Ruby generating a tone

[SirPoonga]

This is odd.  I unplugged my bass for the first time in some time on my ruby.  Without the bass plugged in when the volume is all the way up nothing happens.  However as I turn the volume down a tone is generated, from low to high as I adjust the volume form loud to soft.  And the tone gets louder as I turn the volume down.

I don't know what this means.  Is it just a dying battery?  Is something wrong?

[SirPoonga]

I put a brand new battery in, same thing.  however, if you have seen the pics of my ruby in the band aid box, when I take the circuit out it works normally.  Hmmmmm..

[R.G.]

No mystery. It's oscillating, and the capacitance to the box changes things.

High input impedance, high gain circuits in small boxes have always had this problem.

[SirPoonga]

Why didn't it do it earlier when I made it?  What do I do to fix it?

[SirPoonga]

anyone?

[NaBo]

err, well on the faq page of this site i think there's stuff to help defeat oscillation... even then it'll probably still happen.  suprisingly mine doesn't do it, and its quiet as a mouse... even though it's a rat's nest with leads that are way too long, and i used carbon comp resistors! heheh...  bit of a bigger enclosure though, maybe thats it

but i mean, is it really a big deal?  how often are you gonna be playing your ruby without anything plugged in?  :? ...

[SirPoonga]

That's true, but if it comes unplugged by accident it's rather loud.

I was playing around with it and I figured something out.  I turned it on but I openned the box.  If you look at my past pics I posted it's in a bandaid box.  As a reminder, I am using it as a headphone amp.  So the lid of the bandaid box has input, output, volume.  I have a fixed gain, though I will change that to a trimpot so I can fine tune it.
The perfboard is not secured with standoffs.  It's in a electrostatic bag that is poster puttied to the wall.  The box is just too small to get tools in it, at least my tools.  The battery is in there the same way, poster puttied to the side.
So, I opened the lid.  I took the perf out.  I turned it one with volume at half.  I slowly and carefully put the perf back in while closing the lid.  It isn'; until the lid is almost shut that the tone starts.
A bigger box might do it?  Dang, this is such a cool box.

[lightningfingers]

Have you tried grounding the box?

[SirPoonga]

It should be grounded pretty well.  The circuit is grounded to the box.  I even tested it.  With the circuit outside the box (it's ground at the pot, scratched paint off byt he pot's nut) I touch my continuity tester to a ground on the circuit to the bottom of the box and had continuity.  That means there is a closed circuit from the perfboard, to the pot, to the lid, to the hinge between the lid and box, and to the bottom of the box.

[NaBo]

it's ground at the pot, scratched paint off byt he pot's nut

that woudlnt ground it, unless you soldered a ground wire to the bottom of the pot or something.  dunno what's going on with yours, but the shaft and metal "container" part are supposed to be completely insulated from the lugs and thus the rest of the circuit.  ground to the enclosure at one of the 1/4" jacks (or both).

[SirPoonga]

Since my jacks are plastic that's why I went with the pot.  Yes, I connected the ground form the circuit to the pot nut hence that ground connection.  Forgot to mention that.

[NaBo]

did you use closed circuit jacks?  the kind with a tip shunt?  I think the switchcraft part number is 12A... or 12B maybe...

[SirPoonga]

Not sure what tipshunt means.  I used the jacks in the for sale forum.  Search for my reply there and you will see what I used.

[SirPoonga]

I figured it out, it isn't the ruby, it's the bass.

Here's the story.  I'm new to bass.  Picked this pbass up a couple of months ago to try.  I didn't pick up an amp.  I figured for now I;d just play through my computer.  That's fine playing through my computer but the computer speakers suck.  Then I found this site.  So I decided to make a headphone amp.  I used the Ruby schematic.  Sounds great but there wa the hum hence this thread.

Well, I decided to run my bass through my home theater system for the fun of it.  I plugged it straight into my subwoofer.  The same hum.  So I figure it is something with the bass.  A hum is usually a bad ground.  I took my bass apart and looked at the wiring.  I compared it to Fender's Mr. Gearhead site's pbass wiring schematic.  It wasn't wired the same.  It had the cap from lug 3 of the volume to lug 1 of the tone, lug 2 of the tone straight to ground.  It should be lug 3 of volume straight to lug 1 of tone and the cap from lug 2 of tone to ground.  Fixed, better tone control and no hum:)

[NaBo]

I thought the problem was that your ruby was humming with no input plugged in?

that can be defeated using a closed circuit jack (there is a metal piece that connects to the tip connector when no plug is inserted) to ground the input when there is no plug in the amp's input...  it's the same principle behind using jack orman's (i think it's his?) "alternate" true bypass dpdt wiring method, the one with the bypass jumper that loops around.  It's generally a very good thing to ground the input of any high gain circuit (such as amps) when bypassed or disconnected or whatever to avoid the hum

I THINK... i could be wrong about something, in which case, someone please step in!

[SirPoonga]

You are right.  This thread is about my other ruby problem.  The generating the tone when the guitar isn't plugged in

That still exists.  however since I don't use it unplugged I am thinking to just leave it.  It seems a bigger enclosure would get rid of the problem if I eneded to get rid of it.