There are many guitar effects like reverbs, echo, delays, chorus and
more that output two distinct audio signals and can sound better if the
signals are sent to two different amplifiers set slightly apart from one
another. Here's how to set up two Quilter amplifiers to work with
Method 1 (Effects Loop):
Connect the send of the amp to the input on your stereo effect. Connect one effect output to the return on amplifier number one and the second effect output into the return of amplifier two.
Control both the amps using the controls on amp one. The controls on amp two will have no effect. Both amps will have the same gain, EQ, reverb settings and be equally loud using this method.
Method 2 (Effects Loop):
Connect the send of the amp to the input on your stereo effect. Connect one effect output to the return on amplifier number one and the second effect output into the instrument input of amplifier two.
You can control the parameters of each amp separately. Use this method if you want one amp to be a different volume or have a different EQ setting.
Method 3 (Pedal board into inst. input)
If you have all your effects pre-wired on a pedal board, you may find it easier to use the amp's instrument input instead of the effects loop. Keep in mind that effects like reverb, delay and echo sound different when used before the amp's overdrive stage.
Connect one of the stereo outputs of your pedal board to the inst. input on amp one. Connect the other stereo output to the inst. input of amp two. You will have to set the controls on each amp to get the desired sound and volume level.
Chaining stereo effects
The easiest way to chain more than one stereo effect is to choose one pedal to be the "splitter" that will take one input and turn it into two outputs. Connect each output to the inputs of the next pedal in the chain. The same for any additional stereo effects keeping the "A" and "B" signals consistent through each pedal. The last effect's outputs connect to your two amplifiers using one of the methods above.
Stereo effects can give your guitar's tone more width and richness. Using two amplifiers can give you more overall loudness as well as having a backup in the event that one amp fails.