The Perplexed layout seemed to generate more interest than anything else I've posted so I though I might post this one. This has become a firm favourite for me. I love the sound of this fella!
I had been avoiding JFET ODs for ages because of the biasing thing. But recently because of Chuck's amazing posts instructing us how to measure JFETs to get the best out of them I have been encouraged to get back into JFET circuits. I still don't really understand how they work or what the measurements actually mean but it doesn't matter. I made my self an extremely rudimentary rig to measure IDSS and it's easy, works, and my pedals sound great as a result. I actually have a decent stash of Fairchild through-hole J201s which is what I have been using, but you could of course use MMBF201 SMD transistors.
I only recently built a Golden Falk on the excellent PPCB board. Now I get why people rave about it! Such a killer pedal. I have posted a schematic of my own take on it in Chuck's fantastic thread about the GF, and I don't pretend that I have made a better version. But what I have done is apply some changes that I have made to plexi style amps I have built. I've made a Plexi Breed with a radically smaller Source cap, similar to what I have done with my amps' first gain stage bypass caps. Bear in mind that the 1959 and 1987 Plexis are a continuation of the JTM45, built according to the Fender 5F6-A Bassman schematic. So they are naturally very bass frequency heavy in the Normal channel. That's why the Marshall Lead amps went to split cathodes on the first stage - to make guitars cut through better on the Lead channel.
Anyway, I tried similar values on the first stage transistors in the Plexi Breed and it makes the Normal channel more usable (IMO) while still being able to use it to beef up the Bright channel. But still I felt it was a bit too compressed sounding compared with my Marshalls. Purely my own preferences. I wondered if I could open up the sound a bit and get a sound a bit more like my amps, and the original plexis I have played. So I got rid of the Normal channel altogether and added a Bass pot at the Source of Q1 which is where the low frequency cut-off is determined for that channel. Again, much like bypass cap in the amp. As a result I'm getting a more open, slightly less compressed sound. It also saves quite a few parts. Playing the big open chords like Malcolm Young sounds kinda punchier with more ring. It's probably fairly subtle but I like it. I just find it easier to use. And being 20 columns wide it fits into a 1590B.
I had been avoiding JFET ODs for ages because of the biasing thing. But recently because of Chuck's amazing posts instructing us how to measure JFETs to get the best out of them I have been encouraged to get back into JFET circuits. I still don't really understand how they work or what the measurements actually mean but it doesn't matter. I made my self an extremely rudimentary rig to measure IDSS and it's easy, works, and my pedals sound great as a result. I actually have a decent stash of Fairchild through-hole J201s which is what I have been using, but you could of course use MMBF201 SMD transistors.
I only recently built a Golden Falk on the excellent PPCB board. Now I get why people rave about it! Such a killer pedal. I have posted a schematic of my own take on it in Chuck's fantastic thread about the GF, and I don't pretend that I have made a better version. But what I have done is apply some changes that I have made to plexi style amps I have built. I've made a Plexi Breed with a radically smaller Source cap, similar to what I have done with my amps' first gain stage bypass caps. Bear in mind that the 1959 and 1987 Plexis are a continuation of the JTM45, built according to the Fender 5F6-A Bassman schematic. So they are naturally very bass frequency heavy in the Normal channel. That's why the Marshall Lead amps went to split cathodes on the first stage - to make guitars cut through better on the Lead channel.
Anyway, I tried similar values on the first stage transistors in the Plexi Breed and it makes the Normal channel more usable (IMO) while still being able to use it to beef up the Bright channel. But still I felt it was a bit too compressed sounding compared with my Marshalls. Purely my own preferences. I wondered if I could open up the sound a bit and get a sound a bit more like my amps, and the original plexis I have played. So I got rid of the Normal channel altogether and added a Bass pot at the Source of Q1 which is where the low frequency cut-off is determined for that channel. Again, much like bypass cap in the amp. As a result I'm getting a more open, slightly less compressed sound. It also saves quite a few parts. Playing the big open chords like Malcolm Young sounds kinda punchier with more ring. It's probably fairly subtle but I like it. I just find it easier to use. And being 20 columns wide it fits into a 1590B.
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