Here’s another epic pedal build. The Lovetone Doppelgänger is a phase shifter with lots of extras. It has 4 phase shift stages and two LFOs and options for all of this. The Quadratron is not a direct clone of the Doppelgänger. It’s faithful to the original but makes a few changes.
Both are four stage phaseshifters with capacitors separates by octaves. This is a classic mod for the MXR Phase 45. The Doppelgänger divides these into a a low band and high band and adds a control for the intensity of each band. It has a color knob that sets the intensity of the effect. There is a blend knob to blend the effect with the straight signal. It has a vibrato mode, which outputs only the wet signal. When using this the blend control needs to be all the way up since the dry signal is not present.
The effect has two LFOs and has options to use one or both. When only one LFO is used it modulates both the low and high band phase shift stages. There is a switch to modulate these out of phase, when the low band is on the high band is off. For the first LFO there is a square and triangle option. It has a rate control for each of the two LFOs and switch that extends the slow range for super slow modulation. When two LFOs are engaged the second controls the high band at its own rate.
Most of these options are present on the Lovetone Doppelgänger but Quadratron does things differently. The Doppelgänger used two multi position rotary switches to set all of these options. The Quadratron breaks each option out to it’s own toggle switch. So this gives us 5 switches:
- Speed slow/normal
- LFO square/triangle
- LFO on/off
- LFO in phase/anti phase
- Vibrato on/off
There are two expression pedal inputs that allow control over LFO rate, there is one for each LFO. This seems a little ridiculous. I can’t imagine using two pedals to control the rate of two different LFOs with one fro the low phase shift band and the other for the higher band. You want over the top this it!
This is very close to the original Lovetone Doppelgänger but not quite the same. It’s possible to get some different combinations with the individual toggles not present with rotary switches of the original. The Quadratron also provides a true bypass option not present on the Doppelgänger. Overall very close but not quite the same.
the build process is straightforward after a careful look at the documentation. There are many parts but the board is pretty big, well laid out, and labeled. Here are a couple things to note.
Note! not all of the caps are used. There are options to use one cap or another in a a few places. If you want to be true to the original you opt for the electrolytic caps otherwise use film.
I didn’t have any TL022 op-amps on hand but these appear to be lower power general purpose op-amps nothing mojo here. I replaced these with TL062 types, which are a low power version of the TL072, and these worked successfully.
The row of 5 toggle switches requires accurate drilling along with soldering the switches perpendicular to the PCB. I used the drilling guide provided in the docs and paid careful attention to these switches when drilling. To get switches soldered correctly I placed them in the backside of the PCB without soldering. I carefully fit the switches and PCB in the box and put a nut on each switch holding everything in place from the back. Then I soldered. This guaranteed the switches were parallel and perpendicular.
The drill guide was great for the top of the box. When it came to drilling the back it seemed the guide placed the jacks too far outboard on both sides. I was able to correct this with hand tools. You should measure the position of the jacks on the backside before drilling!
Then I disassembled and installed the pots without soldering, put everything in the box, supporting from behind while I put a nut on each switch. Then I soldered. At the same time I put the LEDs in the PCB without soldering and guided them through their holes when the pots were in place, and soldered everything.
I followed a similar procedure with smaller board with the LEDs and switches.
This is another costly project the PCBs were $22! The 1590XX enclosure is $13 that’s $35 already. Then there’s 2 foot switches, 6 pots, 5 toggle switches, and 5 jacks. That’s a lot of parts that cost more than other components.
I used some toggle switches with longer handles. I didn’t like these and bought some switches with the short handles for the next build. I think this one from LoveMySwitches.com would be a better choice.