The Frequency Central Promiscuous Girlfriend is a tube booster/overdrive created by Frequency Central, a circuit first shared on the freestompboxes.org (FSB) DIY forum1. It sits in the territory between a boost pedal and an overdrive: with the Gain control at minimum it works as a clean boost, and turning the Gain up takes you into overdrive territory with diode clipping1.
Controls and how it works
| Control | What it does |
|---|---|
| Gain | At minimum it gives clean boost; turned up it goes into overdrive territory with diode clipping1 |
| Dirt switch | Engages the diode clipping; off gives even more overdrive at high Gain1 |
| Tonestack | Big Muff Pie-style tone section, easily tweaked to taste1 |
Because the circuit uses real tubes, the power board carries two connections for the heater pins of the tubes, pins 3 and 6. One wire can run to tube 1, and a wire then connects on to the pins of tube 2, feeding both heaters from the same board1.
The power supply sits on a separate board to help avoid interference issues. Its voltage doubling gives out approximately +35V, so components in that part of the circuit should be rated at least 50V1.
Clipping and modifications
The clipping is handled by diodes D5 and D6, and different diodes can be substituted in those positions to change the clipping character. When the diodes are engaged, the pedal loses some output volume1.
For builders, Guitar FX Layouts suggests one tweak in particular: change the Dirt switch to a pot so you can control how much of the signal gets clipped by the diodes, rather than switching the clipping in and out1. The tonestack can also easily be tweaked to taste1.
Questions
Does the Promiscuous Girlfriend use real tubes?
Yes. The circuit uses tubes, and the power board carries two connections for the heater pins of the tubes, pins 3 and 6. One wire can run to the first tube, and a second wire then connects on to the heater pins of the second tube, so both tube heaters are fed from the same power board connections.
Can the diodes be swapped for different clipping?
Yes. The clipping is done by diodes D5 and D6, and different diodes can be substituted in those positions for a different clipping character. Keep in mind that when the clipping diodes are engaged, the pedal loses some output volume compared with running them out of the circuit.
What does the Dirt switch do?
The Dirt switch engages the diode clipping. With the switch off, the pedal gives even more overdrive at high Gain settings; flicking the Dirt switch on brings in the diode clipping for a different, clipped character on top of the overdrive.
Where was the Promiscuous Girlfriend circuit shared?
The circuit was created by Frequency Central and shared on freestompboxes.org, usually shortened to FSB, a forum where builders publish and discuss DIY pedal circuits. Guitar FX Layouts later published a verified layout for building it on tagboard.
Can the Dirt switch be replaced with a pot?
Yes, as a suggested tweak. Guitar FX Layouts suggests changing the Dirt switch to a potentiometer so you can control how much of the signal gets clipped by the diodes, rather than switching the clipping fully in or out.
Sources (1)
- Guitar FX Layouts: Frequency Central Promiscuous Girlfriend, Guitar FX Layouts (tagboardeffects.blogspot.com), 2017-02-21