Author Topic: Passive A/B in front of Rangemaster  (Read 246 times)

replaceablehead

Passive A/B in front of Rangemaster
« on: August 13, 2019, 03:53:02 AM »
I'm planning out my new pedal board. And I've decided that based on the pedals I'm looking at in the rig it makes sense for me to split it into a clean path and dirty path.

So I was thinking of putting together an A/B switch to allow me to switch between my rangemaster and fuzzrite going into the regular channel of my AC15 and then all my clean effects, compressor, chorus etc going into the top boost channel.

Now from experimentation it seems pretty apparent that a buffered solution has too many trade off's, I might as well ditch the rangemaster and fuzzrite if I can't play with the volume knob.

So I'm thinking passive. But lots of threads mention bleed from the fuzz, and a loss of overall signal level. From what I've read there is a type of A/B switch that grounds the unused signal.

https://www.fulltone.com/sites/default/files/manuals/fultone-a-b-switcher.pdf

Will that do what I want. The blurb seems to suggest it will, but if so why isn't everyone suggesting this design, or even using anything but this design?

Also for extra bonus, I'm thinkin, could I just rehouse the Rangemaster in a bigger enclosure and use this same wiring scheme to create an a/b pedal with one signal permanently running through the rangemaster. I don't see how one channel would know the difference between routing to a jack first vs going straight to the circuit input. Am I missing something there? I mean obviously I'd be permanently boosting the fuzzrite, but I kind of like that anyway.
« Last Edit: August 13, 2019, 04:19:54 AM by replaceablehead »

GGBB

Re: Passive A/B in front of Rangemaster
« Reply #1 on: August 13, 2019, 05:25:07 AM »
The blurb seems to suggest it will, but if so why isn't everyone suggesting this design, or even using anything but this design?

The blurb itself suggests that few others if any recommend or use this design. The actual truth is something else. It might have been true in the past (the doc has a 2002 date in it) - perhaps before 3PDT stomp switches were readily available - but this is the preferred design, and what you will find in most A-B switchers AFAIK.

replaceablehead

Re: Passive A/B in front of Rangemaster
« Reply #2 on: August 13, 2019, 09:25:40 AM »
Ah well I guess it pays to check dates. I've been reading more recent threads, but none of them dealing with this issue.

The bottom line is will this wiring scheme work for what I'm trying to do? I can't see why it wouldn't, but then the issues with passive A/B switching aren't that intuitive to begin with.




GGBB

Re: Passive A/B in front of Rangemaster
« Reply #3 on: August 13, 2019, 11:55:58 AM »
It will work as far as directing where you want your guitar signal to go is concerned. Im not familiar with how the ac15 inputs work. Are both on at the same time? If so then you may still have some issues with noise generated by your dirt loop - even with the loop input grounded - being audible in the background of your clean signal. Ideally you want to ground/mute the amp input or loop output.

replaceablehead

Re: Passive A/B in front of Rangemaster
« Reply #4 on: August 13, 2019, 06:35:29 PM »
yeah they're on at the same time.

It seems like so many before me I'm discovering the fundamental problems with A/B switches.

So is the potential issue to do with both signals still sharing a common ground?

Are there any other solutions? Are there any active circuit designs without buffering? Fuzz friendly buffers?

At this point I'm thinking I should maybe actually build one and see if I get issues.

GGBB

Re: Passive A/B in front of Rangemaster
« Reply #5 on: August 13, 2019, 08:51:58 PM »
This issue is just noise from the circuits. Even though the input to the loop may be grounded, some noise might be produced by the pedals which is then amplified by the amp. This could be typical background hiss from amplification of the noise floor - it would be exactly the same as when you turn the guitar volume down to zero with your pedals on. Some (dirt) pedals are quiet, some are not. (High) gain pedals amplify not just the input signal, but also any extraneous noise including that coming from the active devices themselves. It may not be a problem for your specific situation (your specific pedals).

The solution is a more complicated switcher - with enough poles to change the active loop and ground the inactive loop output (which is the amp input) as well as the input. That can be done with a 4PDT instead of the 3PDT, but since you need to tap in to the signal going out of the loops in to the amp, you need more jacks:



replaceablehead

Re: Passive A/B in front of Rangemaster
« Reply #6 on: August 13, 2019, 10:12:33 PM »
Thank you so much. I don't think this solution would ever have occurred to me.

So you could do this with a 3PDT, you'd just loose the LEDs, correct?

GGBB

Re: Passive A/B in front of Rangemaster
« Reply #7 on: August 13, 2019, 11:06:58 PM »
Right - lose the LEDs and you only need a 3PDT.

replaceablehead

Re: Passive A/B in front of Rangemaster
« Reply #8 on: August 13, 2019, 11:11:27 PM »
huh, odd that I've never seen this mentioned in all the threads I've looked through, nor have I seen it used in any of the commercial pedals. It's a few extra jacks, that's hardly prohibitive. Well actually in fairness it's more than a few, but still.
« Last Edit: August 13, 2019, 11:37:16 PM by replaceablehead »

GGBB

Re: Passive A/B in front of Rangemaster
« Reply #9 on: August 14, 2019, 12:08:39 AM »
I guess most people using A-B switchers to select their amp channel are switching their effects (if any) along with the guitar. Effects out into the switcher, rather than switcher outs into two effects chains and then each into the amp. So nothing is left connected to the amp input, and the switcher directly grounds the amp input (just like unplugging does). I expect that's how they were intended to be used anyway. But that's not something I'm in the loop about - so maybe I'm wrong and everybody does it like you do now :). In any case, your setup is a deviation from the intended use I think.

replaceablehead

Re: Passive A/B in front of Rangemaster
« Reply #10 on: August 14, 2019, 01:37:13 AM »
Well I am a bit of a rebel  8)

I can see why more people would want to bring all their effects across to the new channel. But I'm also sure a lot of people would want to use different kinds of effects on the clean channel than on the dirty channel. The whole point of this is so I can have the TB going into the darker channel and I don't have to switch off the compressor. I've tried every other possible combination, but it's always a compromise.

I feel like I must have read at least a dozen threads on this topic, I saw plenty of references to the Fulltone and Eric Johnson layout, but nothing along these lines.
« Last Edit: August 14, 2019, 01:47:37 AM by replaceablehead »