Hi, My MFA D-75 is late 80's vintage and uses 4 6550,KT88, or KT90 power tubes, 2 12AX7 input tubes, 2 6CG7/6FQ7, and 2 OA2 (for voltage regulation, I believe). It puts out 75-80 watts per ch depending on power tube type. This amp has a nice combination of virtues and is atypical for a mid-priced push-pull amp (about $2500 new) in that it is very extended at the frequency extremes, not at all rolled off in the treble and quite extended/tight in the mid/low bass. The only thing lacking in some listener's minds is a lack of that classic warm, tubey glow in the mid-range. It's also fair to say it doesn't have the transparency and "you are there" magic of small powered SET amps (what push-pull amp does at this price level?). I do believe it is much more linear sounding than most tube amps. In my system it sounds its best by far with Ei KT90 tubes and Mullard/RCA small signal tubes. Using KT88 tubes results in a definite loss of body/harmonics in the midrange. It is extremely quiet, highly dependable, and has separate level controls for trimming the power tubes. I feel it is a great amp in the $1-1.2k range.
