& Speaker Amplifier
Direct Drive Amplifier For RAAL-requisite True-Ribbon Earfield Headphones
0.3 Ohm – infinity
Output Power (one chanel driven) :
10W /8Ω, 20W/4Ω, 40W/2Ω, 55W/1Ω @ 1khz/sine
Ribbon Headphones Drive
2 x RAAL-requisite SR-1a
100mv/ in/sin. 15hz – 500kHz
10Hz(-1dB) – 100kHz (-2dB)
< 0,5% at 1khz
Signal to Noise Ratio:
Better than 90dB
IN1- 2 RCA, IN2 – 2 XLR
Max Power Consumption:
150W , without signal 25W
H 90, W 218, D 320mm (3.54 x 8.58 x 12.60 inches)
5,3kg (11.68 pounds)
Waterproof Flight Case w/Handle & Casters $250 USD
A BJT quasi-complementary, single rail supply with a cap at the output, single-ended input… Simple, yet very effective in minimizing TIM and a range of other types of distortion. Naturally, the topology had to be adapted for driving very low resistance loads with absolute stability, and still offer plenty of room for tweaking the sound in the desired direction.
Most modern topologies are very tight in holding their operational parameters, so working points are hard to change and component selection doesn’t matter as much. However, with simpler topologies, aside from inherently healthy sound, there is a lot that can be done with correct component choices and their operational regimes. Also, having a cap at the output ensures that no DC current will pass to the ribbon drivers which could fatally damage them.
Quasi-complementary output provides another interesting feature in push-pull designs, as opposed to complementary pairs. Basically, both halves of the push-pull are identical. No difference in dynamic behavior of parasitic capacitance at input or output of BJT’s and that goes a long way in removing a certain coarseness in sound quality.
All semiconductors were carefully chosen according to their sound, when operated in the most appropriate working point for their ratings, using sockets for swapping without thermal shock, through endless hours of listening and measuring.
The final choices are a new generation of power BJT’s for output, with linear current gain and 300W of dissipation for easy drive of two sets of SR1a headphones, while input and drive stages are very sensitive to the type of transistors, so the best in those roles are certain older types of BJT’s.
Special care was taken in choosing the optimum capacitor for the output to avoid any sound penalty.
There is no protection of output from short-circuit. As with high current peaks, output protection is often the cause of instability. All components were chosen to avoid oscillation and compensations are minimal, preserving speed and authenticity of presentation.