[sdiy] NE571

[Dan Snazelle]

thanks

great advice...as the regular bypass caps didnt seem to do anything

OF COURSE part of the problem may be the polivoks filter that is on the board...it is possible that the LM4250 based filter
may be very sensitive to ground related issues....(this is always the problem with adding multiple circuit blocks to a breadboard before you have tested each on its own...but in the interest of time i often try out new circuits in relation to others that are already built up and working.




> From: jhaible at debitel.net
> To: cheater00 at gmail.com; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] NE571
> Date: Sat, 22 Aug 2009 10:36:12 +0200
> CC:
>
> I don't expect anything like fast switching going on inside there (except if it oscillates), but it's a single-supply chip, so all
> the supply current flows over GND. Also, most circuits I've seen with these companders are not just using bypass caps, but
> RC-filtering. Try 47Ohm and 100uF || 100nF for a start. That keeps medium-frequency noise off the GND connection (and not just HF
> noise, as with mere C decoupling). Make sure that the 100uF || 100nF are close to the chip, *and* route the GND like this: (Ground
> Rail or plane) -> capacitor(s) -> (IC-Pin)
> (*not* Rail -> IC -> Cap !)
>
> JH.
>
>
> ----- Original Message -----
> From: "cheater cheater"
> To: "synth-diy"
> Sent: Saturday, August 22, 2009 9:48 AM
> Subject: Re: [sdiy] NE571
>
>
> I'm just a newbie, but..
>
> Is it properly decoupled?
>
> Got any filter caps on the Vcc?
>
> D.
>
> On Sat, Aug 22, 2009 at 8:35 AM, Dan Snazelle wrote:
>>
>> can anyone tell me if the NE571 puts a LOT of noise onto the ground rails?
>>
>> every circuit i build with it ends up bleeding into other parts of the circuit without any connection
>>
>>
>> thanks
>>
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