Thanks so much for doing this, @King Fan . Folks like you are the stuff of what TDPRI is made of. You share experience and knowledge freely in an attempt to make everyone's experience better. That's why I love this place.Thanks, all. This was a lot of fun, at least by covid standards.
This layout is especially aimed at new builders, to whom I often suggest the spacious, flexible 5F2a over the 5F1 Cramp. A layout alone can't contain all the *many* basic build tips you need. For folks planning a 5F2a, I highly recommend the group insights in the initial thread. The smart folks there discuss many build tips and other possible solutions.
And then there are so many other options, like the fact the bigger cab lets you run a 10" speaker (highly recommended). So also check out the many 5F2A build threads over the years -- one I especially liked for its detail and discussion was by our wise friend @theprofessor . Or recently, a nice thread by @Sylas Wojo has excellent insights about key choices, like the tricky hunt for the 'right' PT and OT. My choices in the layout are *far* from the only ones; but I decided to follow Rob's example and show an actual amp with actual parts so the actual details match up.
Another simple option would be to follow Rob's classic 5F1 layout and just add in the few 5F2a bits; tone stack, V1a bypass (which actually appeared in Champs if not on the layout), extra filtering, somewhat different OT, separate power switch....
More experienced builders will have lots of options; our smart friend @corliss1 is currently building one of these point-to-point (and sharing a great build thread).
If I drew a *more* modernized / optimized version, I'd switch both hot and neutral, install Rob's rectifier backup diodes, hang the 68Ks on the input jacks or better yet on the V1 grid pins, run shielded cable to both V1 grids, and maybe a few other things. On my actual 5F2a, I also have isolated (and explicitly grounded) input and speaker jacks, a mild NFB cut on a foot pedal, and a Weber 10A100T -- can you say '1957'?
Sonic mods? Not many. NFB tuning options are popular -- a total cut can work, but is a bit of a blunt instrument. A pot to adjust the stock resistance upwards is often suggested. Maybe an on-off switch for the V1a bypass? But this is a simple amp -- no need to go nuts.
Final thought for folks early in their build careers. Build stock, mod later. Sometimes it seems almost all of the problems we see in *so many* first builds come from mods included from the get-go. Just sayin'....
I'll take a crack at this question.
I'll take a crack at this question.
There are a couple reasons.
Two 16uF caps in parallel equal 32uF. Leo probably used two to save money. He had many 16uF in the bin. May as well put two together rather than put in a costlier 32uF cap.
Reasoning/benefit. 32uF will stiffen the bottom frequencies. I assume this was the main reason for the 32uF.
A second benefit. A 32uF cap will filter out more noise. Single ended amps are know to be noisier than PP amps so a little more filtering is good.
Two caps in parallel have lower ESR than one cap has. Again better for noise.
All good.
This is a great schematic! Question for @King Fan, what's the purpose of the 100k bleed resistor on the 16uf cap? Also, any possibility you have a version of this schematic with 4, 8, and 16ohm speaker jacks? Thanks Again!
This is fantastic! Thanks for the information!
