Rupert bounced me an email from the Avid L requesting a bit of info on tech mains, balanced/unbalanced audio etc. Here is the thread;

I've been having an ongoing discussion with a co-worker this last week about audio wiring. More specifically about lifting the ground. To define, it's when you don't connect the ground wire in a balanced, hot/cold/ground, connection. Now I personally have firm opinions on wiring based on what I have been taught and what has worked for me for years, but I am no expert by any leniency of definition. And I thought it would be informative for all on the list to hear a discussion on some of these issues so that they can evaluate what work is done when they hire an installer. I'm going to ask a few questions that will hopefully not display my personal opinions but open the topic up for discussion. This discussion is more than welcome to cover not only Avid editing bays, but also portable field systems and audio mix stages. I'm also interested in knowing if a clean electrical supply for the building makes a difference in how you decided to wire.

Nine times out of ten you "get away with it" using the same supply throughout a building. The BBC really set the standard in the UK for segregating domestic (aka "cooking" mains) from technical power supply and the reasons have now largely changed because of the move from linear power supplies to switch-mode supplies in pro-equipment. Pre the eighties pretty much everything had a linear supply and so a clean mains supply was essential and so it was common to segregate the mains for the production chain from the sockets used to plug in vacuum cleaners etc. Since then we see a lot more switch-mode supplies which tend to be more immune to mains-bourne noise but the concern now is the large potential difference that can occur between different earth feeds. The worst case is plugging a bit of kit in one room on the technical supply (and hence the tech earth) and connecting it via tie lines to another device that is powered by the domestic supply. Since both devices will (probably) have a common signal and chassis earth an potential difference between the earths will be effectively dumped onto the signal screen - depending on how the receiving bit of kit terminates the feed you get mains hum of the audio and hum-bars on any analogue video. Digital signals are effected in that you're more likely to get transmission errors - splats on the AES audio.

When would you, or would you ever, lift the ground on an analogue audio signal in a deck and mixer configuration? At what point would you lift the ground if you were too (deck or mixer)?

As a "get me out of gaol quick" I'd lift the earth in situation I'd described - I'd make sure I fixed the mains supply problem first though. Loosing the electrostatic shielding that the screen gives you probably looses you six dBs of noise performance as well.

When would you, or would you ever, lift the ground on an analogue audio signal in a configuration where all of the audio passes through a half or full norm patch bay? At what point would you lift the ground if you were too (patchbay or device)? Would you tie/strap/buss (the practice of using a wire to connect all the grounds of all the jacks to one another and then connect to the rack) the grounds together on either the half or full norm patchbay?

The modern practise is to take signal-earth through the jackfield on each position and terminate in ABS krone blocks. If you view your jackfields as a re-assignable resource then you should make them AES capable and that pretty much dictates earth integrity. By having individual screens you also avoid the problem of dumping mains hum onto every feed on a jackfield if the problem I described (above) happens.

When would you, or would you ever, lift the ground on an AES audio signal in a deck and mixer configuration? At what point would you lift the ground if you were too (deck or mixer)?

I'd never lift AES earths! ISTR that when AES was starting to hit in the late eighties the spec document said you should take the shield all the way to the krone block and segregate it with a 10pF capacitor if you had earth mismatch problems - again, you really should get your tech earth sorted! AES is so unreliable an interface (1.4mBits over 110ohm twisted pair cable!) that I tend to put it over 75ohm co-ax whenever possible - see an article on my blog

When would you, or would you ever, lift the ground on an AES audio signal in a configuration where all of the audio passes through a full norm patch bay? At what point would you lift the ground if you were too (patchbay or device)?

Previous answer

When building a cable for analogue audio that goes from balanced to unbalanced do you wire [T/T R/S S/S], [T/T R/T S/S], [T/T R/x S/S], [T/T R/S S/x]? And why that way? (and yes, I do know that one should actually use a matchbox or something, but indulge me please) (T=tip, R=ring, S=sleeve, x=not connected) (balanced is TRS, unbalanced is TS)

With the proviso that you DON'T mix balanced and unbalanced on a jackfield - you run the risk of unbalancing the whole facility and hence destroy any noise immunity that common-mode rejection is bringing you - I take the view that tieing the cold and screen together is no longer a good way to go as most kit now terminates feeds in op-amps rather than a rep-coil. Loosing six dBs of level seems a reasonable trade-off compared to slowly burning out the receiving stage in the DA, etc.

I've designed/supervised the install of many small and large facilities/studios/OB trucks over the last decade and without exception I've never had to deal with induced mains hum or noisy audio because of balanced/unbalanced problems by following the principles above. Rep-coils (passive match-packs) are a superb way of isolating audio feeds that may have induced mains hum.

We're getting new fibre!

We're having a new network connection at the office and Sohonet is our new provider. I was talking to an old colleague, John Ferguy who is now technical director with them and he was telling me a bit about single mode fibre. They do everything down nine micron fibres (which are many times smaller than the 62.5 micron multi-mode pipes we use). With much finer launch-angles and glass that is optimised around a single frequency they can get 10 gigabits over fifty kilometres. In this case they run in a blow-tube and when they're ready they send down the fibre with compressed air - very cool.

"I have seen the future of rock and roll, and it's name is Bruce Springsteen" - Jon Landau, Rolling Stone Magazine, 1974

But in this instance it was a new style of high definition TFT-based display. Bightside have a range of displays that aren't rear-illuminated with fluorescent tubes but with an array of hi-bright LEDs that are modulated with the luminance of the image being displayed. The array of LEDs is much lower-res than the 1920x1080 pixel matrix and so the real image (as displayed on the LCD) is modified with a masking signal to get the illumination to the correct resolution and the results are superb. A dynamic range of near 100dBs (that's fourteen stops to the cinematographers) and a maximum light output of 3000 cd/m² (you line-up a monitor for TV grading with peak white at 80 cd/m²!). I couldn't vouch for the colourimetry but it did look pretty close to illumninant-D. The detail in the blacks was astonishing and next to a Sony GDM monitor (which a lot of people use for grading!) the pictures looked remarkable. It was like a light-box with a moving transparency on it! I hope our friends at Filmlight implement a Truelight LUT for this device and I think that you'll see these in film grading suites really soon.

Interestingly there were a couple of facilities engineers and MDs there and they didn't seem to get it - the one quote I'll remember for a while was "we could use one in reception..."! I suppose when folks first looked at colour TV, stereo audio, digital video etc etc there were folks who couldn't see how to make it fit into their workflow and therefore couldn't see any value in it. I was blown away, however.

They also had a very cool compression system for reducing the data-load on 32-bit high dynamic range images.

OS-X on Intel read-me was given to me by Joel last week - we've got a pal who's got it working on his PC and Joel has pulled the ISO so we can try it here. I'll report back on it but there are a couple of things that peaked my interest. Firstly John Dvorak's column on PCMag.com;

There is no question that this would be a boneheaded move, and as I see more and more chitchat about the possibilities, I'm now convinced that this is all a publicity stunt and the Apple community is being used—once again—by the company's marketing department.
That said, I will admit that the possibility does exist that Apple doesn't want its OS in the wild, since it could potentially hurt hardware sales. At least that's the way the company might see it. This assertion does assume that the Apple marketing department is brain-dead....

The implication is that it slipped out of Cuppertino far too easily. This is stealth alpha-testing by Apple!
The other article I saw was in PCW and something there rang true;

.....forthcoming Intel-based Mac OSX operating system on a non-Apple PC. They say on some PCs it appears to run faster than the version on current G5 Macs

This seems to be borne out by Avid who have always maintained it's easier optimise for PC compared to G5 - see a previous blog entry here.

Isla Guagalupe, Mexico, part 3

Channel Five have started their new show - the pre-production title was Shark Watch but it started transmission this evening as Killer Shark Live and I have to say I'm really disappointed - very tabloid and totally lacking in any real science. They used lots of reality footage of people getting munched by sharks and totally avoided engaging the viewer with anything approaching intelligence. It seems like Endemol's MO - I had high hopes for the show given the fantastic location. You can see details of my recce here and here.

Living in London, making space

This isn't at all technical but I caught a couple of nice pics of my eldest boys on my 'phone - Joe is in the cellar doing his Warhammer on a bench I built him (complete with spot lights and speakers hanging off our media server). Dan is in his under-bed studio where he composes and generally makes a racket - cabin beds are a boon when you live and work in London and wind up in a house (or flat) that is a bit smaller than you'd really like.

My four biggest beefs with Avid

• Digi002, ExpressPro Studio, and eight channel audio.
  
  To get eight channels in and out of a Digi002 console you need to use ADAT 'light-pipe' which necessitates a converter of some sort. Quite why a "pro" product relies on a domestic-style interface for multi-channel work is another topic (not too many VTRs, multi-track tapes or disks come with ADAT, but still). The thing that has really bitten us in the backside is that neither of the models Avid recommend work reliably with the Digi002 (the Fostex UC-8 and the Dua2) and the one gadget that does work (the Alesis A14) only works on short ADAT cables (this is a single-mode fibre - in any industrial grade application you'd expect it to work over kilometres, not be limited to three metres!). This flies in the face of Avid's advice - "you can run long ADAT fibres, but don't try and extend the FireWire between the workstation and the Digi002" - well, precisely the reverse is true! Big shout to my colleague Chris Bailey for figuring this all out and to Joel and Rhys who I worked late with last night out in the sticks in Hertforshire testing this (amongst other things).
  
• Mojo analogue video performance - still bad, noisy when in component mode (yet Avid claim it's broadcast quality - where, precisely?!). See a previous post here.
  
• Adrenaline and NTSC reference - when using Adrenaline in 525 mode it has to have a proper Sc-H consistent sync source - this is fine, but by letting people get away with a cheap'n'cheerful black & burst generator in PAL mode you give clients the expectation that they've gotten away with additional expense - if you're going to lower the bar then do it consistently or not at all.
• This pinched from the Avid-L today

  Almost as shocking as the actually time code problem is that Avid refuses to comment on it or address it. Pretty shameful.
  How about if I say that we're aware of it and committed to fix it? Would that be enough? Sincerely, Jeremy Kezer (Jeremy is Avid's principle engineer)

Still, compared to Final Cut Pro and Decklink these are mere annoyances!

Technologists always get it wrong!

I was going over some old BBC training manuals recently and inside the front cover of one was a quote from the chief engineer of the Beeb from the mid-50's - In relation to VERA (the BBC's experimental video recorder that pre-dated 2" Quadraplex - loads of stuff online if you're interested) he said some thing along the lines of;

we'll never need more than three VTRs because even with the second network (what was to become BBC2) we'd only need one per network and a spare

How wrong can you be! Anyhow - he's in good company as a quick trip around famous quotes relating to predicating the future of technology indicates;

There is no reason anyone would want a computer in their home.

Ken Olson, Digital Equipment Corporation (1977)

I think there is a world market for maybe five computers.

Thomas Watson, IBM (1943)

640k ought to be enough for anybody.

Bill Gates, Microsoft Corporation (1981)

Computers in the future may weigh no more than 1.5 tons.

Popular Mechanics (1949)

Why does it prove so hard to be realistic about the future? I think (in part) people find the implications of Moore's Law hard to believe - but it's been good for nearly half a century. In five years we will have the following;

• More than a terrabyte of storage in the PC you buy from PC World
  
• More than ten gigs of RAM in that PC
  
• A graphics card that can manipulate cinema resolution images in realtime
  
• 100BaseT internet connection at home
  
• An OS that crashes more often, requires ten times the resources of today and lets you word-process at roughly the level of efficiency as you could in the early nineties under Windows 3 on a '486!

How is it that the hardware guys give us so much more but the software boys don't do it better? What Mr Intel giveth Mr Microsoft taketh

More on power-over-ethernet

I was keeping my eye on the IEE802.2 spec for POE (see a previous post here) and was a tad bemused for the reasons I'd mentioned in April - however, the new 802.2af version is now out and is a specification that embraces gigabit and hence putting the packets as a carrier on a DC voltage - each of the four pairs can supply 13W at an operating potential of 45v. It's a similair arrangement to how your Sky LNB works or how power is sent down a camera triax. Better than this though, and for legacy compatability, a network switch must first "test the water" by measuring the impedance of each pair, and if the device at the other end looks as if it's POE compliant it can start ramping a voltage. It has to test a few more times before it can lift it up to the 45v level and so should never wind up frying old 100baseT NICs or even other deives that are using the structured cabling (telephones etc.) - a few more details on the excellent Power over Ethernet website.

Me on German television!

Last year I did a little piece to camera for a documentary - see my previous post here and download a little clip of the finished thing here - it's DivX.

I kinda like myself in German!
My hair has got a lot more grey in the year since this was shot.

How technology is helping out charity efforts

Sarah and I did a little presentation at church last night for our friends who are away living in Thailand and working on the Burma boarder with refugees and orphans. Hand in Hand For Asia is the charity that Sarah works for (see the link in the right-hand side bar) and supports their efforts and I'd really encourage you to check out that site and consider if there is any help you can offer.
Anyhow - I was going over in my mind how much we make use of the internet in that area - we do all our communication over Skype (what a cost-saver!) and then there's the website. We get photos and video back from them and we're about to turn the (modest) merchandise section of the website (see here) into a full e-commerce venture. It's even turned Sarah into a web designer!

Podcasting and all that - I'm amazed by how much I like Adam Curry's Daily Source Code given it had quite a Mac emphasis and also seems to have no post-production. He does it live like a trad radio show which seems to fly in the face of podcasting and it's anti-radio paradigm. It is a good listen though.
I did reflect on my MP3 listening habits over the last couple of years that really started in 2001 with Chris Parillo's radio show "Call for help" that used to come out of a station in Des Moine. Someone (I don't recall who) who lived in the area used to snag the audio and make it available as an MP3. He put me onto Total Recorder that I've been using ever since to grab internet radio streams (in effect creating PodCasts from anything that streams).
In closing I'm also really enjoying my friend Kevin Cade's cast First Person Show - he interviews interesting people - that's it!

Phil's IBC report on groovy new cable types!

Some of the most interesting stuff for me was checking out some of the new cable types that Belden have launched. If you click on the data sheet you can see the performance - in the photo the top cable is a sample of their DigiTruck 179DT coax - very similar in form to old-style BBC PSF1/7 but apparently good for 64 metres at single-link HD. I think I'll have to try that before I believe it!
The next cable down in the photo is their new 7731A co-ax - just like a garden hose but supposedly good for 165 metres.
The next one down is a sample of Belden "NanoTwist" cat5 cable - optimized for video-type applications rather than network traffic. The degree of twist difference between the four pairs is minimised w.r.t. normal cat5. I'll be trying this - particularly to see if I can get a Scene Double extender to go any further.
The last piece is called "banana peel" multi-coax. It is intended for A/V applications and can be much more easily terminated than multi SD01.

The thing that disappointed me was that on the fibre front all the cable suppliers were concentrating on the old-school single-mode IP type applications and not the kind of SAN applications we're cabling for.

Possible fuel protests here in the UK

This letter to the Independent seemed to summarize my thoughts exactly - the futility of short-termism. Also - farmers - I wish I could buy fuel for 38p a litre! Yet another example of agriculture being subsidized by the tax-payer - is there any area of farming that doesn't expect to have it's costs covered by other people? I wish my industry could benefit thus.

Mukka Express Coffee Maker

Coffee is one of the things I really enjoy - decent cappaccino or cafe latte - it's all good with me! Sarah got me one of these for my birthday and I have to say it is a superb gadget - really well made. The top and bottom section are both single-piece castings and the screw sections are well machined with proper inset-gaskets. I predict I'll be enjoying a brew out of this bad boy for years to come. The kids like it because it looks like a cow!

The continuing success of the iPod is something I don't really understand - I was chatting with a friend at the weekend who made the observation that people like integrated services and style more than things you can actually measure as being better or more valuable. I personally don't think that caring (as I do) about music, the musicians who make it and the quality of what I listen to that I could EVER own an iPod.

I've bought a couple of these puppies for folks and I am so impressed - £23 for a 256meg flash MP3 player - they also do a 512 & 1gig version.

Ways they score over the iPod Shuffle:

Regular USB storage device - plug it into any Windows/Linux/Mac and it appears as a drive that you can drag tunes onto. You don't have to install iTunes and then lock your music player to a specific computer,
It has a screen - you can see what tune's up next and navigate the very easy to use menus,
Third of the price!
No embarrassing white headphones!
Just the thing for listening to spoken content that hasn't come from iTunes,
Uses replaceable batteries - normal or rechargable - none of that sending it back to Apple when the batteries die (and evey iPod owner I know moans about that!),
Sound quality comparable (or better) than an iPod,
Smaller.

Ways an iPod scores over this:

"It's a design classic, darling"

Now, the thing I really don't get is the new Apple iPod 'phone - a very crippled version of an iPod Shuffle integrated into a mobile handset that didn't win any prizes when it came out! It seems you either want a vanilla handset to make calls and text OR you want something with a bit of grunt - I've been enjoying the Orange SPV series of Windows smart 'phones for two and a half years now (Ben, my colleague who looks after the 'phone contracts at work tells me we're all about to be upgraded to the M500) and they are superb. It seems I ask myself the question every time a new Apple product comes out - why would you want it? It's expensive and under-powered and represents yet another attempt to dumb-down the technology.
I suppose that in the end free-markets always gravitate towards mediocrity - The Sun, The Ford Escort, Westlife, McDonalds, the iPod.

Marconi 2LO transmitter
I saw this at the new BBC Broadcast Center - they donated it to Science Museum a couple of years ago but have it back on loan. It is the Beeb's very first transmitter and could kick out a whopping 1.5kW of radiated power! On the right-hand side of the picture you can see four triodes (made by Osram - not just light-bulbs for those boys!) which I'm assuming makes up a dual-darlington type output stage. Aside from that I couldn't remember enough transmitter theory and valve configurations to guess at which bits did what. There is another good page on the BBC's history site.
I noticed that the transmitter was housed at Savoy Hill House on The Strand - a building now occupied by the IIE, my institute.

MTV desks


Today I had a quick trip to Peckham to look at the first of the fifty-odd desks for the MTV install we're currently working on. My main concern was that we could run the fibres through the rear leg without bending them too much - it's all good. I'll post pics of the them when they're all in Hawley Crescent.

Wow - what a horror! I'm linking to Apple.com! This is a systems design and install we did for Molinare over the summer for the Tour De France. Rupert and Graham fettled the SAN configuration with Tony and I doing the fibres. See it all here.
However - don't believe what you read on manufacturer's websites!

“All the systems worked incredibly well. We had a few glitches to begin with but, thanks to the support of Root6, these were fixed very quickly. Reliability wasn’t an issue — we had very few issues with FCP during the three weeks and Xsan performed fantastically”.

It wasn't all that!

"A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, co-operate, act alone, solve equations, analyse a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialisation is for Insects" - Robert A Heinlein

I've tried to take this view of broadcast engineering - a competent engineer should be able to re-head a VTR, rack a studio camera, install the OS & software so as to make an Avid work, repair & colour balance a monitor, line-up an audio compressor and be able to drive AutoCAD.