Playing with Two Amps. Stereo vs Slaving and Fun With FX Loops

 WARNING:  Never power on your amp and play it without a speaker connected.  Always have a speaker connected (or a speaker load).  If you don't you will fry your amp and it will be costly. 

Stereo Rigs

There are lots of options when you realize you want to start playing with two amps live.  The tone you can dial in with two differently voiced amps and cabinets can be very full and amazing.  You may never go back to playing a single amp again.  Although lunging around two heads and cabs to every show is not for everyone.  Let's look at some options on connecting your stereo rig.

The easiest and cheapest route is to simply get a Y instrument cable and plug straight in.  It is highly likely you will run into ground hum.  You can buy an audio isolation transformer to remedy this.  However this method leaves you with the fewest options.

Y Cable

 The next option is to get a ABY box, which will allow you to switch between amps or play both at the same time or just one amp at a time.  This gives you a lot of control over the voicing and dynamics.  Not all ABY boxes are created equal however.  The best ones will offer you a ground lift to defeat ground hum.  The Radial Big Shot seems to be one of the better boxes on the market.  

ABY Box

Now lets say you like playing with a lot of modulation or delay effect pedals.  Many of these offer stereo outputs which can sound huge and psychedelic.  Pop a stereo Chorus, Tremolo, Flanger, Phaser, or Delay at the end of your FX chain to split the signal to both amps.  Again, you'll probably have ground hum, so try to find an audio isolation transformer to plug one of the outs into.

Through a Stereo Pedal

Amp Slaving and Daisy Chaining

Now lets talk about Slaving, Daisy Chaining and FX Loops.  Slaving is basically taking one amp and sending it's preamp to the power amp of another amp, bypassing the preamp of the slave amp.  Why would you want to do this?  Seems like a waste right?  Well, it can be a solution to a problem I run into a lot here in Japan.  Most clubs have a backline of amps which depending on the venue, that amp might not have enough volume or power you're looking for.  I like the dirty sound of most of the Marshalls these clubs have, but sometimes they are lower wattage or under serviced and just not cutting it.  In this case I'll take the FX loop send of my Marshall (master amp) and run it into the FX loop return of another amp(slave amp).  It simply uses the power amp of the slave amp to boost the volume.  Sometimes you might want to do this for a smaller low wattage amp that has great tone, but low volume.  Maybe you might get a different EQ from the slave amp's speakers.  Hell, I've been know to use a bass amp as a slave amp.  Sometimes the other amp might not have the distortion tone you're looking for, but it has the power.  In my case, most clubs in Japan have a Roland Jazz Chorus.  Great loud clean amp, but the distortion channel just isn't my thing. It should be noted the slave amp will usually not have EQ control.  We are bypassing it. 

Amp Slaving

So that's one solution for an under powered amp,  but if we have a lot of effect pedals, we can also run a "wet"(effect pedals into)amp and a "dry" amp(no effects).  This will give you the clarity of your normal guitar tone with all the effect pedals only going into the slave amp.  It will sound like two different amps and offer more depth of sound.  To do this, we again run the FX loop send of the Master amp into our modulation or time based effect pedals, then into the FX loop return of the Slave amp. 

"wet" "dry" amp slaving

There is another method to linking amps that don't have an FX loop.  We can daisy chain most amps with dual inputs, such as an old Marshall JMP or most Fender styled amps.  JMPs  have 4 inputs.  A low and high input for two channels, bright and normal.  Many people "jumped" these channels by linking a patch cord from the low input of the bright channel to the high input of the normal channel.  This allowed both channels to mix, offering more tone control.  We can use this same idea and take the lower input of one amp and link it to another amps input.  This will run through the second amps preamp, so we can dial each amp.  Hendrix was know to do this with two or three JMP heads.  Sometimes he simply used the Y cable technique. 

Daisy chaining or Linking amps

FX Loops

Lastly, since we're on the topic of FX Loops, lets clarify what they are and what's going on with them.  Your amp has a preamp which controls your EQ and a lot of times the gain or drive of the amp.  A lot of people like the sound of preamp distortion, so this is the source of that.  When we use effect pedals, sometimes we want our delays, reverbs or modulation pedals to come after the amp distortion.  To do this, we can take the send of the FX loop into the input of the pedal or pedals we want to come after the amp distortion, and take the output of the last pedal back into the FX loop return.  Sometimes these "send" and "returns" are labeled differently, such as "preamp out".   Most people prefer the sound of their tubescreamers, fuzzs, and distortion or boost pedals in front of the amp.  Going into the regular guitar input.  Because these gain pedals interact with the preamp.  Lots of people like the clarity of delays or modulation pedals, coming after this distortion or gain.  Some pedals you many find are over powering in the FX loop.  I perfer my Phase 90 in front of my amp.  In the FX loop it is just too overbearing for my tastes.  Maybe try an EQ pedal in the FX loop, and dial in your tone even more.  Or boost it.  There are no real rules, so experiment and have fun. 

FX Loop configuration

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Lesser Know Channel Switching Ideas.

If you're like me, you've been through a few rigs or you've at least re-designed it more than a few times.  I big part of music I love, is the use of dynamics.  Soft to loud, loud to soft.  It's a big part of the emotional part of music. I often have done what many people do in modern times to get these dynamics with an electric guitar and amp.  Either used a boost or distortion/fuzz pedal on a clean amp, or simply use the footswitch on my two channel amp. Pretty simple.  However I've been in situations where the I'm playing through a "Fender" style two channel amp with no footswitching abilities, or with an amp that is a simple one channel amp, and I'd like a quicker volume control than simply using the guitar's volume knob.

So how do we make a footswitch like channel switch on an amp with no footswitch?  There are a few simple ways which I've learn from people much older and wiser than me.

The first technique is actually the oldest idea.  Before there were fuzz pedals or boost pedals, players only had a volume knob.  Gibson guitars actually gave you two channels on their guitars by giving you two volume knobs, one for the bridge pickup and one for the neck.  They actually named these "channels" on their toggle switches as "rhythm (neck PU)" and "lead (bridge PU)"  The intended idea behind this is to dial in your basic tone on the amp with the neck(rhythm) pickup with the volume down enough to barely break up the amp.  When you switch to the bridge (lead) pickup the volume will be fully open and much louder and more distorted.  However it will be much brighter, that's when you'll need to turn down the "tone" knob to cut enough treble as you desire.  This technique works pretty well, and I've used it quite a bit in situations with no pedals and only a Gibson on a good amp.  I love where the toggle switch is on a Les Paul.  You can really hit it on the fly with your thumb.  Most of the guys you probably love from the classic rock era of the 60s and 70s probably started out this way, or continue to use this technique.  check out Page demonstrate it here: 

The next idea uses a two channel, non-switchable amp such as a Fender Reverb.  There are a ton of amps modeled after this amp and you've probably seen quite a few.  The amp actually has two sets of two inputs, for each channel.  To make this switchable by a footswitch, all we need is an ABY box.  A pedal which enables us to spit a signal and gives us the ability to switch between the two channels.  We can set each to different volumes or EQs and have two tones that are switchable by foot.  Simple.

Lastly, we have an interesting idea which actually is similar in principle to the first technique.  We'll simply cut the volume of an amp by using an EQ pedal.  For years I always used the EQ as a boost.  However most EQ pedals also allow you to cut the volume as well. The great part about this is we can shape the tone of the cut signal to customize it better.  EQ pedal off, gives us our loud full volume tone.  EQ on, gives us a clean channel.  I personally like to add a compressor to the clean signal to give it a bit more sustain and fullness. 

Even if you're happy with your setup as is right now, it's always good to have the knowledge of other ideas  You never know when you might need to use them.  I've played shows where most of my pedals aren't working or a cable has gone bad, and I've had to resort to some of these techniques.