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strange amplifier noise

pete326

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#1
Hello,

Since I bought my new amplifier, I'm experiencing strange noises which remind me of blown speaker(rubbing voice coil noise).It's noticable at low volumes and it's really annoying :mad:

If it helps to solve the audio issue, amp uses toshiba (a1941,c5198) output power transistors.The speakers are anyway fine, I tested them with a different amp.

Please help :)
 
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bigron

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#2
Check your wiring connection/polarity both at the end of the amp and speakers. Are the speakers bi wired ?
 

IndianEars

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#4
I suspect there is a substantial amount of DC ( 1 Volt or more) at the output terminals of your power amp.

You can check this with either of the 2 procedures:

1. If you have a Multimeter, switch it to Volts DC and measure at the Speaker terminals, with the amplifier ON and no muisic playing. It should read almost no DC voltage ( less than 0.1 Volt )

2. If you do not have a Multimeter, with the Amp ON & no music playing, disconnect one of the Speaker wires and reconnect. Do you Hear a Fairly Loud 'PLOP" from the speaker ? If Yes, you have DC on the amplifier output and it needs to go for repairs, else it will bake your Speaker Voice coil and eventually spoil the Speaker.

Do revert ...
 

pete326

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#5
I have measured dc voltage on speaker outputs, and I got about 37 milivolts on left channel and 40 milivolts on right.No music playing through.
 

IndianEars

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#6
That is a Very Low DC offset. Certainly no concern on the DC offset.

Could it be scratchy Switches or a scratchy Volume control ?

For the switches, switch then In/Out or ON / Off multiple times quickly.

For Volume control / knobs turn them around a few times swiftly.

Does this remove the problem .... temporarily ?
 

pete326

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#7
Unfortunately, it didn't fix the problem, still dealing with it :(
this has to be a problem with PCB components (maybe capacitors,resistors,transistors...)
I don't know...
 

pcasebpev

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#8
about 37 milivolts on left channel and 40 milivolts on right.No music playing through.
 
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