Archive for the 'Hardware' Category

hey, ALSA’s arecord has a vu-meter

Friday, July 14th, 2017

who knew?

arecord -f cd -d 0 -vv /dev/null


This annoying Sony camers w/ AVCHD files

Monday, June 12th, 2017

To process them in Linux install fuse-exfat, mount the SD with:

mount.exfat-fuse /dev/sdb1 /mnt/

and convert the properitary container to a standard one:

ffmpeg -i /mnt/PRIVATE/AVCHD/BDMV/STREAM/00001.MTS -codec copy myfile.mp4

Changing the Ethernet Mac address

Wednesday, June 7th, 2017

For fun or for profit:

sudo ifconfig en0 ether eb:ec:4a:9a:1e:b8

Of course choose your own truly random hex numbers ;-)

Dell XPS 13 9360 Developer Edition

Monday, April 10th, 2017

Last year Dell was so kind to send me the Intel Skylake based 15″ XPS 9550. As expected Dell recently refreshed the XPS series with the Kaby Lake generation of Intel’s platforms, and I could take a look on the refreshed silicon in the 13″ form factor.

The 13″ edition comes with the same light and sturdy carbon fibre, with a gentle silicone surface. As mentioned in last years post I like it for the thermal and electrical isolation. The same infinity edge display still optimises the size of the case, so that the 13″ display is effectively packed into the size of a conventional 12″ laptop. A really welcome light and compact travel companion.

Latest Mac’s build in hardware test

Wednesday, March 1st, 2017

Historically there was an Apple hardware test that you could boot to check if your Mac’s hardware is all good.

It came to a surprise though, that with newer Macs simply holding the ‘d’ during power on it runs some simple hardware diagnostic, too.

One should probably more often read Apple’s support pages, ..

Oqo 01 power adapter pinout

Friday, February 3rd, 2017

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 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 to archive it prominently here as well:

TEAC HR Audio Player for iOS

Thursday, January 5th, 2017

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 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?

Are 32-bit audio DACs any good?

Saturday, December 31st, 2016

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, …)?

Real world, live, Signal-to-Noise Ratio

Tuesday, December 20th, 2016

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

#Berlin #denismatsuev #gendarmenmarkt

A photo posted by René Rebe (@renerebe) on

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+

[self note:@”u-boot”];

Saturday, December 17th, 2016

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

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′