Need a little help with building an amp.

[Fizazzles]

I started working on building my first amp about a year ago but got discouraged when I tried to design my own amp from scratch with insanely little knowledge about how amps work. In the last year I've read a lot more, taken some basic electronics classes and have decided to start a little slower and modify and existing schematic to better suit my needs and work my way up to designing my own amps. I chose to modify a fender 5f2a schematic and add some things both because I think they will work well and I want to see how these additions will change the amp compared to a non changed version.

Some of the changes I'm making for sure are changing the 12AX7 in the preamp to a 12AY7, and changing the bias on the preamp tubes to have a biasing switch to swap between two different bypass capacitors  on the preamp bias, I was thinking the values would swap between .047uf@25v and 25uf@25v. Those two changes I know I'm making, but I wanted to see if I could add a bass, mid, and treble pots to help hone in the sound I wanted. How would I go about doing that? I was looking at the schematic for the fender 5f8A and I wondered if I could just pull that part of the 5f8 out and stick it in between the preamp and power amp. Take the 12AX7 and wire it in parallel and follow it with the tone stack and feed that into the power amp.

I'd like some help with the amp because I want this to sound nice, preferably good with jazz and blues music styles.

[TIMBO]

Hey mate, Is this what you are looking for...
http://www.thevintagesound.com/ffg/schem/champ_aa764_schem.gif
As for your idea of removing the second triode after the tone stack is not a great idea.

The TMB type tone stack is very lossy (looses lots of signal) and SE amps need that stage to boost the signal before it goes to the output tube.

Paralleling the input tube will fatten the sound, so that can be a good idea.

If you are confident enough with your level of knowledge you could add another tube after the tone stack.
The 6AV6 is similar to one half of a 12AX7 that could be placed after the tone stack.

[labb]

Take a look. Change the power tube to suit...First amp I ever built.  http://www.ax84.com/static/p1/AX84_P1_101004.pdf

[shooter]

Fwiw

I’d start with a pre, kinda like you picked, I chopped it up some.

I would do the input jacks like  a plexi 6v6

I would split V2 ½ driving the TS, ½ recovery TS/driver
I would have a AU7 to play with in V1
You didn’t define loud, if you’re designing for flexability, I would give it a PT to handle 6V6, 6L6, EL34.  going from tube rec to SS bridge gives you a big B+ range, so spec for max I, including filament

Take long time, play 1st time 

EDIT, I would also give the cathode of V1 it's own bias

[PRR]

> two different bypass capacitors on the preamp bias, .... .047uf and 25uf

Also try no-cap. Let us know if you can hear a difference, 0.05u and no cap.

Print out all the early Fender plans and take them to your thinking-throne. He knew little more than you do. He worked it out one product at a time. The Champ went from marginal gain (and overload) to too-much gain and then a more balanced plan. More frills tends to require more gain to cover frill-loss. Try to recreate his progress.

And build to experiment!! Fender used cheap boards and random eyelets SO-THAT he could insert/delete parts at any point without throwing-away a truck full of custom boards. He probably did his development prototypes the same way, running over to the eyelet-punch when he needed a few more terminal points.

[brewdude]

I built a SE amp a while back that used a parallel 12AX7 input and then an early Fender TB tone stack with a 6SJ7 recovery feeding a cathode biased 6V6... well I changed it to a 6L6, and it sounds even better.

[ALBATROS1234]

all good advice, these guys are great for that, i am really new myself just finished my 4th amp, still havent perfected my design which is a mix match of other peoples schematics with small tweaks. like prr was suggesting i doubt if a .047 bypass cap will do much 25uf is standard preamp i like between 20uf and 50uf but have a 100uf and a 330uf in one amp . it seems like higher value = higher gain at least to a point, big diff btw 25uf and 100uf not as much between 100uf and 330uf. i have been breadboarding and experimenting. i use perfboard and radial cap because both are much cheaper. i also like a volume/tone between the 2 triode stages and one after acting as a gain and master volume. i am starting to hear the subtle tube differences and really love and appreciate the harmonic overtones of individual tubes. its fun fascinating and rewarding building tube amps enjoy.

[Fizazzles]

So I took all of the feedback I read about and it sounds like my problem with the original design would be too much gain loss in the circuit.

So right now I would say the two options I've been thinking about would be to use one 12AY7 with the first tone stack (Volume and Tone) wired in between, then follow that with an EL84 as a buffer into the second tone stack (TMB) then run that into a single 6L6 then the OT.  Or the second option would be one 12AY7 with the first tone stack (Vol & Tone) into 1/2 of an 12AX7 as a buffer into the second tone stack (TMB) with goes into the second half of the 12AX7 as the final gain stage into a 6L6 into the OT.

[shooter]

here's probably my best liked build, I borrowed all the pieces n stitched them together

V1 can be done either like I used, or fenderesqe bright/normal
V2a is what I call 2nd gain stage/ TS driver
V2b is a CF to help buffer, match impedance, signal loading
V3 is a 1/2 AX7, 3rd gain stage/ TS recovery, (you could use the other half for whatever you want/need)

again, fwiw