Signal Split

[M0ses]

Hey all. The folks over at the Pups & Electronics section were unable to help me in this, so I'm hoping somebody 'round here knows something.

I'm trying to figure out how to split a signal and isolate the two new signals from each other. I am told that there are effects pedals that can do this - I have never used a single effect in 7 years of bass playing, because I don't really feel any great need for them and I don't have any money to spend on things I don't really need.

But the thing is, a pedal itself cannot possibly accomplish what I am looking for. Specifically, what I want to do is take a signal DIRECTLY from the pickup, and split it so that it goes to two different outputs within the bass itself, but without making those two outputs into one circuit (so that I can send the bridge pickup to both output while sending both pickups to the second output, or any such combination). Is this clear? I'll try to clarify if that doesn't make sense.

Anyway, if anyone knows anything at all about this, please bombard me with all the information you have.

 

[bongomania]

Easy as pie. You have two main options:

1) Buy a transformer from Jensen, and use one of the free schematics on their site for isolating the signal paths.

2) Build a small DIY buffer and put it on one of the paths, or build two and put them on both paths. Either way you get isolation.

 

[M0ses]

Thanks for the reply.

Option number two is the one I want (lol I'm cheap, but also I love DIY). Someone on the electronics forum mentioned buffers also, but couldn't give me any information on them. Google didn't help me at all, either - just told me where I could buy pedals. I have no idea what they are or how they work. Could you please point me in the right direction? I can read and construct schematics. This will require active electronics, right?

Actually I slightly simplified my explanation - there will be three pickups, all switchable. I don't believe that this will make anything more difficult, but it might be worth mentioning. Since I want to be able to have any combination of all three and both outputs, I will need 3 buffers in total, right? My guess is it would be best to combine all thee buffer paths in one output and all three regular paths into one output...

Well like I said I don't know anything about buffers - I need information, please!!

 

[Bob C]

Specifically, what I want to do is take a signal DIRECTLY from the pickup, and split it so that it goes to two different outputs within the bass itself, but without making those two outputs into one circuit (so that I can send the bridge pickup to both output while sending both pickups to the second output, or any such combination). Is this clear?

It seems to me, to do this, you'd need to first separate the pickups outputs. That is, wire your bass in stereo.

Next, you need some kind of splitter that has 2 ins and 3 outs.

Then you need to recombine two of the signals, so that you will have your bridge to A and B, and the neck to A (or B).

There are lots (or at least several) of splitters, routers and mixers that can do this. But before continuing, am I correct that this is what you want to do?

If so, again I believe you will need to have separate output jacks for the two pickups.

 

[Bob C]

MOses,

I was typing while you were posting. So, my answer is not up to date. I need to ask exactly what your vision is for these various routes. What are you ultimately trying to accomplish, in terms of sound, tone, etc?

 

[bongomania]

A buffer is a small active amplifier circuit, typically using an opamp chip or a transistor. Here's an example: http://en.wikipedia.org/wiki/Common_drain .

There shouldn't be three buffered paths and three non-buffered paths. Just go:

pup 1 --> buffer 1 --> switch or vol. pot
pup 2 --> buffer 2 --> switch or vol. pot
pup 3 --> buffer 3 --> switch or vol. pot

The switch or vol. pots would be whatever passive switching or attenuating matrix you were going to rig up for selecting pups, and then the output of that switch/pot rig would go to your output jack (or to an EQ or tone pot and then to the output).

 

[Bob C]

That's really cool. I knew something like that COULD be made, but I didn't know it existed.

 

[M0ses]

I'm thinking something may have been misunderstood. My plan was to be able to have a single pickup go to two different outputs, at the same time without combining outputs. That's the crucial part.

My final vision would be this - three single coils. Each one has two switches assosciated with it - an on/off for each output. A pickup can be switched to off/off, off/on, or on/off or on/on. And each pickup can be in any of those postions while the others are in any other position. Each output would also have a master volume and tone.

Obviously, the signal coming from a pup would have to be split to go to two outputs - but it also needs to be isolated so that the outputs are seperate and not identical, EVEN when a pup is going to both outputs at once (on/on).

 

[bongomania]

No misunderstanding--you just need to Y-split the output of each pup using your switching matrix.

The outputs of each pup would go to the center pins of a DPDT on-off-on switch, with each "on" pole connecting to one of the two output jacks.

I may be missing something (as I'm doing the wiring all in my head), but I think the outputs would be isolated from each other, since the pups would be isolated, and the switches would mechanically separate the signal paths.

 

[cheapbasslovin]

PU1>BUFFER1>SPLIT>SWITCH1A══>>┬VOLUME  POT1>TONEPOT1>OUTPUT1
            └>>SWITCH1B────┐  │
PU2>BUFFER2>SPLIT>SWITCH2A═╪>>┤
            └>>SWITCH2B────┤  │
PU2>BUFFER3>SPLIT>SWITCH3A═╪>>┘
            └>>SWITCH3B────┴>VOLUME POT2>TONEPOT2>JENSEN XFRMER>OUTPUT2

This seems right, but that's a bunch'o'junk in a tiny spot. In mine all the switch 'A's join passively and all the switch 'B's join passively. That part may not be so ideal. You'll need to insulate your output grounds from each other to maintain isolation.

Good luck.

EDIT:::I should say that while I am confident this will accomplish what you have asked for (barring some misunderstanding), I am uncertain whether it will be the most effective method of switching/ isolation available. Hopefully others will edit/ confirm this drawing.

 

[MIJ-VI]

Hi M0ses.

For the sake of additional context, what kind of three pickup instrument are you modding?

 

[M0ses]

PU1>BUFFER1>SPLIT>SWITCH1A══>>┬VOLUME  POT1>TONEPOT1>OUTPUT1
            └>>SWITCH1B────┐  │
PU2>BUFFER2>SPLIT>SWITCH2A═╪>>┤
            └>>SWITCH2B────┤  │
PU2>BUFFER3>SPLIT>SWITCH3A═╪>>┘
            └>>SWITCH3B────┴>VOLUME POT2>TONEPOT2>JENSEN XFRMER>OUTPUT2

What is a Jensen xfrmer? Also, I am still unclear as to how the buffer isolates the signals even though the split is further down the line. If you assure me that it will work, though, I'd be willing to try

No misunderstanding--you just need to Y-split the output of each pup using your switching matrix.

The outputs of each pup would go to the center pins of a DPDT on-off-on switch, with each "on" pole connecting to one of the two output jacks.

I may be missing something (as I'm doing the wiring all in my head), but I think the outputs would be isolated from each other, since the pups would be isolated, and the switches would mechanically separate the signal paths.

But would they still be isolated when the pups are set to on/on, going to to both outputs? Sorry if I seem to be asking the same thing over and over again. I don't completely understand these buffers.



The mod is like I have described, using three of my own hand-wound single coil pups, and electronic components mostly from Stewmac, some from Mouser. The body is an SX P bass, obviously I'll be doing some extensive routing and have to cut out a custom pickguard to allow for the 7 switches (including one to take the battery out of the curcuit to save battery power) and 2 extra pots. Also, since I hate the SX finish I'm redoing both the neck and body, and the frets are pretty bad so it's going fretless. I'm really excited about this project

 

[ehque]

The buffers are in the right place (directly after the pickups). Once the signal has passed through the buffers, they are low-impedance signals, which when mixed, split, or otherwise fiddled with should not be loaded down as badly.

Are you only going to have switches on this bass, or are you going to have knobs as well? A A-both-B triple switch for each pickup allows you an extra hole for each pickup to install a volume knob, giving you way more flexibility than your current setup.

I'm not sure but i don't think the jensen is necessary in this case, the signals already being low-impedance. I might be wrong.

 

[cheapbasslovin]

What is a Jensen xfrmer? Also, I am still unclear as to how the buffer isolates the signals even though the split is further down the line. If you assure me that it will work, though, I'd be willing to try

The buffer doesn't accomplish the isolation, the transformer does. The buffer lowers the impedence so the split doesn't load down the pickups. Bongo suggested contacting Jensen for an audio transformer so I just threw the brand name in there for fun.

From what I read in Bongo's post he believed that you wanted the pickups to be 'either/ or' to the separate outputs, not 'and/ or/ neither'. He thought that the switching was going to provide the isolation as none of the pickups would be run to both outputs at the same time. Unless I misread his post.

 

[M0ses]

Oh boy. This discussion is quickly rising above my basic level of electronics comprehension. I'm just a highschool kid who has never taken any electronics classes, just read some stuff on the internet.

What do you mean by "loading down" the pickups?
How do I know which transformer to use?

I considered volume for each pickup but it would not serve my purpose to a big enough extent unless there was one for each pickup for each output - adding 6 more pots to the four I'm already planning (master volume and tone for each output). And frankly that's simply too many knobs on one bass, plus the 7 switches. Besides not having enough room on the bass, that would also probably considerably darken up the tone and reduce output levels.
Now that I think about it......maybe it would be worthwhile to use those 6 volumes and forego the master volume and tone altogether? Which do you think would be more versatile?

The triple switch you suggested, ehque, won't work because there needs to be a fourth position (off/off).

 

[bongomania]

The buffer doesn't accomplish the isolation, the transformer does.

Buffers provide isolation, not just impedance changing.

From what I read in Bongo's post he believed that you wanted the pickups to be 'either/ or' to the separate outputs, not 'and/ or/ neither'. He thought that the switching was going to provide the isolation as none of the pickups would be run to both outputs at the same time. Unless I misread his post.

Actually you're right about that, I did neglect the "both on" angle.

Hmmm... I still think there would be no problem because the pickups would be isolated from each other by the buffers, so the only issue would be loading or feedback of/from the amps or other devices connected to each of the output jacks. That is, let's say he runs each output to a separate mixer channel, it is conceivable that this could create a feedback loop; or if each output runs to some finicky fuzz pedals, those fuzzes might not sound right. Again though, these are "maybes".

 

[bongomania]

You could rig up something with some five or six position rotary or blade switches, but I wouldn't look forward to that project. The easier way would be to give each pickup two mini-toggle switches: on/off to each of the two output jacks.

Then use a stacked pot for vol and tone for each pup, no master vol/tone is needed, and you've got a relatively clean control array: three pups, each one having two mini-toggles and one stacked pot. Or figure out the wiring for a multi-position rotary switch to replace each pair of toggles.

Google for a thorough answer to "what is loading", but the gist is that audio circuits rely on the controlled flow of current, and when two circuits are connected that both can take in current flow, they will affect each other's ability to perform optimally.

Then you get into the whole "electrons go the opposite direction of current" dealio, and it gets hairy.

 

[M0ses]

Sounds like a good idea. I hadn't thought about stacked pots. But I'd still need 6 pots, because each pickup would need a volume/tone per output. Do you know where I can buy them? Stewmac doesn't have them.

 

[cheapbasslovin]

Sounds like a good idea. I hadn't thought about stacked pots. But I'd still need 6 pots, because each pickup would need a volume/tone per output. Do you know where I can buy them? Stewmac doesn't have them.

[This invalid link has been removed] You best be comfortable with a router. That's a lot of pots.

My reasoning for including the transformer was that I thought it would, presuming the outputs maintained electrical separation, prevent any ground looping that may occur from sending two outputs from the same source. It would provide separately derived signals at each output. If this is unnecessary or improperly applied then I would love to be educated and I apologize to the OP.

 

[scotch]

Interesting thread/idea. I have a feeling that the amount of convoluted switching & splitting (not to mention necessary buffering & isolation) is going to create quite a rats-nest of components/wiring/batteries in a small space. Sounds like a breeding ground for noise, eventual shorts, and control system confusion...

Although I still am skeptical about any tonal benefits & don't understand the impetus, what about 3 output jacks sent to an outboard junction box to handle the electronic chores? Lighter, simpler bass; less noise potential; easier electronic build; and there may be some outboard pre-built devices to get you halfway there (not sure, though..).

Good luck, though! The only way to innovate is to experiment!