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Hello & howdy, I just joined this forum a few days ago and this is my first post. Some of you might remember me as JBelshe from alt.guitar.amps about 7 or 8 years ago. I got a lot of good technical info there, but that place just got too toxic for me. I looked at it recently and it seems to have only gotten worse. Having lurked here for a few days, I can definitely say I prefer the polite discourse on this forum.
Anyway...
My brain hurts! I've immersed myself in this for several days now, trying to design a new circuit for my Bassman.
It's been years since I thought about this stuff and there's a pretty steep learning curve right at first.
See, I built an amp a few years ago. I started with two old Fenders, a Bassman 135 that had been through a house fire, and a The Twin which had been through a flood. I completely disassembled both amps, cleaned and inspected the parts and salvaged what I could, bead blasted the chassis, then used components from both to build one amp that I called the FireWater. It was basically an AB763 Twin Reverb, but without the Normal channel and no vibrato, but with a presence control and a two knob reverb (added dwell control). Fewer tubes meant more juice for the tubes that were there. Keystone turrets on G-10 with nylon standoffs and neoprene grommets for isolation. I ran it through a 1969 Dual Showman 2x15 cab loaded with Altec Lansing 421-As. It was loud as hell and sounded like a classic Fender, only much beefier. I could never get it to break up, either. Turning it up only made it sound fatter and fatter. At the time I was plugged into the Texas music scene, so I took it on the road with the band and had lots of great professional musicians play through it and they all gave it rave reviews. I wish I had pictures of that amp...
Hats off to Ace Pepper of Thundertweak for answering a lot of stupid questions for me during that build! I lived about a mile away from him at the time, he's good people.
Flushed with success, I gutted my 1967 Fender Bassman Amp that I'd had since 1986. When I first started getting into working on amplifiers I looked inside this one and corrected some mistakes they'd made at the factory like that kooky AB165 bias scheme, then made some improvements on top of that like replacing the nasty brown caps with green Xicons, retubed it with Ruby STR-7025s and Phillips 6L6WGBs. It sounded incredible! Well, even after the corrections I'd made there were still some problems. It'd make some odd buzzes and pops, which usually went away after I pounded on it a few times, but I wanted to rebuild it to the standards of the FireWater amp, so I snipped out the circuit board.
I have a few improvements in mind for this one, one of which is an easily accessed bias point and control:
I had been building the FireWater amp for a certain steel guitar player whose name isn't worth mentioning. This guy had been a good friend of mine for several years at that point... or so I thought. He never paid me for the work, just walked into my house when he knew I'd be out of town, said hi to my roommate and walked out with the amp -- then left the country. That kind of soured me on the whole experience.
Then a lot of drama happened which I'll fast forward over, but suffice it to say that some health issues forced me to move back to the old home place in Oklahoma. The last couple of years have been pretty tough, but I'm on the mend and I've gotten my shop (at least somewhat) set up again and I'm trying to get back on track. Maybe I can get this amp together and make it rock, then look ahead to the next one.
My tentative plan is to make the Bass channel like the the Normal channel on a blackface AB763 circuit, and the Normal channel like the AB165 circuit. The power section will be from the AA864 circuit. I've also considered leaving the Bass channel out entirely and just making it a one channel amp (that's the only one I ever used, anyway). You guys have any ideas on this? I welcome any input...
I'm also doing something different with this one. I need some sort of grid to lay out the circuit on, and in the past I'd used a square grid, but I was in the Goodwill Store one day and had a brainwave: I bought an old Lite Brite for a buck and pulled the front grill off (you know, where you stick the colored pegs).
Today I scanned this grill, played around with the image, et voila!
Feel free to print that off and use it if you like. The honeycomb allows a more efficient use of space, which might be an issue if you're working on something pretty tight...
Thanks in advance for any advice you guys want to throw my way!
Justin Belshe
Anyway...
My brain hurts! I've immersed myself in this for several days now, trying to design a new circuit for my Bassman.
It's been years since I thought about this stuff and there's a pretty steep learning curve right at first.
See, I built an amp a few years ago. I started with two old Fenders, a Bassman 135 that had been through a house fire, and a The Twin which had been through a flood. I completely disassembled both amps, cleaned and inspected the parts and salvaged what I could, bead blasted the chassis, then used components from both to build one amp that I called the FireWater. It was basically an AB763 Twin Reverb, but without the Normal channel and no vibrato, but with a presence control and a two knob reverb (added dwell control). Fewer tubes meant more juice for the tubes that were there. Keystone turrets on G-10 with nylon standoffs and neoprene grommets for isolation. I ran it through a 1969 Dual Showman 2x15 cab loaded with Altec Lansing 421-As. It was loud as hell and sounded like a classic Fender, only much beefier. I could never get it to break up, either. Turning it up only made it sound fatter and fatter. At the time I was plugged into the Texas music scene, so I took it on the road with the band and had lots of great professional musicians play through it and they all gave it rave reviews. I wish I had pictures of that amp...
Hats off to Ace Pepper of Thundertweak for answering a lot of stupid questions for me during that build! I lived about a mile away from him at the time, he's good people.
Flushed with success, I gutted my 1967 Fender Bassman Amp that I'd had since 1986. When I first started getting into working on amplifiers I looked inside this one and corrected some mistakes they'd made at the factory like that kooky AB165 bias scheme, then made some improvements on top of that like replacing the nasty brown caps with green Xicons, retubed it with Ruby STR-7025s and Phillips 6L6WGBs. It sounded incredible! Well, even after the corrections I'd made there were still some problems. It'd make some odd buzzes and pops, which usually went away after I pounded on it a few times, but I wanted to rebuild it to the standards of the FireWater amp, so I snipped out the circuit board.
I have a few improvements in mind for this one, one of which is an easily accessed bias point and control:
I had been building the FireWater amp for a certain steel guitar player whose name isn't worth mentioning. This guy had been a good friend of mine for several years at that point... or so I thought. He never paid me for the work, just walked into my house when he knew I'd be out of town, said hi to my roommate and walked out with the amp -- then left the country. That kind of soured me on the whole experience.
Then a lot of drama happened which I'll fast forward over, but suffice it to say that some health issues forced me to move back to the old home place in Oklahoma. The last couple of years have been pretty tough, but I'm on the mend and I've gotten my shop (at least somewhat) set up again and I'm trying to get back on track. Maybe I can get this amp together and make it rock, then look ahead to the next one.
My tentative plan is to make the Bass channel like the the Normal channel on a blackface AB763 circuit, and the Normal channel like the AB165 circuit. The power section will be from the AA864 circuit. I've also considered leaving the Bass channel out entirely and just making it a one channel amp (that's the only one I ever used, anyway). You guys have any ideas on this? I welcome any input...
I'm also doing something different with this one. I need some sort of grid to lay out the circuit on, and in the past I'd used a square grid, but I was in the Goodwill Store one day and had a brainwave: I bought an old Lite Brite for a buck and pulled the front grill off (you know, where you stick the colored pegs).
Today I scanned this grill, played around with the image, et voila!
Feel free to print that off and use it if you like. The honeycomb allows a more efficient use of space, which might be an issue if you're working on something pretty tight...
Thanks in advance for any advice you guys want to throw my way!
Justin Belshe
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