stereo to mono box...

SimpleSi · Post by **SimpleSi** » Fri Apr 25, 2014 8:58 pm

I'm looking at making an enclosure with parts from Jaycar..

ideally will have 2 mono in's and outs..

for stereo in and out.. ie

Strymon left out and right out can plug into it via patch leads then i can run the box to my 2 amps..

now the twist..

I want to put a switch in that can turn the signal into mono without me having to unplug my patch leads that are in stereo..

I'm just wondering if anyone has done this - so that I can switch the stereo input to a mono output or back to stereo - I'm not always using 2 amps.

I'm curious if I have the switch as a "right signal" cut... or have it let both the left and right join together to output to just the left out for mono.

I'm not sure if option 2 will cause any noise or electrical problems because of both left and right going out 1 output jack or if I'd be better off having it just cut the right channel out (which would probably cut tone because the pedals are defaulted to stereo)

if I sound confusing I'm sorry - this all makes sense in my head...

I can draw up a diagram/picture if anyone has ideas..

Also considering putting diodes in the signal chain so that signals won't backfeed...

Simon

Eruera · Post by **Eruera** » Fri Apr 25, 2014 9:28 pm

Uhhhhh diodes would be bad, the signals are AC.

To achieve this I think your best bet would be using a TRS plug for the right output so that you can potentially spoof the pedal into thinking there is only a plug in the left jack when you're in mono mode (assuming it does the usual thing of looking for continuity between ring and sleeve to tell if there is a plug in the jack)

SimpleSi · Post by **SimpleSi** » Fri Apr 25, 2014 9:31 pm

Eruera wrote:Uhhhhh diodes would be bad, the signals are AC.

To achieve this I think your best bet would be using a TRS plug for the right output so that you can potentially spoof the pedal into thinking there is only a plug in the left jack when you're in mono mode (assuming it does the usual thing of looking for continuity between ring and sleeve to tell if there is a plug in the jack)

ah of course. AC - i assumed the signal chain was DC..

how would a TRS allow me to switch from mono to stereo?

Eruera · Post by **Eruera** » Fri Apr 25, 2014 9:40 pm

In alot of pedals they use a TRS jack since putting a TS plug into shorts the R and S together. It's this that usually turns on a pedal when plug something in since it completes the circuit. Strymon may be doing some wizardry but I would think the easiest way for the pedal to tell whether you're plugging into both jacks or just the left (mono mode, if it has one) would be to 'look' for the connection between R and S of the right jack that a TS plug would cause. Using a TRS plug you can choose when this connection is made, allowing you to make the pedal think there is nothing plugged into the right hand jack.

It's all based on the assumption that they're determining operating mode this way, but it's where I'd start.

You could always try just ditching the right channel to ground and see how just left sounds (there may not really be any difference between left and right)

SimpleSi · Post by **SimpleSi** » Fri Apr 25, 2014 9:48 pm

Eruera wrote: It's all based on the assumption that they're determining operating mode this way, but it's where I'd start.

You could always try just ditching the right channel to ground and see how just left sounds (there may not really be any difference between left and right)

So in theory I could just not have anything plugged into the right output of this box and it would basically divert to mono because of the lack of continuity on the right channel?

Without any switch on place.

Or would you think it would be best to ground/short the right side with a switch.

Eruera · Post by **Eruera** » Fri Apr 25, 2014 9:51 pm

You'd need some way of making/breaking continuity between R and S still. Is the BigSky last in your chain? Why not just plug into left only when you're going mono and both when you're going stereo?

SimpleSi · Post by **SimpleSi** » Fri Apr 25, 2014 9:58 pm

http://imgur.com/Vfa9CmH

This is my board.

The last 3 pedals are in stereo

Eruera · Post by **Eruera** » Fri Apr 25, 2014 10:07 pm

That makes it a bit more tricky since the BigSky doesn't have the capability to sum a stereo input to mono output. Do you use any panned delays or anything? If not then you probably won't lose much just taking the left out of the BS when only using one amp. If you really wanted you could make a box that sums the left and right outputs on the bigsky, this could be switchable.

SimpleSi · Post by **SimpleSi** » Fri Apr 25, 2014 10:11 pm

Eruera wrote:That makes it a bit more tricky since the BigSky doesn't have the capability to sum a stereo input to mono output. Do you use any panned delays or anything? If not then you probably won't lose much just taking the left out of the BS when only using one amp. If you really wanted you could make a box that sums the left and right outputs on the bigsky, this could be switchable.

My flashback delay pans.

Other than that. No.

What do you mean by sums?

I'm guessing you mean joins them at the output to 1 out.

As you suggested I could always just plug the left out into my amp and see if it sounds any different..

Its stereo in.. But with mono out it might work

cholera · Post by **cholera** » Sat Apr 26, 2014 12:52 am

You guys seem to know what you're talking about. Can one of you tell me on a related topic, if my stereo pedals are wired together in stereo (flanger, reverb and a delay last, all in stereo) is it likely to work if I just used a mono return from the delay, because sometimes I use the board with a mono head? These pedals are always in the FX loop by the way. So basically I want to know if I need to unplug all the 2nd patch cables between the flanger/reverb/delay.....? I could always try it out, but just thinking about it while my gear isn't at home.

Miza · Post by **Miza** » Sat Apr 26, 2014 7:40 am

cholera wrote:You guys seem to know what you're talking about. Can one of you tell me on a related topic, if my stereo pedals are wired together in stereo (flanger, reverb and a delay last, all in stereo) is it likely to work if I just used a mono return from the delay, because sometimes I use the board with a mono head? These pedals are always in the FX loop by the way. So basically I want to know if I need to unplug all the 2nd patch cables between the flanger/reverb/delay.....? I could always try it out, but just thinking about it while my gear isn't at home.

I think that's exactly what Si's problem is.

Wants to run his rig in mono or stereo without unplugging all the 'right' patch leads.

Hey Si, do your amps have multiple inputs? Maybe you could run both cables to the one amp? Then the amp might just join the signals. No idea if that would work in practice...

bender · Post by **bender** » Sat Apr 26, 2014 7:47 am

Other than ping-pong delay, you probably won't notice much of a loss if you simply ditch the R channel. Chorus, flanger and reverb add spatial information (simply put the L and R channels sound different so that the output sounds much wider) but no positional information (ie they don't put more of your guitar's signal in one channel vs the other) so there won't be anything missing as such, but the modulation effects often have the inverse LFO waveshape on the second channel so it'll effectively halve the rhythm of the modulation effect (it'll still sound full, but it'll be a noticeably different pace). This will be more with pronounced ping-pong delay and stereo tremolo (depending on the depth) since they are effectively modulating the position within the stereo field (ping-pong delay alternates which channel the repeats come out of and since stereo tremolo is modulating amplitude it's effectively acting as a panner). Best thing to do is just unplug one of the outputs and see if it's a noticeable change and , if so, if it's a problem.

TBH I'd be surprised if the pedals were doing anything clever electronically with the outputs when operating in stereo vs mono so I doubt there'll be a need to do anything special with a TRS plug on the R channel.

If you're building a switch that sums the signals to mono (which is a good plan if unplugging the R channel sounds too different) you might need to build in some attenuation since you'll effectively be adding 6dB to the signal. If you want to get really clever you could build in a 6dB pad (which is just a couple of resistors) that is switched in when operating in mono. You'll just need to figure out the impedances involved.

SimpleSi · Post by **SimpleSi** » Sat Apr 26, 2014 8:02 am

benderissimo wrote:If you're building a switch that sums the signals to mono (which is a good plan if unplugging the R channel sounds too different) you might need to build in some attenuation since you'll effectively be adding 6dB to the signal. If you want to get really clever you could build in a 6dB pad (which is just a couple of resistors) that is switched in when operating in mono. You'll just need to figure out the impedances involved.

How would I work that out?

I'd have to have a diagram to solder it together..

My electrical knowledge is just domestic.. Being a sparky and not really a service technician. Lol.

SimpleSi · Post by **SimpleSi** » Sat Apr 26, 2014 8:09 am

Miza wrote:
cholera wrote:You guys seem to know what you're talking about. Can one of you tell me on a related topic, if my stereo pedals are wired together in stereo (flanger, reverb and a delay last, all in stereo) is it likely to work if I just used a mono return from the delay, because sometimes I use the board with a mono head? These pedals are always in the FX loop by the way. So basically I want to know if I need to unplug all the 2nd patch cables between the flanger/reverb/delay.....? I could always try it out, but just thinking about it while my gear isn't at home.
I think that's exactly what Si's problem is.

Wants to run his rig in mono or stereo without unplugging all the 'right' patch leads.

Hey Si, do your amps have multiple inputs? Maybe you could run both cables to the one amp? Then the amp might just join the signals. No idea if that would work in practice...

1 input only.

Even if I used the 2 on my fender.. One is high input and one is low.

bender · Post by **bender** » Sat Apr 26, 2014 8:32 am

SimpleSi wrote:
benderissimo wrote:If you're building a switch that sums the signals to mono (which is a good plan if unplugging the R channel sounds too different) you might need to build in some attenuation since you'll effectively be adding 6dB to the signal. If you want to get really clever you could build in a 6dB pad (which is just a couple of resistors) that is switched in when operating in mono. You'll just need to figure out the impedances involved.
How would I work that out?

I'd have to have a diagram to solder it together..

My electrical knowledge is just domestic.. Being a sparky and not really a service technician. Lol.

My knowledge is pretty limited but I think the input impedance of your amp determines the resistor values. Here's a link to a detailed explanation (working out the K value still makes no sense at all to me but there's an excel spreadsheet part way down).
http://www.uneeda-audio.com/pads/

Summing the outputs could result in hitting the front end of your amp harder than you'd like but you won't know until you try.

The first thing you should do is simply set up your full rig, then try various combinations of the effects you use, each time comparing both amps running to just one (either by unplugging the R channel out of the last pedal or turning the second amp down). If that sounds fine, build a switch that disconnects the R channel from your pedals and sends the L channel to both outputs (or just use the left out of the last pedal in your chain when only using one amp). If it's too different, build a switch that combines the L and R outputs from the pedals and sends them to both outputs (or only to the L output). If that is overloading your amp too much, add a pad or a volume control.

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