SD9 without input buffer

[lukasott]

Does it in any way affect the circuit's tone? I already have a buffer in my signal chain, and I'm not sure if it's necessary. From what I understand, buffers can increase noise, especially the transistor-based buffer used in the SD9. Have you had any experience with this? What's your opinion

[antonis]

From what I understand, buffers can increase noise, especially the transistor-based buffer used in the SD9.

Buffers don't increase noise..
(they just pass signal noise to the succeeding stage..)

IMHO, non-inverting op-amp configuration (like in SD9) doesn't need buffering, as long as input impedance (bias resistor value) is considered acceptable..   

[Mark Hammer]

True, one at a time they don't add audible noise.  But, as an active circuit, if you have a dozen buffers in a row, there can be an audible bit of cumulative noise.  Not enough that you run for the noise gate, but likely enough that you'll notice when you cut the power.

But again, that's the cumulative effect of many buffers, and not what is contributed by a single one.