I need help with a mod to a ross comp clone

[jball85]

Im relatively new to this stuff so my reading comprehension is lacking when pertaining to electronic circuits if anybody is bored and feeling up to drawing a simple picture/diagram for this mod it would be much appreciated thank you. Or if you know where to find one drop a link for me.

If you use a 3-position on-off-on SPDT toggle for this, then the sensible way to wire it up is as follows.

Replace the 150k resistor on the board with a 10k+150k pair in series, installed like a "St. Louis arch" with their junction pointing up; be sure to leave a little extra lead from the 150k resistor sticking out on the component side of the board, which you'll need for the other steps below.
Run a lead from the junction of the 150k+10k pair to the common (centre lug) on the switch.
Run a lead from the other end of the 150k resistor to one of the outside lugs on the switch.
Solder a 39k resistor from the unused lug of the toggle to the other *outside* lug.
Done.

When the switch is in the centre position, it isn't connected to anything, so the effective resistance is the sum of the 150k and 10k resistors, or 160k. When the switch is in the side position where it connects directly to the other wire going to the board, it shunts the 150k resistor, making the effective resistance 10k. When it is switched to the other side position, you have a 39k resistance placed in parallel with the 150k resistor, yielding a combined parallel resistance of 30.9k, which yields around 40k when summed with the 10k in series.

[k.rock!]

                                 |
                           ____|____
                           |_______|
                       ____|   |   |_____
                      |          |    |       |
                     39K       |    |       |
                      |______^__|       |
                                 |            |
                                 |            |
                                 |            |
                                / \           |
                           10K   150K     |
                             /       \        |
                            /         \____|
                           TO BOARD
                      IN PLACE OF 150K

There ya go!

-Kaleb

[k.rock!]

When the switch is in the centre position, it isn't connected to anything, so the effective resistance is the sum of the 150k and 10k resistors, or 160k.

So for this to be true will need an ON-OFF-ON switch so that the center is indeed disconnected from any of the other 2 positions.

When the switch is in the side position where it connects directly to the other wire going to the board, it shunts the 150k resistor, making the effective resistance 10k.

The wire that ties up the right lug with the bottom end of the 150K is shorting the resistors. To make it easy to see, remember that current always choose the path with the LEAST resistance to flow. So if you put a wire in parallel with a resistor, the current will go through the wire and not the resistor. So in this case, only the 10K remains "active".

When it is switched to the other side position, you have a 39k resistance placed in parallel with the 150k resistor, yielding a combined parallel resistance of 30.9k, which yields around 40k when summed with the 10k in series.

You would have something like this

               __150k__
              |           |
---10k----|--39k--|-----   

So when the 150k and 39k are in parallel, you will have ~30.9k like you said and added to that, you'll have the 10k, which will give you around 40k.


I just thought it would be a better help if I broke that down for you instead of giving you a "recipe". This way I guess you can learn a little more

Good luck!


-Kaleb

[cjkbug]

is this for the realease speed mod?

[k.rock!]

Sounds like it, yeah...

[cjkbug]

I once built a Rangemaster with selectable input caps. But instead of arranging them on a switch, they used a pot to blend between them. It's tough to say without seeing the schematic and layout but I wonder if that would work here. I built my Ross with the release switch mod, but I would much rather have a pot.
     What layout are you using? I might try to work this out on a breadboard, as I'm sure it would be useful lots of places, or better yet see if someone else already did it for me.

[jball85]

Im using the General Guitar Gadgets pcb, I read that you could use a pot but couldn't find any clear directions on how to do that. I suppose I should read up on how to make a custom pot, but then how would I wire it to the board?

[cjkbug]

I'm gonna check out some stuff on fsb and see what is mentioned. I used a guitar pcb layout with the switch and It sounded awesome. but I think a pot would be cool. add an"attack" pot and your really cookin'

[jball85]

I was hoping I could score a pcb off of byoc for the 5 knob compressor, but they don't sell pcbs for some reason. If anyone knows how to add the other knobs like the wet/dry mix to a generic ross comp board (especially GGG's) feel free to post ideas.