Single ended - 6n2 preamp and 6p1 power "PrinceTown" + 6n2 FXLOOP - Build Notes

[jonhysfl]

Good afternoon!

I've been designing a amp around the 6n2 preamp tube and the 6p1 Power Tube.Been calling it "PrinceTown".
Here's the tubes that i want to use ('cos they're so cheap):
6n2:

The 6p1 tube:


I've taken seriously inspiration by the fender princeton preamp stage.
Since i'm relatively new to this tube amp world, i've looked at many Hi-Fi chinese amps that use this tubes in PushPull and Single Ended configurations:



I wish to it sound similar to a fender amp from the 60's, since the 6N2 is basically a russian version of the 12AX7, and the 6P1 reminds a lot of a 6v6.

The design for the amp is here:
https://oshwlab.com/jonhysfl/tube-amp-6n2-6p1-sch


As usual, is open source, and i'm posting this here 'cos i need your opinions on the board design, and component choices that i made. The project is still unfinished and untested since i want to hear how i could improve it.

I've also made a version with DC-Heated filaments:
https://oshwlab.com/jonhysfl/tube-amp-6n2-6p1-sch_copy


So, i'm still trying to learn how can i improve this project, if anyone can help with a tip on the board design, or flaws that are apparent, i would be thankful.

With that, the pins in the board with the voltages, output from the preamp stage and input for the power stage, B+, filament heat, are designed to fit a simple fx loop, based on this schematic:


I call it the "ToxicLoop" just for fun.
The board design, is also here:
https://oshwlab.com/jonhysfl/fxloop_6n2


I've been struggling alot to calculate the output tranformer, but from my online search a 5k/8ohm/16ohm should be a good fit for this application. Since where i live is hard to find Hammond transformers, i will order this from a local builder. Same for the power transformer, for the AC heated version, its a 230 230, 6.3 6.3 and for the DC version, 230 230, 5v, 5v (the rectifier will  take this to around 6.4V).


To anyone that replys, thank you!

[vibrolax]

Hi.

I'll try to respond to your request.
The schematics you have posted appear to be simple Chinese "hi-fi" amps, not guitar amplifiers.

Your goal appears to be "How do I modify a chinese hi-fi amp design using 6N2 + 6P1 to sound like a 60's Fender guitar amplifier"?

Experienced guitar amp designers/builders hesitate to answer this question, because that is not a sensible way to approach making a guitar amp.

A more sensible way is to start with the schematic for a simple Fender guitar amp like a Champ, and then see if it is possible to modify that design to use 6N2 + 6P1 tubes.

One can modify a Fender Champ (or Princeton) design to use a 6N2 preamp and 6P1 power amp, but it may not sound much like a Fender Champ or Princeton.

Adjust the power supply design to provide the proper voltages, currents, and filtering,
Adjust cathode, plate, and grid resistor values.
Get the correct output transformer power rating and impedance ratio.
And voila, you have a guitar amp.

That is what I did to build my first tube guitar amplifier.

I asked an experienced DIY builder whose work I admired to help me calculate the needed cathode resistor value for a single-ended 6S4 triode.  He told me (courteously) to figure it out for myself.  This was absolutely the correct answer.

In my opinion, it is best for inexperienced builders to avoid things like DC filaments, effects loops, etc. unless you are building from a known good design.

In general, it's too much work to check a proposed new or modified design by a person who hasn't built anything yet.

Build something simple enough you can figure it out yourself, even if it's simpler than what you want.  You'll save yourself (and others) time and effort in the long run.

Respectfully,
Jon