splitter box

[vdm]

hey everyone,

sorry to bring up a topic that no doubt has been discussed before, but looking in the archives all i could find was mixers and i simply dont need the amount of hum rejection in GEO's ABY box.

all i want to do is take a guitar signal and have two outputs of the same thing, one of which should have a volume control so 2 different levels can be attained if i need it.

i'm making this for a friend for his sampler so he can plug it into an amp but also send another one to a headphone amp for the drummer in our band. we're doing a lot of electronics and the idea of making a metronome to connect through midi was a bit out of my grasp because i don't know how to program PIC's.

any help would be great, but im hoping to run it on a 9V battery as simple as possible.

thanks
trent

[Gringo]

Have you checked the splitter-bled at www.runoffgroove.com? The first half should do what you describe.

[Mark Hammer]

Get hold of the TL074 datasheet/appnotes from Texas Instruments ( http://focus.ti.com/lit/ds/symlink/tl074.pdf ).  You will find a nice simple splitter in it, based on a quad op-amp (page 17 to be exact).  Stick a 10uf cap and a 10k pot on each of the three outputs, and you're good to go with 3 isolated outputs with individual output levels.  A 1M resistor between the input and ground couldn't hurt either.

I made one and boxed it.  Works fine, except that I find a slight "rev-up" time when I power up (I use the stereo input-jack method for connecting the battery).  A little disorienting, but after 2-3 seconds it behaves well.

Note that the gain is set to 11, by virtue of the 1M feedback resistor in the first stage, and the 100k resistor to Vref (the junction of those four 100k resistors and the 100uf cap).  You can adjust this by tinkering with either the 1M (R1) or the 100k (R2) resistor.  Making R1 bigger and/or R2 smaller increases gain.  Making R1 smaller and/or R2 bigger reduces gain.

Use of a single 9v battery does not provide gobs of clean headroom, so increasing gain much beyond what's shown is probably unwise, unless you stick it very early in the signal chain before any other sort of boost has kicked in.

[Kleber AG]

Sorry Mark for a dumb guess,
But with that two big 100K voltage divider and a big 100uF filtering, wouldn't the 100uF take all the current at the power up for some seconds, because the 100Ks are slowly charging the "big" cap?

Maybe lowering the cap to 47uF or 22uF solve that? Or reducing the voltage divider 100Ks to 10K fix it?

I'm guessing as a dumb cause I found this spliter very interesting, imagine it with two TL074

Thanks for the circuit Mark!
Kleber AG

[Mark Hammer]

Don't thank me, thank TI (well, actually Electronics Today, where I stumbled onto this around 1981).  Yeah, lowering the cap value would probably reduce charge-up time.  I just built it as shown way back before I could reason through those things.  Patience comes easy to me.  I left the circuit as is and learned to wait the 2 seconds.

[vdm]

hey thanks for that mark! i never would have thought to just look in the app notes of a data sheet :wink:

with the 10uF cap and 10k pot on each output, correct me if i'm wrong but the cap is acting as a coupling cap in series with the output and the pot is acting as a voltage divider to ground (standard volume control)??

thanks very much for your ongoing help!

trent