Shiit Magni is Nice, but Miss Bass Control

Hey All,
I have been supplementing my Adcom SLC-505 controller with a Shiit Magni pre- headphone amp. I still miss a bass tone control! As part of this re-building of an active pre-amp, I would like to place a passive stereo bass control (James?) in front of this 25K "Schiit" load. A 6db insertion loss could be compensated by bumping-up the gain via the switch. What would be a good circuit that would mildly boost or cut bass?
Thanks!
Paul
 
The four band Schiit Loki Mini+ has outstanding specs. I think I'll get that.
You know, I could take that, my little Schiit Magni, my Topping DAC, my NAD endpoint streamer, and my homebuilt switcher, and put them in one nice chassis. I would call this invention a "control pre-amp." Nah, separates are cooler!
P.S.: adason, is that Leon Russell or the Bhagwan Shree Rajneesh?
 
Got the Schiit Loki Mini+ and it's installed - best I ever heard.
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Small adjustments especially, like this slight trim on top to take the glint off 80s digital recordings.
Also, adding some bass to Mercury Living Presence recordings, maybe because monitors back then had murky bass, or because they needed room on LPs.