Buffered/Transformer Isolated Splitter

[JamieJ]

This is an isolated splitter pedal that is really good at dinging hum.

It's a simple TL072 buffer into a transformer with a phase reversal switch. The transformer isolation aspect of the circuit seems to be inspired by some of RG Keens ABY isolated splitter circuits. I used a different transformer to the original but they have the same specs.

I haven't actually properly tested this out yet so it may be a tad premature. I really enjoyed building the circuit on Vero. I might try and build a few other pedals this way.

I decided to not bother with any designs/name for this build as it will just be under my board. When I was thinking about names I did a bit of googling for name inspiration and urban dictionary made me piss my pants and emailed @jjjimi84 straight away - see below. I was tempted to call this build Dans Dinger for a while but changed my mind.


I'm a big fan of the TPS show. I haven't ever bought anything from the gigrig before but love their stuff so I feel bad about building this but I might buy a bit of TPS merch as an offset.

 

[Bricksnbeatles]

Kudos to Dan.

 

[giovanni]

I would like to build one of these, would you mind sharing the schematic?

 

[jjjimi84]

Well it is the same color and girth.

 

[JamieJ]

@giovanni - I got the schematic from this site

Humdinger V2 - EasyEDA open source hardware lab

In EasyEDA open source hardware lab, open source square pools all kinds of electrical design engineerings together to realize resource sharing easily.

easyeda.com

 

[giovanni]

Thank you!

 

[giovanni]

No protection diode on the power?

 

[JamieJ]

No protection diode on the power?

Sorry I missed this. No there isn’t and I didn’t bother adding one. I might add one though - good spot.

 

[Dan0h]

Dude thank you for sharing this. I might give it a go. Please let us know your thoughts after using it.

 

[Dan0h]

This gets even better. I have a pile of tl072s and an extra 1:1 transformer I bought in error. Sweet.

 

[fig]

I have a pile of tl072s

Have you ever considered heaps? [I can just hear the groaning]

Righteous execution Jamie!

 

[giovanni]

Heaps and piles and stacks.

 

[Dan0h]

Have you ever considered heaps? [I can just hear the groaning]

Righteous execution Jamie!

When I visited Australia they used “heaps” a lot. Now when I hear that term it takes me back.

 

[Klhnikov]

Hello, and thank you Jamie, I just finished my version of the ABY Box shematic you provided ( with 3PDTs + phase switch + diode )
Here is the schematic...
The pedal works perfectly well, just needs to mention that there must be something plugged into A output before I use the B out, should never use only B plugged in because it needs some ground, and B output is transformer isolated. I can now split my sound between my tube amp (A output) and an Audio interface on my laptop (B output). Thank you again

 

[Nacht]

Hello, and thank you Jamie, I just finished my version of the ABY Box shematic you provided ( with 3PDTs + phase switch + diode )
Here is the schematic...
The pedal works perfectly well, just needs to mention that there must be something plugged into A output before I use the B out, should never use only B plugged in because it needs some ground, and B output is transformer isolated. I can now split my sound between my tube amp (A output) and an Audio interface on my laptop (B output). Thank you again

I will try it. Thanks for posting the schematic.
Is it all good no errors in the schematic?
What makes the output B working only if out A has something connected to it? Is it "fixable"
Thanks a lot

 

[Nacht]

May i ask what are you using to hold the board in place?

View attachment 18971

 

[Stickman393]

Kudos to Dan.

*tips cap*

 

[jwin615]

I will try it. Thanks for posting the schematic.
Is it all good no errors in the schematic?
What makes the output B working only if out A has something connected to it? Is it "fixable"
Thanks a lot

Due to the transformer isolation of the ground, which is a good thing.

 

[Nacht]

Due to the transformer isolation of the ground, which is a good thing.

I'm not sure to understand how that works.
I did not build it yet.
As i understands it, the ground at the output gets isolated from the input ground but... if out A has no isolated ground, and the fact that it needs something connected to it, thus making a ground connection to the pedal...
Does it mean the ground on out A comes from the pedal to the amp A, then amp B gets ground from the amp A through the power cord of the amp, and then out B of the aby pedal isolates the ground to amp B input socket, isolating the ground only between out B and the input of amp B?
I've seen quite a few schematics that use a transformer on both A and B outputs of the aby pedal... that means ground is isolated on both, how could that work?

 

[giovanni]

Theoretically, there is only one ground. In practice though, we have different circuits in our home wiring, which means that if two different grounds from different circuits end up getting connected, they may actually be at slightly different voltages, which will cause interference (noise) because the voltage difference will create a current (this is commonly referred to as ground loop). This is pretty significant if two amps end up sharing the grounds. So when using an ABY splitter, you are lifting the ground of one of the outputs just to break the connection of the ground of the outputs, in order to avoid the grounds on the amps to be connected and thus creating a ground loop and consequently interference (noise). The input ground won’t matter as much, comparatively (although I know ground lift is often use by itself so it must have an effect). That’s why you only need one isolated output. If you have two, you may reduce noise a tiny bit more.

Please take all this with a grain of salt since my knowledge is a bit rusty.