Adapter required for Euro L-1000T

The European Kenwood L-1000T (and I get the feeling that most of them sold in Europe, as FM was out-of-fashion when the fantastic L-1000T was introduced) requires this particular adapter, or so it seems right now:

PAL Male to F-Connector (Coax) Female
Radio Shack #278-261

"PAL adapter" for short.

Unfortunately, after adding a second adapter to the B input, the B input still cannot be selected.  I'm not sure if this is because I don't have the correct remote, I was thinking it would auto-select the B input if stronger, but I couldn't find any station where that happened.

Remote Control for FM in every room

When my 4 day Chrismas holiday began, I had only one remote for controlling my wonderful Kenwood L-1000T FM tuner, and it only worked in the living room aimed in a very tricky way at the actual L-1000T because of how it is tucked behind the speaker.  I had to reach and wave the remote until it finally worked.  I did have a learning programmable remote control that I had never gotten to work, and another brand name programmable remote still in it's packaging.  Without remote control, it's is not desireable to scan FM channels but rather simply to keep it fixed to just one favorite, which can get boring particularly over a Christmas holiday...

Now I have easy remote control of the L-1000T in the living room, and in the bedroom and kitchen as well, through my network of remote control extenders.  Remote control extenders receive a remote control infrared signal in one room, send it via radio signals to another room, and then transmit the infrared signal toward the equipment that is to be controlled.  Most of the ones I use are from Radio Shack and they are small black rounded pyramids with short antennas.

And now I also have two working remotes, one being the Sony RM-VL610 learning programmable remote that had never worked before (now I can't find the unopened one).  I've spent much time listening to different stations in bedroom and kitchen.  With just one control, it is almost always in the wrong room, but with two remote controls I can have one in kitchen and one in bedroom, so they are always there, I don't have to remember to carry it with me.

The trick was finding the instruction manual to the Sony learning remote, and successfully getting it to learn the L-1000t remote codes.  Even with the instructions, it was tricky because the instructions themselves are not very clear in parts.  It's often unclear when you simply press buttons as opposed to holding them, or vice versa, and when you are supposed to let go.  In fact, in one particular case, you are supposed to hold a button, and the manual just says "press" and not "press and hold" but if you read to the end of the section, in the Notes section it tells you that you are really supposed to "press and hold".  Actually, it works either way, most of the time, which makes things even more confusing.

Once I had programmed the remote, which I was doing in the kitchen, I found it worked through the kitchen wireless remote receiver.  And then I tested it using the bedroom, and voila, the programmable remote actually worked better in the bedroom than the actual Kenwood remote.  So I could use the Kenwood remote in the Kitchen (or living room) and the Sony in the bedroom.  I then found I could program buttons on the Sony to control the HDMI switch in the kitchen (something that I had tried but never been able to do before) and also the Samsung TV in the bedroom (another thing that I had tried but was never able to do before).  So I'm on my way toward being able to use this programmable remote to control many things, making bedroom remote control life in bed far easier.

One other thing I had to do before I made any progress was to re-orient the remote control transmitter in front of the L-1000T.  The current orientation of the L-1000T and the remote extender are shown in the photo above, the remote extender is in the lower left corner on top of a pile of collectable Allied Radio catalogs which boosts it to the correct height.  Sometime in the past few weeks I had been trying to remote control the L-1000T directly, thinking the remote extenders were not letting me get at all the obscure functions.  So I had angled the L-1000T badly for the remote transmitter so it was not working at all.  So I had to do a lot of fiddling with the angle of the Kenwood and the angle of the remote transmitter to get it to work again.  It mostly didn't work from the bedroom, but it did work from the kitchen, after much fiddling.  I tried attaching a bunch of tie slips to the antenna on the transmitter to make it work better in the bedroom, but that approach didn't help.  I was finding I could use the Kenwood remote in the bedroom so long as I as standing right next to the bedstand light in a particular spot.  As inconvenient as this was, at least it verified that the remote control extenders were working correctly.  It took using the Sony programmable remote for reliable and easy bedroom operation.  One can guess that the Sony programmable remote puts out a higher signal level than the Kenwood remote, and that makes it work better through wireless extenders.  Or, perhaps it puts out a "clarified" signal with exaggerated on/off edges, the kind of thing you get when you use a "sharpness" control on some TV's.

A learning programmable remote is absolutely required for this application.  Programmable remote controls with a bunch of presets never or almost never have settings for extremely rare components like the Kenwood L-1000T tuner.  But since preset types are much easier to use than learning types, preset remotes have mostly driven learning remotes off the shelves.

making more of the L-1000T

In the early hours of December 24, I finally hooked up the Lavry AD10 digitizer to the Behringer DEQ 2496 which applies EQ correction for my European L-1000T.  I used a Monster Standard 8 foot optical cable.  With that digital connection, I was able to bypass the inferior digitizer at the input of the Behringer itself, and therefore enjoy the benefits of the better Lavry digitizer in other rooms, when listening to the L-1000T remotely using my Sonos system.  It also allows me to select the L-1000T in the living room without having to change the EQ mode of the DCX crossover, which can also perform the EQ correction, and yet still enjoy the benefits of the Lavry front end.

The benefits of this change seemed clearly audible in other rooms, which previously could not enjoy the benefits of the Lavry at all.  In the living room, I could previously, and can still, listen straight from the Lavry into the AES input of my Tact.  When I listen that way, I have to get up and turn the EQ mode of the crossover from OFF to ON.  That setup still seems to provide the last nth degree of performance, seeming to have slightly better incredibly real 3D imaging.  But it's a pain to get up and turn the EQ mode of the crossover on and off, far simpler just to switch inputs on the Tact, where I can select the digital output of the DEQ as input.

As compared with using the digital input of the Behringer, using the Lavry provides an especially musical sound, with utterly transparent but non-electronic sounding midrange.  By comparison, the Behringer has a slightly etched sounding midrange that sounds like hifi reproduction, not real music.

It's funny how (or if) I can hear this even going through a second level of digitization in the Sonos system itself.  Sonos lets me listen to line inputs from every room having a Sonos box.  The Sonos line input must be an analog input, which is then digitized to 44.1khz by the box and transmitted through digital signals on the CAT-5 cables that connect all rooms in my house.  Each other Sonos box can pick up this signal and play it back through a digital output which gets fed into the Tact preamps in living room and bedroom, and the Yamaha HTR-5790 receiver in the Kitchen.  When listening to the L-1000T in the bedroom, for example, here is the chain of connections:

Kenwood L-1000T source, using variable output adjusted to within 3dB of Lavry dynamic range

6 ft Radio Shack RCA cable

dB systems selector switch with Teflon jacks

0.5 meter Cardas crosslink cable

unbalanced-to-balanced adapter plugs

Lavry AD10, which samples produces optical digital output at 24/96

Monster Standard 8ft optical cable

Behringer 2496 DEQ programmed to correct European 50uS to 75uS (slight treble shelving)

Balanced-to-unbalanced audio adapter plugs

6 ft Radio Shack RCA cable

Sonos 80 analog input in Living Room

CAT-5 cables and switches

Sonos 80 digital output in bedroom

Blue Jeans digital coax connector

Tact Preamp digital input

...Behringer DEQ for EQ and DCX for crossover

Parasound HCA-1500 power amp

Revel M20 monitors

SVS 1642 plus subs (connected to DCX)

Yes, it goes through all this stuff, but mostly in transparent digital.  With the Lavry at the front end, it all sounds so good you could imagine a direct analog electronic connection to the original source.  The fact that it's all going through a second level of analog-to-digital conversion in the Sonos 80 is not audibly apparent.

The Lavry and Behringer are connected at 24 bit 96 kHz digital.  When I'm listening in the living room, I can either select the Lavry directly from the Tact, or connect to the optical digital output of the Behringer--in which case the Behringer is being used in pure digital mode, with digital input from the Lavry and digital output to the Tact.

I bought the Monster Standard 8ft optical cable at Radio Shack a few weeks ago.  It has a sticker on the plastic case it came in saying "E-Z Open Package."  It was easier than some, but still a big pain.  It took a fair amount of torque to get the back plastic panel of the package to tear off, and as it was tearing off tiny pieces of plastic and paper (from the E-Z Open sticker itself!) flew off.  I had to wipe down my leather chair afterwards to brush off the specks of plastic and paper.  And then, the package still didn't open enough to remove the cable ends, which were held behind a second plastic panel.  After many attempts, I finally got the second plastic panel to tear off, removing the cable ends, and without tearing the cable apart.  Once again, this produced tiny bits of plastic flying through the air, but this time I was no where near my chair.  Then, the cable itself was held together with a soft plastic wrap that did not tear or easily unwrap.  I had to use the tiny scissors from my Swiss Army knife to gut the plastic strip without damaging the cable.

This is a HUGE contrast to what was a truly easy open plastic package, the package that my $400 list price Nordost Baldur balanced cables came in.  It did indeed snap right open, and without apparently producing tiny bits of plastic and paper,   And the inner plastic retainer panel was then held in with friction and could easily be pulled out or put back.  Once opened like this, the Nordost box was re-useable.  The cables were held together with soft re-useable velcro tape.  In contrast, the Monster box now fully pulled apart is clearly a piece of trash (having a very vague resemblance to the jaws of a shark) featuring rough edges that you never want to see again.

Aside from the considerable difference in list price, another feature of the Nordost cables is that they are made-in-the-USA.

And then nothing beats the ease of opening Cardas cables, which come in a large but very heavy duty ziplock style bag.  Also made-in-the-USA of course.

Somehow when you pay the extra bucks for a true premium made-in-USA cable, you get nice packaging as part of the deal.

One of the reasons I had been slow in making this change, was that I often like to keep the Kurzweil K2661 keyboard connected to the living room system, also through the Lavry.  If I have the keyboard selected in the living room, as I often do, I couldn't listen to the L-1000T without going into the living room and changing the selection on the dB systems selector switch.

Well I decided that it would be OK to listen to the K2661 through the less high quality line input of the Tact, which has 16 bits of resolution according to Stereophile.  Note that the balanced output of the K2661 first goes through a Jensen ISOLINK transformer to change to unbalanced.  With that connection, unfortunately, I have to turn the volume way up because the output is apparently quite a bit lower than the 1.6V max input of the Tact with most program.  I'm thinking of putting another line amplifier in between, such as the Classe CP-35 I am not currently using.

Test Patterns

Here is a discussion of analog and digital video resolution and links to test patterns.

The pattern I used  pattern seemed to show 525 line video resolution in 480i displayed on my Samsung 40 inch 550 series LCD monitor displayed in 16:9, using Mac Mini mini DisplayPort output through component video adapter into Sony RDR-HX900 which serves as analog video selector, then into a DVDO which converts to digital at 1080i, thence to HDMI throughout my house.

I was thinking 525 was a limit but it's actually 540.  But quite possibly 525 is more practically achievable.  Anyway, this is quite good for a 480i component video display.

I did find that reducing sharpness to zero or at least below 10 gave the best display on the Samsung.  That is what you generally find with digitally perfect images.  "Sharpness" doesn't add real resolution, it only adds artifacts which appear like resolution with a very lousy picture.

But hooked up this way, there was visible jittering in the top 1/10 of the picture.  The jittering was not very visible from a distance, but appears to make picture softer.

HDMI handshaking

Well I've often wondered what HDMI interfaces actually do in the seconds that it takes for them to make a new connection.   Here's a great discussion:

http://www.hdmi.org/CEDIA2011/6-QuantumData-CEDIA_Seminar_[Compatibility_Mode].pdf

Here's the book, literally, on HDCP.

Here's a little Gefen EDID echoing device for solving problems like the one I had putting video from MiniDisplayPort onto my HDMI switch. (I just now bought one.)

Here's another discussion of HDMI troubleshooting at a high technical level.

The Artifacts

The artifacts I see from the Mac->Belkin->Monoprice->Sony->DVDO hookup described in last few posts, as viewed on my Samsung, are clearly interlacing artifacts, specifically the artifact known as combing.

http://www.neuron2.net/LVG/interlacing.html

This might or might have nothing to do with the Apple and it's output, which I have suspected is far from perfect, in 480i.  But perhaps there is nothing wrong with the Apple 480i at all.

In fact, I have another bit of evidence, this combing grows and shrinks over time, perhaps a second or so.  This suggests a possible ground loop in the connection between the Sony and the DVDO.  This would not have changed with the new Mac Mini (which, like the laptop, has two prong power connection which avoids ground loops).  Maybe...it was previously there and I just never noticed it before.

That wouldn't necessarily explain the added softness I seem to sense compared with the S-Video output of my Titanium Powerbook.  Though perhaps I didn't pay enough attention to that before to compare fairly.  I do know that on still images especially the DVDO upscaling (as with most upscaling) gives a smoother, film-like quality compared to the brisk sharpness of 480i.

Though, I may have improved that a bit by adjusting the Underscan control in the Mac Display Preferences. Funny I did not see this control at first, and I was aggravated that it wasn't there.  Because it wasn't there, or I overlooked it, I spent more than an hour fiddling with the adjustments on the DVDO to no avail.  (For some reason, with 1080i output, the DVDO was not able to apply this underscan effect to compensate for the monitor overscan.  The Zoom and similar features could only expand the image, not make it smaller.  And changing from 16:9 and 4:3 didn't help either.

This puts more of the image on my TV screens (I've adjusted it now so you see everything) and thereby shrinks the image a bit, which makes it seem like better focus.

Still much room for improvement, and I still think the Powerbook display at 480i was much better.  The digital output to component that I am using now should be about 50% better still than the S-Video hookup, but it seems like the opposite.

I need to get some test patterns I can play through the Mac.

Better than expected: L-1000t over sonos

I have been listening to Kenwood L-1000T tuner, which is physically located in the living room, in other rooms using the "line input" feature of my Sonos system.

Currently this is hooked up like this:

Kenwood fixed output->Behringer DEQ 2496 (fixes eq)->Sonos box
Sonos box->system

Thus it goes through two complete analog-to-digital and digital-to-analog conversions, one inside the Behringer DEQ, and other within the Sonos system.  The latter uses 44.1Khz sampling at 16 bits.  The Behringer uses very good 96/24 converters but has rather mediocre analog circuitry.

Anyway, it sounds nice in the bedroom, and very nice in the kitchen.  I was really enjoying listening to college radio on Monday night.  Even with all the intermediaries involved, it sounds even more lively (rhythm!) than the Marantz 2130 which is actually in the Kitchen.

So here's something which shouldn't be that good, but actually is.  Actually I think digital-to-analog and analog-to-digital conversions are relatively harmless for audio.  Experiments have put 100 such conversions back-to-back and still the differences are not large enough to show up in blind testing.

I could actually hook this up using the Lavry for conversion rather than the Behringer, and I hope to do that soon.

More thoughts on the mediocre standard definintion video

I'm absolutely sure that I have seen better Standard Definition (480i) video than my Mac is now producing through the Belkin adapter (to get HDMI) and the Monoprice adapter (to get analog component).  It's very soft looking, and if I get up close, I can see weird artifacts.

480i done correctly can be a beautiful format.  It ways all most people ever knew in video until about the year 2000.  For 10 years I was the proud owner of a $3299 list price Sony TV made in 1997, a 32XBR100.  This was probably the best NTSC-only TV ever made.   It did not support any extended format features.  It did not do progressive scanning even.  But it did a perfect job of decoding NTSC from either composite (!) or S-Video inputs.  The composite inputs were decoded by one of the best Digital 3D Comb Filters ever made.  (I think the one in my later 34XBR960 is also very good.)  The 3D comb filter eliminated interlace artifacts.  In 2008, when I got a very nice 550 series Samsung 42" LCD to replace it, I was extremely disappointed that it could not eliminate interlace artifacts (from component video inputs) as well as the 32XBR100 had.  I then bought an ancient Faroudja de-interlacer (which originally sold for $15,000) and a DVDO scaler to get back what I once had.  But neither of those were as good as the Sony was either.  Neither of those expensive converters actually has a 3D comb filter.  But the DVDO is a nice unit and I still use it today to digitize analog sources onto my digital TV network.

And don't get me started on LCD vs CRT.  LCD has lagged for years the dynamic range, bright-to-dark, of old CRT sets by a country mile.  LCD has no problem with bright, but it has a problem with near-black, the so-called "shadow detail."  With fancy LED lighting schemes, LCD may be finally catching up.  I don't buy TV's often, so I'm not quite sure how good they are now.  People I talk to generally don't get that LCD is not the same as high definition.  It's just that they both came on the scene at about the same time.  And almost nobody has seen CRT TV's as good as the "XBR squared" models I have had, the 32XBR100 and the 32XBR960.

But now that we have High Definition TV, few if any manufacturers do a decent job with Standard Definition anymore.  I think that's basically the problem here.  They just can't be bothered to do it well anymore.  And they might say that nobody demands it anymore.

The 480i component video I now get is not nearly as sharp as the 480i S-Video I had been getting from my Titanium Macbook Pro, made in 2003, which had an S-Video jack right on the side.  That was also going through the DVDO adapter I am still using now.

 So where is the problem now?  I doubt that anything bad is done by the Belkin adapter which converts mini DisplayPort to HDMI.  It looks to me like this is not a conversion at all; the display port is simply carrying essentially the same lines as an HDMI cable.

It could be that there is a bandwidth limitation in the Monoprice adapter which converts HDMI to Composite Video.  But since this adapter is capable of 1080p, you would think it would have no problem with 480i.  And the box says it has 10 bit converters, that should be good too.  Many early DVD players, even the most excellent ones (like my $1500 Sony DVD-7000), had only 8 bit converters.

I have a suspicion a lot of loss is occurring in the Mac itself, via a very lossy 480i codec.  Actually, I just read this website explaining video codecs, and 480i is not a codec.  But 480x720i is a codec, and that is the one being used.  Video codecs are usually at least a little lossy.  I suspect one of two things (or both)

1) Apple didn't much bother to make a best-possible 480x720i codec.  After all, who uses that anymore?  They can't be that critical if they are still using such an old (the original) format.

2) Apple didn't want to make a good 480x720i codec.  Standard Definition video is the one video source that can be copied by all VCR's and most other video copying devices.  My Sony RDR-HX900, one of the last consumer video recorders Sony ever made, only accepts interlaced inputs in Standard Definition.  While not all electronic manufactures have interests aligned with the movie industry, none of them want to offend the movie industry either.  And one way they do this is by not making it easy, in fact making it increasingly hard, over time, to copy video, any kind of video, even when there is not active copy restriction system like HDCP in effect.  Manufacturers remember how Sony was sued by the movie industry (and Sony now *is* the movie industry, or at least one of the biggest players) for making the Betamax which could be used to record broadcast TV and movies.

3) Apple softened the 480x720i codec specifically so it would not look as bad on standard definition displays that have lousy comb filters.  Actually, only "composite video" in standard definition even needs a comb filter.  Neither S-Video nor Component Video require a comb filter.  But just in case someone might be using composite video, after all what does anyone do with 480i anymore, the codec is softened to reduce artifacts if viewed through a composite video connection.

If indeed the problem is the lossy codec that Apple uses in the Mac, I'm not sure what I can do about that.  Basically nothing unless I can find a better replacement version, which is unlikely, I am afraid.  Now in theory I could have the Mac output 1080p, and have some other device downscale to 480i.  But guess what...nobody makes scalers that downscale to 480i !!!  Or at least I have not found one.  It seems like converter makers also follow the written and unwritten rules to make 480i less and less available.  My DVDO will produce 480p (even from a 1080p source) but will not produce 480i.

But it's also possible the main limitations are in the Monoprice HDMI to composite adapter.  And in that case, I can simply use another adapter.  I will do that very soon.

Trouble and success with mini DisplayPort

On Saturday and Sunday I continued watching video through the mini DisplayPort using the 8 foot Belkin HDMI adapter.  It worked OK, but the images looked very blurry, up close you could see obvious jagged-edge type artifacts.  It seemed like I could adjust UP the sharpness control on my Sony XBR-960 TV and Samsung LCD to make it better, similar to what has been claimed on web.

This is curious because what what sharpness controls do is actually distort the picture by boosting high video frequencies, similar to the use of the Treble control on old hifi equipment.  This doesn't actually increase true resolution, it lowers it actually, but might have an objectively beneficial effect if the source has excessive high video frequency rolloff.  Has Apple somehow pre-compensated for old analog sets when it makes connections at 480i. since such sets were frequently set with high "sharpness" control settings?  Or did they just use an especially lousy 480i video codec?

But another question was why, in this setup, I was being restricted to 480i.  There were no copying devices hooked up to the system.  HDMI goes first to a 5 way switch which is about 2 years old.  Then it goes to a 4 way splitter that is about 5 years old.  All of this handles 1080i perfectly, in fact that's what it often does.  In fact it even handles 1080p, except my 2005 CRT TV does not.

Somehow, when DisplayPort sees this HDMI switch, it refuses to engage any resolution higher than 480i.  No other devices have had that problem.  I tried re-hooking, different inputs, and powering up and powering down, and fiddling with the Display preferences, but DisplayPort has decided that you have a 480i device, you only have NTSC and PAL resolutions to choose from.

I disconnected the computer, keyboard, display, mouse, and cables and took them to the bedroom and hooked directly to my 1080p Samsung TV.  THEN the display port had no problem doing 1080i or 1080p, directly to my TV.  I tried both the Belkin and Rocketfish adapters, and they worked identically in this setup.  I normally use the Rocketfish Mini DisplayPort to HDMI adapter in the bedroom with my bedroom macbook pro.

So I brought the computer and stuff back to the living room, and tried using the Rocketfish adapter.  Once again I could only get 480i.  Since the two adapters behaved identically, I think the defective "intelligence" is actually in the DisplayPort itself.  After going back to the Belden adapter, and after lots more fiddling, I was stuck with no visible output just as I had been on Thursday night.  In the worst cases, the Display preferences don't even show a second display connected.

One of my theories is that mini DisplayPort is paranoid.  It agressively downrezes to 480i if it sees anything "fishy" on the output as part of it's copy-prevention protocol which goes above and beyond HDCP.  Even just an HDMI switch can engage this feature.  Apple does says that you can use the DisplayPort output with one adapter, and no more.  A switch is not an adapter, but still enough to give DisplayPort fits.  (This theory is a bit inconsistent with my later successes, read on.  Perhaps the DisplayPort is paranoid about the wrong things.)

It's also possible that something on my video network is reporting back it's capabilities incorrectly.  But since all my other 1080i devices on the switch work fine in 1080i, I think I can fairly say that the mini DisplayPort is not acting as switch (or splitter) friendly as true HDMI components.  Thus I am not surprised at all that Apple doesn't make an actual HDMI adapter.  They may know their interface is bugged, and it may be bugged deliberately.

So this was not looking well for connecting miniDispayPort to my Sony RDR-HX900 video recorder.  That connection through the Sony was the way I used to view the computer output, as it also conveniently switches in some other 480i components, with all of them, including video stored on the Sony itself, getting converted to 1080i with my HDHO adapter on the output.

But in fact, I hooked the mini DisplayPort to a miniDisplayPort to Component Video adapter (interestingly no longer advertised on the Monoprice website, but I found it searching on Amazon) and it worked fine.  I got clear 480i direct into my Sony.  I could select 480p, but then the Sony output went dark.  I checked the Sony manual and found that while the Sony allows 480p output, it only allows 480i input.  So this is the best I could do with any adapter.  Actually, the display preferences in this case let me select up to 1080p...the Monoprice adapter works with 1080p even if my old Sony does not.  I was also able to play back videos I have downloaded from commercial erotic websites also, with no problem.  I did not try playing DVD...I have little doubt that would not work.

And most strangely, the video even looked better this way.  The jagged edges were gone.  It's possible the image doesn't have any more resolution, in fact it might have less, but I think it looks better somehow (no side by side comparison possible now).  Possibly it's because the Sony decodes 480i better than most things.  Then the Sony output goes through an Anchor Bay DVDO to generate DVI, which gets adapted to 1080i into my HDMI switch.

So after this weekend, I cannot claim not to be a happy camper.  For years I resisted upgrading my Mac fearing that I would loose my old video setup.  Now I have my old video setup back, working fine*, and it looks about as good as before if not better, driven by a computer that doesn't strain (and often crash) under the load of YouTube video like my old one did.  Technically, my old Powerbook setup used S-Video and this new one uses Component, so it could be slightly better even, and I think it does look better now, despite the earlier lousy looking 480i on HDMI.

(*The hard drive in the Sony RDR-HX900 needs replacing.  The old one keeps old recordings, but won't keep new ones.  I bought a replacement harddrive a few months ago, didn't replace it when it seemed like the old harddrive was working again, but then I found it would not keep new recordings.)

It would still be good to have a direct Mac connection to my video system through HDMI at a higher resolution than 480i, then I could watch web videos at higher resolutions than 480i.  I never had that capability before, but I can see it would be nice.  Though I fear the limitation may be with the Mac DisplayPort, my positive experince with a component video adapter bodes well that a possibility still exists.  Perhaps there is some kind of communication problem with my video network that the Mac is sensitive to, but could be fixed with a gadget like the one sold by Geffen which forces a particular description of display capabilities onto the HDMI line.