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A question about A/B switching


(@havocdragon)
Trusted Member
Joined: 16 years ago
Posts: 53
Topic starter  

I have quite a plethora of pedals and my band is playing shows right now...one of the things I wanted to try doing was creating an A/B for my distorted/clean tones.

However this is a bit different in set up...I would go out from my guitar into a ab switch...line a has distortion and things I use with distortion and line b has a clean booster and a compressor all this would go back into a y plug at the amp. My question is would this work? The reason for this is I use a graphic eq for some boost for some leads, not to mention a combo of a distortion and overdrive pedal to get my tone, there are a few songs that I go from a solo into clean picking...it would be nice to just pop the A/B channel and be done instead of having to hit all 3 pedals.

I am wondering if this would work or if there are some better ideas?

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(@gnease)
Illustrious Member
Joined: 18 years ago
Posts: 5058
 

the weak point in your set-up is the Y-cable as an output combiner. passive Y-cables can be safely (meaning 'not damaging', 'good sounding' is another thing all together) connect one output (guitar, effect) to drive two inputs (guitar amps). Y-cables should not be used to connect two active outputs to a single input, as there is no active buffering to keep one output -- say pedal chain A in your case -- from driving not only the intended input, but the other output connected to B. That can cause impedance loading issues, as outputs have much lower impedances than inputs for these types of audio interfaces (voltage I/O devices). You may also get also sorts of clipping and modulated noise from driving signal into an active output. But it also can work just fine. It really depends upon how the circuits are designed. Instead of the Y-cable for signal combining, it would be better to use either a buffered mixing pedal -- must be an 'active' combiner or mixer, or a second A-B switch to connect only one path at a time to the amp. of course, unless this second A-B switch can be slaved to the first, you now have click two switches each time you wish to change effects path. clearly, not what you want. and then one problem with the active mixer/combiner approach is the "off" branch of effects are always connected to the amp. if that branch is high gain, then it's likely to produce a lot of noise -- esp when the guitar is disconnected (by the input A/B switch). so that noise still ends up in at the amp.

what I would try:

|==>effects chain A =>A
guitar =>Buffer=>Y-cable=>| [A/B switch] output => to amp
|==>effects chain B =>B

this puts the Y-cable where it's useful -- but note the preceding buffer. that's to maintain a nice, high impedance for the guitar to keep from rolling off the high freqs. it should be something like an MXR MicroAmp. the A-B switch ("flips" around and) moves to the output of the two chains, where it connects the amp only to one effects chain at a time; so then, no extra noise pumped into the amp via a Y-cable.

-=tension & release=-


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(@havocdragon)
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Joined: 16 years ago
Posts: 53
Topic starter  

Thanks that made a whole lot of sense!

Time to go get myself a y adapater and an a/b box!

I am curious though...why would the mxr micro amp be necessary at the beginning?

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(@havocdragon)
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Joined: 16 years ago
Posts: 53
Topic starter  

Would something like an mxr 10 band eq work as the impedance barrier between the guitar and y plug as well?

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(@kent_eh)
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Joined: 16 years ago
Posts: 1885
 

Would something like an mxr 10 band eq work as the impedance barrier between the guitar and y plug as well?
Should do nicely.

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So I looked like I was deep


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(@anonymous)
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Joined: 14 years ago
Posts: 8308
 

Thanks that made a whole lot of sense!

Time to go get myself a y adapater and an a/b box!

I am curious though...why would the mxr micro amp be necessary at the beginning?

he is just saying you want a pedal with a buffer at the beginning. a buffer will boost the signal and you won't lose as much fidelity over a long chain.


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(@gnease)
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Joined: 18 years ago
Posts: 5058
 

the buffer doesn't so much boost the signal (though it can) as provide the guitar with a very high impedance -- hopefully similar to the input of an amplifier. consider: if one parallels two effects boxes with a Y-cable (no buffer), that will present the guitar with a lower impedance than one effect pedal alone. if we assume both had input impedances of 500k ohm, then two in parallel will be 250k ohms. that much lower load impedance can result in a noticeable loss of treble for some guitar. adding the buffer amp prevents this.

and agree with above, the EQ pedal will work as a buffer. in fact, that's a very good place in the lineup to put the EQ. moreover, I have both the MXR 10-band EQ and a MicroAmp and can confirm either does the job quite well.

-=tension & release=-


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(@anonymous)
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Joined: 14 years ago
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i thought you might say that. i was just giving a simple answer for us non-electrical engineers.
edit:that wasn't supposed to sound snarky, it was just a joke.


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(@havocdragon)
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Joined: 16 years ago
Posts: 53
Topic starter  

Thanks again guys...so far this all is working great, I had to get a few more pedals and cables to make this all work!

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