Analog Delay: 4x MN3005, Tap Tempo, MIDI, etc

 Ultimate Analog Delay

with 4x MN3005 (upto 1.2s), Tap Tempo, MIDI Tempo Sync,

Effects Loop, Modulation control, SLAM, Sub-divisions!

I'm pretty sure this is the most complicated pedal project that I've ever worked on.  I've had other amplifier projects that were more complicated but to cram the complexity in a small package is another challenge in and of itself.  To be honest, I had failed on my first attempt.  I thought I designed everything correctly but couldn't able to dial out a terrible hum that plagued the analog goodness.  This was my second attempt and had to redesign everything back from scratch.

Well, here is the inception story:  After successfully building my DM-Deluxe Analog Delay pedal, I've had few requests from people to build them one.  I never did build another one because 1) it's quite expensive build, 2) it just takes too much of my time, and 3) it's not fun for me to build something that I've built already (there is not a challenge in it anymore).  Anyhow, I've built this Tap Tempo Tremolo pedal for this friend that I came to know through numerous projects that I've done for him.  One day, he asked me if I could build something like DM-Deluxe but supersize it.  He wanted a longer analog delay that basically uses 3 or 4 MN3005 chips and add features like MIDI tempo sync and effects loop for the wet signal.  Well, that definitely peaked my interest.  I rarely saw, if at all, a DIY pedal builder successfully building a 4x MN3005 analog delay pedal--let alone a tap tempo analog delay.  The closest I've seen was a BYOC Analog Delay Kit.  According to their online schematic, that uses 4x MN3205 BBD chips (most likely cheaper V3205) which is not the same as vintage MN3005s that I would be using at a higher voltage rating.  BYOC also uses way too many clock drivers in my mind (5x MN3102s!!).

So this was my design process:  I knew that one MN3101 clock driver chip is capable of handling upto 2x MN3005s.  So that was my basis of the whole build: use 2x MN3101 chips to drive 4x MN3005 BBD chips which is simpler and just as effective.  My initial approach was to follow the Boss DM-2 outline.  However, soon I realized that using 4x MN3005 and running at a higher voltage, really shifts the tone and the output level of the wet signal.  Figuring out the right filtering and leveling was the most difficult part which took me a bit of hair pulling to figure out.  I have the original 90's big box EHX Deluxe Memory Man.  I always loved the fat delay sound that it has when compared to Boss DM-2 which has more sweeter sound than fat to my ears.  I wanted to capture that through the filtering and it sounded pretty comparable when put on side by side.

From my survey of how others build analog delays, most adjust the feedback level in the circuit after the wet signal passes through the REPEAT knob.  I always thought this was a bad idea because you'll get one good clearing sounding repeat and then it'll lose much volume from second repeat forward.  When I build analog delays, I always make adjustment of the feedback level before the wet signal goes through the REPEAT knob.  This results in consistent and gradual volume decrease over long delay time without being chirpy.

Another difficult part of this build was dialing in the trim pots.  There were 10 trim pots to adjust (there is one more on the lower board if you were counting).  These were not "listen and adjust" type of trim pots.  I had to take good amount of time looking at the oscilloscope and adjust little and then repeat this process over and over.  It was a game of patience but this was necessary to bias all the BBD chips.

This was my first time building a stacked circuit.  I had to make sure that no noisy components were near the audio paths and used multiple sockets to create a "bus" between top and lower circuits (only because I don't like having many wires running all over the boards).  As you can see, I had to lay down some components (mostly electrolytic capacitors) to fit the top circuit board in place.  Also there is an another circuit board (not pictured) for tap/midi controller chip because I wanted to keep the digital clock noise away and separated from the analog circuits.

Here are some of the specs of this pedal:
- Using 4x MN3005 BBD chips (the originals not the reissue), it achieves about 1.1-1.2 seconds of maximum delay time.
- Tap Tempo functionality with MIDI tempo sync as well as sub-divisions.  External Tap input.
- Modulation controls (rate, depth, and phase)
- Effects Loop for wet signal
- SLAM control for instant oscillations
With the wealth of features and awesome pure analog goodness on steriods, I'm confident to say that it rivals any analog and digital pedals out there.  You name it: Electro Harmonix Deluxe Memory Man Tap Tempo 1100, Way Hugh Aqua Puss (or Supa Puss), MXR Carbon Copy Tap Tempo, etc.

And finally, it's going through a custom painting process.  It looks great already!

 Now, I'm just trying to figure out how to transform my DM-Deluxe into this monster!

Spirit in the Sky Fuzz

Spirit in the Sky Fuzz

This project started as a request to recreate the fuzz sound in the song Spirit in the Sky by Norman Greenbaum.  If you are familiar with the gear talk that has been going on about this song, no one really knows what kind of fuzz circuit was used to create that signature sound.  IIRC, the fuzz was actually an unidentified homemade circuit built into the guitar.

Although there are plenty of good recommendations for recreating Spirit in the Sky sound, I decided go with my own instinct on sound and my experience building many different fuzz circuits.  Since I could essentially "tune" any fuzz circuit to achieve what I want it to sound like, I decided to go with the Fuzz Face circuit because of its tweakability and simplicity.  The Fuzz Face needs no introduction and certainly when the vintage originals are costing $1000+ these days.  Love it or hate it, this widely known fuzz is so simple that it's highly recommended as a must-build circuit.  This must have been my 1XXth time that I've built a Fuzz Face.

The requester did not have a good experience with Fuzz Faces in the past.  So I wanted to not only capture the Spirit in the Sky sound, but also the best Fuzz Face sound in its stock form!  The request was to use the best parts possible.  So I got some vintage NOS components and personally hand picked germanium transistors with lowest noise while providing good fuzz sound.  You won't see any trim pots in here because I've done the math and bread boarding to get the exact resistor values needed to set the optimal biasing points for both transistors.  One thing about Fuzz Face circuit is that both transistors need to be biased to make it perform at its best.  This is due to the inconsistency in the germanium transistors.  You could potentially get away with biasing only the second transistor (or none at all), but in my experience, that would only get you so far from being the best sounding fuzz.

Below is the finished pedal.  Notice the 4 knobs compared to 2 knobs on original Fuzz Face.  The extra 2 knobs are for BIAS and BASS control.  BIAS sets the second transistor from hot to cold biasing.  This gives different shades of fuzz sound from over-saturated to spluttery-dying-battery sound.  BASS sets the amount of "thickness" of fuzz.  With these two controls added, dialing the Spirit in the Sky sound, stock Fuzz Face sound, and other fuzz sound is matter of few knob twists.

It's important to note that knowing how to use a fuzz pedal matters.  Just like many amps, fuzz pedals are instruments and need to be used with interaction in mind.  From pickup controls on the guitar to amp settings, all of that matters when dialing a fuzz sound.  Understanding this interacting relationship between instruments should reward you with plethora of fuzzy goodness!