Quite frankly, there is often room for sharp criticism of some digital audio playback. Most audio lovers have heard the usual complaints about the so-called “digital sound” of computer music files processed through a DAC (digital to analog converter) and played by a stereo system. A host of of typical negative judgments include -- “Cold, grainy, too analytic, etched, ragged, fatiguing, harsh, shrill . . .”
The most dramatic characterization I’ve heard is “Sounds worse than a dozen burning banshees on steroids singing bad opera.” Or maybe, “Stop shattering my music” catches the feel of it. Yes, I have heard this harsh sound. I too have switched it off in disappointment as so many listeners have. But ultimately this story has a happy ending.
In defense of computer audio and digital music -- like everything in the audio universe, the sound depends on the system. It greatly improves the sound quality of thin files to add one simple, inexpensive audio component that makes digital music more pleasurable again. I have added a vacuum tube buffer to my otherwise solid-state, digital-source audio system with pleasing, positive results, reported below.
I began a sound improvement quest after an insight about my past listening as compared to what I listen to lately. I had sold off a grandiose tube-amplified system in preparation for an international move. Then I abruptly started listening to solid-state, powered studio monitor speakers. My experience with tubes had sensitized me to hear differences. The sound of solid-state amps disappointed me. This motivated improvements I could make based on my experience with tubes.
For the prior 10 years I had blissfully enjoyed tube-amplified playback of exclusively digital sources (CDs and computer files.) The systems were each four stages of tubes in a traditional system configuration --
Digital Server >> Preamp >> Power Amp >> Speakers.
None of the usual negative adjectives applied when tubes were used to amplify digital sources. That music had been deliciously authentic. Apparently tubes somehow "reconstruct" sound that gets damaged in some way during the crossover between the digital and analog domains.
So I hypothesized adding tubes might improve the sound of my new, more compact, solid state system. Some clues came from Decco and AMR, two successful audiophile companies that both use tubes in their high-end hybrid amps. I decided to test a simple but high quality headphone amplifier, one that has been getting a lot of praise online, in the preamp position as a tube buffer. What happened then was surprisingly pleasing.
Assuming well-mastered, decent recordings of organic performances or well-crafted electronic compositions, digital playback can sound sweet enough to pass even a discerning listener’s scrutiny and never get tagged as “digital sounding.” A tube buffer stage can even improve the sound of analog-sourced solid-state systems, helping them sound less transistorized. Naturally, nothing can help bad files that are upsampled from low quality recordings or poorly mastered.
In digital audio, the traditional preamp component is often left out. I now consider a tube buffer stage essential in digital audio playback systems. It's easy to insert one in-line to breathe a more natural, lifelike sound into computer audio systems. I don't know exactly how this happens. I hope some day to explain it. I just know it happens from many hours of comparative listening. So I leverage it and feel comfortable recommending it.
Adding a tube buffer has made it possible for me to enjoy 320 KHz CBR Mp3 files. Previously, CD quality (16 bit /44.1 KHz) was my lower limit of tolerance. CD quality (16/44.1) files sound more like 24 bit music to me when even one tube stage is added in-line after the DAC and before the power amp, like this --
Digital Source >> DAC >> Tube Buffer >> Power Amp(s) >> Speakers.
Generally, I estimate each file quality level from the lowliest Mp3’s to 24/192 is improved at least one step, sometimes more.
Ironically, it seems the often-cited negative traits of digital sources had rescued my tube-amplified systems from deserving the usual criticisms of tubes. There was no smeared sound, tubbiness, overly warm timbres, weak bass, audible noise, etc. I now believe the typical “faults” of tubes and digital files, when combined in a well-balanced system, can sum up to great sounding playback.
Who would have guessed old and new audio technologies could be coupled with such results, with each compensating for the faults of the other as sometimes happens in good marriages? Decco and AMR know about this and exploit it successfully. Maybe other companies aren’t paying enough attention.
Two specific configurations I tested follow. The digital source is either an Apple New iPad (“iPad 3”) or a MacBook Pro, each playing files served over the Internet or retrieved from disk. The iPad is sometimes the digital music server. It can access music files on the MacBook’s disk via Apple Home Sharing. The MacBook can also source a music bitstream instead of the iPad.
System 1. iPad >> TEAC DS-H01 Digital Docking Station >> Bravo Audio Ocean Headphone Amplifier >> Audioengine A5+ Bamboo Powered Speakers + S8 Powered Subwoofer
System 2. MacBook Pro >> AudioQuest Dragonfly USB DAC >> Bravo Audio Ocean Headphone Amplifier >> Audioengine A5+ Powered Speakers + S8 Powered Subwoofer
The files tested originate from download (24 bit) or from MOG.com (Mp3/320 KHz) or Qobuz.com (16/44.1.) The music is an eclectic mix that includes many genres. I continue to listen with other speakers and Sennheiser HD600 headphones as well.
Both systems sound quite similar to me, presenting great detail, realism, and accuracy, similar to live performances when recordings allow, with lots of air and a big, deep soundstage. Accurate attack and decay help reveal the true timbres of instruments and voices. Bass is tight and punchy. Yet the music is all smooth and warm, with no harsh or fatiguing aspect. The gold is there in gifted voices. Instruments sound right on. The ambience of live venues comes through. I close my eyes to visualize the performance and all is right in the universe because each thing sounds like its real self.
The Bravo Audio Ocean Headphone Amplifier ($129.99 MSRP) is the star of this show. It's an excellent little tube amp based on a single 12AU7 dual triode that passes the stereo signal to a pair of MOSFETs for power amplification. The designer chose components well. This amplifier has been enjoying great reviews on Amazon and in the online headphone forums. The build quality is nice and it has lots of power and a rich, sweet, articulate sound with fast, punchy bass when you use a good quality tube. The separate power supply is included. I recommend the JJ Electronics Long Plate ECC802S as a first rate upgrade for the stock generic 12UA7. The tube you select largely determines the sound you get. Make it a good one.
Granted, a headphone amp is not the perfect component as a tube buffer because it has excessive gain. Simply keep the gain in this stage low so there’s no distortion and it serves very well. Try it with the volume knob indicator pointed to the LED and adjust up or down a bit until you find the sweet spot.
You may have more than one volume control in your system configuration. System 1 above had three and four were present in System 2. So be sure to cross-adjust for the best sound. Try to maximize the amount of drive from the buffer stage and then set the listening level using whatever other volume controls you have configured. Once you set the sound level balance you should be able to leave it alone except for your overall volume control.
As an added benefit, the Ocean Headphone Amplifier will sound fabulous driving just about any headphones you might have around. Check Amazon.com and the headphone forums online for star-studded reviews and commentary on this Bravo Audio product.
The Bravo Audio Ocean as a tube buffer makes music sound a lot like what I heard through the PrimaLuna Preamp and Amplifier I formerly listened to. The TEAC Dock’s Burr-Brown PCM 1796 DAC chipset has a clear edge over the AudioQuest Dragonfly’s ESS Sabre chipset, to my ear. But both are wonderfully listenable for hours on end.
Why not test this for yourself? Then if you need further verification, test again with someone whose judgment you trust. Just make your trials blind – don’t prejudice your expert listener by revealing much in advance.
I believe if I keep integrating tubes and solid state in this manner to play digital sources I’ll keep enjoying music that pleases like the company of friends – a mature couple whose very differences in personality make them quite complimentary and interesting together.