Power Amplifier Looking for improvements

[rinchan6]

Hi guys.

I was here last year or months asking for help how to design a power amplifier. I was told to read books and all references I could get. After some efforts and money of course I was able to make my own power amplifier for my room which I designed. The diagram is attached.

It has a gain of 31dB with 500mV sensitivity on an 8Ω load.

My problem is whenever I turn the amplifier On or Off there is a "thump" sound and the speakers look like its gonna rip off.

I wanted to know other opinions about amplifiers and how they design one.

 

[davenn]

hi ya Ken

the usual way to stop the "thump" in hi power amplifiers is to use a delayed relay in the speaker line
ie. when the power is turned on, there is a second or two of delay before the relay switches the speaker outputs into circuit. This allows the amplifier to power up and settle before the speaker lines are connected

cheers
Dave

 

[rinchan6]

hi ya Ken

the usual way to stop the "thump" in hi power amplifiers is to use a delayed relay in the speaker line
ie. when the power is turned on, there is a second or two of delay before the relay switches the speaker outputs into circuit. This allows the amplifier to power up and settle before the speaker lines are connected

cheers
Dave

I like the idea of putting a relay but I believe that doesn't solve the problem when you are switching it off.

Also, I just remembered that when I turn the volume of the amp to the lowest using 50K pots, I still hear audio on the output. Does increasing pot value solve this problem? I haven't tried it since I ran out of pots.

 

[KrisBlueNZ]

Anti-thump circuits also monitor the AC from before the bridge rectifier and use a monostable or similar circuit to detect very quickly when the mains has disappeared, so they can drop out the relay before the main supply rails have had time to discharge.

Google anti-thump relay circuit.