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-   -   Noise on the RIAA phono preAmp (http://www.diyaudio.com/forums/chip-amps/98530-noise-riaa-phono-preamp.html)

diarav 20th March 2007 06:28 PM

Noise on the RIAA phono preAmp
 
Hi,
I constructed the RIAA phono preamp from ESP site.
http://sound.westhost.com/project06.htm (the single supply one - bottom of page)

The preamp board is mounted inside the turntable and is sounding fine initially. But after about 20 to 30 mins of operation, it starts giving out strange crackling noises at irregular intervals. I dont believe the problem to be attributed to any rumbling.

Could it be because I am not using a regulated supply (about 18V) at PS output. Just the 13.2V from output to Bridge rectifier to a 1000uF Electrolytic.

Or what else could cause the problem?

sreten 20th March 2007 07:44 PM

Hi,

Could be a dodgy joint. A regulator would be a good idea.
Also download the NE5332 datasheet,
the circuit does not show the PS decoupling capacitors needed.

:)/sreten.

peranders 20th March 2007 07:49 PM

A good RIAA amp must have a regulated _good_ power supply. Remember, you want to amplify microvolt signals as the weakest.

Despite from that, have you checked all solder joints? How about voltage ratings of your electrolytic caps? Anything gets hot?

diarav 23rd March 2007 05:27 AM

Thanks for your responses , peranders and sreten.

I did not check so far for any thing getting hot - this is enclosed within the turntable box and I am yet to open it.

I wanted to get inputs on possible causes before looking into it.


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