"Pulldown resistor" question

Started by samrsmiley, August 19, 2008, 11:23:13 AM

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samrsmiley

I'm building a rangemaster clone from GeoFex's schematic.  He recommends using a 2.2m resister to ground before the input cap to stop the stomp noise.  If I'm using a 6 way rotary switch to change that cap to different values, can I put that resistor before the rotary switch, or do I need to use one with each of my caps?  Thanks for any help!
Sam

ayayay!

I would say just the one 2.2m is fine before the switch.  If that doesn't work then there's your answer I guess.   :icon_lol:
The people who work for a living are now outnumbered by those who vote for a living.

earthtonesaudio

If you don't hear pops, or if they're small enough not to bother you, you can leave that resistor off. 

But, if you get big, mean pops (bigger caps store more charge and are capable of bigger pops), the resistor will help.  Also if you leave an end of a cap "floating" then it's more likely to act as an antenna.

ianmgull

Hey Alex, what do you mean by "floating"? Are you saying that having only one end of a cap can act as an antenna? Does it matter what the one end is connected to? 

earthtonesaudio

By floating I mean, you have one end of the cap connected to your circuit somewhere, and the other end is not connected to anything, or just left "floating" in space.

If you have a floating cap whose other end connects to the input of a high-gain circuit, it wouldn't be too hard to pick up interference.  Tying the floating end of the cap to ground (using a pull-down resistor for example) greatly reduces this possibility.

I think the Seymour Duncan Tweak Fuzz has the selectable caps at the input, and their ends are all tied to ground through resistors.


Basically if you build it and it works fine without them, great!  If you get pops or radio stations, it might help to put the pull-downs in there.

samrsmiley

OK, that makes sense, seeing that schematic before.  Also, is it OK to have all the ends connected to the same strip?  I'm using vero board.  Basically I have 6 wires from the rotary switch going to each of the caps, and then all the caps end up on the same strip.  It doesn't work yet, but I think I have some other errors to work out too (like forgetting to connect the pot!)  Thanks for any help, and I'll let you guys know when it's done!
Sam

earthtonesaudio


samrsmiley

It's done!  Not that many errors, and lots of electrical tape later, it's working.  There's no radio freq so far-but I've only used it in the basement with a V-Amp, not on a gig with my AC30 yet.  Sounds good, I like .01 mf better than the original .005 mf input cap, but the effect sounds good.  I put it in a ZVex box that you can get on Small Bear right now and that with a rotary switch is really tough to fit!  But with the electrical tape to stop shorts it's good to go.
Thanks for the help guys!  Next stop TS9/808