Stereo splitter with multiple outputs

[randyrefalo]

I want to build a simple splitter device where I can input a stereo ¼ instrument TRS and then split the stereo signal into the two ¼ female mono outputs.  The input is from a bass guitar with two pickups wired in stereo, with a separate output for each pickup.  This particular bass has passive pickups.

This should be very simple to build – but what if I wanted to have two or three mono outputs for each pickup to drive multiple amplifiers and DI's used for recording?  Again, this should be simple to build but I think when a pickup output is connected to multiple amplifiers the impedance and other tonal characteristics change.  I would like to have two or three mono outputs for each pickup that are essentially the same signal and tone-wise as the original signal that came from the pickup.

Any ideas or advice out there?

[dmaher]

I have an idea but dont really have the knowledge past the sales pitch. I think you might be right about issues with just splitting it off, not to mention I think there'd be losses. How about buffers?

[flo]

Use a stereo input jack.

Lead each of the two signals to a simple opamp buffer and hookup multiple mono output jacks to each buffer's output:
Signal from stereo input Tip -> opamp buffer 1 -> outputs 1, 2, 3
Signal from stereo input Ring -> opamp buffer 2 -> outputs 4, 5, 6  

Use a dual opamp like the TL072.
Opamp 1: Pin 1, 2, 3.
Opamp 2: Pin 5, 6, 7.
V+: Pin 8
Ground: Pin 4

Schematic for one single opamp buffer from AMZ FX - ©2002 Jack Orman:
Basic Buffers
http://www.muzique.com/lab/buffers.htm

Note: "Vr" (=bias voltage of 4.5V) is made by dividing the powersupply voltage (9V) into half with two 100k resistors in series between the powersupply and ground.

[Ben N]

Another approach: http://www.muzique.com/lab/splitter.htm

[Top Top]

Use a stereo input jack.

Lead each of the two signals to a simple opamp buffer and hookup multiple mono output jacks to each buffer's output:
Signal from stereo input Tip -> opamp buffer 1 -> outputs 1, 2, 3
Signal from stereo input Ring -> opamp buffer 2 -> outputs 4, 5, 6  

Use a dual opamp like the TL072.
Opamp 1: Pin 1, 2, 3.
Opamp 2: Pin 5, 6, 7.
V+: Pin 8
Ground: Pin 4

Schematic for one single opamp buffer from AMZ FX - ©2002 Jack Orman:
Basic Buffers
http://www.muzique.com/lab/buffers.htm

Note: "Vr" (=bias voltage of 4.5V) is made by dividing the powersupply voltage (9V) into half with two 100k resistors in series between the powersupply and ground.

I'm building a splitter on a multi-effects box and I had a question about this circuit.

If you were going to build two splitters out of a double op amp such as the TL072, would you need a seperate 1M resistor (R1) for each of the two opamps, or could you just use one and split it to the + of each op amp?

edit: nevermind - after drawing this out, I realized that if both shared that 1M resistor, then the input from both channels would be shared on both opamps.

What I am still a little confused by is the Vr mentioned in the note. So it would be +9v-->100k-->100k-->(Ground & Vr)? So essentially, everything connected to ground would also be connected to this bias voltage?

I am taking a step into new territory here, slowly understanding a little more about circuit designs, so sorry for the ignorance.

[Taylor]

Try this one:

http://www.muzique.com/images/buff8.gif

It's the same but it shows the biasing.

For the OP, I think you'll probably have better results if you put a buffer for every output. You see, if you connect 3 devices to the same buffer output, those 3 devices' inputs will be connected directly. Since we don't know what the devices are and what they have going on in front of them (like whether they are buffered at the input) you could possibly run into some bad interactions. Opamps are cheap, so I think it's best to be safe.

[flo]

... if both shared that 1M resistor, then the input from both channels would be shared on both opamps.

That is not a problem. If you want you can connect the two +inputs of the two opamps together because they are high-impedance and use only one bias.

But to make two outputs from one input signal, you only need one opamp buffer. Just buffer the input signal with one opamp and then connect its output to both output jacks.
Although the remark of Taylor against this is sensible, I think that most inputs for guitar signals will be high impedance and will not influence each other.

[Top Top]

... if both shared that 1M resistor, then the input from both channels would be shared on both opamps.

That is not a problem. If you want you can connect the two +inputs of the two opamps together because they are high-impedance and use only one bias.

But to make two outputs from one input signal, you only need one opamp buffer. Just buffer the input signal with one opamp and then connect its output to both output jacks.
Although the remark of Taylor against this is sensible, I think that most inputs for guitar signals will be high impedance and will not influence each other.

I actually want to have two separate split inputs on this, very similar to what the OP wants. In my case it is because I want to be able to split one input to two or three different effects, and then be able to split the output of an effect further as well.

I am wondering as well if there should be a separate buffer for each output. The whole input impedance thing is still kind of voodoo to me... don't really understand what it means. I was thinking that if I go for separate buffers on each output, then I would go with the discreet transistor type.

[Top Top]

Bump...

and another question.


Right now in my multi-fx box, when I split the signal using a passive splitter (just a jack wired to two jacks), it seems to work fine, as each of my effects has some sort of gain stage at the beginning.

So if that is working fine, then won't a single buffer split to two or three outputs also be fine? A step up from passive, for sure, right?

Also, could a boost at the front, split to a couple outputs, work as well as a buffer?

[Taylor]

http://www.muzique.com/news/boosters-are-not-buffers/

[Top Top]

Thanks, that is the type of info I was looking for in terms of explaining the properties of a buffer vs. booster.

[Dimitree]

does it make a real difference if the input capacitor is a .01uf instead of 0.1uf and the resistor is always 1M? the cut is audible?

[flo]

So if that is working fine, then won't a single buffer split to two or three outputs also be fine?

Yes that will work fine.