McPherson Anti-Buffer (Pickup Simulator) Inspirational Build

  - Posted in Guitar ( adam)
McPherson Anti-Buffer (Pickup Simulator) Inspirational Build

TL; DR

Another absolutely gem of a pedal idea from Waylon McPherson with some innovative changes (Waylon's, not mine!), to combat buffered bypass pedals at beginnings of chains (my first interest), along with "fuzz" pedal tone-death and chain-suicide issues (we've all experienced).

Let's build it!

The Build

A few (minor) preferential changes I did separate from and addition to Waylon McPherson's recommendations:

  • Utilizing a 42TL019 transformer vs 42TM019, because:
    • It was the only transformer of size and model the place I source parts from
    • After some datasheet comparison, it's very similar in spec to the 42TM019, especially on the Primary transformer side that's being utilized in the design.
  • Added a SPST with a 470pf capacitor on the output side from a very thoughtful, but plagiarized pickup simulator design from AMZ
    • Sort-of a treble bleed toggle minus the resistor?
  • Added an LED, LED bezel, CR2032 3v battery and battery holder
  • Staggered input and output left/right jacks vs. top pedal-mounted

Parts & Sourcing

I sourced my audio components from:

My part(s) list below if you want to replicate the changes:

QTY    SKU                              Description
  1        P-T42TL019                  Transformer - 42TL019, Audio & Signal, 10KΩ:600Ω, PC Mount
  1        C-GD047-100               Capacitor - Orange Drop, 100V, Polyester, Capacitance: .047 µF
  1        C-D470-6000               Capacitor - Ceramic, 6000v, Capacitance: 470pF
  1        P-HTOG-GORVA-M1 Mini Toggle, SPDT, 2 Position, Solder Lugs, Medium Bat
  1        P-H1590BCE-R            Chassis Box - 1590B, Diecast, 4.40" x 2.38" x 1.06", Red
  2       P-K680                           Knob - Plastic, Set Screw, Pinched w/ Line, 0.630" Diameter, Black
  1       R-VAM500KA-SS         Potentiometer - Alpha, Audio, Solid Shaft, 16mm, 500 kΩ
  1       R-VAM500KC-SS         Potentiometer - Alpha, Reverse Audio, Solid Shaft, 16mm, 500 kΩ
  1        P-H501-L                          Footswitch - 3PDT, Solder Lugs, Soft Click (Chrome)
  1        P-L500                           LED Bezel (with Red LED) 5mm (Chrome)
  1        <N/A>                           1k Ohm 0.25w/0.5w resistor
  1        <Optional>                   5mm LED (alternate color) with forward voltage ~2.0-2.2v

You'll also need (potentially):

Transformer Comparison

I wanted to unpack a bit of datasheet information about the 42TM019 and the 42TL019:

Besides some characteristics that do not apply to this transformer in regards to the circuit design, the only stark difference I could tell that mattered would be:

  • The small resistance difference of 450 ohms between the two for primary side resistance
  • The number of winds/turns between the primary transformer(s):
    • The 42TM019 just advertises a ratio of 3.771:1, while the 42TL019 advertises 2000:390 which checks out to be 5.128:1.

Design & Layout

I chose not to go with a typical symmetrical or balanced layout. At the risk of making the tangible pedal "ui" non-conforming to the structured component placement design by "the masses" but still aesthetically pleasing and cool-to-the-eye, I really had a to ensure I had my measurements dead-on.

Believe me: there was alot of staring, thinking and dry-fit exercises involved with component placement. You might be able to call me out on the thinking part, though.

Soldering

One of the stingier tasks was getting the transformer "placement-and-solder" ready. I poached the zip-tie-around-the-3PDT from Waylon's design; why deviate? It's a great idea.

A tip: DO use some electronics silicon if you mount the Orange drop tone cap directly over the audio tone pot. Remember, you're tipping that pedal upside down (to use) and also doubling that capacitor leg as a ground-joining effort. DONT use your hot glue gun if you can help it, but I also 'get it' if you do.

The Pedal

There it is, ready to be used!

Takeaways

The Tone EQ, man!

I would say, definitively, I was MOST impressed what this pedal did after my buffered bypass Boss TU-2 with my "rock" pedalboard rig that this thing is staying on my board and never leaving.

Just as this pedal has, without a doubt, equally impressed me, it also made me absolutely ashamed I've ran this way for dog years like a pretentious, yet naive guitar player that I think I am.

It absolutely added this tightness and "brighter and fuller" subtle EQ edge to my signal feeding the Bogner Shiva. It's ridiculous how noticeable and awesome it is.

The 470pF sort-of treble-bleed "toggle" I brought in from the AMZ schematic I really do like, too. As a matter of fact, I keep it toggled "on", always. I'll have to experiment with the resistor in series, but for now, I like it as-is.

Transformer Primary vs Secondary

I'm wondering what impact switching the input to go into the secondary side of the transformer (with lower impedence and less windings) than primary. Does or would this make a difference at all with a passive circuit pedal like this? My initial instinct tells me it wouldn't be much different than a pickup, so it would, but I don't know how subtle it would be?

I need to do some more self-education, then decide if it's worth adding a 3PD1 mini-toggle addition to this build.

Reverse Audio Pot

Comparing the AMZ schematic to Waylon's choices, I do have to say, I absolutely prefer the reverse audio taper as well; even Waylon's video shows that. I'm sold.

3D printed pedal board mount

I have (yet) to put together a 3D printed pedal board mount plate for this Hammond-like 1590B enclosure.

Resources

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