Musicman Wiring Genius Needed

[sm3rk]

Hope the pics prove useful!

great it was exactlly i was looking for today

btw in what position is that Bright filter (3 pin switch) on?
On my sabre ex-ex-owner changed all the switches (to paralel/SC/serial for both p-u and p-u selector) and the yelow wire is attached to nowhere ... so i dont know if it is on or off :/.

Probably off if i understend it well.

 

[shrigg]

btw in what position is that Bright filter (3 pin switch) on?
On my sabre ex-ex-owner changed all the switches (to paralel/SC/serial for both p-u and p-u selector) and the yelow wire is attached to nowhere ... so i dont know if it is on or off :/.

I don't remember... unfortunately that bass got traded a while back.

 

[sm3rk]

I don't remember... unfortunately that bass got traded a while back.

it is OK the wiring diagram up the page told it to me..

 

[musicfoodmike]

Thanks everyone for all the support here, I successfully modified my 79 Musicman Sabre bass to use the phase selector switch as an active/passive selector switch. I made a diagram of what I did so others can hopefully do the same too.

 

[RobbieK]

Old thread... Shame I didn't see this back in '10... I love stingrays and I've spent a bit of time over the years getting inside their weird little preamps and those low inductance/impedance stingray pickups.

an active/passive selector switch.

Thanks for sharing your work. Is this adobe illustrator? Looks very neat.

FWIW, I'm surprised that you don't get a little pop from the input cap as you switch from active to passive. This preamp was never designed to do active passive so there's no earth reference on the input coupling cap. If you do, it's easy to remedy with a resistor between the input (pink wire) and earth. Anything from 470k to 1M will be fine for this.

And also, FWIW, if you want to keep your volume for passive mode, it can be done. A single stingray pickup in parallel mode can work fine with a 25K pot (although you'll lose a tiny bit of treble). You'll need a slightly different switching diagram, and a resistor on the output cap as well. Not sure how a sabre, with two pickups and series parallel etc would fare, though.

If you want a better sound for passive mode, you can also Invalid Link Removed to have say, a 25K gang and a 250K gang. Then have the switch go to the 250K gang in passive mode. This is also a slightly different active-passive switch, but you won't need the output resistor...

 

[musicfoodmike]

Hi Robbie K, thanks for all this info. Funny you should say, I did hear a pop for the first time this morning, but it was from going from passive to active, and after playing in passive mode for a while, so I may consider that - unless you think it's a result of something else?

I looked again at the schematic, you're right, the volume pot could easily be put in between the output jack and phase selector switch "output" (the lower left corner in my diagram). I may try that, though I don't normally use the volume knob when playing passive - still, could be a great addition to the mod diagram for those who do. I'll give the resistor a try too, thanks.

I drew this up in Pages, Mac's equivalent to Word. It's such a simple program, but with great tools. I also have a background in mechanical engineering and more recently - catalogue/layout design, so it didn't take much for me to put together. Illustrator daunts me!

 

[RobbieK]

Ha, yeah I studied illustrator photoshop, premiere and free others at uni, but illustrator was the most confusing for me and I've rarely used it since.

The reason the cap is popping is because one side of it is held at 4.5V (it's connected to the opamp), and the other side of it is normally held at earth because the pickup is directly connected to it. (A pickup is a long piece of wire with one end earthed.) And that's why it's a coupling cap. It transfers signal from one potential to another. But when you are in bypass, the pickup is disconnected, so the input side of the cap just floats, quickly reaching 4.5V. Then when you switch back to active, the cap is slammed down to earth again, creating the pop. Holding the input side of the cap at earth with a resistor while the pickup is disconnected is the way around this. As I mentioned, anything from 470K to 1M will work fine and not effect the tone of the pickup.

If you decide to use the existing 25K pot as a volume in passive mode, the switching required will disconnect the pot from the pre when you are in passive mode, and the same thing will happen to the output coupling cap. So in this case I would use a resistor there as well.