Jimi-In-A-Box/Captain Coconut style setup- queries

[DiamondDog]

Hey,

I have a neg ground Octiavia, a modded Dragonfly LilDevil, and a Neovibe ready to go into the one enclosure soon. I also have a 16v AC 2.5A power supply brick to feed it. A couple of questions if I may to see if anyone else has any experiences or thoughts I can draw upon.

1. I'll be including a board with the usual suspects of diodes, caps, 7809 etc inside the enclosure, to power the octavia and fuzz. It will be fed of the 16V AC for the Neovibe. Is there any risk of introducing noise with this board inside the enclosure. I have some chokes, which I may throw in for the heck of it.

2. Are there any other noise sources that one should be wary of in this setup?

3. In my travels, I came across this page at Geofex on wrappers. What really interested me was the last diagram, where a circuit was sketched out. In it, it says that "For the cost of a single opamp, you can get rid of most forms of hum by driving the output jack "ground" terminal with the difference between the input ground and the average ground signal on the output jack. This circuit would eliminate hum loop pickup on boards if applied to all effects."

Has anyone got any more info on this especially calculating the value of the resisitors in the circuit?

4. Lastly, in both the Geofex article and the Captain Coconut, there are "breakout" jacks so that additional effects can be used or order can be changes (although I am including switching to allow the fuzz and octave to be swapped.) I remember one Geofex article on true bypass boxes using the Millenium 2, a (100K?) resisitor was across the return-from-FX jack when it was closed. Of course I can't find it now for the life of me.

Dumb question- why?

Thanks!

[DiamondDog]

bump...

[R.G.]

1. I'll be including a board with the usual suspects of diodes, caps, 7809 etc inside the enclosure, to power the octavia and fuzz. It will be fed of the 16V AC for the Neovibe. Is there any risk of introducing noise with this board inside the enclosure. I have some chokes, which I may throw in for the heck of it.

Any time you run AC line voltage into a box, there is a risk of introducing hum. To keep that minimal, keep the AC-carrying wires short and direct, and away from inputs.

In this case, you need to do a couple of other things to be happy with it.
(a) Run the AC wires directly to the 'vibe. Do NOT let either AC wire contact the case by using a power jack that contacts the case; use an all-plastic case power jack.
(b) Patch two wires out of the 'vibe, one from the ground right at the power section, the other from the DC at the power supply filter caps. Run those wires to your 7809 to make 9V for the other two effects.
(c ) don't play any neg/positive ground conversion tricks.

2. Are there any other noise sources that one should be wary of in this setup?

It just makes the usual ones of good wiring and grounding more important.

3. In my travels, I came across this page at Geofex on wrappers. What really interested me was the last diagram, where a circuit was sketched out. In it, it says that "For the cost of a single opamp, you can get rid of most forms of hum by driving the output jack "ground" terminal with the difference between the input ground and the average ground signal on the output jack. This circuit would eliminate hum loop pickup on boards if applied to all effects."
Has anyone got any more info on this especially calculating the value of the resisitors in the circuit?

See http://geofex.com/FX_images/oaspltr.gif, the opamp just before the second output; all resistors must be the same value, and the higher precision they are the same value, the better. 1% is usually good enough.

4. Lastly, in both the Geofex article and the Captain Coconut, there are "breakout" jacks so that additional effects can be used or order can be changes (although I am including switching to allow the fuzz and octave to be swapped.) I remember one Geofex article on true bypass boxes using the Millenium 2, a (100K?) resisitor was across the return-from-FX jack when it was closed. Of course I can't find it now for the life of me.

Dumb question- why?

It's the resistor to ground to make the Millenium 2 work.

[dschwartz]

is the image  down?

[DiamondDog]

In this case, you need to do a couple of other things to be happy with it.
(a) Run the AC wires directly to the 'vibe. Do NOT let either AC wire contact the case by using a power jack that contacts the case; use an all-plastic case power jack.
(b) Patch two wires out of the 'vibe, one from the ground right at the power section, the other from the DC at the power supply filter caps. Run those wires to your 7809 to make 9V for the other two effects.
(c ) don't play any neg/positive ground conversion tricks.

Excellent and logical advice, and understood.

I went for known neg gnd octavia  and fuzz layouts to make things simpler. They have both been built and tested, both as individual units, and together, so I'm trying to take a methodical approach to the build. I'm a simple person; I like to keep my problems simple by using Known Working Bits and building on them.

4. Lastly, in both the Geofex article and the Captain Coconut, there are "breakout" jacks so that additional effects can be used or order can be changes (although I am including switching to allow the fuzz and octave to be swapped.) I remember one Geofex article on true bypass boxes using the Millenium 2, a (100K?) resisitor was across the return-from-FX jack when it was closed. Of course I can't find it now for the life of me.

Dumb question- why?

It's the resistor to ground to make the Millenium 2 work.

<slaps forehead...> Oops... 

Thanks RG and dschwartz!