Pot's and wiring stuff help

omnimutant · #1 05-22-2011, 12:17 AM

I'm currently undergoing a complete overhaul of my old 87 sr800. De-fretted, refinishing, etc.

It had been previously rewired when the pick ups were replaced, before I purchased it (in 1992). It was converted to passive, and I'm pretty sure they retained the original pots, but the wiring job is a chaotic mess. I'd like to attempt to re wire everything correctly, as the previous job was a total mess and not done right. It's hard to explain but none of the knobs function the way they should. I just want to remedy that and make it work right. 1 pot for Master Volume. 1 Pot for pickup selection. The other two for EQ.

Is it possible for someone to explain what wires go where properly so I can fix it.

The Pot's all say M500K0A and then Q4 K (or O4 K, it's hard to tell) under that if it helps...

Also the Pickups (best guess) are probably Dimarzio standard P/J's. They look exactly like these http://www.bestbassgear.com/dimarzio...pj-pickups.htm except the exposed bits are Allen heads and aren't black.

walterw · #2 05-22-2011, 01:33 AM

it's a bit more complicated than that;

if you've "converted to passive", then you won't have "the other two for EQ".

you're gonna have volume, tone, maybe pan/blend, and the occasional G&L-style bass cut knob, but that's it for passive control options.

omnimutant · #3 05-22-2011, 01:44 AM

Ahh...I see. well I didn't convert to passive anyway, they guy that owned it before me did. I guess that's why it's never really worked right as all 4 were connected.

I'm good with Volume, Tone, and Pan/Blend...

How do I achieve this?

omnimutant · #4 05-22-2011, 03:11 AM

After much Google time and research I think I'm better prepared and have a better understanding of how the wiring thing works. I think I can better phrase my question for some help.

Can someone offer a Wiring Diagram help that allows for a Master Volume,Tone,Tone, Blend? Or am I asking too much here? I appreciate any help on this.

Edited:
The more I look Into all of this the more it Looks like I may just have to go with Vol Vol Tone Tone. which is fine. It looks easy enough to do and I can handle that.

DaveyM69 · #5 05-22-2011, 12:53 PM

I haven't got a schematic but Master Volume,Tone,Tone, Blend is quite feasable.

A blend control is basically two volume pots in one but they work in opposite directions with 100% volume of both in the centre.

Therefore, wire the BTT the same as VVTT, then just run the output of that lot through a 250/500K pot for master volume.

omnimutant · #6 05-22-2011, 03:15 PM

Good to know. Thanks for the Info.

walterw · #7 05-22-2011, 10:57 PM

two tones is a bad idea, because they both affect everything, not just their own pickup.

it'll also dull the overall sound, due to excess signal loading. (with passive, each added pot exacts a price on the tone, even when it's all the way up.)

look for jazz bass schematics, either volume/volume/tone, or volume/blend/tone.

(the 4th hole is not gonna be useful for much.)

DaveyM69 · #8 05-23-2011, 01:01 PM

I agree Walter. I personally use Master Volume/Volume/Volume/Tone which is really the same as VBT but no pesky blend (I never have liked them)!

If the OP went for VBT then he may be able to fit a switch for Series/Parallel in the spare hole - that's the most useful mod I added to my bass.

omnimutant · #9 05-23-2011, 01:25 PM

I haven't locked in on anything yet. Still weighing my options while in the process of the finish Job on my bass. Trying to figure out whats going to be the most useful option here. Whats the advantage of a Series/Parallel switch?

DaveyM69 · #10 05-23-2011, 02:15 PM

In series you get sort of a boost - louder a little in volume with my pickups, but also in tone... it's hard to explain but it really makes my bass kick a$$.

Attached is my wiring schematic. The main tone cap is .047uF. The 'Deep Cut' switch adds the second .047uF in parallel which gives .094uF total so more treble is cut when the tone is rolled off. That in combination with series makes for a real deep 'spooky' bassy sound with a lot of punch, or a more 'woody' sound in parallel.

You don't have room for the extra switch but it could be done on a push/pull on your tone knob. If you want independent volumes and series/parallel you could have a push/pull pot for the P Volume or Master Volume (the J Volume won't do anything when in series mode).

Dialing in the tone/pick up blend you want with this setup can take a little practice but it works great when you're used to it and gives a very broad range of tonal options.

Some people say the master volume is of no use with independent volumes - I disagree and find it extremely useful.

omnimutant · #11 06-01-2011, 03:52 PM

Might have found a use for the 4th Pot...
I was pretty set on doing a Master Volume, Master Tone, Blend set up and was going to just have the false knob. However, what would be the harm in adding one of those Passive overdrive controls(like black ice, dirty rice kind of thing) wired to a 4th pot? Some people like em and some don't, but it gives function to that 4th pot. ( but worse case I can just leave it off if it sucks) So the big question is, how do I wire that to my Master Volume, Master Tone, Blend, Signal chain as a 4th Pot?
Thanks for all the help so far.

FunkMetalBass · #12 06-01-2011, 04:27 PM

It depends on how it's set up as to the specifics of the wiring. I can't comment on it. I'm sure it's fairly simple, though (just a couple asymmetrical diodes, IIRC). Without drawing up a specific diagram, you'll just toss it in between the master tone and the output jack.

pickups -> blend -> master volume -> master tone -> effects

omnimutant · #13 06-01-2011, 09:48 PM

From all the sparse info I've been able to gather, I'm hoping this works. Please let me know the errors of my ways.

walterw · #14 06-01-2011, 10:14 PM

those passive clipping things are utterly worthless.

they don't give you "overdrive", more like "underdrive", where your rig just sounds like it's broken.

at least with a dummy knob you won't accidentally cause your bass to sound like s%^t in the middle of a show.

**line6man** · #15 06-01-2011, 10:20 PM

Quote:

Originally Posted by walterw

those passive clipping things are utterly worthless.

they don't give you "overdrive", more like "underdrive", where your rig just sounds like it's broken.

at least with a dummy knob you won't accidentally cause your bass to sound like s%^t in the middle of a show.

I haven't tried one, but yeah, putting Schottky diodes across the signal doesn't sound like it would ever give you a usable tone.
It probably sounds broken, because, well, you're putting two diodes with a fast switching speed and low forward voltage drop in inverse-parallel, parallel to the output! Stupid idea.

omnimutant · #16 06-01-2011, 10:22 PM

Sometimes I play some really dirty sludge metal, so I might find it useful. If not it's an easy fix to remove it, but I'd rather try it at least and see for myself.

Aside from that does my little drawing look like it will work?

DaveyM69 · #17 06-02-2011, 03:41 AM

Quote:

Originally Posted by omnimutant

Aside from that does my little drawing look like it will work?

Yes

Stealth · #18 06-02-2011, 06:53 AM

Two regular 1N4001 diodes would work better, I'd say.

SGD Lutherie · #19 06-02-2011, 07:53 AM

Quote:

Originally Posted by Stealth

Two regular 1N4001 diodes would work better, I'd say.

I used to do that back in the 70s. I used only one diode though.

That was the old Felix Pappalardi/Jack Bruce trick.

Getting back to the OP. If that bass was active, then those are not the original pots. Those are 500K audio taper. I have an '87 SR-885LE and it had the Regulated Lo-Z active pickups and preamp. The EQ and volume pots were parts of the preamp, and the blend control was 100K.

I have it wired up passive now, and only have volume blend and tone. In the hole where the third knob was I have a series parallel switch for the one of the pickups, and I drilled a hole and added a second series parallel switch for the other pickup.

omnimutant · #20 06-02-2011, 12:53 PM

Quote:

Getting back to the OP. If that bass was active, then those are not the original pots. Those are 500K audio taper. I have an '87 SR-885LE and it had the Regulated Lo-Z active pickups and preamp. The EQ and volume pots were parts of the preamp, and the blend control was 100K

That's good to know. I guess they guy swapped out everything then.