My GameboyZero - build no. 1

I've been building a little RaspberryPi-in-an-old-Gameboy project for running lots of old console and handheld games. RetroPie is a superb project that unifies all of this and makes it very easy.

See my first video here.


3.5" Analogue Composite LCD 
https://www.amazon.co.uk/gp/product/B0056WJP1M/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1
3w Class D audio amp: 
http://www.ebay.co.uk/itm/111792407939?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT 
SudoMod: 
http://sudomod.com/game-boy-zero-custom-parts-guide-part-1/
Wermy:
https://www.youtube.com/channel/UCRP1Zx7B4b66ZwkB2Ov5pMw 
Great Scott! 
https://www.youtube.com/watch?v=_MtN_s4tVK0&t=4s

LUTs are sometimes not the answer.

As I often tell people; a LUT can only reduce the dynamic range of a display. For the most part that needn't matter, particularly if you have the whole of the DCI-P3 (or a decent chunk of Rec.2020) in your monitor. Applying a look-LUT to simulate a delivery style is one thing but increasingly people see LUTs as the first answer to monitor calibration rather than getting the display to as close-as-possible before profiling/creating a LUT. Hugh and I did a podcast on the subject.

A problem I've recently discovered with a monitor's internal Rec.709 LUT is that although the monitor has a huge gamut in it's native mode (which you can see from this recording of ChromaSurf's output) but the 709 presets have trouble.

Notice how it can reach a full green value of 0.1879, 0.7317 (Rec.2020 calls for 0.170,0.797); you'd think there would be absolutely no trouble getting Rec.709 right, and in fairness the primaries are fine. BUT, when I use both primary and secondary colour ramps;

I wind up with some distinctly funny looking banding in the secondary colours.

On this 'phone photo it is particularly noticeable in the yellows, but it's there in the cyan and magenta ramps as well. The fault isn't there when the monitor is in native mode (or indeed P3, NTSC or EBU), only Rec.709 (ironically the only colour space we really need for TV!).

So, I'll have to profile it in native mode and spin a 17-point 709 LUT as the one from the manufacturer is clearly got problems.

Another way of stress-testing a LUT is to use the TrueColor LUT stress test image.

Power supply toroid in Mackie SRM450 PA loudspeakers

A friend brought one of these very common PA powered loudspeakers over to the workshop. An internal T4A mains fuse had blown and when I replaced it and re-powered there was a very loud 50hz hum for a few seconds and the fuse in the power cord blew. I assumed it was the audio path that was making the noise and I assumed that one one the probably faults was a short/open de-coupling capacitor that was letting 50hz through to the audio stage.

I found the schematic at Mackie-SRM450 actspk.zip (although this is for the rev.C of the board, but the PSU appears not to have changed).

So - I made sure both fuses were good and with Dave Jones's words "thou shall always check the rails" in my ears I disconnected the output of the large toroid from the two rectifiers/smoothing caps and tried again. I figured I'd make sure the o/p of the transformer was good (there is some de-coupling on the primary). However I got the same loud 50hz for a couple of seconds and one of the fuses failed. The toroid was also noticeably warmer than it had been! So - checking the DC resistance of the primary side showed it to be less than six ohms (so it was pulling an inrush of at least 40A!).

A quick flail around the web showed that the transformer is a known weak point of this design.

 The real bummer is that the transformer isn't stocked by Mackie (or indeed anyone else) and the folks at Save My Light only do a minimum order (ten pieces) from the Chinese factory that wind them when they have enough orders (and the chap there told me he sells an average of two a year).

So, do I just wait or pay him the thousand quid to have ten made?!

Time to keep my eye on eBay for a hopefully working second hand replacement?

UPDATE 16/01/2017: 

So after lots of flailing around the web and finding a few reclaimed ones for more than £150 I came across AJAudio on eBay (Alex Mathew sales@ajaudio.co.uk was super-helpful) and he sold me one for £99.
Job done.

For info - the failed toroid had around 5 ohms DC impedance across the primary whereas the replacement has 8.5 ohms.

It's been shaking the workshop with loud music all afternoon!

My favorite rockumentaries of all time

1. "Still Bill"
   The film follows the life of Bill Withers, from his roots in West Virginia to his career in the United States Navy, to his famed musical career and post-retirement family life.


2. "Sound City"
   In 1991 Nirvana recorded the album Nevermind at Sound City Studios. The band's drummer Dave Grohl was inspired to create the documentary after he purchased several items from the studio, including the Neve 8028 analog mixing console, when the studio closed in 2011.


3. "Muscle Shoals - the greatest recording studio in the world"
   Documentary film about FAME Studios and Muscle Shoals Sound Studio in Muscle Shoals, Alabama.


4. "Oil City Confidential"
   
   A film by Julien Temple about the early days of Dr. Feelgood, Oil City Confidential, premiered at the London Film Festival on 22 October 2009, and received a standing ovation.


5. "Pink Floyd; Wish you were here"
   
   The film gives an extensive insight of concept, recording the songs and designing the album cover. It includes exclusive interviews with almost every key person, who participated in producing the album. It is the second Pink Floyd documentary by Eagle Rock.


6. "You've got a friend; the Carole King story"
   
   In her own words, the story of Carole King's upbringing in Brooklyn and the subsequent success that she had as half of husband-and-wife songwriting team Goffin and King for Aldon Music


7. "Classic Albums; 'Damn the Torpedoes' by Tom Petty"
   http://www.bbc.co.uk/programmes/b00x7chg
   

HDR for Television; HLG, DolbyPQ etc - a primer

I have been such a poor blogger! It's been a month-and-a-half since I set finger-to-keyboard but I have been busy at work and home. Here is a presentation I gave at the Soho Screening Rooms for one of Root6's Tech Breakfasts.


You can download the notes from root6.com.

HDMI, HDCP and SDi out from Bluray players

It's been a few years since the master HDCP key escaped into the wild and so it seems that particular content protection system is fundamentally wounded (if not dead!) but reputable manufacturers still respect the HDCP flag (even if no encryption is present) and the MPAA are still issuing device keys to manufacturers and volume keys to content producers.

So - I have been installing some Oppo Bluray players (nice, high end machines) and they support HDCP rather too aggressively; on a non-compliant display you don't even get the boot screen or any menus! So - an SDi converter is out of the question. 

The usual trick is to use one of these cheap'n'cheerful HDMI splitters which present a device key to terminate the signal but then send it to two outputs having done the decryption. 

Works perfectly with Backmagic HDMI->SDi converters with the exception of the audio; the Blackmagic knows nothings about DTS+ or DolbyDigital (or any of their variants) - it only understands the basic PCM stereo part of the bitstream and so that's what you get in the SDi stream.

However - in the case of these Oppo 103D players they have decoders on board and present the de-compressed audio out of the back as good old analogue feeds;

In these rooms I've fed them to the analogue inputs of the Tektronix WVR8200 test set and hence by selecting a different audio input you can toggle the TC Electronix ClarityX controller between 7.1 from the Avid and surround sound from the Oppo.

New grading room - a few notes.

I've been building a Baselight room recently - the monitor is a Sony X300 UHD/HDR display (expensive!) with an AKA custom grading desk. Here are some photos;

All courtesy of my colleague & pal Graham McGuinness

1. The X300 is a heavy beast at 16Kg and if you want to hang it off a monitor arm - the only one I found suitable was from Novus; we've bought a few things from them recently and they are a very high quality manufacturer. The TSS-range is here but we tend to purchase from our friends at MW/ThinkingSpace as they hold stock and are super-helpful.
2. The X300 out-of-the-box was a tad hot in 2k mode (they distinguish between rasters as 2k/4k - not HD/UHD; just to keep the DCI film snobs happy!). I was expecting the EBU recommended 100Cd/m² but was 125 Cd/m² and a bit blue-in-the-whites, but not enough to bother adjusting unless you were pointing a probe at it! So - this one is correct for rec.709 but the customer (hasn't yet) decided what their wide-colour-gamut and high-dynamic-range workflows will be.
3. I had my friend and carpenter Tony Andrews (Andrews Construction - for all your carpentry and building requirements!) built the lightbox. In the past I've talked about Crown Plain Grey 5574 Matt Emulsion as being suitable for the backwall, but that's now a discontinued paint and so an excellent match is Delux's "CN8 Grey Steel 3".
4. Display Port monitors and Baselight-1 - so running Baselight v.6 on an HP Z840 means you have a four display-port output nVidia card. Historically they would prefer you to use DVI monitors, but this is 2016 and a pair of HP Dreamcolor 27" monitors are being extended via Amulet (my favourite KVM extender). In this case you need to have Filmlight provide a new version of xorg.conf for X to see higher order monitors as primary and secondary GUI displays. 
5. The Blackboard2 control panel is fed over a DVI adaptor hanging off port 2 of the nVidia. Be warned! It runs at a very funny raster (3460 pixels wide!?) at only 15 FPS. It doesn't respond to EDID requests and so consequently you have to use a very simple extender to run it to the suite - no KVM-over-IP, just a fibre balun (I used one of these).
6. Similarity the USB for the Blackboard declares itself as an HID device but then ignores HID-probes, so again, only use a balun to extend the USB, no over-IP.