Let's discuss the 5E2 Princeton (5F2A alternate)

chas.wahl

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Personally, I think that a 10" long 2" deep chassis is pretty small. I bought one once thinking of making a AX84 "Firefly" low-power amp, but that design has a solid-state rectifier. It's very nice to lay out a chassis with some real estate between the power transformer and any other transformers (and you'd be adding both choke and output transformer) to reduce EMF coupling between those, plus I think it's good to have a bit of distance between the power tube, OT and preamp tube too. Fender's 5X# chassis is 13-3/4" x 4-1/8" x 2-5/8", and there's a reason it's called a "gopher coffin". The difference between 6" and 4-1/8" helps to give a bit more girth, but the decrease in length is bound to create some congestion. I've seen 5F2-A circuits in a smaller chassis: the Hoffman Amps 5F2-A board is only 3-1/8 x 5-5/8"+, and that's shorter, certainly, than a "vintage" 5F2-A's board. And here's a link to a 5F2-A built into a chassis the size you propose: http://www.planetgaa.com/amp/my5f2a.html , but note that it uses a "stand-up" rather than a "lay-down" transformer parked in one corner, and the OT is basically standing on the 12AX7's toes.

If sourcing the chassis from Hammond, I would be inclined to use the 1444 14 x 6 x 3. And if you are enamored of the choke-containing circuit (I am) then I would build a 5F2 rather than a 5E2, and also use the higher-value capacitance for the first filter stage: replacing the first 8 uF cap on the B+ with a pair of them, or even using the two 16 uF caps shown on the 5F2-A schematic, with the choke inline between their positive terminals. Whether you keep, discard or modify the first dropping resistor (10k) is an issue that I haven't seen discussed relative to "reinserting" the choke -- but it's easy enough to jumper it or parallel it with a lower-value resistor.
 

rogb

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Personally, I think that a 10" long 2" deep chassis is pretty small. I bought one once thinking of making a AX84 "Firefly" low-power amp, but that design has a solid-state rectifier. It's very nice to lay out a chassis with some real estate between the power transformer and any other transformers (and you'd be adding both choke and output transformer) to reduce EMF coupling between those, plus I think it's good to have a bit of distance between the power tube, OT and preamp tube too. Fender's 5X# chassis is 13-3/4" x 4-1/8" x 2-5/8", and there's a reason it's called a "gopher coffin". The difference between 6" and 4-1/8" helps to give a bit more girth, but the decrease in length is bound to create some congestion. I've seen 5F2-A circuits in a smaller chassis: the Hoffman Amps 5F2-A board is only 3-1/8 x 5-5/8"+, and that's shorter, certainly, than a "vintage" 5F2-A's board. And here's a link to a 5F2-A built into a chassis the size you propose: http://www.planetgaa.com/amp/my5f2a.html , but note that it uses a "stand-up" rather than a "lay-down" transformer parked in one corner, and the OT is basically standing on the 12AX7's toes.

If sourcing the chassis from Hammond, I would be inclined to use the 1444 14 x 6 x 3. And if you are enamored of the choke-containing circuit (I am) then I would build a 5F2 rather than a 5E2, and also use the higher-value capacitance for the first filter stage: replacing the first 8 uF cap on the B+ with a pair of them, or even using the two 16 uF caps shown on the 5F2-A schematic, with the choke inline between their positive terminals. Whether you keep, discard or modify the first dropping resistor (10k) is an issue that I haven't seen discussed relative to "reinserting" the choke -- but it's easy enough to jumper it or parallel it with a lower-value resistor.
That's a most helpful and knowledgeable reply thank you. I was planning to use a plug in octal 1N4007 plug I have instead of 5Y3 and 275-0-275. I have a 10H 100mA choke here so thought of filtering the whole supply for ripple. I built a Mini Dumble in a tiny chassis once so I figured this will be a breeze!
78380_531451970217452_232928319_o_531451970217452.jpg
 

cometazzi

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That's a most helpful and knowledgeable reply thank you. I was planning to use a plug in octal 1N4007 plug I have instead of 5Y3 and 275-0-275. I have a 10H 100mA choke here so thought of filtering the whole supply for ripple. I built a Mini Dumble in a tiny chassis once so I figured this will be a breeze! View attachment 945488


Proper job there. How'd you make the faceplate?
 




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