Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Sweep Gyrator

Status
Not open for further replies.

Reno

New Member
Hi there I have built this sweep EQ which works however, I am having a major hum problem with it.
At first I thought it could have been a ground loop on the board however, I also built this circuit into a mic preamp with a baxandall tone control after it. This circuit worked fine when the opamp for the sweep EQ was removed however when I put it back in it started again. This has given me the conclusion its something to do with the circuit, as it does the same thing on two separate boards and is not a ground issue. Any help would be greatly appreciated as I am pretty much stuck thanks.
 
A 60 (or 50) Hz hum? If so, how clean is your ±15DC source?
 
Hi thanks for you response I think its a 50hz hum but I have not taken note of the hum when the pots have been in center position so it could be either, as when you sweep higher up the hum disappears. I am testing this on Rod Elliott's power supply **broken link removed**
 
I noticed, under NOTES, above the schematic for the power supply you're using:

"The GND (0 Volt) line must be connected to the ground of the equipment being powered. Serious malfunctions can be caused by leaving off this connection."

You don't seem to have a power supply ground (neutral) on the PCB you're using, just ±15VDC (unless the ground connections are all one big ground plane, not shown as seperate traces).
 
Last edited:
Thanks for your response, the GND (0 Volt) is connected on the board you just cant see the ground plane I can post a pic if you want?
 
huong da ca do qua mang
huong dan ca cuoc qua mang
cach mo tai khoan ca do online
cach mo tai khoan ca cuoc online
cach mo tai khoan ca do tren mang
cach mo tai khoan ca cuoc tren mang
cach mo tai khoan ca do qua mang
cach mo tai khoan ca cuoc qua mang
ca do tren mang

Yeah, that too....
 
Thanks for your response, the GND (0 Volt) is connected on the board you just cant see the ground plane I can post a pic if you want?

No need.

By the way, I'm assumig your mains are 50Hz.

I think your only real option, at this point, is to find a scope and look at the ±15VDC lines for noise (that, or try a different PS).

Could be wrong...
 
Thanks for the idea it looks like my only option as I cant see anything else causing the problem
 
Try using a couple 9v batteries as a substitute for the power supply. See if that isolates the problem.
 
Usually op amps have great power supply noise rejection. My guess would be that you need twisted shielded wire for the input and output signals.
 
My guess would be that you need twisted shielded wire for the input and output signals.
....and for connections to any off-board control pots. A screened housing for the project might also help.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top