60 Cycle Notch Filter!

[rooo]

Any thoughts on some sort of 60 Cycle notch filter to help reduce 60 cycle hum?

As a hardcore Tele player (and sometimes Les Paul w/ P90's), this could prove to be quite useful in certain situations.

[rooo]

I have no idea, but perhaps something like this?

http://circuits.linear.com/34

Ideally, you could control the level of the 60hz with a pot or something so you could dip it just enough to hide the hum a bit. The one in the link seems to be fixed to reduce 60hz by -60db.

[rooo]

Eh?

http://www.radio-electronics.com/info/circuits/rc_notch_filter/twin_t_notch_filter.php

[Madferret]

I'd be up for being a bit of a Guinea pig with this too as I'm also a tele player and get pretty sick of the hum.

[Madferret]

Ok so after doing a couple of calculations and then trying awkwardly to get to grips with the Layout editor, here's what I think should be a notch filter for 60hz with an adjustable Q (width).  Whether or not it will do anything is another matter entirely, also I'm not very good with circuit design or op amp pinouts so there's every change this is a total pile of crap.  I'll build it tomorrow as it's a bit late now and let you know if it actually works.

[Dave]

Tssk, hum shmum, personally i think a bit of hum adds character.
Thanks
Dave

[jaylow]

Hello! I was actually going to request for a similar schematic to be drawn up.

I found this: http://members.shaw.ca/roma/nine.html

I was actually trying to build this but I've never taken a schematic and turned put it in stripboard form. I started working on it earlier but it's pretty challenging. Maybe you guys can take a crack at it?

[jaylow]

What kind of pot are you using? I'm sorry if you mentioned it and I missed it. It's pretty late.

[Madferret]

No sorry I hadn't put a value on it, to be honest I've sort of fudged this together from a bunch of ideas and forum threads so I can't remember actually thinking of a pot value.  I'd maybe go with something small like a 4k7 and go from there.  I'm going to test it today so I'll give you some feedback from that.

[jaylow]

I know someone's already working on something, but I was wondering if someone could have a look at this too. It's my first try at going from schematic to stripboard and it just so happened to be a similar project. It would be nice to know if I was on the right track or if I was completely off.

[Madferret]

If you swap R2 and C4 then you'd be able to move half the cuts in column G left and half right and be able to save yourself a column and if you just straight connected the 10uf cap in parallel with the 100k resistor you could ditch the two long jumpers and put one between rows J & K to save yourself 2 columns. Other than that everything looks to be connected but obviously without looking at the original schematic (or better yet building it) I wouldn't know if it's right or wrong.  I'm sure some of the other guys on here would be better equipped to take a look at it.

[jaylow]

Cool. Thanks for the tip! How's your build coming along? If yours is successful, I might just go with yours instead.

[Madferret]

So I'm actually kind of amazed but my circuit actually works, it's not perfect that's for sure but it definitely reduces hum. The main issue I'm getting is that it's distorting a little, like a kind of poor fuzz, I think the Opamp's being driven a little too hard and clipping slightly, actually it doesn't sound bad with another distortion stacked but I want to get it running clean. Also the pot probably isn't doing a right lot and at one point on the taper produces clock noise, it could be a bad pot.

I'm going to do a bit of research to see if I can find a simple way to reduce the signal to the op amp and sort the 'Q' dial out and post the results. If anyone has any ideas *cough*Mark & Miro*cough* it'd be really appreciated.

[jaylow]

What about an internal trimpot to reduce the volume of the signal? Just lower it down to the point where the distortion goes away then close it up.

[Madferret]

Not a bad idea, I'd also been looking at a couple of buffers that use a TL072 to see how they were fitting a clean signal so I've got a few things to try.

[jaylow]

How does your filter work? Any success?