Q-tron PA-12 OTL Tube Amplifier (Stereo 2 x 25W) con transformadores toroidales. Basszilla Platinum Edition MK2, DIY.

Specifications
Type: OTL tube steeo amplifier
Output power: 25W into 8 Ohm at less than 1% distortion
20W into 4 Ohm at less than 1% distortion
Distortion, THD at 1W: < 0.01%
Distortion, THD at 10W: < 0.1%
Frequency response: 5 Hz to 150 kHz (-1dB)
Power bandwidth: 10 Hz to 100 kHz (-1dB)
Rise time: < 0.5us
Hum and noise: < -100dBA
Output impedance: < 0.4 Ohm
Dimensions: 430 x 250 x 290 (WxHxD in mm)
Weight: 44 lbs.
Price: €8000 in Sweden; United States retail to be determined

Sonic Impressions

The PA-12 was going to have to sink or swim while driving the Basszilla Platinum Edition mk2 DIY speakers. The Basszilla, being a 96 dB sensitive loudspeaker, is quite comfortable with low-power tube amplification. And field feedback had it the coupling of the Basszilla with a Futterman style OTL sounds superb, so I expected this to be a successful marriage. As you will shortly see, I was not disappointed...

Eminence Definimax 4015LF woofers
Fostex 208E Sigma midranges
Aurum Cantus G2Si ribbon tweeters
Crossover includes: 14 ga Alpha air core inductors, Mundorf M-resist resistors, and Auricap, Solen, and Aeon capacitors