Dan's Data letters #113
Publication date: 25 June 2004.Last modified 03-Dec-2011.
Born free
Is there such thing as a wireless adapter for existing, wired headphones? I have a great pair of Sennheisers, but I do get annoyed by the cable every once in a while. Can a wireless adapter be bought that plugs into the headphone jacks on the headphones and on my sound card?
Lochlan
Answer:
Yes, such adapters exist, but as far as I know none of them are consumer products.
The cheap and nasty option is to use a little FM transmitter (like the ones that let you tune into the output of your MP3 player with your car stereo; these things have been around for a long time, and every electronics store has a $10 kit to make one), and a portable stereo as your FM receiver. That'll work, and with a decent transmitter will give you music all the way out to the back fence, but it's pretty low-fi and will inevitably suffer from reception problems.
The other end of the quality spectrum are pro "personal monitor" systems, which are like wireless mics in reverse - you wear a belt pack with an antenna and a headphone socket, and into that socket you can plug the 'phones of your choice. These systems can be genuinely hi-fi (though they aren't necessarily), have diversity antenna systems that can deal with industrial RF noise levels, are built like tanks, and are pretty expensive.
Shure's PSM systems are good examples. The starting price for the base PSM 200 setup (including transmitter, one receiver, and some perfectly good in-ear 'phones that you don't necessarily want) is around $US700, though dodgier dealers may have it for less.
AKG's current base model is a couple of grand US.
This, obviously, leaves a gap in the market for a $US200 consumer version with a bit less range, a bit less toughness, fewer features, et cetera. As far as I know, though, nobody's filled that gap.
(If anyone out there knows of an affordable hi-fi wireless headphone adapter that isn't built into a pair of headphones, tell me!)
Distributed computing
I want to run a laptop in our car, with the screen detached from the main part of the laptop so I can mount it on the dash and have a cable running to the "motherboard", etc, which will be tucked away somewhere. Can this be done? Is any special type of cable needed? I'm hoping for about 1.5 metres between the two.
Shannell
Answer:
No, you probably can't do this. Laptop RGB ribbon cables often have very restrictive maximum length limits - like,
one foot - because the hardware at either end can be simpler if it doesn't have to worry about much wire. Laptop hardware
in the glovebox and a display on the front of the glovebox, or up on the dash above, might be possible, but you can
forget about a normal VGA-lead cable length.
Of course, you can use a regular desktop LCD monitor with many laptops, or with more normal PC hardware (one of those tiny Via Epia boards would do).
Baby book-reader
Having recently purchased a Franklin eBookman for the paltry sum of 70 Aussie monopolies, it soon occurred to me that it wouldn't take long to spend more than that on batteries for the damn thing, so I went out and bought some rechargeable AAA NiMHs. Having a bit of a look around for the highest capacity I could find, I was surprised when that turned out to be only 850mAh. Surely there must be higher capacity than this. If AAAs can reach 2000mAh and beyond, then surely they must be able to manufacture higher capacity AAAs than this? Right?
It also got me thinking about the advantages or lack thereof of alkaline rechargeable technology. I am not sure on the drain the eBookman has on the batteries, but would alkaline rechargeable be a better choice, or are they only good for circumstances where 1.5V per cell potential is mandatory?
Nathan
Answer:
AAs have so much more capacity partly because of their size, and partly because of supply and demand.
AA NiMH cells are likely to be about 14.2 by 50.5mm in size - which adds up to about 8 cubic centimetres in Geometry Lesson Land. In the real world, the plastic wrap around the outside and the positive terminal assembly on the end and the metal casing all around the cell eat a significant amount of the volume. Energizer have a nice PDF-format cross-section of a cylindrical NiMH cell here.
AAA cells are about 10.4 by 44.5mm - that's only about 3.8ccs, less the same kind of overhead. AAAs have a bit less wrap and a bit less casing metal, of course, but they're still not going to manage more than 3.5ccs of internal volume, versus maybe 7.5ccs for AAs.
From those numbers, you'd expect AAAs to have about 47% of the capacity of AAs. But, as you say, they don't; the best AA NiMH cells these days have 2300mAh capacity, but the best NiMH AAAs have only made it, as you say, to 850mAh. That's about 37% of the AA high water mark.
D cells have the same sort of shortfall. They're about 33 by 61mm, which gives a rough-guess volume of more than 52ccs, with proportionally less of that volume taken up by overhead.
The same rough guess would, therefore, give D-cell capacity about 6.5 times that of AAs, but that hasn't been achieved. 9Ah NiMH D cells are commonly available, but that's only about four 2.3Ah AAs worth.
Which is where the supply and demand part comes in. There's a lot of pressure to make higher capacity AAs, because the AA cell is far and away the most popular single power source for all kinds of small-but-not-minuscule gadgets. AAAs are much less popular - the teeny-cell market's being eaten up by custom lithium ion packs - and things that run from C and D cells generally already run long enough from old cells, much less the current generation. It's AAs that have really needed to be beefier, so it's AAs that the research and development's been focussed upon.
Regarding rechargeable alkalines - forget 'em. Anything that runs OK from regular alkalines will run OK from rechargeable alkalines, but I've written about their problems before. Their fatal flaw is that they don't like being run flat. Unless you need their low self-discharge (they won't go flat on the shelf very fast, unlike NiMH cells), they're therefore not very appealing; you have to charge them about as often as you'd have to charge NiMHs.
That's not a lens...
How's this for a piece of photographic artillery?
What's up with the specifications, though? They say this thing has a "10X-30X" zoom lens. What the heck does that mean? Don't most people start counting at 1?
Steve
Answer:
First up: The above-pictured camera does indeed look pretty butch, but if you want a camera that you really
shouldn't be seen to point at the President of the United States of America, you can't go past the old
Zenit Photosniper. Delightfully, they still
make
them!
Anyway, international photographic non-brand Kowa Prominar (who seem to mainly be a telescope and binocular company these days, though their old medium format cameras remain moderately popular among people who dig such vintage gear) has apparently been threatening to release the TD-1 digicam for a while. The TD-1 is, as you might suspect, not a general purpose camera; it's for people who want at least a ton of telephoto, with the option of two more tons.
The weird "10X-30X" zoom specification indicates that the TD-1's zoom lens starts where most 10X-zoom digicams leave off. Further, actually; its 35mm-equivalent zoom range is apparently 450 to 1350mm, and most 10X-zoom cameras only go to something like 380mm equivalent, at most. So the TD-1 only really has 3X zoom, but its widest angle setting is rather more telephoto than even most 35mm-camera telephoto lenses can manage. A 300mm lens on a 1.6X-focal-length-multiplier camera like my EOS-D60 is 450mm-equivalent.
The problem with profound zoom, except of course for the fact that this camera is going to be utterly useless for most normal photography, is keeping the darn thing steady. The TD-1's lens manages a respectable f2.8 at its widest setting and a good-for-this-length f4 at maximum zoom, but the TD-1 only goes to a miserable ISO 200 sensitivity, so any fantasies you may have of hand-holding the thing in less than pretty good daylight can be discarded right now, compadre.
There's a basic rule of thumb that says that you can't get a sharp hand-held photo with any exposure time much longer than one-divided-by-your-35mm-equivalent-focal-length seconds. 50mm? 1/50th. 100mm? 1/100th.
So at 1350mm-equivalent you need an exposure of 1/1350 of a second, or faster.
You'll get that at f4 and ISO 200 on a pretty bright overcast day, but you won't be able to pull it off it in any weather if you've taken your TD-1 into the woods to hunt wildlife. With normal night-time indoor light levels, ISO 200 f4 exposure times are going to be more like one second, so you'll need not only a tripod but also a subject that doesn't feel like moving. The TD-1 does apparently come with a cordless remote shutter release, though.
The TD-1 also only has a three megapixel 2048 by 1536 maximum resolution, so its monster zoom isn't quite so impressive when compared with a mere six megapixel camera, which'll do something like 2832 by 2128, if it's got the same 4:3 aspect ratio as the TD-1. Crop out a 2048 by 1536 rectangle from the middle of a 2832 by 2128 frame and you've "zoomed in" by a factor of about 1.4. A camera with a 1350mm-equivalent telephoto and a three megapixel sensor is equivalent to a six megapixel camera with a 975mm-equivalent lens, or an eight megapixel camera with an 850mm-equivalent lens, all other things being equal.
And then, of course, all other things aren't equal. The Kowa camera may have a really good lens that puts it significantly ahead of, say, an EOS-10D with a 300mm lens and a 2X teleconverter (if that doesn't seem to add up, remember to factor in the 1.6X multiplier that the smaller-than-35mm sensor in the 10D gives, and pay attention, 'cos I'll be asking questions later). Or it may not. And it may have a top-class image sensor and well-tuned firmware backing it up. Or it may not.
In any case, if it's actually going to cost $US2000-odd, this thing'd better be pretty darn special. That kind of money will buy you a six megapixel EOS-300D with its bundled not-too-awful 18-55mm lens for general purpose photography, and one of Sigma's surprisingly un-dreadful 50-500mm zooms (800mm-equivalent on the 300D, so better than eight-tenths as much real total zoom as the lower resolution TD-1 manages, assuming equal lens and sensor quality), and leave you rather more than $US100 change for a cheesy tripod and/or remote shutter release cable. OK, the Sigma lens can only manage f6.3 at full zoom, so it'll need about 2.5 times as much exposure from other sources to match the f4 TD-1 lens, but the 300D delivers quite clean results at ISO 400 and isn't very grainy even at ISO 800, so that solves that problem. And the 300D's a proper digital SLR that you can stick any number of other lenses on, not a single-purpose spotting-scope-with-memory.
At half the price, the TD-1 would be a niche market sensation. For two grand US, unless its optics and sensor are stunningly terrific, it's just a novelty.
Also: Yes, I did notice this on Kowa's main page.
Change my pitch up
I found this Web page and as a musician and a man who knows everything, I was wondering what your opinion is on it?
Greg
Answer:
I don't have perfect pitch (though, like pretty much everyone
who can carry a tune, I've got OK relative pitch perception), and although these David Burge ear training courses
(one for absolute pitch, one for relative pitch) have been around for a long time,
opinions differ on whether they've
got much value.
The courses are unquestionably rather hard work. People have reported taking many weeks to get through all of the tapes (it's eight CDs for the perfect pitch course, today; back in the tape days a certain amount of scorn was heaped on the notion of teaching absolute pitch via a wobbly, warbly cassette player...), so you could easily run out that 40 day guarantee they offer. The perfect pitch course also, apparently, really needs you to have a friend handy to play notes for you for some of the exercises, which is a bit of a limitation. You can get ear training software from other vendors (including for free, online); that lets the computer handle random note and chord playing, so you can learn solo.
Perfect pitch can be a handy thing for a musician to have (depending to some extent on what instruments they play), but it's hardly essential; being able to name-that-note and sing a given pitch on demand, after all, isn't much more than a party trick. Many people who have perfect pitch are annoyed by it as much as they're helped - if, for instance, they watch one of those movies that's been converted from 24 frame per second film to 25 frame per second PAL video by just speeding it up by 4.2%.
(I confess to having deliberately messed with such people's heads by tweaking the tuning on my keyboard from A=435Hz to A=445Hz while playing something.)
In any case, there are lots of other courses and software applications aimed at improving pitch perception. The Burge courses are not necessarily the best.
110V ones and zeroes
I recently bought a Furman power conditioner in order to get rid of the popping that my desk halogen light makes in my powered monitors. It seems to do the trick, and yes, it is probably overkill for my fledgling studio, but it was reasonably affordable.
Anyhow, there are eight outlets on the back panel of this device, with four of them labeled as being for "analog" devices and four for "digital" devices. The extent of my devices are the speakers and a mixer, which I've decided classify as analog. My next big purchase will likely be a MidiVerb4, which looks to me like a digital device.
My question is: What's the difference? Is there one?
Andrew
Answer:
It's far from certain that there'll be any difference at all, but the distinction is not just snake oil. Gadgets with
high-clocked digital circuitry and/or inexpensive switchmode power supplies can send more noise back down their mains
cables than simple analogue devices. The extra filtering on the conditioner's "digital" sockets isn't there to protect
the digital gear from anything; it's there to protect everything else from the digital gear's noise. They've presumably
just put an extra low-pass filter on the "digital" sockets, to stop any kilohertz-and-above waveforms being passed
back through them to the transformers.
As I said, though, there's a good chance you'll never hear a difference, no matter how you plug stuff in.
Eat At Joe's!
I love your site, but I just had to bring to your attention the fact that the top banner on your front page is (at least for me, right now) a University of Phoenix flash ad with really irritating sound. (Like all ads with sound aren't irritating.)
Now, I'm not sure if this is the kind of banner you're soliciting, but it doesn't seem to fit into the "scheme" of the rest of your banners.
If I'm just nitpicking on something you don't mind there, hey, don't mind my single voice of bitching and/or moaning...your site is still great. Keep the articles coming.
Chris
Answer:
Annoying ads? Nope, don't see 'em!
I fully support ad-blocking of all kinds; I sure as heck do it myself. I'm not too proud to take money for the various (and, as you say, sometimes rather peculiar) Burst Media ads on my site, and my actual personal sponsorship and affiliate deals are different - but they're just text links and peaceful static banners, not the annoying kinds of ads.
If you don't like the other ads, then you ought to block them, as I do. I'm not one of these site owners who gets all snippy about people "freeloading" by having the temerity to load an HTML file without loading all of its embedded elements.
