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!
