Loops 7 through 10 are stereo capable on the Mastermind PBC. You can use them with mono pedals or stereo pedals. Using mono pedals is easy – just connect them with standard 1/4-inch cables and you’re good to go. However, as soon as you want to start using stereo pedals, you’ll be required to use some special cables to make sure everything works correctly.
Before we get to the cables, we should go over the pushbuttons on the rear panel. These are also crucial for proper mono or stereo operation.
Mono -> Stereo (out) – This button, when in the “out” position converts a mono signal coming in to the In 7-10 jack to stereo. This is done simply by connecting the incoming signal to both the left and right sides of the internal audio path. When this button is in the “in” position, the In 7-10 jack’s tip and ring are connected to the internal audio path’s left and right sides. The "in" position leaves the incoming signal unchanged. If nothing is plugged into In 7-10, or a mono signal is plugged into In 7-10, the signal will be mono. If a stereo signal is plugged into In 7-10, the signal will be stereo.
Mono Output – This button, when in the “out” position connects the left side of the internal audio path to Output A and the right side of the internal audio path to Output B. When in the “in” position, the left side of the internal audio path is connected to both Output A and Output B.
How to set these buttons can be summarized like this:
Mono signal into In 7-10 (or nothing plugged into In 7-10), mono output – Mono -> Stereo IN, Mono Output IN
Mono signal into In 7-10 (or nothing plugged into In 7-10), stereo output – Mono -> Stereo OUT, Mono Output OUT
Stereo signal into In 7-10, stereo output – Mono -> Stereo IN, Mono Output OUT
Now, on to cables… please note that these only apply if you’re using one or more stereo pedals. If you’re running all mono, you can use standard cables.
If you have a pedal with a stereo input and/or stereo output, you need an insert cable for each stereo connection. An insert cable has one TRS connector on one end and two standard (TS) 1/4-inch connectors on the other. This splits the TRS stereo connector on the PBC to individual left and right connections that your pedals need.
If you have a pedal with a mono input, you need a ring disconnect cable. This is a name I just made up, because I don’t know of any “official” name for such a thing. This one has a TS plug on the pedal input end and a TRS plug on the Loop Send end. The tips of both jacks are connected together, and the sleeves of both jacks are connected together. The ring on the TRS side is not connected to anything.
If you have a pedal with a mono output, you need a mono to stereo converter cable. This cable has a TS plug on one end and a TRS plug on the other, but unlike the ring disconnect cable, the tip on the TS end connects to both the tip and ring on the TRS end. The TS end plugs into the pedal output, and the TRS end into loop return on the PBC.
There are other ways to do it, and depending on circumstances, you can, for example, use a normal 1/4-inch cable instead of a ring disconnect cable. But, it depends on the pedals you’ve chosen, what order you’re using them in, whether you’re routing in series or parallel etc. Following the above instructions will make any configuration work correctly.
The curious among you might wonder why we need these cables. The insert cables, I hope, are fairly obvious. The PBC combines its left and right connectors into a single connector to save space. Effect pedals have separate left and right connections. An insert cable converts from TRS to individual left and right plugs.
Mono pedals need to have their output converted to stereo. Otherwise, you will only get signal out of one side when the pedal is activated. The mono to stereo converter cable does this by taking the pedal’s output and sending it to both the left and right side of the loop return jack.
Mono pedals or stereo pedals with a mono input are a little trickier to understand. If you plug a TS (mono) plug into a loop send jack, the right (ring) side of the signal is connected directly to ground, shorting it out and making it inaudible. If you compare a TRS plug and TS plug, you can see that the area that contains the ring on a TRS plug is part of the sleeve on a TS plug. The right side of the internal audio path is connected to the sleeve through the TS connector. At the minimum, you’ll lose the right side of the signal. If the previous pedal in the audio path is mono, but converted to stereo, you’ll lose both the left and right sides of the signal. Using a TRS connector with the ring disconnected prevents this unintended connection to ground – the right side of the signal connects to the TRS connector’s ring, which is not grounded, and will not have any effect on the signal.
I hope this all makes sense. As always, please feel free to contact us with questions. If you follow the above recommendations for switch settings and cables, you will end up with a working system. You can get the specialty cables made at places like Best-tronics or Alphatone Audio.