(Re)building a Hi-Fi Room

ca. 2006

Eight years ago I vacated this space, not knowing that I would be back someday...

Late Spring 2016

Altec 861 cabinet

Among those that didn't make it into the 20 foot container in 2008 was a pair of Altec 861 cabinets loaded with generic 15" drivers. I used one temporarily to get some sounds going in the room while I figured out how to repurpose the other cabinet.

Amplification

Grommes LJ2

 This sweet "Little Jewel" PP6V6 integrated mono amp fired up with no problems after almost 8 years of silence.

Rek O Kut B12GH + Velvet Touch

My hand-carried Velvet Touch tonearm "blu-tacked" on a ROK B12GH and mounted on a state-of-the-art crate plinth. 

After a thorough cleaning and re-lubrication of the main bearing, Papst motor and replacement of motor mounts, the dreaded motor vibration is still felt on the tonearm finger lift. I have to send the idler wheel to Terry Witt for a rebuild and plan on building a heavy plinth.

Unlike the fussy Rek O Kut, this Pioneer PL6U is running quietly on its original lightweight plinth after I replaced the 3 perished rubber motor mounts with rubber grommets + light cleaning and re-lubrication. It sounds great with a $40 Stanton 500 cartridge!  

Pioneer PL6U

Line-level sources

KLH Model Twenty One

Classic Hi-Fi FM table radio found in a bicycle shop. 

Western Electric 111C
+
UTC A20

Stereo > Mono transformer mixer for the iPod Nano

Hi Eff Speaker

Since the Altec 861 (aka Madrid) share a similar internal volume with the Altec 614, I went to Lowe's to get 3/4" plywood cut to the size of the front panel. Using a Harbor Freight Router + Jasper Jig 200, I cut a hole for a rear mounted Altec 414A and a rectangular 2" x 7" port to mimic an Altec 614.

Altec 2-way

Altec 861 loaded with an Altec 414A running full range augmented on top by an Emilar EH800 horn or Altec 32A horn with an Emilar EA175-16 compression driver.

Work in progress...

3D printed WP12024 horn from Lycan R&R

In late September, I received a message from Trieu of Lycan R&R, asking if I'd be interested in evaluating his 3D-printed prototype pair of multi-cell horns.

Before proceeding further, this blog entry contains a lot of hyperlinked texts to either previous entries or other sites pertinent to the article (e.g. "Lycan R&R" above). Mousing over and clicking those texts will open the link on another page. Thanks!

Design notes from Trieu: "These horns are slightly wider. The original KS12024 has a rather narrow 50° horizontal dispersion. When updated to the 1" driver opening, the wider initial diameter of the of the 1" driver would not allow for the throat geometries to work correctly. I felt the slim vertical profile of the original KS12024 is important sonically.

The best way to maintain it is to increase the horizontal width via a wider angle. So I increased the horizontal dispersion to 62.5° allowing for the proper expansion and geometries of the throat piece. BTW, I used carbon fiber infused PLA filaments."

je2a3 amp

Twenty three years ago, I built my first 2A3 amp in the basement of the very same house I'm staying in right now. This was a pair of PP2A3 amps with a Mullard-Style driver circuit pumping 8W per channel of pure Class A to drive 82dB/1W/1M (in)efficient BBC LS3/5As, with external preamplification.

As I enter another phase in life, I am back in the same house, mellower with age but hopefully wiser, building a single channel, single-ended 2A3 amp with 3.5W output to drive a 99dB/1M/1W efficient Altec 2-way horn system, with a phono and line stage on board.

This project started with a chassis and choke (amongst other things) handed over by Joe Roberts at the Capital Audio Fest last July. Additional parts were either donated by my hamfest/radio show buddy, Chong Ong or ordered online, like the Hammond 272X power transformer, which came from Steve at Angela Instruments. Back in the 90s, I could have built this amp (except for the output transformer) using parts sourced from hamfests and radio shows. But times have changed, sadly for this project, the only parts I got from a hamfest were the tube sockets ;(

I had been exchanging emails with J-Rob regarding the WE/Altec 32, Emilar horns/drivers, ROK idler TTs, viscous damped tonearms, vintage cartridges like GE RPX, Shure M3D, etc. Among the tubes he suggested I try in lieu of my favorite octal 6SL/SN7s and 5-pin 27/37 and 56/76s, which are getting quite expensive, are the Loktal equivalents + the "Mickey Mouse" plate and grid-capped 2C22/7193 med-mu triode.

WARNING: the 2C22 is not for the faint-hearted, there is over 200VDC in the plate cap if accidentally disconnected while the amp is operating!!!

As depicted in the above block diagram, this is classic (nothing new = boring) JE Labs ;) I used 2 x 7B6 loktals in the RCA derived RIAA phono stage sans variable EQ. A stereo > mono mixer via a WE111C repeat coil to process digital sources was integrated into the chassis, then a single medium-mu triode 2C22/7193 acts as a line stage preamp cap coupled to a Radiotron SE2A3 amp.

!!!WARNING!!! 

The voltages found in this circuit can be lethal, build at your own risk!!!

The chassis was painted in Silver Hammerite, but wiring had to wait due to actual music making and more important projects ;)

Fancy-schmanzy boutique parts were not used in this amp - just plain old carbon resistors, paper in oil caps and electrolytics in the tube rectified/choke filtered power supply.

The amp section is currently fitted with a Noguchi PMF-15WS OPT I got in Akihabara. It sounds really good! You just have to take my word for it since I don't have a scope and audio generator to prove it ;)

At a later date I might swap in the PMF-10Ws, but ultimately I'd like to permanently install an American made OPT, maybe an Edcor or ask/beg Mike L. at Magnequest to wind a single TFA204 OPT just to keep the amp an ALL American classic ;)

Time Out

ala  Turk

Altec 2-way XO Redux

This is an update on crossovers I use for the Altec 2-way speakers.

JEL N1600 Crossover

JEL N1600C + HF EQ
optimized for the 802 driver fitted with the original
16 ohm 20275 diaphragm

The above crossover circuit, as discussed in this previous post, was optimized for my cherished pair of green Hammertone Altec 802Ds fitted with the original aluminum 20275 diaphragm, which has an aluminum wound voice coil. To my ears, this diaphragm has a more prominent midrange response which necessitates rolling off the upper midrange/lower high frequencies of the 414A woofer for flatter response.

JEL Universal Altec 2-way XO

For the Altec 802 driver equipped with the 34852 (16 ohm) or 34647 (8 ohm) diaphragms, which have copper wound voice coils, I recommend the 6dB/octave crossover circuit below which is hinged at around 2500 Hz + high frequency EQ boost. This aluminum diaphragm has less energy in the upper midrange giving a tonal balance that sounds more extended in the high frequencies compared to its 20275 predecessor. In this implementation the Altec 414A woofer is connected as a full-range driver inspired by Joe Roberts. 

JEL Universal Altec 2-way XO with HF EQ circuit

Altec 414A + 32A/802/GPA 34852
+
JEL Universal Altec 2-way XO

I've also used this crossover successfully with the Altec 802 driver fitted with the Symbiotik diaphragm, Emilar EA/EC175 and Renkus-Heinz SSD1800/1400. Please take note of the different capacitor values for 16 or 8 ohm drivers.

Simplest Crossover

If you want the simplest crossover, my buddy Joe Roberts listens to his Altec 414A/802/32 set-up with the woofer in full-range mode + a 1.5uf paper in oil cap for the compression driver, no L-pad or HF peaking EQ circuit. See his Audiokarma post for more details.

Shure Mic Transformers

Ben C was hunting for Altec 32s, Emilar EH800s 
and EH500s at Jammin' Jersey

Tipped off by my buddy, Ben C (dude in the middle), I scoured eBay for Shure Mic transformers that can be repurposed for MC step-up duty. These transformers typically sell for under $50/pair shipped within the USA.

They don't have model numbers so I'll identify them based on their step-up ratio.

Primary DCR = 35 ohms and 3500 ohms in the secondary. 

I measured a step up ratio of about 1:17, which suits the Denon DL103 and DL103R well. It can be a pinch hitter for the Ortofon SPU in my system, but ideally more gain is needed.

This unit has slightly less gain at about 1:12, primary DCR = 20 ohms and secondary = 2000 ohms. What it gives up in gain is made up for by slightly wider bandwidth. If I were to split hairs, I'd pick this over the 1:17 model above if I were using a DL103 exclusively.

The tonal balance of both Shure transformers is actually quite similar to the Altec 4722 with just a touch less transparency and authority throughout the audio band. At their present asking price, I can highly recommend these transformers to those who want to sample the delights of listening through a classic Denon DL103 low output moving coil cartridge.

Happy listening!

OJAS 529B Horn

During my visit to the OJAS listening room late last year, Devon asked me to evaluate a pair of horns OJAS developed in collaboration with Lycan R&R. The OJAS 529B is a 500 Hz horn rescaled from the large format Altec 329A for use with 1" format Altec/GPA compression drivers.

  This horn was designed with a throat inspired by the Western Electric 32 horn to avoid the harshness and distortion I (as well as others 😉) associate with the Altec 811 and 511 horns, 

For more details about this horn's evolution and construction, please click here.