JE Labs

Monday, February 8, 2021

Happy Birthday Mommy!

Picture of me and my Mom taken by my Dad

My beloved Mom would've turned 87 today.

She was a very loving, dedicated and supportive wife, mom, and grandmother!

Mommy with her youngest grandchild

Mommy completed a Bachelor of Science Degree in Education, major in Math.

She also loved music and played the piano.

While teaching high school mathematics, Mom took music courses that would lead towards an Associate's Degree in Music Education. Meanwhile, Dad had just returned to Manila from post-graduate studies at The Juilliard School and got appointed as a faculty member at the same music school where my mom enrolled.

That was the beginning of their beautiful and idyllic love story!

That's me, the first of four brats!

Our Family, early 80s

Dad and Mom's 25th Anniversary
December 1983

90s Family Pic

Mom and Dad's 50th
wedding anniversary, 2008

Mom and Dad, Feb. 8, 2014
Mom's 80th birthday

Dad and Mom's 56th

wedding anniversary, 2014

Mom
May 2015

Mom and Dad's 58th
wedding anniversary, 2016

Christmas 2016 was the last time the family was together.
Tish and I flew back to the USA on January 23, 2017.

Sadly, Daddy left us on May 23, 2017.

Mommy joined Daddy on January 23, 2021.

We sorely miss you, Daddy and Mommy, but we're very happy you're together again!

Friday, January 22, 2021

6C8-G

I've always found tubes with grid caps fascinating. 😉

I've been evaluating a project using this tube.

Stay tuned!

Saturday, January 2, 2021

Looking Back to the Past for a Better-Sounding Future

'80s Nostalgia

Early to mid '90s

I was based in the DC metro area in the early to mid 90s.

When I wasn't playing gigs or teaching, I serviced classic audio equipment and Audio Note, UK Kits for Angela instruments.

Mid-late 90s

Sound Practices 17 Homebrewer Article

2000-2008

Main Listening Room

Monaural Hi-Fi

Home Theatre with SET amps

The Attic 2008-2016

2017

2018

Man Cave 2020

Near-field

Monaural HiFi

Stereo

🎆 Welcome 2021! 🎆

Tuesday, December 15, 2020

nos TDA1541 tube DAC

I've become cynical of the latest is best mentality because in my 30 years of searching for sound that pleases my ears, I've always gone back to move forward. From this experience, I've learned to use planned obsolescence to my advantage by investing in old school components that have achieved classic status.

There is a common denominator between the Philips TDA1541 DAC chip and the Western Electric 300B directly heated output triode vacuum tube. The former brought digital sound to everyone’s homes in the '80s, while the latter amplified talking pictures in movie theaters in the '30s. Both have also been rediscovered for their distinguished musical abilities.

This tubed TDA1541 sans oversampling multi-bit DAC evolved from my frustration with its bitstream and delta-sigma successors, revisiting and studying multi-bit CD players and DACs, performing Magnavox CDP + DAC mods, and other digital audio experiments.

!!!WARNING!!!

The voltages in this circuit are potentially lethal! Build at your own risk!

If you are a metrics-obsessed audiophile who spends more time arguing in audio forums instead of listening to music because you can't trust your own ears and would rather buy a component approved by a hifi guru and/or his/her test equipment, STOP 🚫! You'll be offended by the contents of this blog, especially this project!

However, if you agree with Radiotron Designer's Handbook, 3rd edition published in 1940, that the THD metric should be abolished and better test procedures and standards established, you may proceed.😊

This project starts with the deconstruction of an already obsolete DAC board still available from eBay sellers. Since the TDA1541 chip has been out of production for over 20 years, I scavenge them from the CD player graveyard.

I incapacitated the analog section of the DAC board by removing the high speed/fast slew rate op-amps and low ESR signal capacitors, which will be replaced by a slower and harmonically more satisfying circuit from a bygone era.

Non Over Sampling (NOS) measures like a broken component but my ears prefer musicality over accuracy, so the SA7220P chip was tossed and the circuitry bypassed. Speaking of accuracy, to what? I wasn't at the recording session, so I don't obsess about it.😉

This picture shows the spots where I tapped the right (AOR 6) and left (AOL 25) analog outputs of the TDA1541 chip. The DAC's delicate and jagged left and right analog output stream will be connected via shielded cable to a cutting edge I/V converter + vacuum tube smoothing circuit advertised and marketed by savvy Mad Men as retro-tech art.😎

I was very impressed by the sonic flavor introduced by the Western Electric 396A/2C51 in the buffer section of my 21st century Xiang Sheng DAC 01A. But in this particular application - gain stage + buffer - the WE396A couldn't deliver the Carnegie Hall and Village Vanguard atmosphere I was trying to recreate. Caveat: the yellow WE logo doesn't offer a 100% satisfaction guarantee.

So I rewired the B9A 9-pin sockets for a pair of 6CG7s, which I've already used successfully as a buffer for my TDA1543 DAC. These are the Noval-based equivalents of my favorite medium gain (mu)/medium transconductance (gm) 6SN7 octals, esteemed for their linearity as an audio amplifier.

The circuit topology is very similar to my line stage preamp with the first triode section configured as a gain stage direct coupled to the second triode section wired as a low impedance cathode follower/buffer. No negative feedback is applied in the circuit to maintain signal purity. This tube circuit also functions as a sound processor, which is beyond the abilities of fast slew rate op-amps.😄

I recycled a power transformer from a Heathkit mono FM tuner. Using a 6X4 tube rectifier, the rectified 480VCT @ 60mA secondary feeds a capacitor input filter, then the B+ rail is split via 2 x 15H @ 30mA chokes to provide 295 volts of ripple free DC to each channel. The 6 volt DC supply, which lights up the 6CG7 filaments, is provided by a separate filament transformer. This archaic method of building a power supply enhances the DAC's tonal character!

Finally, I assembled the Back to the Future DAC on an organic 3/4" thick Baltic-Birch bread board. Even if it has a USB input, DSD, MQA and other so-called Hi-Res files are downsampled to 16-bit/44.1kHz PCM. That makes it 100% compatible with at least 90% of music streamed on the web. Since it makes my two-for-a-buck 4.75” silver discs from thrift stores and flea markets come to life, I don't ask for more.

Let's have some chips...

The reputation of this ubiquitous DAC chip was built upon regular production run TDA1541s, which can still be acquired for under $50. BTW, this is a DEM (Dynamic Element Matching - see TDA1541 FAQs) chip, not an R2R ladder DAC chip, as it's commonly misidentified.

So there's no reason for angst if hand-selected and tested single and double crown S1 and S2 TDA1541A chips command SothēBy's prices or reside in private audio museums in Asia. Buyers should actually beware of high dollar re-stenciled regular TDA1541s studded with crowns. They will work but won't sound any better than the chip I meticulously unsoldered from an '80s junked Magnavox CDP.

1kHz square wave from Stereophile Test CD3
Stock Magnavox CDB560 CD player

Fortunately, I got a chance to sample a genuine single crown S1 graciously donated by Gary B. This select chip made my DAC sound a bit more transparent and cleaner, with a touch more detail and resolution. But I have to reaffirm that not having an S1 isn't a deal breaker. In fact, the darker and warmer sounding regular TDA1541s and TDA1541As can be a blessing in systems that are a bit hot in the top end.

1 kHz square wave from Stereophile Test CD3
nosTDA1541tube DAC

Not very relevant to this NOS DAC project, but AFAIK, the only difference between TDA1541A and the non-A is that the A can do 8x oversampling while the non-A is limited to 4x. But let's not go there anymore. Been there, done that...

NOS and Digital Filters

Before I even became aware of NOS DACs, I had been using line transformers as digital sound processors. If you're worried about non-oversampled digital artifacts destroying the irreplaceable diaphragms of your Altec 3000 super tweeters, look for bandwidth limited military surplus transformers.

But the true analog-sounding line transformers JE Labs uses are those that have a flat response from 30 to 15,000 cycles, like the bokeh'ed pair of Western Electric 111C repeat coils and the UTC A-20s in front. There are so many sleepers out there branded with more letters and numbers, so don't limit yourself to UTC or WE.

My Analog Distortion Generating DAC

I’m happy to report that this repurposed '80s state-of-the-art digital music maker using Mid-Century Modern era devices and sensibilities has been fulfilling my analog-biased musical expectations at the end of this second decade of the 21st century. The DAC bread board doesn't exactly match the LeCorb and Mies aesthetics of my man cave, but I've been enjoying digital encoded music like never before, such that I can't get myself to rebuild it on a nicer chassis.