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true bypass for Paia Ring Modulator and Phaser?

Posted: Mon May 20, 2013 12:07 pm
by BoojiBoy
I have a Paia Ring Modulator CA9 and an older discontinued CA Phase shifter that I am wondering on how to wire up with the standard 3PDT true bypass foot-switch.
The power jack and dual 9v battery s have me a bit confused. I have the standard barrel power jacks.
Anyone have a wiring diagram for the above mentioned?

Re: true bypass for Paia Ring Modulator and Phaser?

Posted: Tue May 21, 2013 1:05 pm
by PAiA-Scott
Many of the projects presented in Electronic Projects for Musicians, such as the ring modulator and the phase shifter are designed for power from a bipolar, or dual-polarity, DC power supply. These two projects have power supply wiring points on the board labeled (+), (G), and (-). The positive DC supply goes to (+). The ground or zero-potential, circuit-common power connection is to (G). The negative DC supply is to (-). When two nine-volt batteries are series connected, the plus pole of one connected with the minus pole of the other, and, this node connected to G, the ends of this series connection have positive and negative DC power supply polarities. The free plus pole is the positive DC supply and the free minus pole is the negative DC supply +9V, 0V, -9V DC.

A single DC power supply can be adapted to provided dual-polarity supplies using a resistor voltage divider. Two series connected, equal valued resistors will split one voltage in half. When the mid-point of these two resistors is connected to a project's G (0vdc, circuit-common), the two power supply poles become positive and negative DC supplies. A nine-volt battery connected to this resistor circuit would result in +4.5v, 0v, and -4.5v supplies. The lower the resistance of the resistors the better, but power is wasted with them connected across the power source (and if too low they'll heat/burn). They can have greater values when an op-amp circuit "buffers" or "follows" the divided voltage. The Questions and Answers section of the EPfM book shows schematics and describes this uni-polar to bi-polar modification.

Some ICs are available for converting a positive DC supply to a negative one. These are usually called Charge Pump circuits and basically switch DC on and off rapidly so it appears to following circuit sections as "AC" which is then rectified and filtered for the needed polarity. A device which only requires a nine-volt battery or DC Adapter for power might include circuit sections to perform this function so it operates with bi-polar supplies.

Consider too, another wall-mounted DC power supply can be connected, with the one you have, for the dual-polarity DC power supplies (same connections as the two nine-volt batteries). Or, an AC output, wall-mounted transformer can be used and wired to a board with rectifier and filter circuits (and perhaps voltage regulators for even cleaner DC). Our 9770R-12 kit does this for dual-polarity 12VDC supplies.

The switching for Bypass is discussed in Chapter 11 of the EPfM book, but basically you have the input connected to a switch terminal that will contact the device input or a bypass link and the output connected to a separate switch terminal that will contact the device output or the same bypass link provided for the input. A DPDT push-on/push-off footswitch can be wired to send a guitar through or around the effect unit signal path. A 3PDT switch can also have an LED wired so that when the selection is for Effect In, current flows through it and it lights to indicate the effect is selected. This third, two-way switch section would work to connect the LED with power to it or not. The connection to voltage for the LED must be through a resistor to set the current flow, unless the LED is a special type with this described as being internal.

Chapter five of the EPfM book covers powering the projects with examples for wiring, and power on/off switching, for two nine-volt batteries.

Re: true bypass for Paia Ring Modulator and Phaser?

Posted: Tue Nov 26, 2013 7:04 pm
by BoojiBoy
Thanks! I had to dig out the ol' book and take a gander.
The thing that is throwing me off is the "SG "on the Paia ring mod.
It is wired to the ground of the output jack.
In most 3pdt true bypass schematics I am looking at the ground off of the power section, be it two 9v batts. or jack is running sleeve to board ground and the ring to the power source, so I am at a loss as what to do with the black wire/sg part.
I am going to keep it dual 9v batts untill. I can scrape up some parts to build a proper power supply.
Thanks for all the help!
Luckily , the phaser is pretty straight up!