[sdiy] [synth-diy] Success - hum in 303 output gone

Neil Johnson neil.johnson71 at gmail.com
Fri Dec 13 23:42:47 CET 2013


Hi,

>> I went for the largest inductor in the ballpark:
>>
>> http://de.mouser.com/ProductDetail/Bourns/70F501AF-RC/?qs=sGAEpiMZZMsg%252by3WlYCkU6J1Kh%252bkI7ZW63PlG49mKtY%3d
>>
>> Bourns 70F501AF-R

Firstly, that choke is pretty much at the limit of its DC current
handling (30mA per datasheet).  Anything above 30mA and it stops
behaving like a choke, just a piece of wire (the core saturates and
there's no more magnetic magic happening).

>> wasn't any buzz. The LEDs were bright enough to see in a normally-lit
>> room. When the blinking LED turns on, the other two go a little dim.
>> That's all really.

Secondly, if the source of the noise is the LEDs switching, have you
considered routing the LED power circuit (supply and ground) directly
to the PSU, perhaps their own dedicated smoothed supply rail.  That
would reduce the amount of LED switching noise from reaching the audio
circuits.

Neil
--
http://www.njohnson.co.uk



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