ProtoDAC TDA1387 X8 project

[hifinet]

I have no experience with the project. What sounds good to me is the "grounded base (discrete) cascoded stage" and the "passive I/V followed by a single-ended output buffer". I will pass on the "9th order LC filter", since it's unnecessary. I can't hear anywhere close to 24.1kHz or higher. Why do I need a 40dB attenuation filter at 24.1kHz? I already have two.

Quote from the Burr Brown PCM56 datasheet page 7:

"A low-pass filter is required after the PCM56 to remove all unwanted frequency components caused by the sampling frequency as well as those resulting from the discrete nature of the D/A output. This filter must have a flat frequency response over the entire audio band (0-20kHz) and a very high attenuation above 20kHz. Most previous digital audio circuits used a higher order (9-13 pole) analog filter. However, the phase response of an analog filter with these amplitude characteristics is nonlinear and can disturb the pulse-shaped characteristic transients contained in music."

I have a great deal of respect for Abrax. He is an actual EE, and his products have quite a following. In a brief interaction with me, he did make this statement: "Having recently done comparisons between NOS without filter and with filter I hear clear differences. I guess I can only attribute them to images being heard indirectly via intermodulation as I can't think of another explanation. Perhaps its that my amps are more susceptible than others' to IMD as there are guys on this forum who hear nothing wrong with NOS DACs without an anti-imaging filter."