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! 🍻🍻🍻










Friday, May 17, 2019

A visit to J-Rob's and the Silbatone 755A box by Dr. Stefano Bae

OB/755A


Despite the fact that Joe Roberts and I both revere the 755A, he never thought highly of my open baffle set-up. To this day, I'm still baffled as to why he featured my home-brewer article in Sound Practices. 😉 I enjoy the engulfing planar-like airiness of the 755A/OB combo which Joe finds lifeless, boring and lacking in snap. 


OB + 755A

Could the dip in this RTA trace be indicating a lack of snap? 😜


Custom-built Altec 618 + 755A


J-Rob custom 618 cabinet

  Back in the mid-90s, I owned a pair of original Altec 618s. Those sounded boxy and colored, perhaps due to their lightweight construction. So I traded them for a pair of early sand casted 811 horns...😧 Oh well, live and learn. 😁

When my friend Chong gave me a pair of well braced vintage DIY 618 boxes (allegedly built by an ex-WE engineer and used to house a pair of WE755As), I understood the snap that ticked the Joe-man.


ex-J-Rob Altec 618 + 755A

This is the nicest and most modern looking RTA trace in this survey! Loaded with Altec 755As, the sound is snappy and dynamic while retaining that warm and realistic sheen in the midrange, which evades most speakers marketed in the past 50 years. Although some listeners may still find that quality a vintage coloration...

A visit to J-Rob's


People don't always have to agree to remain friends


Case in point: Joe seems to prefer the Japanese 755 - Lafayette SK98/Hamlin/Pioneer PIM8L - over the ferrite 755C. However, if push comes to shove, I'd take the 755C over the various permutations of the PIM8/20L even if I played a role in reintroducing its virtues to the world. Maybe it's just my sentimental attachment to the 755Cs since they were my very first high-efficiency drivers?

J-Rob sez, "I shouldn't even be talking to you since you like 755Cs." 😆



When I visited Joe in the summer of 2018, he had a pair of 4 cubic foot WE753A look-alike cabs that house Western Electric WE728Bs driven by a spruced up Dyna SCA35 which was recently replaced by a J-Rob cloned Peerless A100 PP 6A5G amp built during the Sound Practices era. Signal source is a Mac Mini>Tidal>Audirvana>Wavelength Audio Brick DAC.

Despite the natural high frequency roll off of the 12" WE728B, it sounded very full-range because of its rich overtones. That is, overtones as musicians use it to describe musical instruments. A high quality violin, piano, or any musical instrument for that matter, possesses rich overtones and this has nothing to do with high frequency extension. Even FFT analyses have failed to identify why del Gesus and Strads sound harmonically richer and have greater carrying power in a good acoustic space compared to a painstakingly crafted modern violin.

I was looking forward to hearing the Silbatone SE300B amp on the floor but Joe hasn't gotten around to re-wiring it for 120V, and also to LPs, but the Gates CB500 was waiting for a resurfaced idler wheel. Then he showed me his next project - Klangfilm horn repros (center background) + Altec and JBL large format compression drivers.



Finally, I was introduced to the pair of Altec 755As perched on top of the WE753C-like cabs. I was quite impressed with the sounds emanating from the 755As!

This 755A/box combo was featured in the Silbatone exhibit at the Munich High-End 2018 Show. Prior to that, Joe spoke fondly about the box and gave DIY hints in this Audiokarma thread. I was hoping that he'd be inspired to update his Junkyard Jukebox blog for a formal presentation of this cabinet design before he went on a sabbatical from the internet.

Since there's no sign that he'll be back anytime soon, with his permission, I took it upon myself to write about this 755A cabinet breakthrough.


Silbatone/Dr. Bae WE/Altec 755A box plan
Copyright Silbatone Acoustics


I re-drew the box plan based on a quick sketch Joe uploaded in the Audiokarma thread. Please note that this cabinet plan is published solely for the Audio/DIY community as a public service of Silbatone Acoustics. 

Under no circumstances should this be used for commercial purposes! 

Let's see if that works...truth be told, I am well aware that there have been a few enterprising individuals who have benefitted commercially from projects published in this blog. So I'm not holding my breath.


John Piro Clone Build
Interior walls + back lined with two layers of Kimpak

I sent the drawing to my buddy John Piro shortly after my Altec 753C cabinets were delivered.



Can anyone distinguish JP's clone from the original Silbatone box? 


Dr. Bae designed Silbatone box + 755A

J-Rob comments:

"The cabinets were designed by genius Silbatone engineer Dr. Stefano Bae as a group project for the Silbatone-sponsored DIY/Western Electric forum in South Korea. 100 pairs were quickly sold out, immediately driving up the world price for 755As. The original uses Silbatone's custom silver litz wire, which is said to be an essential ingredient of the original recipe, and top shelf WBT connectors.

Over the years Silbatone designed and made literally dozens of experimental boxes, including back horns for up to four (755A) drivers per side. This was probably the most successful, although rather modest.

My analysis of this untuned little cabinet is that it falls under the 'small box with a hole in it' design paradigm."



Unlike before when I felt the need for at least SE300B power to make the OB/755A sing, now I'm enjoying near-field sounds from my JP cloned Silbatone/Dr. Bae boxes + Altec 755As driven by an SE46 amp with tiny Noguchi FM6WS Finemet OPTs.



The SE2A3dx which normally drives the Altec 753Cs in the main listening area had no trouble driving the Altec 755As in Silbatone boxes to moderately high SPL levels.

 Even without the silver litz wire and high tech WBT connectors, I heard all the virtues of the slant 618 box + open baffle combined = detail, snap, macro and micro dynamics from the 618 box + airiness and lack of vintage boxy colorations from the open baffle.

The Dr. Bae/Silbatone cabinet transported the 70 year old 755A design to the 21st century in a monitor-sized package!






Friday, May 3, 2019

First Philippine Triode Festival June 15-16, 2019

Makati City, Philippines

Featuring a G.I.P. Laboratory + Harana Audio collaboration

GIP 597A field coil high frequency horn

GIP CH-65 midrange horn + GIP 555W field coil compression driver

GIP 815 = 15" field coil woofer loaded in Harana Audio V-Vent II bass cabinets

+

Flea-powered triode amplifiers built by Filipino enthusiasts and guests from our Southeast Asian neighbors.



The Enablers


more info