Mini Mixer to Mini Headphone Splitter

[Ettore_M]

Hey guys!

I didn't know if I should post it here or in the Tech Help section (Tech Help seems to be only for madbean PCBs..), but here it is:

I've built the Mini Mixer by GGG (only not with 4 inputs, but 7! "If it's worth doing, it's worth OVERdoing"!  ).



It works great and I can't hear any tone sucking at all. But now I want to build the opposite thing: I want the (one) input to be splitted to 6 stereo outputs for headphones. I don't want it "true stereo". I'll just wire the output on both lugs. You know.. 

What I'm wondering is this: Could this circuit (the Mini Mixer) be "reversed" like below to split the input to a number of headphones? The part values are, of course, random.. 

Any input on this is appreciated! 

Hector

[jkokura]

Not precisely. The mini mixer is only one direction, you can't just go backwards with it.

What you're looking for is a splitter, not a mixer. In that case, you'd have a buffer for your input, then the signal would literally split into as many outs as you'd want, with an output buffer on each output. Simple Op Amp buffers are perfect for this. If you want volume control on each output, just use a simple level control, an A100K pot on the output.

Jacob

[Ettore_M]

Not precisely. The mini mixer is only one direction, you can't just go backwards with it.

What you're looking for is a splitter, not a mixer. In that case, you'd have a buffer for your input, then the signal would literally split into as many outs as you'd want, with an output buffer on each output. Simple Op Amp buffers are perfect for this. If you want volume control on each output, just use a simple level control, an A100K pot on the output.

Jacob

Thanks for the info to splitters, Jacob!
But I didn't mean that I just simply wire the Mini Mixer backwards. Did you see the schem I posted in the end? Couldn't that work or is it entirely wrong? 

Also, Do you have a splitter schematic on mind or do I have to get creative? 

BTW, could this thing that I want be achieved with your Headphone Amplifier by putting more outputs? 

Thanks again!

Hector

[jkokura]

I did look at the schem you posted, and while it might work, I don't think it's the best solution. Essentially the problem is that none of the outputs are isolated from each other. I think you should have an output buffer for each output. If you were just splitting once, and you don't need it to sound good, than it might work.

As for the headphone amp, it's sort of the same idea. What you actually should be using as a guide is this: http://www.madbeanpedals.com/forum/index.php?topic=1798.msg13480#msg13480

This is a low parts count simple buffer. Split as many times as you want, and add as many of the buffers as you want outputs.

Jacob

[Ettore_M]

I did look at the schem you posted, and while it might work, I don't think it's the best solution. Essentially the problem is that none of the outputs are isolated from each other. I think you should have an output buffer for each output. If you were just splitting once, and you don't need it to sound good, than it might work.

As for the headphone amp, it's sort of the same idea. What you actually should be using as a guide is this: http://www.madbeanpedals.com/forum/index.php?topic=1798.msg13480#msg13480

This is a low parts count simple buffer. Split as many times as you want, and add as many of the buffers as you want outputs.

Jacob

I see what you mean now.. 

But, why should re-buffer the buffered output? Couldn't I simply add more buffers after the voltage divider? And after every buffer I could put a volume control as you said..

[jkokura]

Sure, that sounds fine.

One benefit to using an input buffer would be to control the gain, or add an eq/tone stack. Aside from that, you can daisy chain this output buffers to your hearts content.

Jacob

[Ettore_M]

Nice! Thanks, Jacob!  That's what I wanted..

You know, I want this to be as simple as possible to build, because I want it built in a few days! 
But this could be a really nice project, if ,before the buffer-splitter, I put your Headphone Amp and then put controls for Gain, Tone and Volume. Maybe next time.

BTW, would it work better if I put the amp of yours before the splitter, ior not?

Thanks again!

Hector

[jkokura]

Yeah, use the out of the headphone amp to go into the splitter. That would work fine.

Jacob

[Ettore_M]

Thanks a lot, Jacob! You've been a great help!
I'll start this tomorrow. I got to do the board on Eagle first, and I think I have the parts for this (I have two SMD TL074. They'll be of use and hopefully do the job nicely!). I'll post my results when finished.

Hector

[Ettore_M]

That's what I came up with! For the layout, I used what I had in stock.
Jacob, is everything looking ok? It's pretty much your schematic with more outputs.. 

Hector

[stecykmi]

you may want to use smaller bias resistors, 10Meg seems a little high. I would use 100k.

[jkokura]

Pretty much any value between 10K and 10M will work. I personally use 1M on mine. 10M was a part of the original design someone else included, and I believe I mention that in the build docs (sorry if not).

Jacob

[jkokura]

Oh, and the schem/layout looks alright. I should also note that you can easily use 1uF caps instead of 10uF, and often, film caps are good to use in that place as well.

I would say that while your layout looks workable, I would likely do it differently.

Jacob

[Ettore_M]

Pretty much any value between 10K and 10M will work. I personally use 1M on mine. 10M was a part of the original design someone else included, and I believe I mention that in the build docs (sorry if not).

Jacob

Ok! Thanks, Jacob! I'll use what's handy. I'm pretty sure I have 10k, 100k and 10M. Probably 100k as they're used in the infamous Klon Buffer!

Oh, and the schem/layout looks alright. I should also note that you can easily use 1uF caps instead of 10uF, and often, film caps are good to use in that place as well.

I would say that while your layout looks workable, I would likely do it differently.

Jacob

I doubt that I have that big film caps in stock. But, sure thing I have electrolytics!
Thanks for the advice, though! 

I bet you could do it better! You do have more experience!
But I think the layout works pretty well for me. I wanted it as small as it can get!

Hector

[garfo]

I've built that project as well.I've noticed that there is a little bit of volume drop on the output.I will try lowering the 100k resistors that sets the overall output.Besides that, is tl072 the best opamp for this buid, or is there anything better?

Hey guys!

I didn't know if I should post it here or in the Tech Help section (Tech Help seems to be only for madbean PCBs..), but here it is:

I've built the Mini Mixer by GGG (only not with 4 inputs, but 7! "If it's worth doing, it's worth OVERdoing"!  ).



It works great and I can't hear any tone sucking at all. But now I want to build the opposite thing: I want the (one) input to be splitted to 6 stereo outputs for headphones. I don't want it "true stereo". I'll just wire the output on both lugs. You know.. 

What I'm wondering is this: Could this circuit (the Mini Mixer) be "reversed" like below to split the input to a number of headphones? The part values are, of course, random.. 

Any input on this is appreciated! 

Hector