[sdiy] prob with noise circuit?

[Dave Magnuson]

----- Original Message ----- 
From: "Pete" <23isgood at gmail.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Monday, May 30, 2005 8:52 PM
Subject: Re: [sdiy] prob with noise circuit?


Ok its working now. I had tried the 741 and nothing came out until I used a
TL071. Thanks Paul! Now I have a new prob though. I get a low frequency hum.
Do you also have to ground the op amp? Are the offset null pins used for
ground? Thanks for helping out guys with my basic questions.

pete


What are you using for a power supply?  Perhaps this is your problem?

Try using a filter on the supply inputs... each supply line goes through 
small (10 ohm to 100 ohm) resistor, then followed by both 10uF and .01uF 
caps to ground.

Another problem could be the length of your wiring...  long leads will pick 
up hum.   This is exaggerated by the high gain required in the opamp stage.

Finally... it could be a ground loop between your amp and the circuit.

Dave