Fender 5C1 vs 5F1

[Pixel]

I am gathering parts for a 5F1 and stumbled across the schematic for the 5C1.

One of the things I wanted to do sometime was to build point to point using just the tube sockets and terminal strips. The 5C1 uses octal tubes which have big fat sockets which are easier to hang components on. The 5C1 also has ridiculously few components.

Is there anything wrong with the 5C1 compared to the 5F1?

[The Dude]

Most would build the 5F1 just because of the more common and readily available 12AX7 tube. IMO, it's not really that difficult to solder 9 pin sockets for the design your talking about.

[Enzo]

Nothing wrong with any of them. They are really very much the same. You have a high gain pentode in one replaced by two triodes in the other, the end result is about the same. I am sure there are tonal nuances differing, but if you build two 5F1s they will sound a little different from one another too.

You know, if you want to build with octal sockets, you could replace the 12AX7 with a 6SN7, which is also a dual triode, and be pretty close.


Those octal sockets do have nice big terminals, but really, the miniature sockets of a 12AX7 have plenty if room. after all, as far as I can see no pin get more than two component leads stuck through it.

[g1]

6SJ7 can be harder to find and more prone to microphonics, even when new. That and the contact bias arrangement (of the 6SJ7) are 2 strikes against it in my opinion. Otherwise no real difference and both sound great.

[Helmholtz]

5F1 has power amp feedback.

Also 2 cascaded triodes can produce way more gain than a single pentode - so room for mods with 5F1.

[Enzo]

You could change the grid leak bias of that pentode to cathode bias.

[Mick Bailey]

I like the octal amps and have found Soviet 'Radio' branded equivalent tubes have been pretty good. Sovtek also rebrands the 6SJ7 - they still have the old Cyrillic markings and the last ones I bought were dated 1972 although boxed and screen printed with the latest Sovtek branding. I've had a few microphonic issues with these however.

Building the 5F1 point-to-point is straightforward though if the tube socket retaining screws are used to mount one end of the terminal strips. If you just use these you get 4 useable terminals each side of the tube, ignoring the grounded centre mounting terminal. If you extend the strip length to include another screw location, you get 6 terminals each side - plenty for this build. The reason for ignoring the ground terminals is they often don't provide the best point on the chassis for a ground and can give rise to noise issues. I would mount the PSU caps and resistors on their own strips.

[Pixel]

Wow, that is a lot of great information. Made my head hurt a bit reading up on the different biasing methods. Seems like there isn't a compelling reason to go with grid leak if you could just as easily choose a cathode bias.

I'll ask some pipe cleaners to pretend they are components and do a dry run on a 5F1 setup like Mick said.

If a 6SN7 leaps out at me I may get the octal fever again though.

Thanks so much!

[Enzo]

Maybe 6SL7 might be a better choice than 6SN7.