In every project, there is a "doubt stage". This happens when after some tests, you wonder whether this whole project is a really good idea or just a huge waste of time.
The tests
It happened to me. After the original excitement, I tested on my breadboard the CD4049 based 3-channel circuit and honestly, I was not amazed at all. The sound that I liked years ago did not have the same "waow" effect : too fuzzy, not very vivid or open, rather flat and sometimes harsh. I has to be honest with myself: the CD4049 is not the right thing for this 3-channel preamp project !
Aouch! This IC was the core of the project! I have to start from the beginning, which brings me to the question: why do I want all this? I am (quite) happy with my sound now. OK, my Boss GT-PRO might be a little old, and its sound is not that "open", but thanks to an DIY analog booster before and a double (stereo) analog DIY cabinet simulator after, the sound is not digital anymore and is fully playable. So what's the point?
Yes, but...
After years of playing with the GT-PRO, I feel like the sound is always the same. There are tons of amp simulations and I used only 3 or 4 of them... So what do I want ?
(New) list of features
- Simpler interface with only 3 main sounds, Clean, Rhythm and Lead
- An integrated treble boost with a variable frequency filter
- A real Clean sound, open, chimy, with singing tones, ready to break-up a little with high output pickups or the on-board booster of my Lady Blue guitar
- A Rhythm sound that is not so much driven, but thick and mellow, very Brian May-ish, and very (very) sensitive to the guitar volume pot. I want a clean sound when the volume pot is at 1 or 2 on the guitar.
- A Lead channel that is naturally compressed, with a good note-to-note separation and a good sustain (though it is very guitar-dependent...)
- A MIDI controlled channel selection
- A stereo output using a pseudo-stereo image: adding 10-20 ms of delay on one output
- The possibility (inspired by Steven Wilson) to assign one channel on the left and another one on the right. Imagine a clean-overdriven sound!
Instead of relying on ONE circuit for all 3 channels, I will search for one circuit per channel. I preselected the following pedal schematics as a short list. Maybe that the next step is to build them all and to compare them.
Some inspiring schematics
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| RunOff Groove Azabache for Clean Channel |
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| Dr Boogey for Lead Channel |
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| Nobels ODR-1 for Rhythm Channel |
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| Fulltone OCD for Rhythm Channel |
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| Wampler Plexi Drive for Rhythm Channel |
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| Zendrive for Rhythm Channel |
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| ZVEX Box Of Rock for Rhythm or Lead Channel |
As you can see, wide is the choice! And I guess that I will add a very open yet warm compressor at the very beginning of my signal chain. The Orange Squeezer is a good candidate.
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| Orange Squeezer compressor |
New feature : I want to be able to select left and right channel independently. Which gives the overall architecture:
As a conclusion: I am far away from having my preamp ready or even completely imagined. Stay tuned, I will keep you posted of the evolution of my project.