cable plugged in the snake Or you have a bad DI box or mic plugged in.

Happy hunting

Intermittence is usually an issue of a loose connection - whether it's in a cable, inside a speaker, inside the mixer, or power-related. I would check them all, starting with the audio connections.

normally a Hum is caused by a bad ground,, if it only happens when the unit warms up it could be the output drives are failing. , check the grounds to the unit first, then the wires to the speakers themselves, if they all check out ok,, you need to take it to a repair shop dealing with receivers

do you have a low hum from the speaker when u turn it on? if no, then take it to the repair tech. probably power on indicator is okay but power supply does not reach the pre-amp or the power amp section. case maybe bad filter capacitor or bad series power line resistor. get it checked. i sincerely doubt internal speaker loose connections.

Try just the power amp on ..nothing connected
no Dakiom thingy either. It's a matter of elimination. Start at the output device and work back. Keep the Dakiom out of the loop.
If there's hum with just the Adcom..then it's the ADCOM

The feedback unit should be connected between the pre-amp section and the power amp section. As you descrubed the ST-out and P.Amp IN are the ones to use.

Dan

You need to provide me the specs of your amp, your speakers. Impedance important. You are experiencing overload, overheating caused by overload. You have a wider frequency range using a mixer and that affects the output stage of your amp and can cause to fail.

I am from Yamaha service before and they have speakers that has 4-6Ohms impedance only. And you have to know your amp if capable of handling such low impedance. you may not have problem with the power but it should be impedance.

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