DKT88
Active Member
I am looking for technical comments on a DAC design that uses resistors and audio transformer (a so called passive no feedback stage) in place of an active output stage. As an example, I was looking at an older Neko D100 DAC (based on the old pcm1794a). The designer makes this claim:
The unique aspect is the passive transformer-based output stage. A passive analog stage because was chosen avoid the possible audio degradation that can happen with an active analog stage. There are many good active designs, but there is also a lot more to analog music reproduction that THD+N measurements because music is much more complicated than sine waves.
Evidence of the passive design's benefits can be seen in the noise floor, which is at the limits of the Audio Precision ATS-2 (this is a measuring instrument that analyzes distortion) at around -130dB. This offers excellent sine-wave linearity even without feedback (as seen in the linearity graph on the web site). I wanted there to be as little as possible influencing the signal fidelity after it comes out of the PCM1794A chip. The output transformer is part of that, as well as providing a nicer solution to removing the PCM1794A output's DC offset than a capacitor which is used in other passive designs.
I can't find any measurements that support his performance claims.
The unique aspect is the passive transformer-based output stage. A passive analog stage because was chosen avoid the possible audio degradation that can happen with an active analog stage. There are many good active designs, but there is also a lot more to analog music reproduction that THD+N measurements because music is much more complicated than sine waves.
Evidence of the passive design's benefits can be seen in the noise floor, which is at the limits of the Audio Precision ATS-2 (this is a measuring instrument that analyzes distortion) at around -130dB. This offers excellent sine-wave linearity even without feedback (as seen in the linearity graph on the web site). I wanted there to be as little as possible influencing the signal fidelity after it comes out of the PCM1794A chip. The output transformer is part of that, as well as providing a nicer solution to removing the PCM1794A output's DC offset than a capacitor which is used in other passive designs.
I can't find any measurements that support his performance claims.