Using two combo amps together

Rocker

Background: I like using basic SS amplifiers, the amps that are part of beginners guitar & amplifier kits.  Volume levels are low and I use a few simple pedals for my sound.  A friend and I get together for a guitar session every couple of weeks, he too uses a small basic amplifier.  One problem with those type of amplifiers is that they tend to be very 'boxy'.  I solved this problem by using two amplifiers in the room, the connections being made from my POD2, a simple stereo setup.

Question: As I understand it, both speaker cones need to be moving in the same direction to sound 'right' rather than each cone moving the opposite way to its companion.  My problem is that I can't tell which way my kit is working.  It might be right or wrong, there is a 50% chance either way.  I have three jack sockets and can wire them up with the tip of A to B, and C to the barrel.  Plug the guitar into A and plug B or C into the amp, one will be the correct polarity and the other reversed.  Could this cause any problem to the amps or the POD?  Apologies if I used the incorrect term to describe what it is I am looking for [polarity].  I have an isolation device which prevents hum due to ground loop.

Thanks

Fingers657

Do you remember the late 70s early 80s Television comedy series SOAP?
https://youtu.be/0BHQT3Omqtw?feature=shared

ecc83

Hi Rocker, you can't reverse the polarity of the guitar signal because it is not "balanced" and will hum like a c**t. The only place you can flip polarity* is the speaker of one of the amps. Put the combos speaker to speaker and play a bottom E chord. The sound should be full and 'bassy'. If it is thin you need to flip one speaker connection. Probably easiest to do by cutting the cable AMP OFF! and using a bit of 5 amp lekkie's 'chock bloc'. Beware the speaker spades if fitted if you don't know what you are at you can wreck the speaker.

*You say you have an "isolating" box? That might use a transformer and so that could have its winding flipped if practical to get at.

Dave.

greejn

Last edition of That Pedal Show was all about using 2 amps.

ICBM

If you set both amps to the same volume, put your head in front of and nearly between them and play something, then if the sound appears to come from a source in the middle in front of you then the speakers are in phase, and if it appears to come from an indeterminate 'wide' source with a slightly 'airy' character to it, they're out of phase.

Sometimes, if the sounds of the two amps are very different, it can actually be quite difficult to tell, but the closer you get to a simple pure tone - use the neck pickup of the guitar - the easier it is to hear.

The easiest way to reverse the phase of one amp is to swap the speaker connections, if it has push-connectors - if it doesn't, then you'll either need to solder or use a chocolate-block connector.

One problem you may find if one or both the amps have switchable clean and dirty channels is that the two channels are not necessarily in phase with each other either!

snowblind

If the sound with the two amps is no longer "boxy" and at the same time doesn't appear somewhat indistinct and lacking detail then chances are your amps are in phase. As referenced above "That pedal show" just did a video on this very subject. 

Ultimately you really want something like an ABY box eg a Radial Twin City, Lehle, GigRig or anything of that ilk which offers, phase reversal and isolation. This will give you the best results. You can also start playing around with wet/dry setups and all that other fun stuff. Note that cheap splitters like that red Fender branded unit you see everywhere are not sufficient for the job. 

rsvmark

I was gonna say that

https://youtu.be/LH9FO1EMIPQ?si=pozZXR18TBwsqsju

Lebarque

ecc83

Essentially all that is needed is a tin with an op amp in it and there are two ways the polarity inversion could be done. A transformer which outputs two jacks one in phase one flipped. Or simply a non-inverting op amp stage followed by an inverting one. Lot cheaper than a decent transformer and higher fidelity. Bellringers should be able to do that for about a score.

Oh! If'n I was ten years younger and could see! This time next year Rodney we'd be miwyonairs!

Dave.

57Deluxe

I experiment with 2 amps all the time and for me, the trick is to have modulation set on one so that there is more 'movement'.

Even my  SuperChamp XD with its tremolo setting, is highly noticeable when in conjunction with my really loud 60w Fender Supersonic dialled with some grunt.

Is an addictive occupation (but only when the neighbours go out).

jdgm

57Deluxe said:

I experiment with 2 amps all the time and for me, the trick is to have modulation set on one so that there is more 'movement'.

Even my  SuperChamp XD with its tremolo setting, is highly noticeable when in conjunction with my really loud 60w Fender Supersonic dialled with some grunt.

Is an addictive occupation (but only when the neighbours go out).

Agree with this; for me it's 2 small combos, one with a trem going, sounds magnificent!