Hands On with the Antumbra Glow

October 2, 2015 2 comments

Remember a few years ago how Philips paired one of their flat-panel TVs with some image processing and colored glow tubes along the sides to make your video blend into the wall behind it? I was always fascinated by the concept, but those TVs were astronomically expensive at a time when I was a student without nearly as high of a gadgets budget as I have today. Others have done some work to replicate the concept, but every implementation I’d seen until now was very hacker-friendly, and very consumer-unfriendly. We’re talking flashing your Arduino with downloaded open-source code and wiring up some hardware yourself.

Clearly, there had to be a better way. And it turns out, someone was working on it.

Back in early October of 2014, I apparently made a small impulse purchase online: a pre-order for the Antumbra Glow. I say apparently because I’d completely forgotten about it until it turned up in my mailbox a little while ago in an unassuming, tiny package. (Then it sat around for a little while longer, because I was rearranging my furniture.)

That’s it! A USB cable, a module only a little wider than a quarter across, and a business card with a URL to download the software.

I like minimalist packaging, so this got my attention right away – they’d have been hard pressed to go any smaller, that’s for sure.

Sleek and a little hard to photograph, it’s a nearly completely featureless white square with one opening for the cable, and a tiny high brightness LED mounted in the center. There’s a dime-sized velcro dot on the back ready for you to peel and stick to your mounting location on the back of your monitor or TV. The setup, at least on my Windows PC, was absurdly simple: download the software, install in about 30 seconds, plug the Glow into the PC, and fire up the control app.

The software itself isn’t flashy – it’s just straight and to the point. Unfortunately I don’t have any screenshots available for that part to show it in more detail, but you can turn the lamp on or off, set the color manually, pull the color from whatever is displayed on screen according to one of 3 methods, or cycle through various ambient color fade effects. A few solid colors below, but the coolest part is that it will display the color matching whatever’s on the screen, making the video effects blend into the wall behind it.

All in all, I’m floored with how well this thing works right out of the box. Hardware start-ups are always more challenging than software start-ups, and this one looks like it was launched by a team who were at the time (and may well still be) college students.

It’s not perfect, but it’s a great little product. The app supports multiple attached Glow devices, too; I find that a single Glow in the back center of my 46″ LCD doesn’t always light up quite as much as I might enjoy.

My one complaint was a very early version of the control application used a massive amount of CPU power (a full 25% of my 8-core AMD FX-8350) but that’s all fixed now. Works great on Windows 7 and 10.

All in all, it’s absolutely worth the $35 with free shipping it costs to get one.


The Speaker Spotter – September 30th, 2015

September 30, 2015 1 comment

It’s back! Another installment in this occasional series, “The Speaker Spotter”, picking out the most interesting speakers available on my local Craigslist. Today’s Speaker Spotter focuses on bookshelf speakers for the best sound possible in a small package. As always, I’m not affiliated with any of these sellers, and if the ad is gone then it’s likely the speaker sold already.

Here’s what’s interesting this week!

Bose® Direct/Reflecting Speakers – Model 201 Series II
$40 in Lakewood, WA

Bose doesn’t get a lot of love in audiophile circles, but I’m a pretty big fan myself, and these 201 Series II speakers are back from the era where they devoted a bit more to quality engineering than many of their products do today. I’ve heard various sets of 201s myself, and they provide a great room-filling sound with pleasant tone characteristics, as long as you don’t expect too much volume or earth-shattering bass.


Boston Acoustics CR-8 Speakers
$100 in Port Townsend, WA

Boston Acoustics is a venerable audiophile speaker brand, and these little 2-way bookshelf speakers designed for 15-125W of power can deliver a pretty great 90 dB efficiency and should give a great, detailed sound. Some people find them to be a little bright, though – I prefer a bright sound signature personally, so that sounds right up my alley!


Pioneer CS-33a Vintage Speakers
$149 in South Everett, WA

Pioneer vintage speakers are nicely well regarded, and these feature those beautiful latticework grilles they’re known for. Great looking shape for a speaker that was built in 1971! They’re very efficient but only accept up to 35W of output power, so proper amp pairing is a must with these.


Tannoy Revolution R1 Bookshelf Speakers
$150 in Shoreline, WA

Tannoy is a well-known British hi-fi brand, and their speakers are top notch, from their flagship Westminster GR on down. These little speakers support bi-amplification and deliver 87 dB sensitivity at 8 Ohms, and I expect will sound fantastically accurate for any music source. Nice under-stated design and cherry finish, too!


KEF 101/3 Reference Speakers
$199 in Lynnwood, WA

KEF is another UK speaker brand, with a very interesting time-aligned coaxial driver system to help these speakers present as more of a point-source, which can reduce certain kinds of phasing distortion you’d get from separately positioned drivers. This gives them a cool, monolithic design – although they, too, support bi-amplification just like most higher end speakers. They’re 6 ohms nominal, but that’s not a problem for many amplifiers these days, and they’re middle of the road efficient at 87 dB 1W*1m.


Heco Phon 3 SF Speakers
$200 on Snoqualmie Ridge

These vintage German hi-fi speakers are a bit of a mystery. They look to have an interesting 3-way design, and the labeling indicates they’re 4 Ohm impedance speakers for 60-100W of power handling. Beyond that, they’re a bit of a mystery! Looks like this could be an interesting addition to any speaker collection.


Polk Audio RTi A1 Bookshelf Speakers
$205 in Seattle’s Crown Hill neighborhood

Polk Audio’s offerings go down pretty far into the economy side of the spectrum, but their higher end offerings are quite good, and these RTi speakers are a respectable offering. They’re 89 dB efficient and offer extended treble frequency response to 27 kHz. Looks fantastic in the beautiful cherry finish, too! These routinely sell for around $300, so this is a pretty solid deal.


ERA Design SAT 5 Bookshelf Speakers
$350 in Kirkland, WA

These are interesting little high-end bookshelf speakers. Nominally 6 Ohms ant 87 dB efficient with a long-throw 4″ woofer and horn-loaded 1″ dome tweeter, I expect they sound extremely crisp and efficient, and with that woofer design punch above their weight in the bass department – and High Fidelity Review agrees! Looks great in piano-black, too.


JBL L-96 Bookshelf Monitors
$500 in Kirkland, WA

Anyone familiar with vintage speakers knows JBL and knows how great they sound. Recently re-foamed, these should be in good shape for decades to come. They’re pretty efficient at 89 dB, and the titanium dome tweeter provides incredible clarity and detail in the upper ranges. So much so, in fact, that people often turn the treble down a bit. A great addition to your collection if you’ve got the room and the cash!


Like what you see? Click through to the ad and contact the seller!

Check Out LED Filament Light Bulbs: Classic Styling Meets High Efficiency

September 29, 2015 2 comments

I’ve been using CFL bulbs in most of my light fixtures for a number of years. They’re a pretty solid, mature technology by now and have a ton of benefits over classic incandescent and even “eco-friendly” halogen bulbs. Where a 60W incandescent bulb might put out 800 lumens, and a halogen might use around 45W for the same amount of light output, CFLs offer the same light output from only around 15W of power. Lower waste heat has been a big goal in my lighting choices, since I live in an apartment which has very high heat retention, and lower-heat bulbs made a real difference.

One of my CFLs started making a buzzing noise after a few months, though, and when I pulled it for inspection I found a major hazard. The top had come separated from the base, leaving the guts fully exposed which had started to vibrate!


That was a pretty dangerous failure. I pulled that one from service and replaced it (look for an article a bit later where I trace out the circuitry). I’ve been reading a bit about the new “LED filament” bulbs which combine the even greater efficiency of LED lighting with the classic filament look of the old-school incandescent bulbs, and so I ordered a few to try out.


They’re pretty cool looking. It’s not quite the same as an incandescent (you can barely see the wires in those style of bulbs, these have visible tubes) but it’s pretty close. These are made possible by a new “silicon on glass” manufacturing method. The silicon LEDs are “printed” onto a glass substrate, which is then dipped in an epoxy resin coating to diffuse the light and provide the correct color balance. It’s a great way to get LED efficiency, when you need a light bulb that’s a bit more aesthetically pleasing than the chip-tower design:


LED filament bulbs are incredibly efficient, too, only a tiny bit less so than a “standard” chip LED unit.

They’re made by a wide number of manufacturers by now, in the USA, Japan and China. I ordered a set of Chinese bulbs from eBay for myself, but they’re on Amazon as well. The Chinese ones are a bit cheaper, although Internet sources report the Chinese bulbs use a type of epoxy which becomes brittle after several hundred hours of operation – so if you find yourself moving your light bulbs between fixtures, or you’re using them in a mobile application, you might invest in a US or Japanese variant. The bulb I showed above, consumes only 8W of electricity and puts out 850-900 lumens, making it even more powerful while still being more efficient. eBay seller “torylee2013” has a good reputation and sells many styles of LED filament bulbs direct from the factory. They arrived in about a week and a half, with free shipping, too.

CrystalLED has a great “how it’s made” video, well worth a five-minute watch:

All in all, I’ve been very satisfied. They’re only slightly warm to the touch even after hours of operation, and look great. The one downside, though, is they do strobe a bit. It’s not even slightly noticeable in general, but it does give the blades of spinning fans a bit of a slow-motion effect if I’m looking for it. Nothing that I consider a problem!

I’ll be moving forward to replace all of my CFL bulbs with LED filament bulbs over the next few months I’m so satisfied.

LED Filament bulbs on Amazon

LED Filament bulbs on eBay

torylee2013’s eBay store

Sherwood S3000-V Stereo FM Tuner Repair

September 28, 2015 2 comments

From the Rain City Audio Repair Blog:

This Sherwood FM Stereo tuner came into the shop recently. It’s owner successfully completed a re-cap of the unit, but the specialized tools for performing an accurate FM Stereo alignment are beyond the reach of most hobbyists, and so he sent it into my shop for final adjustments to make it perfect. The owner reported it worked well on mono, but the stereo light never illuminated, and the dial tracking was a bit off.

The owner had done a good job on the re-cap, with nice clean joints, replacing all but the two output electrolytic caps.

Initial measurements validated the alignment; in mono it was receiving at about 1.6% THD.

Up first was a mono FM alignment, adjusting the cascode RF amplifier, oscillator, and IF chain to bring all the tuned circuits into proper adjustment, improve dial tracking, and center the tuning meter.

After those, and several more adjustments on the bottom side for the lower cores, distortion dropped off to around 0.05% under ideal conditions.

Unfortunately, there was no action on the stereo circuit even when fed from the Sencore SG80 generator. I spent some time tracing out the circuit to understand what’s going on:

One common problem on this style of tuner is that if the stereo indicator lamp has failed, the entire rest of the stereo circuit won’t operate. In this case, the lamp is a NE-2H neon bulb, which can lose its neon with age and fail to strike.

Swapping in a new bulb was the first step.

Success – now the receiver responds to the 19 kHz pilot signal!

Time to finalize the alignment, including the 19 Kc, 38 Kc coils and transformers, the 19 Kc null, and separation adjustment.

The 19 Kc null serves to remove residual 19 KHz audio from the final output signals. It’s adjusted for lowest 19 Kc level which provides proper stereo response.

All set! The indicator light correctly responds to stations transmitting in stereo, and there’s about 10 dB of separation between channels. Much more often just isn’t possible on a tube MPX design. All in all, it sounds great!

Categories: Uncategorized

Vintage Documentary: How Stereo Turntables Work

September 2, 2015 Leave a comment

Documentary Tube on YouTube has digitized an excellent early video documentary discussing the newest hi-fi invention of the time: stereo! In this 4-minute video, the narrator compares mono with stereo recordings on vinyl. Worth checking out!

Adding Capture to a Vintage Scanning Electron Microscope

August 31, 2015 Leave a comment

Applied Science over at YouTube has a great video about adding a capture capabilities to a vintage scanning electron microscope, including some great videos of that instrument in action. Check it out:

Creek 4140 S2 Overhaul and Voltage Conversion

August 23, 2015 Leave a comment

From the Rain City Audio Repair Blog:

This Creek 4140 S2 amplifier is a bit newer than most through the shop, although it’s getting up there. This particular one was constructed in 1989, and came via eBay from the UK configured for 220V power. The owner wanted it checked out and converted over to a U.S. power supply.

It’s an unassuming little amplifier, delivering 30W per channel at 0.1% THD. Inside, it’s pretty simply built but very clean. The shop has a universal power transformer that accepts nearly every plug style in both voltages, so it was easy to check out. The amplifier “worked”, although you had to crank the volume all the way up to maximum – the signal was getting attenuated along the way but it was still passing all the way through.

Because of the small number of capacitors in this unit, I recommended they all be replaced, and found that two of the small signal capacitors had gone very low in value towards being open. With the capacitors replaced, the unit came to life on 220V just fine.

The owner supplied a 120V transformer for this amplifier to swap. Theoretically, according to the schematic, the transformer has a split primary which can be wired in series or parallel for either voltage, but in practice there was no sign of the extra taps, so it was just a direct swap-over.

Transformer leads are enameled wire, which needs to be scraped down to the bare copper in order to take solder. Then the leads were joined back to the same colors.

Finally, it was time to swap the plug with a U.S. fitting.

Time for some testing! The Creek 4140 S2 is rated for 20 Hz – 20 kHz, with 0.1% THD at 1 kHz. How’d it do? The Audio Precision System One analyzer gave some insight. Frequency response from 20 Hz – 20 kHz was flat +/- 1 dB, which is fantastic.

On the extended range frequency response test, the actual -1 dB point was at 20 Hz on the low end and 30 kHz on the high end; +/- 3 dB at 10 Hz and 60 kHz. The channels are slightly imbalanced, even after bias adjustment, but not enough to worry about tracking down.

The amplifier delivered < 0.07% THD at 1 kHz, and overall had acceptable distortion performance.

Quite a few parts came out of this one!

A listening test proved this little amp sounded great, and so it was time to clean up and send it home.


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