Homemade 5F2A Tweed Princeton amp, first build

SG John

Ambassador of Cool Guitars and Amps.
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Like I've mentioned in a few other posts, I started hanging out with these guys from different bands in the local scene who work at M.I.T., and have Saturday morning "Amp Club." They get together to drink way too much high test coffee, and then build and/or troubleshoot amps and maybe some pedals. They pass on their knowledge, and have a pretty nice selection of parts handy to build stuff. I was introduced to them this summer by my friend Chris who had gone to nursery school with Tim, the owner of the house. They are all a great bunch of highly intelligent geeks who have been in various bands, Tim's being my favorite... Archbishop's Enima Fetish.

When I was introduced to them, Tim told me that "You must come back now and build an amp or two." So, I started researching what to build. SInce I bought the book by Dave Hunter, "The Guitar Amp Handbook", I thought I would start with a 5F2A Fender Princeton, since that circuit was the basis for descriptions of how each section of an amplifier works. I wanted to learn as much as I could, especially so that I could play along with the many informative posts by Ivan, Steve, and Sysco, and many others here.

So, I bought a chassis, some transformers, tube sockets, tubes, and a couple of other little bits. All the caps, pots, resistors, and other odd electronic parts I was able to pull from bins in Tim's cellar. They were surprised I bought all the "right" stuff for the build, as most of the people going through there are always looking to get stuff done cheaply, on a musician's budget. I used the Fender schematic and the Weber layout drawing for reference. After a couple of months of random Saturday visits, I finally finished it in December. It fired up and worked first time, but there was a bit of internal distortion that may have been caused by a cold solder joint. Since I needed to tidy up the wiring anyway, I hit all the joints with the soldering iron. After that was done, I had an empty DST Engineering box for a U84 TNT amp and 10" speaker. Bob D. gave it to me when I bought a U84 TNT head, so I could have a speaker for it. There was a Fender badged Eminence speaker in it. I modified it a bit, and mounted my Princeton in it.

Now that I've played with it a bit, I can say that it likes P-90s and single coils better than humbuckers. I need to mess with the tone stack, as it needs to always be on twelve. If you roll off the tone knob, it starts to sound like there's a pillow in the speaker. Other than that little issue, I'm quite happy with it. Especially since it was my first build, and it works. Now to try a KT-66 powered JTM45 after I save enough money to buy the necessary hard goods.

Gratuitous porn:


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You lot, blimey, what kinda people are you with all these skills... Terrible place, I wanna go home.

Very impressive build, and the feeling of it working first time rather than smoke puffing out and a fire starting must be great.

Far be it from me to question Ivan, but how can that be a good choice for a first build??? It looks like a 10th or 15th build. A 1 watt, 1 tube amp with about 3 resistors and maybe 1 capacitor would be a good choice for a first build, or better yet a pedal, a very simple pedal.
 
Far be it from me to question Ivan, but how can that be a good choice for a first build??? It looks like a 10th or 15th build. A 1 watt, 1 tube amp with about 3 resistors and maybe 1 capacitor would be a good choice for a first build, or better yet a pedal, a very simple pedal.
Looking at the job SG John has done, one could easily believe that he has done this before, no doubt about it. IMHO, he chose wisely because
(1) He is familiar with this circuit from it being used in the book he has to describe how each stage of an amp works.
(2) It IS a simple design, about as simple as it gets. These type amps, the Champs & Princetons, were Leo's "student" models. About 5 watt output power, low parts count so cheap to produce. A 1 watt tube amp would be no simpler.
(3) They sound fantastic. These type amps have been used on countless recordings through the decades & continue to be used. Guitarists of the calibre of Eric Clapton & Keith Richards have, at times toured using them on stage. Guys like these can use most any amp they want, so that they have used Fender Champs & Princetons speaks volumes about these type amps.
To really get the best out of this amp SG John, try some old glass in it. NOS/NIB USA made 6V6's are still readily available & reasonably priced, same with the British made types.
For a 7025/12AX7, if you don't want to spring for an RCA, a (50's era) Sylvania will sound great, usually last almost forever & they can had at good prices.
Cheers
 
Like I've mentioned in a few other posts, I started hanging out with these guys from different bands in the local scene who work at M.I.T., and have Saturday morning "Amp Club." They get together to drink way too much high test coffee, and then build and/or troubleshoot amps and maybe some pedals. They pass on their knowledge, and have a pretty nice selection of parts handy to build stuff. I was introduced to them this summer by my friend Chris who had gone to nursery school with Tim, the owner of the house. They are all a great bunch of highly intelligent geeks who have been in various bands, Tim's being my favorite... Archbishop's Enima Fetish.

When I was introduced to them, Tim told me that "You must come back now and build an amp or two." So, I started researching what to build. SInce I bought the book by Dave Hunter, "The Guitar Amp Handbook", I thought I would start with a 5F2A Fender Princeton, since that circuit was the basis for descriptions of how each section of an amplifier works. I wanted to learn as much as I could, especially so that I could play along with the many informative posts by Ivan, Steve, and Sysco, and many others here.

So, I bought a chassis, some transformers, tube sockets, tubes, and a couple of other little bits. All the caps, pots, resistors, and other odd electronic parts I was able to pull from bins in Tim's cellar. They were surprised I bought all the "right" stuff for the build, as most of the people going through there are always looking to get stuff done cheaply, on a musician's budget. I used the Fender schematic and the Weber layout drawing for reference. After a couple of months of random Saturday visits, I finally finished it in December. It fired up and worked first time, but there was a bit of internal distortion that may have been caused by a cold solder joint. Since I needed to tidy up the wiring anyway, I hit all the joints with the soldering iron. After that was done, I had an empty DST Engineering box for a U84 TNT amp and 10" speaker. Bob D. gave it to me when I bought a U84 TNT head, so I could have a speaker for it. There was a Fender badged Eminence speaker in it. I modified it a bit, and mounted my Princeton in it.

Now that I've played with it a bit, I can say that it likes P-90s and single coils better than humbuckers. I need to mess with the tone stack, as it needs to always be on twelve. If you roll off the tone knob, it starts to sound like there's a pillow in the speaker. Other than that little issue, I'm quite happy with it. Especially since it was my first build, and it works. Now to try a KT-66 powered JTM45 after I save enough money to buy the necessary hard goods.

Gratuitous porn:


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Awesome, man - congrats on the build...
 
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