Test breadboard circuits in a smart way without hassle? Looper?

[Sophia2001]

Dear fellow DIY builders,

I am running into a "problem" that perhaps one of you can help me with. I use breadboards to test schematics before soldering. I often find it a hassle to hold my guitar in my hand and fine-tuning components at the same time.

I had the idea to buy a looper pedal, like the TCE Ditto and place it between the guitar and the breadboard. This allows me to play a riff, loop the riff, and test my breadboard without any hassle holding the guitar.   

- do you see any problems arising from this? Could the Ditto affect the schematic?
- If not, is the Ditto a good choice?
- How do you approach this "problem"?

Looking forward to your ideas!

Sophia 

[antonis]

Maybe this..??

[Elektrojänis]

Looper can be usefull for testing just as you described. There are some things you need to consider though:

1. Sometimes it is important how the circuit reacts to your playing and how it feels when you play. This is especially true when the circuit changes the dynamics of the signal like compressors and stuff that distorts (distortion, fuzz, overdrive). You cant really tell how it feels when playing when it's the looper that's playing.

2. Some circuits react to the impedance of the signal source. The looper will most likely have output impedance that is low and flat across the frequency spectrum. Guitar pickups have highre output impedance and its inductive. Inductive that means the impedance gets higher when the frequency gets higher. This mostly affects Fuzzes (more to some than others).

However, I think a looper can still be very usefull for testing. It's just good to know the limitations and keep in mind that things might feel and sound a bit different when you actually play through the circuit yourself (in real time).

[GibsonGM]

I built a breakout box for this purpose, seen to the left of the BB's. It has power, effect/bypass switch, and I built an audio probe that can be switched in and out (with indicator LED).  The signal wires plug right into a bank of multiple BB's that have pwr/gnd connected to each other (with LED power indicators - nobody likes tracing a bad BB power supply!).  I connected its ground to a piece of copper sheet, so there is always a ground handy to clip a meter lead to etc. Sorry pic is crappy.

This way I can play while testing and compare to bypassed signal, and not worry about dead batteries or whatever. I also use R.G.s "quick and dirty oscillator" (in a tuna can) when I want hands free, or if something needs to be traced.  It would be cool to build that in, so you could inject with one probe and listen with the other at the same time!

[diffeq]

- How do you approach this "problem"?

mp3 player with several samples on it, because I keep it simple 

[antonis]

Nice, clean and tidy...

[ElectricDruid]

- do you see any problems arising from this? Could the Ditto affect the schematic?

No problems. The Ditto *could* affect the circuit in certain limited situations, as explained by Elektrojänis. In short, the circuit is seeing a buffered output from the looper pedal rather than looking directly at a guitar. If the pedal would typically be used with some other pedal ahead of it, this likely makes absolutely no difference whatsoever. If the pedal is something that *might* be used directly after the guitar, it *might* matter.

- If not, is the Ditto a good choice?

Is it cheap?!? I'm sure it will do the job perfectly well.

- How do you approach this "problem"?

I have recordings of guitar riffs on my phone that I sometimes use for testing, and I also have a cheap MP3 player from eBay for the same purpose. The worse thing about this is you need a 3.5mm minijack to 6.35mm jack lead to plug them in!

[Transistor-Transistor]

I just have a guitar stand right next to me and sit on a swivel chair so I can just kinda turn and set my guitar down in one motion hehe.

[idy]

Yes, looper pedal very helpful and practical for making sure things work.
Also true that when you get down to the "feel" and response to an actual guitar you need the real thing or some kind of pickup simulator... you need the real thing

[GibsonGM]

Nice, clean and tidy...

I Do know where everything is...this is a well-oiled machine... 

[bluebunny]

I also use R.G.s "quick and dirty oscillator" (in a tuna can)

Nice pun. 


If you want a real guitar, tune it to an open chord.  Then you can "play" with one hand and twiddle with the other.

[GibsonGM]

Good one, Marc! I've done recordings of guitar...chords followed by single passages, hoping to use that as an input.  But levels never match up, as as mentioned, nor output impedance of the player, and there's no 'feel' that way.  I always need to bang away and see how something acts with varying player dynamics.   

My little box is just a desktop version of an enclosure w/bypass, really.   Lets me 'get ready' with the axe, and hit the bypass toggle. If it squeals and farts, well just flip it back off and put the guitar down, ha ha!  It also offers solidly attached rather than the flying jacks which we're all used to...which always pull loose even on a working circuit, causing endless problems.

I was going to add an NE5532 headphone amp to that, but thought better of it, ha ha! Not in testing, no.

[Sophia2001]

Thanks all!

Sophia