Originally Posted by btbluesky
I've just tested the 4 files, 30 secs, and 1 mins. They're all okay with my Havana. Seems you were just unlucky.
Well, it's too bad you're the only one who could test the Havana with those samples. I would have liked to understand if the problem was localized to some units or some setups.
For instance, I was running the DAC on 100V/50Hz while I assume you're in the US? (120V/60Hz).
Also, maybe my amp (Lehmann BCL) has wide bandwidth and is picking that noise and amplifying it more? I guess this is high frequency noise outside audio range but through some amplification circuits, it could result in noise back in the audio range. c.f. post from Dan Lavry which I read through an other thread recently:PSW Recording Forums: Dan Lavry => Why do Non Oversampling Filterless DAC sound so good
"A DA without a filter introduces image energy that is nearly as high as the energy in the audible range. In the case of non up-sampling DA, the audio content is centered at the sample rate, twice the sample rate, 3 times…. And it goes up to very high frequencies. The amplitude decay curve is rather slow…
Assuming that you could not hear above 22KHz, you say that the image energy will not be heard. But in fact, the DA output signal, both the audio and the images at frequencies above audio must go through some electronics before reaching your ears. Such electronics may be a preamp, a power amp, a speaker, a headphone amp and a headphone… or in a music production environment the signal may be sent to an analog mixer…
It is one thing to ask an amp, or a speaker (or whatever gear is there) to “process” a signal with energy content that is limited to 20Hz-20KHz (or say 10Hz-50KHz) accurately. It is another thing to expect accurate results when the signal contains relatively high energy at high frequencies. When you try to do that, you will find out that the image energy interferes with the electronics in many way. It degrades the transfer curve, which causes inter modulation at all frequencies including the audible ones, it can ruins circuit badly.
I could say much more, but those reasons are more then enough to explain that non up sampling has problems, and why no filter is bad news.