Recent content by signalpath

You're thinking single-path architecture. The quiescent noise floor of today's best single-path DACs is around -116dBu BB/UW (assuming FS of around +18dBu). That's a dynamic range of around 134dB BB/UW, and that's pounding against the limit of low resistance design (DAC / IV / Buffer). To...

Yes, 130dB is roughly today's limit of single-path DACs (all DACs today). We're experimenting with multi-path. The low-path has a 40nVrms quiescent BB/UW noise floor, while the high path has +29dBu headroom. That's a dynamic range and linearity of 175dB. It's somewhat analogous to HDR...

Audiometric testing from long ago (using headphones) found the threshold of hearing to be -8dBSPL at 3kHz. There may be blood flow effects at play, but we can hear program / tone well under a noise floor (see Fielder AES papers from the 1980s). Dynamic range numbers are agnostic to freq range...

We can reasonably correlate an electrical dBFS to an acoustic dBSPL, in a fixed test environment.

Two thoughts. 1) With headphones, ambient noise can be at or below the threshold of hearing (-8dBSPL). Do the psychoacoustic math. 2) I know of one upscale home entertainment install that uses a Makara subwoofer (+143dBSPL) -- more commonly used in studios and live. In a 32-bit audio delivery...

Yes, that looks nearly identical to our own -105dBFS plots. Nice work. And this is the best looking -105dBFS sine wave we've seen. Every other DAC we've tested is worse, often far worse, or just pure noise. Thanks for the link to your test s/w. I think it's time to move on from the AP2722 and...

Good. What are you using to generate the initial digital sine wave? Also, how is the vertical scale interpreted (the "-60 to -50" scale)? -- what waveform viewer program is that? How does this scale translate into Vrms?

Thanks. As long as you're not using the "notch" inputs, that setup looks good. The DO300 website cites 5.2VFS. For visual waveform prints, I think it's time to jettison the trusty AP2722 and start using an external ADC. We're in fact working on an advanced multi-path ADC currently. This is such...

Thanks. I checked my notes. The waveform I shared was 30uVrms, which at 5.2V max I think is -105dBFS. What system are you using to capture a visual waveform? And what preamp for the +60dB gain?

Our AP2722 injects its own visual distortions starting around 50-60uVrms. To overcome this, we use a low-noise preamp (Millennia HV-3) with -133.2dB EIN (BB/UW) @ 60dB and 50R. The signal path is thus: AP2722 30uV Digital Sine Wave ==> DUT ==> HV-3 Preamp @ 60dB Gain ==> AP2722 (analog display)...

Good performing DACs are always a pleasure to talk about. The DO-300 price-performance is excellent. That said, my original point is that ALL single-path DACs today exhibit poor low-level waveform performance, and such performance is both measurable and perceptible. This was in response to the...

In the pro audio world, we listen to reverb tails. Pathological, indeed :). We listen to music and ambience until the moment we lose perception. Of course, recording levels this low are only as good as the recording itself (room, mic, adc, pre, technique, program, etc). Some studio friends did a...

Sure. Here's a DO-300 sine wave at -100dBFS. That's quiet, but perceptible, especially with good fitting headphones. The AP2722 analog plot exhibits self-noise at this level, so we developed a special measurement technique. I can share the signal path if anyone's interested. Every other...

That's not our experience. The very best DAC we've tested (DO-300) exhibits horrific waveform distortions 20dB above the commonly accepted threshold of headphone listening. With certain tests (complex-generated reverberant tails at pronounced levels, etc.), there are clear differences between...

Yes.