Over the weekend I did something some may frown upon, but I'm happy I did: I took my 33000 serial# EP3 and converted the circuit to a pre-9450 Serial# circuit. I did this for a few reasons but it all started once I looked into those EP booster type pedals, I found that the "magic preamp" circuit was NOT the circuit in the front end of most EP3 echoplexes. The circuit they choose to copy is from the small 400-500 unit batch of EP3s at the beginning of the model's creation. I then took some serious time and investigated the WHOLE schematic of both iterations of the echoplex and found numerous changes. The big deal is you've got all three kinds of changes: adding, subtracting, and changing. This means there is quite a bit of difference between the circuits, and I have a feeling the "Good" ones famous tones have come from might be from that elusive batch of 400 in the beginning. Here is a diagram of whats different: Since too much time had passed since hearing the unit stock, I can't quite comment on the overall tone of the preamp, but I do feel like it sounds better in that respect. Overall, I seem to enjoy playing it in the signal chain more then before. But because of the tricks our minds play on us, I can't say for certain its a huge change. The BIG surprise, was how the unit now handled multiple repeats. Before this conversion, I could really only live with 3-4 repeats before the echo was deteriorating too much and sounded bad. After the mods, I can REALLY crank the repeats just a hair under ocillation and the echo just goes forever. Every repeat is just as good sounding as the previous, just a little quieter. It turned my Echoplex into a reverb tank if I set the knobs right! I highly recommend this conversion. Its a bit of a hassel, but last night I was jamming with my echoplex for hours and really felt it blended better with my rig and became far more versatile.