DIY "Keeley"-TS9 mod questions

[red]

I doubt the transistor change would have an audible effect. You'd be better off changing all the higher rated resistors (anything 100K or higher) to metal flim. Carbon films at high ratings tend to be a little hissy.

I don't expect to completely cure the noise, just cut it down as much as possible. I found this article that stated:

"Note that in going to higher gains, you will inevitably increase the noise in the output. This may be curable to a degree by changing the input transistor to a quieter part (MPSA18 or 2N5089 is good) as well as swapping to a more modern and quieter opamp like the LM833 or both."

The Keeley Baked Mod page also specifies:

"I also change the input transistor to a MPSA18 for lower noise operation."

Now, I like the RC4558P very much, so I won't be changing that, but I though I'd give the transistor swap a try. It might not cure all of the background noise when going to higher gain, but it if cures some of it I'll be happy.

I wouldn't worry about that 0.02 cap. It's at the start of the input buffer and I've never seen any mention of it being tonally important.

Well, this is where I've seen a mention that it might be tonally important. I've also tried it out - I put a 0.1uF cap there and I got more bass than I had bargained for. But I really like the 0.02uF cap, and I don't think mr. Keeley changes that value, so I'll just swap it for a 0.022uF metal film for better quality and leave it at that.

BTW, your bass didn't increase with that switch to a 0.1uf cap--it just compensated for the 2.4K resistor. The two form a frequency filter, and when you cut the one in half, you have to double the other to keep the bass response the same. If you really want more low end, increase it to 0.22uf.

Indeed you are right, sir. I did try a 0.22uF, I thought the pedal got too muddy though and went back to the 0.1uF.

Thank you for your reply!