In looking around for a decent antenna, I found a rather good site run by someone who obviously knows their stuff and confirmed my suspicions that there’s no such thing as a digital aerial. I’m well within the Sutton Coldfield transmitter footprint and as such a decent Log40 antenna should do me fine. From the roof, I even have line-of-sight to the transmitter, which is somewhat of a bonus

I’ve also chucked £15 at a dedicated DAB dipole. If my experiments with in-car DAB were anything to go by, a decent antenna will pay dividends. I’m a complete DAB laggard, however if I’m going to be on the roof I may as well stick an antenna up there for it.

ATV seem to sell all the right bits at the requisite quality for an install that isn’t going to fail within a couple of years, so it’s probably worth checking them out.

So far, it would appear that LaCie, Western Digital, Iomega, Synology et al have completely failed to produce a DHX2-authenticated NAS even though the various Lion developer previews have been around for ages now.

What’s more, this hasn’t stopped the very excellent Netatalk project from supporting DHX2. Admittedly it’s still in beta, but at least it’s there and it does work. As my local file server / satellite recorder / general dogsbody machine is running Gentoo Linux, compiling and installing the latest beta is trivial and fixes all of the problems, allowing my iMac to continue to use it as a Time Machine volume.

For those interested, a very comprehensive howto for installing the Netatalk beta is available here.

This is what the battery usage graph said after a day:

How much power usage?!

A bit thirsty aren’t we?

Also, the thing appears to not discriminate between user-selected 2G and auto-discovered 3G. As I live in the back of beyond but somehow manage to get very marginal 3G coverage, I usually keep my phone pegged to 2G to stop it meandering all over the place. Presumably this would skew the results somewhat…

It turns out there’s a not-often-publicised little app squirrelled away in the /Applications/Utilities folder.

Open this up and a veritable smörgåsbord of audio options are presented. Why this isn’t in the usual “Sound” control panel section, or at least why there’s not a link to it from there, is beyond me.

Either way, you can use this gadget to set the optical audio output to be a 24-bit, 96KHz bitstream. It actually normalises the resolution and rate of anything Core Audio is asked to play to what’s set here, hence the reason the FLAC files were popping out at 16/48. A quick modification:

…and the Amp happily picks up the new bitstream:

And you know what? I’m not sure my ears are good enough to perceive the difference… I have Dire Straits’ “Brothers In Arms” in both formats and perhaps I can hear a more accurate rendition of the very top end, but to be honest my ears’ frequency response rolls off quite steeply after 18KHz nowadays Such is life: by the time you can afford a system capable of reproducing high definition audio, your body no longer has the bandwidth to acquire it accurately.

Still, I have a new set of words on the front of the amp and that makes me happy

It had three individual faults regarding the DSP board and related assemblies:

1. A dry joint on one of the power supply pins to the connector for the ribbon cable that links the DSP board to the processor board
2. A broken conductor in the linking ribbon cable
3. An indicated DSP RAM data bus error

I used the service manual I found to work out how to put the Amp into diagnostics mode which indicated the bus error. Also the various tests indicated that no audio was coming off the board, hence processed analogue (Dolby ProLogic) and digital (PCM, Dolby Digital, DTS) signals were just producing silence.

Work had very kindly lent me a Tektronix TDS2024 digital storage oscilloscope (DSO) which simplified the diagnostics procedure massively as being able to ‘see’ the signals within an assembly makes finding where things are broken a deal easier.

With an analogue signal being played into the amp, I could see it appearing on the interconnect header and then making its way to the OpAmp immediately before the DSP. Knowing where to find the signal was just a case of following the schematics provided in the service manual. The output of the OpAmp that fed the AD/DA converter was mashed to say the least and it looked like half of the waveform was missing. Right – power rails

The board is supplied with signal ground, power ground, +12v, -12v and a pair of +5v rails. Everything checked out with the exception of the -12v rail. As -12v was coming out of the power supply, something between the DSP board and the PSU had to be open circuit somewhere. On removing the processor board (which required the removal of most of the rest of the boards in the unit) the problem stuck out like a sore thumb: there were a half dozen dry joints on the ribbon connector that led to the DSP board, one of them being the -12v line.

These were desoldered and then re-soldered and the unit retested. -12v was now back and the output of the OpAmps looked much happier. In analogue bypass mode, audio now passed through the DSP board correctly.

Seeing this cable had obviously been removed previously (it was in a bit of a state) I decided to test each conductor end to end for continuity. This actually checked out, but once back in place and bent into the shape it would stay in, one of the conductors went open-circuit. This was the digital pulse train from the processor board to the DSP, instructing it what to do. Wiggling the cable brought random data up on the DSP status register when in control mode, so I scraped away the insulation close to either connector and soldered on a Kynar wire to replace the existing conductor. The DSP status register now settled down and did not leap around when the board was wiggled.

Re-running the signal diagnostics, PCM audio was now being processed from one of the optical inputs when in RAM bypass mode, however as soon as RAM buffering was introduced the whole thing got very confused. The diagnostics still showed that there was a data bus error between IC801 (the Yamaha YSS928-F DSP IC) and IC802 (the 4Mbit DRAM chip). These are placed right next to one another on the board so I figured the signal paths should be OK, so instead decided to inspect the physical connections. Nothing looked amiss on the DSP chip, but there was a little copper glint from behind the legs of the RAM package. Inspection with a jeweler’s eyepiece showed what looked like a strand of speaker cable shorting out a couple of the pins.

Much fiddling with a razor blade, needle and some canned air managed to remove this wire thread from between the chip legs. Diagnostics were run again and now everything passed with no errors reported. The Amp was restarted in normal mode and, unbelievably, everything works perfectly.

Result

So – service manual. I’m a great believer in the concept of the internet knowing everything and after much Google-fu, it did indeed produce the goods, however as the damn thing was in such an obscure place I’m hoping this post may be slightly more helpful to various people

Unfortunately the file is RapidShare hosted, hence you’ll have to put up with a five-minute download wait, but the link does work Click the “I want to wait” button on the bottom-right of the page, wait, and you’re then presented with the download link.

Yamaha DSP-AX620 AV Amplifier service manual

Hope that helps someone!

Having said that, I’ve recently bought a new DSLR camera and found that the video it churns out to be astonishingly good. Yes, it’s a pain to handle and yes, it has a CMOS sensor so it has a rolling shutter, but again for the kind of stuff I’ve found myself shooting (mainly outdoors) it’s done a marvellous job.

This leaves me with the problem that my existing Core-2 laptop wasn’t exactly man enough to properly wrangle the photos and video this thing churns out, be it either multiple exposures for HDR image processing or high-def footage. The first thought was to build a top-spec PC, but to be frank I’m starting to get bored with build-it-yourself hardware, especially if it’s not doing anything particularly specialist.

Looking round at all of the pre-built machines from the usual suspects (Dell, HP, local PC vendors, Overclockers UK etc) was a deeply depressing slog through uninspiring boxes of chips and specs and mundane hideousness, so I ventured into the Apple on-line store.

No matter what you think of Apple machines, their store is quick and clean and you can find what you want easily and with plenty of pretty pictures. So I bought an iMac

It wasn’t a spur-of-the-moment thing – I did actually do some due diligence by playing fantasy PC with the Overclockers price list and tried to build an equivalent spec PC complete with OS, monitor, keyboard, mouse etc. and at the end of it all found that I was saving perhaps £100 by going down the build-it-yourself PC route.

As much as I’d like to think I will upgrade my machine piecemeal in the future the reality is I very rarely actually do so. They tend to have a life cycle of approximately three years with me as a workstation, by which time any upgrade parts available are a complete non-starter as to make the upgrade really meaningful you usually end up with a new motherboard, chip, memory and graphics card. As such they’re usually stuffed in a cupboard somewhere and left to depreciate or re-cased and stuffed into a rack as a poor excuse for a server.

So, I now have an all-in-one with the hardware user-friendliness of a pissed off gorilla, but it does look very nice and the entire computer fits in the same amount of space as my previous monitor used to. It has enough IO – optical audio gives me multichannel sound (now that I’ve repaired my amplifier), gigabit ethernet gives me 112 megabytes-a-second access to my data via a Linux server providing native Apple AFP file shares, the two Thunderbolt ports (while currently useless as general purpose IO given there are no available storage or connectivity devices available) which allow me to hook up my old 24″ monitor and my video projector simultaneously, four USB ports (three used: one for keyboard, one for printer, one for phone) and a FireWire 800 hole that is currently plugged into a 1TB desktop hard drive.

It also has the amazing attribute of it running in almost complete silence. True, if you set it a massive render to get on with it does get a little more shouty, but nowhere near the level of my previous machine.

So, I’m a happy bunny and a new Mac switcher, and from Gentoo Linux, no less. As OSX is just BSD in a pretty dress, using the command line feels very familiar and with projects like MacPorts and Fink it’s almost as good as Gentoo

Overall, I’m very pleased and would strongly suggest anyone who’s put off by Apple’s pricing to give it a fair chance. I was genuinely surprised that actually they weren’t as expensive as I thought considering what you got for your cash.

For those of you who don’t know, the amount of addresses available on the “Internet Classic” (IPv4) is very close to being exhausted. To solve the problem, a new version of the Internet Protocol – IPv6 – was conceived. Uptake of this new protocol has been depressingly slow, however it is starting to gain pace.

In order to be a good net citizen, this site along with the others that I run has now been “dual stacked”, meaning it can be accessed by both the classical IPv4 internet and the new, shiny IPv6 internet.

To promote the use of IPv6, many large internet content providers such as Google, Facebook, Yahoo!, Akami and Limelight Networks are running World IPv6 Day in association with the Internet Society, the idea being that they make all of their content available via IPv6 as well as IPv4 on the 8th June, 2011.

To find out more about IPv6 and why it’s a Good Thing, take a look at Think Broadband’s IPv6 page.

If you want to see if you’re already IPv6 enabled, visit http://test-ipv6.com/.

If you want to try out IPv6 but your ISP does not yet support it (only a few such as W3Z and Andrews and Arnold and ClaraNet currently do), you can get a free IPv6 tunnel that routes the new IPv6 internet over the top of your existing IPv4 connection from places like Hurricane Electric’s Tunnel Broker service.

First off, their web site is actually useful – it very quickly guides you to the products you want with very little fuss, complete with accurate measurements, type cross-references etc.

Ordering was as easy as any other on-line retailer.

Both an order confirmation and a dispatch confirmation were e-mailed through with a .PDF invoice attached to the dispatch note – very nicely done and I wish more companies would bother to do this.

When the batteries arrived (next day) they were very well packaged and sealed in a tough plastic bag ensuring no acid could spill, and along with them was a single-sheet safety guide mentioning that there could be hydrogen gathering within the plastic bag, hence to open in a well-ventilated area.

Also stuck on the car batteries themselves were easy-to-remove labels that indicated where shipping plugs and sealing tape had been applied, ensuring nothing was missed when installed into the truck.

And finally the batteries themselves – they appear to be very well made for the price and do exactly what they should do!

Very, very impressed with the whole service top to bottom and as a bonus I now have a truck that can start after leaving the door open for a couple of hours

Not often I plug a company directly, but I think it’s worth giving them a link in the sidebar given that I’ll be going back to them for the leisure batteries in the not-too-distant future…

I was pratting around for most of this weekend and managed to leave the door open for a few hours, hence the courtesy light was also on for a few hours. Given that their should be upwards of 180Ah of capacity between the two of them, you’d have hoped starting after a 5-watt load for four hours wouldn’t pose a problem. It did.

Testing the aux battery had it pegged at around 22Ah and the primary was at 47Ah, so both are pretty well stuffed. The car starts OK even after it’s been stood, but woe betide you leaving anything electrical switched on between start attempts.

Anyway, a new set of batteries has been ordered from Tayna – note that the two batteries are identical with the exception of the polarity! The driver’s (main) side is a 250H while the aux (passenger) side is a 249H – nearly messed that one up £65+VAT each wasn’t too bad and certainly beat Halfords and the other couple of local motor factors.

I’ve used Numax batteries before and never had a quarrel with them, so they should at least last their guaranteed three years. As I understand it, they’re a Johnson Controls brand along with Varta batteries and in the past I’ve found the quality of a Numax and Varta to certainly be comparable. Only time will tell I guess…