Magnavox CDB473 and Philips TDA1541

With barely 400 CDs and just a handful of SACDs and DVD-As in my collection, I didn't invest heavily on silver discs as much as I did on LPs. Likewise, I've spent much less on digital playback hardware.

However, due to the resurgence of interest in vinyl LPs and streaming, used CDs are available all over at bargain prices. Since I'm not committed to burning all my silver discs to a hard drive having had my own share of failures in the past, I was inspired to look into maximizing my CD playback system.

Sony DVP-NS755V

For the past 15 years, I relied mainly on this Sony DVD/SACD/CD player. It showed me that SACDs had an edge over CDs. Yet it proved that neither format was on equal footing with my LP set up. This is a polite sounding machine that also doesn't do anything great. Prior to the Sony, I owned an early bitstream (ca. '93) Philips CD921. It sounded sooo boring, I connected the digital out to an Audio Alchemy Dac In The Box to spice things up a bit until it (the CD921) prematurely died.

Nevertheless, I was still missing the lively sound of my first CD player, a Magnavox CDB472 I purchased in 1987. I had an inkling that the "bitstream" buzzword of the 90s was not an effort to improve sound quality but a watered down technology/marketing hype for manufacturers to maximize profits. Since I was more interested then (as now) in older technology, I placed digital audio tech aside, focused on learning how to build triode amps and high-efficiency speakers.

Denon DVD-2910

To re-acquaint myself with the few DVD-A titles I have, I acquired this reasonably priced Denon DVD-2910 multi-format compatible relic from the mid-2000s. It weighs almost 10 pounds, is built like a tank, is mechanically and functionally more refined compared to my entry-level Sony above due to higher quality materials (more metal). If this didn't sound better, it can serve as a CD transport for an external DAC. Fortunately SACDs did sound better, but not sure about CDs though...

Time Travel Machine

Philips TDA1541A

Ever since I embarked upon improving my internet streaming set up, I had to refresh and update my knowledge of Digital Audio, PCM, DSD, DACs, etc. It was inevitable that I'd encounter R2-R vs. delta-sigma debates in internet audio forums. I also discovered that there's a sub-culture of CD collectors/music lovers/DIYers (as opposed to meter readers/latest is best audiophiles) who maintain that the most musical sounding CD players are those 80s machines fitted with the more complicated and expensive-to-manufacture 16 bit Philips TDA1541 chip.

Under the hood of a CDB473

Out of retro-tech nostalgia, it was only fitting that I trace my steps back to my first CD player in ca.'87, the Magnavox CDB472, which used this ubiquitous chip. I did a bit better this time around with the higher model CDB473 which is equipped with a co-ax digital out, and can also be used as a CD transport. Considering that this unit celebrated its 30th birthday in December of 2017, it is a glowing testament to Philips' excellence in engineering and manufacturing that it still works today. 

Let's see how the Magnavox's 16 bit DAC chip which was truly designed for Red Book CDs fares against the Delta-Sigma DAC chips found inside the Denon and Sony.

Magnavox CDB473

From the very first CD I fed into the tray, the Magnavox sounded more transparent and dynamic while the Denon and Sony sounded comparatively veiled and compressed. Even my wife heard its superiority. The CDB473 may not possess ultimate refinement but there's an honesty in its musical presentation that draws the listener into the music, just like analog LP does. 

Truth be told, I don't remember the CDB472 sounding this good back in the 80s. But I had a totally different system then and was just beginning to wean myself off of the influence of underground audio journals of the era, which were largely pro-vinyl LP/anti-digital CD. I guess hindsight is indeed 20/20 with regards to the Philips TDA1541. I was too young to learn and appreciate its virtues. Besides, a year after this CDB473 was manufactured, Philips introduced bitstream technology, followed in the late 90s by Delta-Sigma, both claiming greater linearity. These were the technologies that dominated the market from the 90s to the present and also the sound I associated with the playback of 16-bit/44.1kHz mastered CDs.

Raspberry Pi 3B+

The FM tuner has been a de rigeur music source in my audio system. Between the dwindling quality of FM broadcasts and proliferation of internet radio and music streaming apps like Pandora, Spotify, Tidal etc., I had to jump the bandwagon with my first generation iPad mini.

But as I delved into how to get the best sound from the internet, I realized that I could improve upon the iPad mini > USB DAC set up for not much $$s.  I've seen Blogs and YouTube videos on how the Raspberry Pi 3B+ (henceforth, RPi3B+), a 40 something dollar single board computer, can be configured as a hi-fi music player.

 A discussion of the RPi3B+'s sonic merits in the Joe-list initiated by a long-time audio DIYer, Larry Moore, was pivotal in my decision to try it. He recommended using the RPi3B+ with an I2S Allo Boss DAC, moOde 4.1 + a linear power supply. Since I already had a couple of USB DACs, I just opted for the cheapest RPi3B+ bundle with a 5V/2.5A SMPS (switched-mode power supply), a molded transparent acrylic case and a couple of 16GB micro SD cards from Amazon.

The software for the RPi3B+ is contained in a micro SD card, which is inserted in the bottom mounted front slot. At the back is an ethernet port + 4 USB ports which can be loaded with USB thumb drives filled with music files and/or connected to an outboard DAC. On the right side, there's a mini USB for 5V power, an HDMI port and a 3.5mm below hi-fi grade audio out. 😞 To the left is a 40 pin GPIO header where an I2S S/PDIF device or DAC can be attached, which supposedly offers even better sound due to less jitter.  

 Once the software is loaded and configured the RPi3B+ will be operating "headless" (no monitor or touch screen). All functions are accessed and operated via a web browser on an iOS/Android device or laptop.

moOde 4.1

moOde GUI

Installing moOde 4.1 was not an easy task - not for me, at least. I had to bring the TV near the router to function as an HDMI monitor and plug a USB keyboard on the RPi3B+ to type commands which reminded me of WordStar word processing on an IBM XT/AT in the 80s. After two trials using the EZ install process and valuable assistance from the good guys at Hi-Fi Haven, my moOde 4.1 build was a success. 

The only glitch I had with moOde 4.1 is that Airplay doesn't work with the following DACs via USB: AQ Dragonfly Black, XtremPro X1 and Topping D30. So far I can only get moOde 4.1 Airplay to work with the Xiang Sheng DAC 01A below. I'm hoping that an update will address this issue. 

Volumio

Volumio GUI

After the moOde 4.1 initiation, installing Volumio was a breeze. The software is downloaded as a file, "etched" on a 16GB micro SD card and then set up for Wi-Fi connection. No MS-DOS style typing required. Everything went smoothly even for a not-too-tech-savvy computer user like me. There were no issues with Airplay connection, regardless of which DAC was connected to the USB port. The choice of internet FM radio stations is at par with moOde 4.1 and there's a "plug-in" for YouTube. There's also support for Spotify subscribers. Since I only have a Spotify free membership, I "Airplay" from an iPad.

Sound

I wouldn't have known that the software itself can influence the sound in computer audio if I didn't embark on a Raspberry Pi journey. The more complicated set up procedure and USB > DAC issues notwithstanding, moOde 4.1 rewards the listener with deeper and punchier low frequencies, crisper high frequencies and more lucid midrange. Volumio sounds as if the leading edge of transients are slightly rounded off. The difference is actually quite subtle and only discernible after extended listening to both platforms.

According to MikeyFresh, a moderator at HiFi Haven who helped me a lot with the moOde install, "Moode is a very lean distribution, perhaps that's why it can sound better, it runs super efficiently and thus taxes the RPi3's CPU and RAM very little, which in turn produces less EMI/RFI to contaminate the signal." 

iPad mini as controller, RPi3B+ and Topping D30 DAC

I'd hate to bid adios to my beloved Scott LT110B and Dyna FM-3 tube tuners, but the RPi 3B+ is getting more air time nowadays. 

!!!STOP PRESS!!!

I initially considered the cheaper Hifiberry Digi+ Pro, but based on the positive reports I've read on the internet from RPi users, I took the plunge and got the more expensive Allo Digione S/PDIF HAT (aka Hardware Attached on Top) instead. A layer of electronic hash was removed by this I2S device and took the sound quality to another level = more analog, less digital. 

XtremPro X1 USB DAC

I was too wound up after playing a gig one winter Sunday evening. Watching episodes of the Grand Tour over a couple shots of Ballantine Scotch Whiskey was not enough to relax my mind. So I ended up "window" shopping on Amazon. 

This tiny USB DAC piqued my interest and I thought I could use it for my Lenovo laptop. Given that the above specs were very similar to my current AQ Dragonfly Black at less than 1/3rd the price, I bought it and called it a night.

 A shootout with the AQ Dragonfly Black was inevitable. I will just admit outright that this $29.39 USB DAC blew away the Dragonfly Black! The XtremPro X1 is more dynamic, transparent across the audio band and extended at both frequency extremes. Although I'm just a casual headphone listener, the healthier output voltage of the X1 was also an advantage through my 90s vintage Grado SR60 cans. 

Unfortunately, the XtremPro X1 does NOT work with iOS devices as-is (see update below) but there were no issues with the aforementioned Lenovo and my 2013 MacBook Pro. 

Apparently, this USB DAC has had quite a following in Europe. 

Important Update!

As suggested by a kind reader, Miguel (see comment below), 

this issue

can be by-passed through a generic 2 port USB 2.0 Hub. This Eyeboot model from Amazon did the job for $5.99. 

How to:

Plug the 2 port USB hub wall wart to an AC source,  

XtremPro X1 DAC > 2 port USB hub > iOS camera adapter > iOS device, plug your headphones to the 3.5mm socket or connect to your preamp or integrated amp, happy listening!

XtremPro X1 + Eyeboot 2 port USB Hub = great value for the money!

Line Transformers Redux + Art Dudley + AQ Dragonfly Black

My boring digital life

Tascam DA-P1
courtesy of pgr.tv

Probably the most significant digital audio gear I ever owned was the Tascam DA-P1 DAT recorder. This machine recorded my recitals, chamber music performances and served as a back-up and playback deck for my CD projects from the mid 90s until the early 2000s. It was rendered obsolete when HD based recording became the industry standard.

DAC in the Box
courtesy of Wiki Commons

I never invested in a high-end CD player. The most I ever did for CD playback was get an Audio Alchemy DAC in the Box fed by the digital output of a consumer grade Philips CD player. When the Philips CD player conked out in the early 2000s, it was replaced by a Sony DVD/SACD player.

Line transformers as Digital Sound Processors

Tamura line transformers

Ever since I inserted a pair of Tamura 600:600 line transformers as a digital sound processor (DSP) between the CD player/DAC and my preamp line inputs, I didn't see the necessity of upgrading the Audio Alchemy DitB. I don't know if this holds water but my empirical rational for this is, magnetic coupling filters digital artifacts and RFI noise from the DAC output, which is manifested as harshness to my ears.

Art Dudley Listening

If I don't consider the few issues of Stereo Sound Tube Kingdom and MJ I picked up in Tokyo in 2015, it's been a long while since I subscribed to, let alone bought, a single issue of Stereophile, The Absolute Sound or any audio magazine. After the demise of Sound Practices in the late 90s, the only audio magazine I read was Art Dudley's Listener.

Although I've never had a chance to meet Art personally, I know he is a fine gentleman. I've been following his Stereophile column online and he has given credit to my musings on the open baffle as well as the Altec 755A. He even sent me a private message when my father passed away earlier this year. I was looking forward to meeting him at the Capital Audio Fest 2017 but missed the event because it coincided with the Harrisburg Symphony's November Masterworks.

iPad mini + UTC A20 line transformers

Due to my current location, access to quality FM programming is practically nil. I've relied mainly on digital streaming via iPad mini + DSP to widen my choice of free music. 😜

USB DAC

Audioquest Dragonfly Black V1.5

When I realized that the iPad mini's internal DAC can be by-passed through an Audioquest Dragonfly USB DAC, I searched the archives of Art Dudley's Listening to see if he had anything to say about the AQ Dragonfly USB DACs. After getting Art's stamp of approval, I placed an order for the cheaper Black.

Stereo > Mono

Whether I was listening in mono or stereo, this was the best $100 (ok, + $38 for the Lightning to USB 3 Camera cable adapter) investment I ever made in digital audio. The degree of improvement was at least as significant, if not greater than, when I started playing with transformer DSP(s) between the digital source and my line preamp input(s).

Stereo set up =
AQ Dragonfly Black > a pair of UTC A20 wired 1:1
> preamp line stage

The combination of the iPad mini + AQ Dragonfly Black + DSP = smooth analog-like detail across the audio bandwidth. So I take back my word, I need this USB DAC. 😎

Thank you Art and here's to us meeting some time soon. Cheers! 🍻

Stereo > Mono Line Level Mixer - ***Revised 4/12/21***

Mixing line level stereophonic signals into full dimensional monophonic ;)

Here's a DIY project for mono aficionados that's so basic, I should have uploaded it many years ago. But other things got in the way.

Just like an MC step-up, these are entirely passive devices. 

The simplest way to convert stereo to mono is to connect left and right channels via a Y connector. But there's a more elegant way than just shorting two channels.

Resistors can blend two signals into one better by...

...using Allen-Bradley carbon composition for warmer sound ;)

Line Output Transformers

This single UTC A-20 transformer was in a box lot of tubes and parts I picked up at a radio show. It's a high quality transformer designed for mic, mixer or line matching applications. Instead of trying to find a mate for MC step-up duty, I repurposed it for a greater calling in my mono rig.

With a claimed bandwidth of 10-50,000 hz and dual windings in the primary and secondary, it is perfect for mixing line level stereo signals into mono!

Left and right channels from a stereo source are fed into each primary winding. The summed mono output is taken from the series-connected secondary winding, which goes into the line level input of a mono preamp.

April 12, 2021 update!

The Covid 19 lockdown was a good opportunity to reassess past projects.

I realized that my original practice of connecting the left and right stereo channels to the split primaries of a single UTC A20 line transformer was sonically inferior to the 2 x Tamura line transformers with their secondaries connected in series as shown above. 

The classic UTC A20 and A21 are still very fine contenders but two are needed instead of one. Use the specs above as a guide for hunting transformers under the radar. 

If you prefer modern transformers, I highly recommend contacting dave slagle of Intact Audio. He winds fine sounding transformers to spec using high quality materials.

He generously provided the following technical explanation as to why my original recommendation was flawed.

• if the L & R outputs share the same core they are effectively in parallel even if the secondaries are connected in series
• if the L & R are on discrete cores and the secondaries are in parallel the circuit can be drawn as one channel driving the other through two transformers
• if the L & R are on discrete cores and the secondaries in series then the load is also part of the series circuit so a high impedance is reflected back

Subjectively, using a single transformer I heard truncated frequency extremes, compressed dynamics and less detail. With two transformers the sound was cleaner and more articulate with more extension at frequency extremes. Dynamic nuances at micro and macro levels improved significantly. There's also a greater sense of space and ambience!