Tuesday, July 16, 2019

KS12027 Horn


The KS12027 horn perched on top of my repurposed Altec 861 cabinet loaded with an Altec 414A woofer should actually be residing inside a ~ 4 cubic foot slanted cabinet with a Western Electric WE713C compression driver  bolted to its throat + a WE728B 12" woofer = Western Electric WE757A monitor speaker system.

I was honored to host this KS12027 horn and provide more modest accommodations for a couple of weeks courtesy of my audio preservationist buddy John Piro.


He rescued this KS12027 horn with a damaged 0.7" aperture and repaired/modified it so that mere mortals like myself can sample its delights using a more pedestrian 1" exit Altec 802 compression driver. 

Mono Hi-Fi set up: Neat P58H + Calrad SV16 + GE RPX or DL102, JEL SE2A3 mono integrated amp with Hashimoto H-203S OPT.

All of my listening was done with the above set up.

Altec 414A + mod'ed KS12027 + 802 + GPA34852

From the moment I mounted the KS12027 + Altec 802 combo above the Altec 414A woofer, the first adjective that came to my mind and stuck for the rest of its stay was, natural! Just like its WE/Altec 32 and KS12024 relatives, this is also a horn that doesn't sound like a stereotypical horn. In fact, the articulation (attack and decay of notes) and overall presentation of harmonic overtones via the KS12027 is even more natural and realistic. It made the Altec 32A/32C and Azzolina KS12024 sound merely like very high quality Hi-Fi which mainstream audiophiles may find more appealing. These findings were echoed by my friend Ding during his recent visit to the man cave.

Altec 32C, KS12027, Azzolina KS12024

Even if I loved the KS12027 so much, I didn't want to get attached to something I may never be able to own. So this past weekend I met up with John at a ham fest and handed back this valuable piece of audio history. After giving him my rave report, which is hardly representative of what most audiophiles like nowadays, he was not dissuaded. He is still seriously considering reproducing them. 😎














Monday, July 1, 2019

Darling Amp, JE Labs Style


It's been 20 years since jc morrison started hosting the new york noise audio design exhibition at his Hoboken, NJ loft. One of the highlights of that year's exhibit was Darlingfest '99 as reported by Jeremy Epstein in the final issue of Sound Practices. The Darling amp was the brainchild of Bob Danielak and was published in Sound Practices Issue 15.

Jeremy's octal driven Darling amp made a lasting impression on me but I never got a chance to build my own version due to a busy performing schedule.


While I was organizing my workshop in the basement this past winter, I found power and output transformers from a Sony TC500A tape recorder + other parts to build a Darling amp.  


The chassis cleaned up nicely with a wire brush. Then I drilled, cut and punched the necessary holes before spraying a fresh coat of silver Hammerite.


I chose the 6F5 hi-mu triode with a cool grid cap as the input/driver tube.


To qualify as a Darling amp, the indirectly heated 1626 transmitting triode  output tube is de rigueur.


The TC500A donated a healthy 6CA4 rectifier.


!!!WARNING!!! 

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


My interpretation of a Darling amp is ready for testing and listening!

Bench Testing

Both channels driven



P = V²/L

2.415 x 2.415 = 5.832/8 = .729 or 729mW per channel


Hum and Noise = 1.8mV

100Hz

1kHz

10kHz

I did not expect this level of performance from the cheap looking Sony OPTs, which I also verified while listening to the amp!


Bass extension is surprising from this 3/4 watter! It is deeper and tighter compared to my Tango'ed SE171A amp. However, in the midrange, the true Directly Heated Triode shines. The 1626 was just a touch veiled in comparison. Although it sounds more powerful than the similarly rated SE171A, it also doesn't overload as gracefully. I remember hearing a similar phenomenon when Steve @ Angela Instruments asked me to build the Simple 5691 > EL34 SE amplifier. The Simple 45/2A3 clips with more finesse. Is the cathode causing the relative lack of transparency and harder clipping?


The days of $5 Type 45s and 2A3s are long gone. But NOS 1626 tubes can still be acquired for under $10 a piece. Since it has a cathode, with careful wiring less than 2mV noise is achievable on AC heating which is quiet enough for me even on headphones. There's no need to hunt for hard to find 25-75 ohm, 2W hum nulling pots. That's just a couple of reasons as to why a Darling amp derivative is one of the cheapest and easiest routes to a DIY SET amp nowadays.

Did I mention that it also does a great job driving headphones?

headphone adapter/attenuator schematic for 
efficient headphones ex: Grado SR80, Koss KPH30i/Porta Pro
Lower efficiency/high impedance classic headphones like the 600 ohm AKG K240 Monitor, 
Sennheiser HD420, HD6xx and Orthodynamic/Planar magnetic: Echo TDS-16, 
Fostex T10 and Yamaha YH-1, can be driven directly from the speaker terminals


Happy listening!









Saturday, June 15, 2019

Thrift Store CD Players for Red Book Aficionados

Multi-bit CD players

When I started using and hacking Dynakit tube equipment, they were about 25 years old on average. During that same time frame, I bought my first CD player which was fitted with the Philips cutting-edge TDA1541 16-bit DAC chip. 

Fast forward some 30 years later, SACD and DVD-A have been commercial failures, CD sales have been on steady decline and took a recent nose dive in sales. Except for cool LP lovers and bandwagoners, most people nowadays are either downloading or streaming their music.

So I'm buying cheap CDs unloaded by downloaders and streamers. Stuff I couldn't afford or justify in the 80s and 90s, while hunting for unloved CD players whose lasers may die any time soon...

Yep, I don't go with the flow, I never did... 😉

Sony DVP NS900V

After rediscovering the 16-bit Magnavox CDB 473, I wasn't too keen on acquiring another sigma-delta chip'd multi-player. However, for 1% of its original selling price, this Sony DVP NS900V was an irresistible deal! The fit and finish on this unit exudes quality.

Red Book Mastered CDs decoded by this machine sound polite but lack the excitement delivered by the better multi-bit players below.😒 That's why I didn't bother to take under the hood pics.😜 Maybe the SACD performance is slightly better than the Denon DVD-2910? Even if this is a slower handling machine for CDs, I can use it as a transport when my Philips lasers die. 😉

Shure SV40

Very robust build! The all-metal construction makes this Shure SV40 seem as hefty as the NS900V above. Not sure who OEM'd this unit. I read references to NEC and see traces of Sony in the transport. 

SV40

This Burr-Brown PCM54HP chip'd unit is very audiophile-oriented. The midrange has depth and detail, with a tight and deep bass + extended highs. Even if I'm yearning for more warmth in the midrange, I understand why Burr-Brown multi-bit DAC chips have an avid following. It is well deserved! 

Scott DA952

I didn't want to pay the $7 tag for something that looked chintzy, but then it was a $1 red tag sale day and it had a red tag, so I relented.

YM3020 DAC

The YM3020 is a 16-bit Yamaha chip. A buck got me a dark, mechanical and 2-dimensional sounding player. 😞 Mediocre at best. I should have spent the dollar on a CD instead. 😔

Fisher AD-870

Fisher was acquired by Sanyo in 1975, so I took a chance on this '86 Studio-Standard CD player hoping that it might have a Sanyo LC788X chip which are supposed to sound decent. No dice, it was fitted with a Yamaha Y3015 chip.

Y3015 DAC

Another mediocre CD player. 😞 It sounded bright, mechanical and flat. I don't know what's going on with these Yamaha chips.😖 At least my six bucks went to charity.😊

Magnavox CD2000

This Magnavox CD2000 and its CDB492 twin are entry level models from the late 80s to early 90s. They were manufactured in Mexico, equipped with the CDM-4 transport and the economy Philips TDA1543 16-bit chip, which has found its way in a few high end DACs like the Border Patrol, amongst others. 

Instead of the  "16, 18 or 20 bit, dual or quadruple DAC, 4, 8 or 16 X oversampling" emblazoned on the front panel, this was an understated "16-bit dual D/A converter + Digital Sound Processing" print. I didn't find a Philips SAA7220 oversampling/digital filter chip inside so it's safe to assume that this is a non-oversampling circuit. Based on my internet research, the output stage has a brick wall type analog filter(?). Here's a video of the CDB260 which looks very similar under the hood.

CD2000/CDB492

These machines don't have the ability to resolve detail like the Burr-Brown'd Shure SV40 above or the two TDA1541 players below. However, the midrange is seductive and a fine aperitif to Non-OverSampling (NOS). If you are squeamish about not being in the in crowd, skip this broken/defective design. This is strictly for music lovers!

Magnavox CDB610

I've made it my mission to rescue any 16-bit Magnavox/Philips CD player I find in the wild.😄 This CDB610 was made in Belgium in the early 90s. It has a more upmarket feel compared to the Mexican-made CDB492/CD2000.

CDB610

Even with the SAA7220P/A oversampling/digital filter chip added to the TDA1543 DAC, this machine couldn't sonically equal its TDA1540 or TDA1541 siblings below. Based on sheer musicality alone, the NOS Mexicans above and Sony CDP190 below have the upper hand over this Belgian. However, I'd rather listen to my Red Book CDs via this Belgian than through a time slicing DVD/multi-player. 

Sony CDP190

I found this '89 model Sony CD player along with a pair of Rat Shack Minimus 8s at a thrift store I've frequented for years but never found anything interesting. It doesn't look too promising under the hood. Well, there's nothing there....except behind the front panel.

CDP190

I was surprised to learn that somewhere behind the SMD and SOIC laden circuit board of this early '90s entry level Sony is a Philips TDA1543A DAC chip. The "A" version was exclusively designed for the Japanese input format which is not I2S compatible, unlike a regular TDA1543. Sony did a good job using its in-house chips for oversampling and digital filtering because this machine sounds cleaner than the similar spec'd CDB610.

The midrange of the NOS CD2000/CDB492 + slightly more bottom and top end extension = CDP190!

Sony CDP505ESD aka CDP222ESD

This model belongs to the Sony ES (Elevated Standard) series. In spite of the deluxe parts - Nichicon and Elna caps, discrete bypass capacitors surrounding the TDA1541 chip (instead of SMDs in most Magnavox/Philips) - I don't think this was truly a top of the line model since it was also sold as a mid-range CDP910. Besides, the real Sony ES models I've seen were all metal. Even if this has slightly more heft than the CDB650 above, the chassis is also a plastic + metal composite. It is safe to say that both models were designed to compete head on. Sony used its own CXD1088 digital filter instead of the Philips SAA7220P/A, B or C found in Magnavox/Philips CDPs.

CDP505ESD

Compared to the Belgian made CDB650 below and the CDB473, the TDA1541 + CXD1088 combination renders a clean and clear midrange, tighter and deeper low end response + more extended and airier highs. The net result is a slightly recessed midrange tonal balance. Perhaps this sounds closer to the truth, but I prefer a bit of sugar coating. 😉

Magnavox CDB650

The CDB650 player received a highly favorable review in the March 1987 issue of Audio. A couple of months later, in the June 1987 issueWalt Jung wrote an article on how to make it sound even better. This spawned a cottage industry of modifications to Philips based CD players. The build quality was a notch better than the later CDB47X series, which did away with heat-sink fins for the power supply.

CDB650

IMHO, the "filtered output" was a useless expense. It causes a very audible high frequency roll off. (Did the Philips executives in Eindhoven really think Red Book CDs sounded that harsh then?) The money saved from that filtered circuit could have gone into better quality parts like Sony did above. Used via normal output jacks, this model sounds as good as the later CDB473. The midrange has a three-dimensional spatial rendition the TD1541 DAC chip has become known for + very good extension throughout the audio bandwidth. 

I am preserving the Magnavox CDB650 and Sony CDP505ESD in their original form for posterity since TDA1541-equipped machines have become a rare sight in thrift stores lately!

Magnavox FD1041

First generation 14-bit, 4 x oversampling Philips/Magnavox CD players with all-metal transport and chassis have achieved collectible status. I had to settle for this entry-level, mid-sized player with a plastic CDM-2 transport and a plastic + metal chassis to sample the sound of the first generation Philips DAC chip. 

FD1041

Philips employed 2 x TDA1540 14-bit DAC chips + the SAA7030 digital filter to yield (close to) 16-bit resolution in their first generation machines. The frequency extremes is probably at par with the economy TDA1543 equipped players above, if not better. But definitely not as extended in the frequency extremes nor does it have the ability to resolve detail like the CDB650, CDP505ESD and some of the better TDA1543 chip'd CDPs. Instead, one is rewarded with a glorious 3-D midrange. A certified classic!

TDA1541 + TDA1543

Aside from having produced musical sounding DAC chips, the Philips swing arm laser/transport design was very stable (least prone to mis-tracking) and reliable. As the saying goes in technology, always buy from the original inventors. Philips and Sony invented the CD format and based on this informal survey, the best sound came from these two manufacturers.

Philips Swing-Arm CD Transport

 Unlike classic tube equipment which can be repaired, restored and/or modified, the lasers in these 30-year-old CD players have a finite life. AFAIK, replacements are either very expensive or unobtainium. Be wise and don't gamble too much $$s. 

As enthusiastic as I may seem about Red Book CDs, I believe that this technology never quite equalled the LP in terms of musical satisfaction. I only enjoy it now since the software is practically being given away.












Saturday, June 1, 2019

My FM Tuners


Last February I mentioned being distracted by my favorite FM stations in metro Philly. Here are the tuners I've been tuning with. 😉

Vacuum Tube


Sherwood S-3000-II

This mono FM tuner courtesy of J-Rob got me started exploring the airwaves of the area. It blends perfectly with the mono hi-fi installation in our mid-century-modern themed living room. Aside from MCM aesthetics, it made me realize that there are a couple of noteworthy FM stations in our area, which inspired me to restore my out of commission FM MPX tuners and acquire a few more.😉

Scott LT110B

I acquired this tuner from Angela Instruments while working there as a tech in the early 90s. It was later aligned and tweaked in the workbench of the late Tom Cadawas. When it started having issues pulling stations a couple of years ago, I boxed it up. I recently unearthed it and traced the issue to a cracked solder joint in the antenna terminals. This tuner is the most modern sounding of the three tube tuners - tonally reminiscent of the Yamaha T-2, but with narrower stereo separation.

Dyna FM3

This Dyna FM3 factory-wired sample died during my sojourn in Manila. I discovered that each section of the quad filter capacitor all read "0" uf! After replacing the quad capacitor it performed back to factory specs - darker in timbre than the Scott, similar tonal balance to the Sherwood. A tube lover's delight!

Solid State


Yamaha T-2

Back in the early 80s, I bought my NAD 3020 from a fellow in the NYC metro area who was listening to WNCN on this tuner. It left an indelible mark in my memory since I never thought FM broadcasts could sound that good! Alas, I couldn't afford it then, so when I found this at a flea market, I grabbed it! Radio X Tuners (highly recommended) tweaked it to equal or exceed factory specs. It lacks the tube warmth in the midrange but goes deep in the low frequencies with extended and airy highs. Stereo separation is superior to any of the FM tuners in this survey.

Kenwood KT80

I remember seeing this KT80 tuner with its matching KA80 integrated amp at a closeout sale back in the early 80s at Harvey Electronics' West 45th store in NYC. Slim-line was the fashion statement of the era. It may be a notch below the Yamaha T-2 sonically, but still very listenable.

NAD 4300

I got this NAD 4300 tuner because of the AM section, which, unfortunately, is unlistenable! However, the FM section is pretty good. It sounds at par with the KT80, if not better, in the frequency extremes but not quite in the T-2 class. It offers 8 presets + a tuning knob, which almost feels like a true weighted knob/dial string assembly.

Kenwood KT880D

I almost didn't take the KT880D seriously due to its late 80s digital age/jet black/slim-line styling + modern comforts of preset buttons, auto tuning, etc. My ears can't get attuned to the dry and analytical sound. But I'm keeping this (or not?) because it pulls in the most stations and does the best job of squelching FM background noise/hiss.

Coda


Stellar Labs 30-2435 Omni

All the tests were done using either of these two antennas. The Stellar Labs Omni is mounted on a mic stand while the Winegard HD6010 is in the garage attic. I haven't tried them outdoors because I'm afraid of heights. 😆 

If we play the numbers game, the S-3000-II, LT-110B and FM-3 are no match in terms of sensitivity, selectivity and stereo separation (note: the Sherwood is mono) compared to any of the solid state designs above. Even when properly aligned, tube tuners are prone to drifting. However, tube tuners offer fatigue-free listening and FM background hiss and birdies are a lot easier to psycho-acoustically tune out.

All these tuners would have been obsolete if I didn't live in a metropolis that still offered quality FM broadcasts. Here's to my favorite local FM stations: WRTIWPRB and WXPN! 🍻🍻🍻