Rat opamp question....again :)

[Mad Al]

Hello folks. I'm all set to build a Rat clone, and I have this opamp trilema, so to say. I want the circuit to be least noisy as I can get it to be, since I'll use it in some more or less quiet situations (jazz gigs, for example). So, I had some good experience with TL 07x chips. The best option would be to put TL070 in it, and increase the value of the compensation cap, but, the thing is that where I live I can't seem to find that chip. Anyhow, once I read that Scott Burnham, the creator of the Rat by mistake put a 47 ohm resistor instead of 470 omh in the position of the R4 in the circuit, and that somehow messed up with the slew rate and that's what it gave the Rat its famous sound.

So I was thinking, if I use TL071, which is, as I read, some 40 times faster than the LM308, and use a smaller value resistor in that position, or even downright  use a jumper wire, would I get a similar result as with the "legendary" LM308 and less  noise?

[GGBB]

In a nutshell no.  The 47ohm in question controls part of the op-amp's gain.  Lowering it will raise gain and because that is only one part of the gain section, you'll throw of the tonal balance as well unless you also adjust the 560ohm and 2.2u and 4.7u caps.  And even if you do that right so as to maintain the same tonal balance, you'll still have more gain - probably way more gain - especially if you want to push the limits of the TL071 like the 47ohm pushes the limits of the LM308, which means it isn't going to sound the same anyway (plus - more gain means more noise).  TL070s are scarce but available.  The OP07 is another quieter-than-LM308 option and is not at all bad sounding IMO like is so often claimed (in comparisons I've heard it was hard to tell it from the LM308).  Also IMO, the LM308 doesn't sound noisy in the RAT - it's a dirt box after all.  I use a RAT in my setup for my church worship band and it's fine - and I have no noise gate.