Output impedance of BA-3 as preamp?

[jazzzman]

I am considering building a BA-3 to use as a preamp (eventually with an F4). I am trying to design a stepped attenuator to place at the output of the BA-3. (I am given to understand that sonically it is better to have the attenuator after the preamp, assuming my sources (a cd player and a phono preamp) do not cause over-modulation in the preamp.) I know that the input impedance of the F4 is 47k, but I need to know the output impedance of the BA-3 front end to make the calculations.
Anybody can help?
Thanks.

 

[Zen Mod]

around-ish 1K2

 

[rayma]

I need to know the output impedance of the BA-3 front end to make the calculations.

There's a 332R in parallel with the output to ground, so it's something less than that,
added to the 100R in series with the output. Probably 5k would be good for the attenuator.

 

[jazzzman]

Thank you Zen Mod and Rayma, that is just the information I needed.