René Rebe

I got a nearly unused Oqo 01+ a few years ago for my vintage computer collection. You know, because it has “rare” Transmeta Efficeon cpu in it. As the original power supplies are apparently prone to fail, it already came without a power supply and I had to always use the lab supply on my desk (don’t ask, just the usual computer scientist office desk ;-)

Back in the day I found a bloodspot.com post form Ekawahyu Susilo, were he measured the pins - however, given the usual bitrot in the interwebs the post is now gone, and I peeled the most useful photo out of the archive.org to archive it prominently here as well:

(1) is VCC1, (2) is GND, and (3) is VCC2. Pin (4) is connected to GND and pin (5) is connected to VCC2. As far as I have found, VCC1 (5-6V?) is used for charging, while VCC2 (may be better lower at just 5V?) is used to directly run the Oqo, …

Update: now with video! ;-)

This thing, when you buy a Teac HA-P50 for some Hi-Res Audio testing, and the matching iOS app (you know, for hi-res, FLAC and such, …, sigh) produces extremely audible clicks and pops that sounds like buffer under run / overflow / whatever - on a recent iPhone 6s no less.

What the heck are the vendor’s thinking to ship such crap to their premium paying customers?

Funny thing, other apps, such Apple’s own Music.app do not have this clicks and pops, … ???!!!

Judging from the App review an at least one year old problem:

PS: And why the heck do they sell the Teac HA-P50 for US$199 in the states, and for 299€ in Europe?

I took a closer look at the latest 32-bit DACs and wondered how much better they can be over other state of the art 24-bit DACs, so let’s take a quick look:

ESS9012: DNR: 133db, THD: 120dB - 32 bit
AK4497EQ: SNR: 128dB, THD: 116dB - 32 bit

compared to classic vendor’s 24-bit reference DACs:
CS5381: SNR: 120dB, THD: 110dB - 24 bit
WM8741: SNR: 125dB, THD: 100dB - 24 bit
PCM1792: SNR: 129db, THD: 128dB - 24 bit

and some more reference points:
vintage 1996 CS4328: SNR: 120db, THD: 93dB - 18 bit
PCM5102 (as in TEAC HA-P50): SNR: 112dB, 93dB - w/ 32-bit interf.?!

So they are not really much better than other state of the art reference DACs, e.g. the Cirrus Logic Crystal DAC, and the TI Burr Brown DAC has even mostly better spec? Hmm, …

And in case of the PCM5102 as used in the Teac HA-P50 portable headphone amp I am actually quite disappointed that it’s technical specs are not really better than a vintage, 1996 Cirrus Logic CS4328. Back in the day their state of the art reference DAC.

And what are the theoretically limits for 24 bit (simplified):

20*log10(2)*24 == 144dB

and for 32 bit:

20*log10(2)*32 == 192dB

So which theoretical limit are those DACs approaching?, …

I rather have an honest 24-bit DAC than a 32-bit marketing wanna be. And even the 1996 CS4328 already accepts surplus bits on the serial bus. So you could already call those “with 32-bit interface”, ..:-)

Update: Even more curious are the newer TI, Burr Brown chips:

PCM1792: SNR: 129db, THD: THD+N: 0.0004% - 24 bit
PCM1795: SNR: 123db, THD: THD+N: 0.0005% - 32 bit

Huh? Why has the Advanced Segment 2009 DAC worse spec than the 2004 one (beside consuming less power, …)?

Yesterday we were at Denis Matsuev, piano, live in Berlin.

#Berlin #denismatsuev #gendarmenmarkt

A photo posted by René Rebe (@renerebe) on Dec 19, 2016 at 11:43am PST

Given all the recent hi-fi testing I realized the Signal-to-Noise Ratio (SNR) in real life is actually not that great, …

…, with all the people moving, breathing, clothes fabric scratching and aircon ventilation, making some background hiss, …

…, plus in the Berlin winter all the coughing, …

and we talk here about some digital 24, or 32 bit 130dB+

ah, this bare to the bits uboot CLI, sigh:

mmcinit
ext2ls mmc 0
ext2load mmc 0:1 0×10400000 /uImage; bootm

fsload 0×10400000 boot/uImage
set bootargs ‘console=ttyS0 root=/dev/mtdblock1 rootfstype=jffs2′
bootm

saveenv

Recently I spent some time finally finishing my DIY DAC and needed some signal generator for digital AES/EBU, coax / spdif audio to test and evaluate it. Turns out sox is pretty handy for that:

sox -r 48000 -n -t alsa spdif synth sine 1000 # square, triangle, sawtooth

Update:

sox infile.wav outfile-left.wav remix 1
sox infile.wav outfile.wav remix 1,2

If sox can not read your macOS recorded file with:

sox FAIL formats: can’t open input file Recodging.aifc: Unsupported AIFC compression type ‘in24′

You can let it use libsndfile to load the file anyway:

sox -t sndfile Recordings.aifc converted.aif

Update 2:

ffmpeg -i movie.mov -vn -acodec copy out.mp2

I am a longstanding fan of analog audio connectors, such as the headphone jack. During the iPhone7 rumors I long pointed out the many drawbacks of wireless audio: very lossy SBC -few combination support the also lossy aptX-, charging, connectivity issues etc.

While I still boycott the iPhones without headphone jack I run into the issue myself testing a Sennheiser Momemtum M2 Wireless the other weekend. Turns out on iOS Garageband does not use bluetooth by default, if you select it anyway, the App even warns about latency, and then if you actually use it iOS is such a degenerated crap, that it Garageband not allow you to use a Lightning connected audio input with Bluetooth audio out, … !!! What the heck?!?!

And when you do the Joe-user task of watching video? It is not even lip-sync anymore - the audio is seeable lagging like half a second or so, … !!!

Sad new wireless world :-/

I only realize now, in good old Linux tradition the command-line-interface of Bluez 5 was totally renewed compared to what was used the last decade up to Bluez 4.

So instead of “hcitool scan” and such you now have to run all the commands in some command line interpreting shell, sigh:

$bluetoothctl

[bluetooth]#list

[bluetooth]#show controller_mac_address

[bluetooth]#select controller_mac_address

[bluetooth]#power on

[bluetooth]#agent on
[bluetooth]#default-agent

[bluetooth]#discoverable on
[bluetooth]#pairable on

[bluetooth]#scan on

Update: some more details

In the 192kHz article I recently mentioned that Microsoft’s Surface Pro 3 with it’s ALC288 codec would max out at 48kHz. Turns out the Surface Pro 2 uses a ALC280 that surprisingly supports up to 192kHz. WTH?

/proc/asound/card1# grep rate codec#0
rates [0×5f0]: 32000 44100 48000 88200 96000 192000
rates [0×560]: 44100 48000 96000 192000
rates [0×560]: 44100 48000 96000 192000
rates [0×5f0]: 32000 44100 48000 88200 96000 192000
rates [0×560]: 44100 48000 96000 192000
rates [0×560]: 44100 48000 96000 192000

Believe it or not in 2016 I came across updating some aging x86 hardware, and it did not want to boot from our usual so2stick.sh T2 USB pen drive disk images. After some research and debugging it turned out syslinux has the answer:

On these BIOSes, you’re generally stuck booting them in USB-ZIP mode.
…
A standard zipdrive (both the 100 MB and the 250 MB varieties) have a “geometry” of 64 heads, 32 sectors, and are partitioned devices with a single partition 4 (unlike most other media of this type which uses partition 1.) The 100 MB variety has 96 cylinders, and the 250 MB variety has 239 cylinders;

And this stupid hack indeed works, sigh. PC BIOS programmers, a very special kind of bread, … :-/