I finished up my latest preamp last week. I used Fdeck's HPF concept, but used a 12AT7 instead of the FETs or opamps. (He encourage me to post.) Took about 3"x3" of turret board space. Used the TCJ Filter Calculator with 24db Butterworth filter. Works like a champ. Made it switchable to hear the difference. Next amp won't have the switch . Did splurge and use NOS Mullard 12AT7s. Preamp itself is a 12AX7 in the V1 position with different options for cathode resistor/LED and 3 different choices for bypass - none, full, and partial. Tone stack - James with mid-shift control. Output - paraphase using 12AT7 driving XLR to Hypex 1200W(peak) power amp (2 400W modules bridged w/SMPS). Also, driving a Jensen DBE with a cathode follower using the other 1/2 of the output 12AT7. The power supply is John Broskie's PS-1. Have used these several times and for the money, sound pretty good in a reasonable amount of space. Absolutely no hum. Total weight - 14 lbs. I am getting rather old and my all-tube heads (TraceElliot and DIY) are staying home much more frequently.