Chuck D. Bones
Circuit Wizard
I became curious about the High Top (J. Rockett Top Boost), so I breadboarded it. Sounded nothing like the demos, so after a little visual inspection I found one capacitor (C7) hooked up wrong. Once I had that sorted, it sounded great. I read Rockett's manual and it pretty much works as advertised, although I could not verify whether the Alnico setting was more "swampy." The CERAMIC/ALNICO switch is mainly a boost between the 1st & 2nd stages with a tiny bit of the top and bottom rolled off in Alnico mode. With the EF86 switch off, it's fairly clean unless you're playing very hard. The tone controls are all very effective and it takes some fiddling to find the right balance between the TREBLE & CUT controls.
Although it works great in stock form, there were four little things I changed to make it more to my liking.
1. Changed VOLUME from B50K to A50K. With B50K, unity was down below 9:00. This pedal is pretty loud, even with over 20dB loss in the BASS & TREBLE controls.
2. Replaced R18 with a jumper. Now the EF86 knob "goes to eleven." Try it, you'll like it.
3. Increased R20 to 56K. This centers the bias on Q2 and improves the clean headroom.
4. The bandwidth of the 2nd stage extends beyond the range of human hearing. I observed ringing above 20KHz, which may have been an artifact of the breadboard. I'm always pleasantly surprised when a breadboard doesn't oscillate. Anyway, I added 10nF in parallel with R12 to roll off the gain above 20KHz and that fixed it.
5. OK, 5 things. I installed one 499R resistor in place of R3 and left out R16. Either way works the same and I was building a breadboard. Apparently Rockett had too many 1K resistors.
I ended up using low gain transistors for Q2 & Q3 as recommended in the BOM. I tried higher gain transistors and noticed very little difference. Tried germanium for Q2, made no difference.
It's a very nice clean or dirty boost. Works well with single coil pickups or humbuckers. I could see putting either the EF86 or the ALNICO switch on a stomp switch. NB Rockett has ALNICO on a stomp switch.
Although it works great in stock form, there were four little things I changed to make it more to my liking.
1. Changed VOLUME from B50K to A50K. With B50K, unity was down below 9:00. This pedal is pretty loud, even with over 20dB loss in the BASS & TREBLE controls.
2. Replaced R18 with a jumper. Now the EF86 knob "goes to eleven." Try it, you'll like it.
3. Increased R20 to 56K. This centers the bias on Q2 and improves the clean headroom.
4. The bandwidth of the 2nd stage extends beyond the range of human hearing. I observed ringing above 20KHz, which may have been an artifact of the breadboard. I'm always pleasantly surprised when a breadboard doesn't oscillate. Anyway, I added 10nF in parallel with R12 to roll off the gain above 20KHz and that fixed it.
5. OK, 5 things. I installed one 499R resistor in place of R3 and left out R16. Either way works the same and I was building a breadboard. Apparently Rockett had too many 1K resistors.
I ended up using low gain transistors for Q2 & Q3 as recommended in the BOM. I tried higher gain transistors and noticed very little difference. Tried germanium for Q2, made no difference.
It's a very nice clean or dirty boost. Works well with single coil pickups or humbuckers. I could see putting either the EF86 or the ALNICO switch on a stomp switch. NB Rockett has ALNICO on a stomp switch.
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