Education on Resistors and Noise

[Guitarist1983]

I'm one level up from a newbie - built 5 pedals from kits, pcb.   My latest build is a Big Muff and like a newbie, I used some carbon and some metal film resistors.   Lots of hiss.   I proceeded to read about noise, and decided to install Metal Film into R2, R12, and R19 which feed the base of the transistors with the audio signal (I think).
http://www.kitrae.net/music/Images_Secret_Music_Page/BIG%20MUFF%20CIRCUIT%20GUIDE.pdf I noticed a slight reduction in noise, but there's still plenty remaining.

However, before replacing 10 more carbon resistors with Metal Film, I thought this would be a wonderful educational opportunity for an expert to teach us newbies about which resistors in a circuit (such as a Big Muff) contribute to the audio signal and could contribute noise.    Any experts wish to take this on?

Questions:
Which of these resistors affect noise/signal quality the most/least, given NPN Transistors:
Transistor's Emitter to ground (i.e., R22)
Transistor's Collector to +9V rail (R13)
Transistor's Bias Resistor (R14)
Transistor's Feedback Resistor (R9)
Input Resistor (R2)
LPF by Tone control (R8)

Thanks in advance.

[PBE6]

Any resistor (or other component) in the audio path will contribute noise, but you're always going to have audible noise with the Big Muff because of the huge voltage gain (something like 60-65 dB in total).  Any noise generated in the preliminary amplification stage(s) will be amplified again and again down the line so focusing your efforts on the front end will likely give you the best results, but don't expect "low noise" no matter what you do.  If you're really after noise reduction, lowering the gain in one or several of the gain stages might be a better bet.

[PRR]

In general: high-value resistors in series with signal, in the first stage, are likely culprits.

Full understanding of noise analysis takes time, and is confusing for a while.

Specifically to the Muff: The 39k in front is a non-negligible noise source, even if the resistor were Ideal. This one should be good Carbon Film at minimum, metal film may be a hair better.

But that's not all. The 39k and 100k have dropped precious signal to 71% before it gets to the transistor. And actually the 470k NFB resistor drops it more. Measured signal at first transistor Base may be 20% of input signal!

This input stage was NOT optimized for lowest hiss. It has good gain and may have happy overload sound, but lowest hiss is not going to happen this way. No change of values or materials will improve it much, not without adding heavy load to a guitar output.

We could radically redesign that first stage, but then it may not be "a Muff".

[PRR]

You can try this "inspired by" set of values. Everything higher-Z except R2 is lower. NFB predominantly series instead of shunt. I expect a just-significant improvement in S/N. And really not much above what an "Ideal" input amp could do.... high gain MUST bring-up universal hiss.

While there, I noted that C4 already gives subsonic response, no reason to increase it. Other caps limit the bass. Note that extended bass conflicts with snappy overload recovery. EH may already have a good set of cap values.