The Speaker Spotter – March 3rd, 2016

Posted on March 3, 2016 by jwk

Some interesting stuff on Craigslist in this week’s The Speaker Spotter, a curated selection of Seattle’s local speakers for sale online. As always, Retrovoltage is not affiliated with any of these sellers and you should click through the link to the original post if you’re interested. If a link is dead, most likely those speakers are gone!

Vintage JBL L55 Speakers
$250 in Burien, WA

Just south of Seattle, this pair of vintage JBLs have some cosmetic damage to the cabinets but look to have intact drivers, and will for sure have that vintage JBL sound you can’t find anywhere else. As far as the condition, well…speakers are meant for listening, not watching, anyway!

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Bose 901 Speakers
$325 in North Kenmore

This looks to be a solid deal for a set of Bose 901 speakers, which come with their original equalizer and paperwork. They seem to be in decent cosmetic shape, although with an equalizer that old it probably could use a once-over for the best sound. Series I and II have cloth surrounds, so there are almost never driver issues with these older pairs, too.

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Tannoy DC-200 Dual Concentric Speakers
$425 in Lake Stevens, WA

It’s a bit of a drive, but if you’re a fan of Tannoy it might be worth it to check out these DC-200 Dual Concentric Speakers. Their current owner reports he’s their second and they’re in good condition. I’m not very familiar with Tannoy speakers, other than having heard the name a bit, but they seem to use concentric/coaxial drivers like KEF and some older EV speakers. Looks worth checking out!

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KEF Q65 Tower Speakers
$250 in Olympia

While we’re talking about concentric drivers, here’s a KEF Q65 with a 6×9″ bass driver and concentric mid/tweeter, UK built and ready for bi-amping if desired. They look to have a decent frequency response, 38 Hz – 20 kHz at 91 dB sensitivity. I’m always a fan of strangely-shaped drivers, too.

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Phase Research Transmission Line Prototype Speakers
$140 in Everett, WA

These look interesting, and worth including, since I’m a sucker for anything that’s a one-off, prototype, or just a generally-unloved speaker from the ’70s. These are from 1978 and feature an interesting driver array and transmission line cabinet with rear opening. I wonder how they sound!

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Totem Acoustic Hawk Speakers
$1600 in Olympia

Speaking of transmission lines, if you’re in the market for something a bit higher-budget, these might be a good choice. They look like they’d be a great speaker if you’re looking for something that delivers tight sound, while still having a nice “furniture” look and likely wife-acceptance-factor. Spendy, though!

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ESS Tempest B2 Speakers
$350 in Everett

ESS was and is famous for their “air motion transformer” (AMT) tweeters which are a very interesting electrostatic hybrid design. Plenty about them written elsewhere, but if you’re looking for that kind of speaker in a large bookshelf form factor, this one’s for you.

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Dali Helicon 300 Home Stereo Speakers
$1995 in Tacoma, WA

These boutique-brand speakers feature a 6.5″ woofer, and both silk dome and ribbon tweeters. I bet they’re fantastically accurate while still being smooth in the high end. Great looking finish on these, too. I’d love to give them a listen!

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Carver Loudspeakers
$2000 in Redmond, WA

Haven’t seen enough ribbons and planar tweeters yet? Or maybe your speakers have a small surface area and you’re craving wide open spaces? These gigantic Carver electrostatic planar speakers might be what you need. They look to have two active elements, upgraded ribbons, and each appears to be about the size of your average door. I’ve never heard these myself, but Carver has a great reputation for amps, of which this seller also has many.

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New Bench Storage

Posted on February 26, 2016 by jwk

Some pegboards, and wall mounting some parts bins, really cleaned up the benchtop!

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Posted in Commentary, Photos | Tagged , , | 2 Comments

555 timer teardown (and a Retrovoltage drum trigger project)

Posted on February 23, 2016 by jwk

Ken Shirriff’s blog has a fantastic and detailed teardown of a 555 timer, the ubiquitous decades-old timer circuit that turns up in so many places:

If you’ve played around with electronic circuits, you probably know the 555 timer integrated circuit, said to be the world’s best-selling integrated circuit with billions sold. Designed by analog IC wizard Hans Camenzind in 1970, the 555 has been called one of the greatest chips of all time with whole books devoted to 555 timer circuits.

Given the popularity of the 555 timer, I thought it would be interesting to find out what’s inside the 555 timer and how it works. While the 555 timer is usually sold as a black plastic IC, it is also available in a metal can, which can be cut open with a hacksaw revealing the tiny die inside.

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via 555 timer teardown: inside the world’s most popular IC.

Ken takes us through the history, use, die, and individual transistor circuits implemented on the die on his blog. It’s a fascinating read well worth spending an hour exploring.

I don’t get into 555s that often myself, but last summer Retrovoltage built an LED flasher circuit centered around a 555 for local Seattle band Breakaway Derringer‘s drummer. (They’re a great band that’s worth checking out if you enjoy cowboy punk rock!)

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The 555 operates in single-shot mode, driven by a drum trigger sensor to switch on a TIP31C power transistor supplying power to LED strips.

The drum project was based on an Instructable that he found. You can find that Instructable here…but if you do, pay careful attention to the pin numbering on the schematic, which borders on nonsensical and definitely does not match the physical layout of the chip.

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He’s only using one, but you can do some pretty neat effects with this idea.

Posted in Collections, Commentary, DIY, Gadgets | Tagged , , , , , , | 1 Comment

Antique Radio Shop near Kunming, Yunan, China

Posted on February 22, 2016 by jwk

My friends over at Crimson Lotus Tea sent me this photo of an antique radio shop near Kunming, Yunan in China they ran into during a recent trip.

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They’re stacked to the ceiling in the shadows. Looks like a fun place to explore!

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Building the SSTRAN Part 15 Low Power AM Transmitter Kit

Posted on February 21, 2016 by jwk

Have a bunch of old tube radios, but nothing good on the air in your area? That’s a common problem, and SSTRAN has the solution! I just built one of these to give as a gift, and thought I’d write up the experience. It’s a somewhat complex kit to build with quite a few parts, but if you’re decent at soldering and have some patience, you shouldn’t have any trouble.

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Everything came neatly packaged in a box with a detailed set of instructions. Inside, the parts were kitted out based on their type and which step of the build process they’d be useful.

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The instructions are very detailed, including which color codes you can expect to find on the coded parts, and the assembly steps follow a logical path building up the bare PCB. There are even tips about how to get the best solder joints and soldering techniques on the plated through-hole board.

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One chip, a surface mount IC, came pre-soldered; everything else was for the recipient.

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I followed the instructions, documenting each step along the way. Resistors first:

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Small chokes next:

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Rectifiers and small-signal diodes:

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Next up was the resistor network, a set of 9 x 10K resistors in a SIPP arrangement with a common pin.

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The board is starting to fill up! Next up were the IC sockets. This is always a nice touch – it’s easy enough to put ICs directly on the board if you’ve perfected your technique but can be tricky, and it’s easy to burn up an IC by accident. Sockets make it easy to fix a mistake.

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Jumpers and switches next. Later these are used to set the frequency range according to tables in the back of the manual.

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Next up were the small fixed capacitors:

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Getting there!

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Just a few more parts: jacks, the ceramic trimmer for the output circuit, front panel controls, and some other bits.

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Transistors were one of the last items to finish on the board:

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Followed by big power supply chokes:

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Last was the voltage regulator’s heat sink, and the crystal.

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Time to fire it up!

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The transmitter accepts L+R audio input, downmixed to mono internally, and a power supply; the antenna and counterpoise are also connected via an RCA jack. There are adjustments for audio gain, audio compression, and modulation. These controls interact somewhat, and vary a bit depending on what you’re using to receive, so tend to need to be tweaked for best sound quality once you’ve got the system on the air.

The next step was to tune the output. The construction manual lists an easy procedure to measure a voltage across a set of points while adjusting the trimmer. Here I did diverge a bit to use my spectrum analyzer with a small antenna and measure the output that way, since I had already been using the analyzer earlier.

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Finally, it was time to snap it together into its case:

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All done!

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This was a very straightforward project to assemble, and I expect it should be able to be completed by anyone. It took me about 4 hours to complete this project (stopping to take photos along the way); if you’re on a mission I think it could be done in as low as 2 hours. If you’re pressed for time or are new to the hobby and want to go slowly, it’s easily divided up into steps which you can work on one at a time, a few minutes a day, until you’re finished.

As far as performance, it sounds great playing through a selection of vintage tube radios – just like it’s supposed to! I’d highly recommend this kit if you need a low powered AM transmitter solution for your own collection.

[SSTRAN]

Posted in DIY, Electronics, Projects, Radio | Tagged , , , , | 3 Comments

Retro 1956 Cyclometer VTVM – Hycon Model 615

Posted on February 19, 2016 by jwk

A pretty cool, very rare piece of test equipment turned up on eBay recently: a 1956 Hycon model 615 AC/DC VTVM. This was a precursor of today’s digital, using analog servo circuitry to drive the numeric digit display.

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These were a big-ticket item back in the day:$374.50 in 1956 would have been around $3,200 in today’s dollars, adjusted for inflation!

Hycon 615 ad

Cyclometer drive displays started turning up in the 1930s, and disappeared by the 1960s as direct digital read-outs (numitrons and decatrons, nixie tubes, and later VFDs and LED/LCDs) became available. They were initially used in clocks, with cyclometer meters appearing in the 1950s and lasting for about 10 years. Most turned up in even higher-end lab equipment, with cyclometer displays being quite rare on benchtop equipment.

This would be a great collector’s item, especially if you could get it running again! If the servo motor is good, it should be possible; there’s a schematic over at Hycon Model 615: Radiomuseum.

[Vintage 1956 Hycon Model 615 VTVM Vacuum Tube Voltmeter *Non Working*]

 

Posted in Electronics, Gadgets, Test Equipment, Vintage | Tagged , , , , , | 2 Comments

Building a Better Voltage Regulator

Posted on February 17, 2016 by jwk

Glancing through my feeds, I stumbled across a note on The Paleotechnologist describing a new replacement for the venerable LM7805 linear regulator IC. It turns up in a ton of devices, pretty much anything with a medium-current 5V rail including some stereos, computers, power supplies…mostly anything you can think of. And the old version isn’t that efficient:

Take the LM7805, for example. It does a good job of regulating voltage — from a minimum of about 7V or so, it will provide a steady 5VDC output. The only real problem is that it does this by basically adding a dynamic resistance to simply burn off the excess voltage at whatever current you’re using. If you were to power a 5V, 1A load through a LM7805 connected to 12V, it would need to dissipate 7W of power, since it would basically be acting as a resistor; that 7V voltage drop, combined with the 1A of current, means it would be putting out 7W of heat. Without a BIG heatsink, it would quickly get too hot to work. Also, you’d be wasting over half of the power for the device, even if the rest of your circuit was 100% efficient.

via A Better Voltage Regulator | The Paleotechnologist.

Looks like CUI came out with a new, drop-in 7805 replacement which implements a DC-DC switching converter for voltage regulation, rather than a linear regulator. Way less heat and lost power with this module! I’ll probably spec it in future projects if I end up needing to replace a 7805 in some old gear, looks very interesting!

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The folks over at Hack-a-Day have already found a hobbyist who put this module through it’s paces. Daniel over at Daniel’s Electronics Blog does some bench testing the switching drop-in replacement for the 7805. to test it’s efficiency.

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The graph of efficiency versus load is shown below, the peak efficiency is around 92%. Not bad for a 12V input.

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Not bad for a 12V input indeed, the linear chip would be wasting a ton of power as scorching heat with the same conditions.

The Paleotechnologist: A Better Voltage Regulator

Hack-a-Day: BENCH TESTING A SWITCH MODE DROP IN REPLACEMENT FOR THE LM7805

Daniel’s Electronics Blog: Testing a DC-DC Converter Module

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The Speaker Spotter – February 14th, 2016

Posted on February 14, 2016 by jwk

Another installment of the occasional series “The Speaker Spotter”, showcasing interesting speakers for sale right now on the local Seattle Craigslist. As always, I am not affiliated with any of these postings. If the linked ad doesn’t load, it’s likely the item already sold. If you like what you see, you should contact the seller by clicking through to the original posting.

Soniphase Fully Horn-Loaded Speakers
$1795 in Kent

The seller describes these as similar to Klipschorns or La Scalas, and indeed they look very similar to a K-Horn except a bit narrower, and with a port at the bottom front. 15″ woofer down to 35 Hz without a corner (and lower in one), and treble to past 20 KHz sounds like a good combination to me.

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RTR DR-1 Electrostatic Hybrid Speakers
$1999 in Kent

“These completely unique speakers were manufactured by RTR in around 1980 or 81. They utilize a cylindrical electrostatic element from 350hz/up and an innovative three-woofer bass section from 350/below.” These speakers look unlike anything I’ve ever seen, but I’d love to listen to a pair. Shared without further comment because I’m unfamiliar with the entire RTR line-up – but I’m fascinated.

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Marantz Imperial 6G Speakers
$160 in Olympia, WA

Solidly designed, no-frills speakers, these are pretty efficient and have a 10″ woofer and a phenolic ring tweeter. I’m a big fan of the way the phenolic ring driver manages to sound both clear and accurate, but without any rough edges; any speaker with the ring tweeter is worth a look anyway. The dust covers on the woofers are pushed in but it looks like the grille cloths are intact. Not a bad set of speakers for a starter vintage system.

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Coral BX 2000 Speakers
$175 in Olympia, WA

I’ve always understood Coral speakers to be a great example of “kabuki” speakers which had their driver selection and placement dictated more by aesthetics than acoustics, although some of them can sound pretty good. I’m not sure where these fit into the line-up, but they have interesting fan-shaped diffusers over the twin mids and twin tweeters, and what looks like a 12″ woofer. I’d guess it probably sounds somewhat similar to a Sansui.

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“Speaker Factory” Speakerlab Speakers
$300 in N. Seattle

Speakerlab built great products down to their entry-level models, both kits and manufactured speakers. They were fond of using components fairly similar to what Klipsch used at the time, and used some really innovative designs. By visiting the Speakerlab web site, I found these are Speakerlab 4s. (Page 23) I’m a fan of the Electrovoice T-35 tweeters used in these and many other Speakerlab speakers, I bet they sound great in a mid-sized system.

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Speakerlab Tower Speakers
$200 in Bonney Lake

These are an alternative driver arrangement of the Speakerlab 7s from the looks of it: tall horn mid, EV T-35 tweeter, and pair of 12″ woofers with one being a passive radiator. With the mid oriented vertically, though, I think these would have a very narrow sweet spot. Great to focus on your hifi chair, maybe not so great if these are going to be paired with a stereo system by a couch. Very interesting!

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Speakerlab 7s
$350 in Everett, WA

Another set of Speakerlab 7s, again in a nontraditional cabinet. These are in rough shape compared with the previous set. The T-35 is mounted vertically in this set, with the midrange horn mounted horizontally along the top. Fortunately, the builder set up the T-35s to be directional so there’s a “Left” and “Right” speaker which will allow for adjusting the sound field a bit more accurately.

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Speakerlab K-Horns
$450 in Marysville, WA

This is a set of the later-generation Speakerlab Ks. The earlier generation was a very close clone of the Klipsch Klipschorn, being fully horn loaded. These have a folded horn with either a 12″ or a 15″ woofer, a front-firing 8″ cone midrange, and vertically mounted EV T-35 tweeter. I bet they sound quite good, and could be used in a room a little smaller than the full-sized K-Horns. The prices vary wildly on them, but this seems to be fair.

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“Large Vintage Speakers, Horns & Woofers” 
$300 in Lakeridge

These look really interesting, like they might be a clone of an Altec Lansing of some kind. The woofers need to be refoamed. The owner doesn’t know what brand the drivers are, either. These do look like they’d be a really good project, and you might get lucky with the drivers.

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Microtower MT-1 Stereo Speakers
$35 in Lakewood, WA

Definitely coming in at the bottom end of the price range, I’ve actually featured these before at a slightly higher price. They’re just kind of novel. These are a pair of enclosures with two 4.5″ drivers mounted in the top and a lengthy cavity and port opening on the bottom. Maybe an early type of waveguide cabinet? I don’t think these would win any awards for sound quality, but they might be interesting to listen to.

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Posted in Audio, Collections, Speakers | Tagged , , , | 3 Comments

ARCANE RADIO TRIVIA: Electric Banana

Posted on February 13, 2016 by jwk

Arcane Radio Trivia found a really cool banana-inspired portable record player, allegedly from the Andy Warhol era.

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Plays in any position…even upside down! I’d love to see one of these in person. I wonder how many were ever manufactured in the first place.

I recently found this… Supposedly it was inspired by the work of an Andy Warhol. It’s based on his painting of a banana that served as album art for the Velvet Underground. The Warhol Foundation has reported that it was not officially licensed.  They are rare as you might imagine, but they do have one at the International Banana Museum in Mecca, CA.  The image above comes from an old issue of  the Speigel catalog. Regardless.. one of the strangest record players I’ve ever seen.

via ARCANE RADIO TRIVIA: Electric Banana.

Posted in Uncategorized | 2 Comments

Like Classic Receivers? Check Out This Blog

Posted on February 3, 2016 by jwk

If you’re reading this, you’re probably at least somewhat interested in vintage stereo gear, since that’s a huge amount of what I work on. There’s a lot of it out there! I just discovered a great new blog that showcases a different vintage receiver every few days, with a quick photo summary and some links to more information or to find some on eBay.

ClassicReceivers.com

They’re showcasing a Harman Kardon 330B right now.

Worth checking out!

 

Posted in Commentary, Internet | Tagged , | 2 Comments