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Old 24th May 2013, 04:50 AM   #1
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Default LM4766 tiny hum/hiss is normal ?


I have built an Ebay kit with LM4766.

ES9023 + LM4766 DAC AMP KIT

There is very quiet hiss/hum. I can hear only closer than 5cm... my ear is very close to the speaker.

Is this the normal level or can it be improved ?

Thank you.
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Old 24th May 2013, 10:58 AM   #2
AndrewT is offline AndrewT  Scotland
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The signal noise ratio of chipamps is not great. It is adequate. Read the datasheet.
A faked chipamp could be very much worse.
regards Andrew T.
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Old 24th May 2013, 01:17 PM   #3
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Thank you.
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Old 25th May 2013, 07:45 AM   #4
blu_glo is offline blu_glo  England
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Nanoloop -

Outside of a metal box amplifier circuits do pick up the noises of the world. Once inside a fully screened enclosure, the situation will be much improved.
Ditto open circuit inputs - they are still technically aerials, even apparently screend RCA sockets! put a shorting plug in (old crappy phono socket with signal and earth soldered together and see if there's a marked difference. The same applies when you actually plug in a working source as the (normal) op-amp output will try to keep things quiet untill you play something.

5 cm from the speaker? You've done well!
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Old 25th May 2013, 01:48 PM   #5
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I am only being a little facetious, but a very faint noise can be heard when I am closer than 5cm from a sea shell.

As others have suggested, it seems that you are well into second- and third-order effects. I will add, though, that whether it is a hum or hiss may offer some hint of the source. A hiss (white noise) could be ambient noise picked-up like little aerial antennae. A hum (50/60Hz) suggests that it originates from the power outlet or house wiring.

Overall, the results you describe do not seem so bad, especially if it is just the kit and not in a shielded enclosure like blu_glo describes.
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Old 26th May 2013, 04:01 AM   #6
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Thank you all. It seems it is normal so no need to do more modifying.

The sound is very good - very strong bass especially. I am surprised it can sound so good.

Thank you again.
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Old 6th January 2014, 03:23 AM   #7
arifs is offline arifs  Pakistan
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This is in my opinion good, because sound can only be heard from, 5 cm, which is not usually the distance one listen to a speaker from. I have built one and quite happy as unlike poor transistor kits it dosent pick power supply noise.
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Old 6th January 2014, 04:47 AM   #8
Mihkus is offline Mihkus  Estonia
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When mine was hissing... it was oscillating like crazy.
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