Power supply question

[juan_felt]

Hi,

I'm building this headphone preamp
http://www.redcircuits.com/Page119.htm
And I added a Dc jack to power it with a power supply. I realised that with a normal one it makes some noise(like effect pedals), so I tried with a regulated and filtered power supply that I use for my pedals and the noise was gone.

Is it possible to add to the circuit the components of a power supply that filter the noise? What would happen if I plug an already filtered and regulated supply to this (with the same components already on the circuit)?

Thanks!

[induction]

That would work fine as long as you give it enough voltage. A 9V regulator needs a supply of 12V or more.

Edit: Your schematic already has a power filter (C5), but a regulator circuit does a much better job than just filter caps alone. So you would add a regulator and a couple of caps to your schematic. (And some diodes if you want to protect against polarity reversals or accidental grounding of the regulator supply pin while the regulator is charged up.)

[Kipper4]

Like this Induction?



https://imageshack.com/i/nf3fkphj

[induction]

Attach the 9V node of this:

to the 9V node in your link (and reduce C10 in your link). I would increase C1 or parallel it with something bigger.

Warning: the pre-regulator filter caps (C1) must be bigger than the post-regulator filter caps (C0 in this schem, C1, C3, and C10 in your link), unless you put a protection diode across the regulator like D1 in this:
.
If the output pin has a higher voltage than the input pin, current will run backward through the regulator and kill it.

[Kipper4]

And this simple solution would lessen noise more than what was in my picture?
That would be great because I have quite a few 12v dc power supplys from old phones hanging around and could put them to good use.
Even make a dedicated noiseless breadboard or pedal 9v psu.

[induction]

Yes. In my experience it's much quieter. Even with good filtering, you can get bad hum from op-amp and transistor circuits that have biasing resistors attached to V+. Ripple from V+ gets transferred to the input of the gain stage via the biasing resistors, and gets amplified along with the signal. Regulators reduce the ripple quite effectively. I've done A/B experiments with heavy cap-only filtering vs. regulators with less heavy filtering. The regulators win by a landslide, even when you use very crappy 12V adapters for the source voltage.

Try it. You won't be disappointed.

[Kipper4]

Thanks for that I will.

[J0K3RX]

I am in agreement with Mr. induction but if you don't have a 12v adapter then this does a pretty good job...

http://beavisaudio.com/Projects/Huminator/index.htm

[tommycataus]

+1 to induction, I tried the huminator on the Beavis Audio site and it didn't work for the supply I have. I currently use the exact circuit illustrated above with the 9V regulator in its own separate enclosure, although C1 in mine is 1,000uf. Noiseless.