SHPB10 We started with 250 OHm DT-990 Beyerdynamic Studio headphones connected directly to the Fractal DAC passive output (distortion of active linear circuits completely eliminated) this served as temporary reference. For driving headphones with lower impedance we need some kind of amplifier or buffer and here is where the problems started. We lost resolution and the transparent realistic music reproduction of our reference as soon as we added any conventional amplifier or buffer circuit. To rule out DAC related [...]  Read more >


SVC24 We have to attenuate the DAC output signal one way or the other. What would be better than connecting the DAC output directly to the power amp (minimum losses) and simply use digital (software) volume control? This approach always feeds full DAC output noise into the power amplifier, regardless of volume setting (noise is not attenuated together with the signal). This translates to poor SN ratio, something we want to avoid in order to get maximum resolution. Software volume control needs to change the origi [...]  Read more >


OBS100 Servo controlled active open baffle speaker There are many different speaker concepts and we tried most of these. The main problems is coloration (distortion), this is usually caused by multiple standing waves of the same frequency within the speaker enclosure. Another issue is compression of air and the given slip between fixed magnet and moving voice coil. In other words when we apply a certain voltage, the voice coil moves to a certain position. But if we apply slightest mechanical force on the voice co [...]  Read more >
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