Howdy pabbi1! I've been lurking / stalking KGs posts to see if anything cool shows up over here ...
yup, I built a few JTs, I really like them. Only problem with the JT I've seen is playing the input / output impedance game with them. Haven't thrown one on the new KGSS. Nice segue though.
According to Russ, the input impedance of the JT attenuator ranges from approximately 2.2K to 10K and the output impedance is 750R (this is for the 50k "version" of the Joshua Tree, this obviously is not set in stone, and there are resistor calculators on diyaudio). The original KGSS schematic has 500K input resistor for Zin. I was wondering if this combination will "work", or if I should look at reconfiguring the JT? With the relatively high Zin of 500k that the KGSS/BH uses by default, is either output offset (I assume not) or noise a problem? By noise, I mean noise due to stray capacitance between the input terminals and the board inputs? I have heard that this can be a problem when using high values for Zin and that this could have an effect on the high frequency response.
Also, has anyone experimented with a RF filter (R+C) right off the jacks on headphone amplifiers such as these? Of course upstream impedance might have to be calculated and the filter "fiddled" with a bit...
