# Unison Double Tracker In Stereo? *Solved*



## Jovi Bon Kenobi (Jun 1, 2019)

I'd like to try connecting the input buffer to the ring of a stereo out jack for a left wet, right dry configuration. Where exactly is the input buffer on the PCB?


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## Robert (Jun 1, 2019)

There are a few different revisions of that PCB, can you post a pic of the one you have?


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## Jovi Bon Kenobi (Jun 1, 2019)




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## Robert (Jun 2, 2019)

[See below]


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## Jovi Bon Kenobi (Jun 2, 2019)

Awesome! I'll give it a shot. Thank you!


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## Jovi Bon Kenobi (Jun 2, 2019)

So, I soldered in a stereo output jack and reconnected the tip & sleeve. The orange wire runs from the ring lug to a 1k resistor under the shrinkwrap. I then connected that to the point you circled and tested it out by using a TRS Y cable running to two amps. I only had the mono signal coming out of the tip and nothing from the ring.


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## the_grumpy_gnome (Jun 2, 2019)

One A+ for your documentation, another for your tidy work.  

What you may consider is to use a buffer/splitter before you ever get to the first part of the Unison circuit, then turn the Blend on the Unison to max.  That way you split your signal into two paths:  a clean bypass which reconnects to the stereo output and one that's a fully wet signal from going through the circuit.

Here's a simple, easy buffer (three outs, but just don't built the third):  http://www.muzique.com/lab/splitter.htm


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## the_grumpy_gnome (Jun 2, 2019)

Also, this is just and educated guess, but I think the above instructions are to take a new lead from the circuit green spot:


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## Jovi Bon Kenobi (Jun 2, 2019)

Thanks very much! Excellent ideas and thanks for helping with the schematic. Makes more sense now.


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## Jovi Bon Kenobi (Jun 2, 2019)

I may just build the next one with said splitter since I have another board on deck. It's definitely a favorite!


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## the_grumpy_gnome (Jun 6, 2019)

@Jovi Bon Kenobi, when this is finished please let me know how it went.  I'd been considering doing the same thing and forgot about it until you posted and  reignited that interest. Thanks in advance


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## Jovi Bon Kenobi (Jun 6, 2019)

Will do! I just need to learn how to read a schematic first so it might take me awhile


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## Robert (Jun 6, 2019)

You really shouldn't need the splitter circuit, the first stage is already a unity gain buffer....    

The problem here is that (like an idiot) I didn't keep a good archive of the trace layout for that particular revision of the PCB.   I was hoping we could get by using a single resistor, but no such luck....

Use a 1K resistor in series with a 1uF MLCC (or box film) cap to connect Pin 1 of IC1 (TL072 on the left) to the Ring of your output jack... 

That should do it.


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## Jovi Bon Kenobi (Jun 6, 2019)

Bingo! That's it. Ring is dry, tip is wet. Siiiiick! Thank you!


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## Jovi Bon Kenobi (Jun 6, 2019)

Now I just need to figure out how to make this look pretty. Haha.


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## the_grumpy_gnome (Jun 6, 2019)

Robert said:


> ...Use a 1K resistor in series with a 1uF MLCC (or box film) cap to connect Pin 1 of IC1 (TL072 on the left) to the Ring of your output jack.



I'm guessing that the cap blocks DC.  What's the purpose of the 1k resistor?


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## Robert (Jun 7, 2019)

the_grumpy_gnome said:


> I'm guessing that the cap blocks DC.  What's the purpose of the 1k resistor?



The 1K resistor acts as a current limiter in case the ring gets shorted to ground. (For example when a mono plug is inserted)


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## reubenreub (Sep 9, 2019)

So glad I found this on the forum! The Unison Doubletracker sounds so incredibly good with this mod! Any chance of simply adding this as a revision to the boards themselves? I could see it coming in handy for a number of these FV-1 builds and it seems like it wouldn't hurt anything by including it.


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## Robert (Sep 10, 2019)

reubenreub said:


> Any chance of simply adding this as a revision to the boards themselves?



Yep, that wouldn't be a bad idea.    A stereo board is coming one day, but there are times (like this) when you don't really need effected signal on both channels.


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## smithcircuits (Oct 20, 2020)

Hey, so I tried this on an organ donor. I'm taking a line from the buffer (IC1, pin 1) to a separate mono jack to use as a dry out. I have a wet and dry when the pedal is engaged, but no signal comes through the dry output jack when bypassed.... Am I missing something?


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## p_wats (Oct 20, 2020)

smithcircuits said:


> Hey, so I tried this on an organ donor. I'm taking a line from the buffer (IC1, pin 1) to a separate mono jack to use as a dry out. I have a wet and dry when the pedal is engaged, but no signal comes through the dry output jack when bypassed.... Am I missing something?


That's the way it will work, as if you're in bypass then you're also bypassing the buffer, so no single will be getting to it. (ie. The dry out will only work when the pedal is on). It's a limitation of this quick and dirty mod.


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## smithcircuits (Oct 23, 2020)

Ended up using a buffered splitter to get this done. Oh well.


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