KSR Custom Shop Isosceles Pi Deluxe - 1970-1971 Big Muff Pi Clone


KSR Custom Shop

The Isosceles Pi

The Isosceles Pi is an exact copy of an original Triangle Big Muff Pi that was made around 1970-71. It is a clone of a 1st version, second edition Triangle Big Muff known to be one of the best sounding Triangle Muffs. It is described on kitrae’s website as a “V1 Triangle Big Muff 66#11. I have posted two links so you can check it out. All though I have not owned this particular version, I used my experience with various other triangle & Ram’s Head versions such as transistor (Hfe) gain stages and applied it to this clone. This is a unique version of a Triangle Muff as related to component selection and values. It does sound spectacular for sure! See below for more info…..

I have been modding/repairing pedals for many years. After seeing so many homemade muff versions laid out on eBay I decided to give it my own shot. What I can tell you why my pedal is different from the others is I do not use mass production transistors like you get from the majority of boutique pedal makers that you have seen here on eBay, even the big names that are quite successful. You get top of the line components, no expense was spared in making these pedals. I will guarantee complete satisfaction, that is how confident I am with this product. I’m confident due to wonderful feedback I’ve received from buyers in the past from modding their pedals to these specs and the many months spent on the testing phase of this product.

The Isosceles Pi Deluxe Version

The Deluxe version of the Isosceles Pi has an added Linear Power Booster (LPB) added to the circuit. Ever put a booster before a muff for that lead solo break through? It adds extra volume and sustain to cut through the rest of the band. The booster is not just a EH LPB circuit. It is voiced to give a slight treble boost which is really tasty. Much time was spent to optimize the boosters sound and how it reacts when engaging the Big Muff circuit.

Slightly close to what I’ve seen others recently offer (such as a switch to set the volume pot to full volume...not really the same thing; limited). So I added a LPB style circuit to the board, a pot to control the volume of the booster and an additional stomp switch so either MUFF or LPB circuit could be used alone or TOGETHER! Awesome!

Basically this one pedal is two individual pedals in one enclosure. The booster or Big Muff can be used individually or together. The booster is staged before the muff of course. You can adjust the volume of the booster to where you like it as a booster and then you can adjust it again for your taste when using it in combination with the Big Muff.

Both circuits sound awesome. The Muff just absolutely rips!

So enough of my rambling, if you have questions feel free to ask.


  • True bypass wiring for both circuits.
  • Cloned 1970-71 V1 Triangle Circuit Board
  • Contains 2N5133 NOS transistors just as the originals came with.
  • DC Power Jack: The standard size 2.1mm Boss style connector for power adaptors.
  • Heavy duty battery clip.
  • Highest quality Alpha brand pots of the correct value.
  • Neutrik jacks.
  • Highest quality resistors and capacitors.
  • Contains a LPB (Linear Power Booster) styled circuit. Can be used by itself or together in front of the Big Muff circuit.
  • Contains the unique 1970-71 Triangle 66#11 Big Muff Pi circuit. Can be used by itself or together after the LPB circuit.

Most recent forum threads


Where to find one?

your browser doesn't support AJAX?

fx pedal stompbox stomp box guitar effects pedal fuzz distortion/fuzz/overdrive dirt grit
Syndicate content

Subscribe to our newsletter

Also check out Effects Database's social media accounts: