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Balanced Headphone Drive
You may have heard some good things about
'Balanced Headphone Drive'. Audiophile
headphone aficionados agree that balanceddrive is the ultimate nirvana of headphone
listening, the cat's meow of cans, the creme
de la creme of personal audio systems, the
highest of the 'high end'. HeadRoom was first
to design balanced headphone systems with
our BlockHead Balanced Amp way back in
1999. And we've made even further sonic
strides since!
In essence, 'balanced-drive' is an amplifier
design scheme that delivers 'balanced'
equivalent and opposing [negative/positive] audio signals to each side of the headphone driver coils.
Balanced-drive delivers a significant increase in audio performance due to the doubling of slew rate
and voltage swing power, a massive reduction of THD distortion components, and the
virtual absence of crosstalk at the headphones due to the elimination of the common ground plane.
The end acoustic result lends an extremely expansive, 'open-toned' quality to your headphones, as
well as very transparent and refined musical detail, tightly textural low bass, and perfectly
pronounced mid-ranges. Many music lovers say its the closest headphones can come to sounding
like a 'room speaker' listening experience.
How Do I Get a Balanced Headphone System?
First, you MUST have a balanced headphone amp and your headphones MUST be recabled for
balanced drive to XLR left/right stereo connections (as shown pictured above). Balancing
headphones is typically an aftermarket procedure performed here at HeadRoom by our in-house
recabling experts which changes the headphone connection from a standard plug to stereo left/right
balanced 3-pin XLR connections.
You may purchase a brand-new set of reference headphones recabled for balanced drive from us, or
you may send in your existing headphones to HeadRoom to be recabled for balanced drive
operation. Recabling procedures are only available on certain headphones, please visit Upgrading
Your Headphones for more information.
Balanced Drive FAQ
What is Balanced Headphone Drive?
Balanced Headphone Drive is a scheme that uses inverse positive / negative electrical paths to
deliver equal and opposite audio signals to each side of the headphone driver voice coil. When
properly done a significant increase of audio performance is heard due to the doubling of slew rate
and power; the reduction of THD distortion components, and virtual elimination of crosstalk at the
headphones due to elimination of the common ground plane present in standard headphones.
Why Do I Need a Balanced Headphone Amp?
Because balanced drive requires two inverse audio channels at each ear instead of one, a balanced
headphone amplifier outputs four (4) audio channels instead of the two normally found in a regular
headphone amplifier. While a regular headphone amplifier can't drive balanced headphones, our
superb HeadRoom "BUDA" balanced amplifier can drive both balanced and standard headphones
beautifully!
How Do I Know if My Headphones are Balanced?
If your headphone plug looks like the single plug on the left, then your headphones are not
balanced. The black XLR connections on the right are an example of a balanced headphone plug.
Do My Audio Sources Also Need
to Offer a 'Balanced' XLR Output?
In order to achieve best performance from a balanced headphone system, a fully balanced audio
source is needed. Many top CD players and audio components now offer XLR output connections
built-in. Moreover, our killer HeadRoom Ultra Desktop Balanced DAC (aka "THE UDAC") has an
excellent built-in digital to analog converter that acts a fully balanced source, so all you need is a
computer laptop or PC signal via USB -- or an optical and/or coaxial digital SPDi/F audio signal
from other audio components -- for your 'balanced' audio source.
What Type of Connector is Used in Balanced Drive?
There is no official industry standard for balanced
headphone connections, and a handful of balanced
connector configurations exist. HeadRoom uses two
(stereo) male 3-pin XLR connectors, each carrying the
normal and inverted audio channels, and shielded
connections to their respective earpiece. This unique
connection scheme allows us to use the Neutrik combo
jack which includes both XLR and standard 1/4" stereo
headphone jacks to provide you with one amp that
can drive both balanced and standard headphones -- with
a nicely uncrowded front panel!
Does That Mean I Can Plug My Standard Headphones Into a Balanced Amp and Get a Balanced
Signal?
NO! But you can listen to standard headphones on a HeadRoom balanced headphone amp just fine,
you're just not listening in true balanced performance mode.
How Do I Get My Headphones Recabled and Ready for Balanced Drive?
The Sennheiser HD800 can be instantly owner-recabled into balanced drive using the Cardas
Balanced Cable for HD800. If you own Sennheiser HD600 or HD650, an aftermarket Cardas
balanced cable is available for purchase for those cans. Audeze and HiFiMAN planar-magnetic
headphones also have detachable cables allowing for easy cord upgrading. If you seek a different
brand of headphone, check our custom recabled HeadRoom balanced headphones.
What Does The Headphone Recabling Cost?
Recabling cost begins at $249 but varies depending on whether you buy your headphones recabled
initially, your desired cord length, and what type of after-market replacement cable is used on your
recable. See our ready-made balanced headphones here. Current headphones that offer userreplaceable cords are the Sennheiser HD800, HD600 and HD650 plus all Audeze and HiFiMAN
planar-magnetic headphones.
Why Don't You Offer More Models?
The time and significant expense that comes along with recabling is generally warranted only for
the very best of headphones. Moreover, some high-end headphones cannot be recabled due to their
internal wiring construction and/or other headphone design issues.
Can My Headphones Function Both as Balanced Headphones and Single-Ended Headphones?
HeadRoom manufactures a handy XLR-1/4"adaptor , so any balanced headphones may be
converted back to single-ended drive upon demand. Another option is to choose models
like Sennheiser HD650 or HD600 with detachable cabling allowing for an aftermarket balanced
headphone cord to plug directly into the cans. Hence, you can purchase a balanced cable and just
switch out the headphone cord(s) for single-ended or balanced listening as needed.
Besides Replacing Connectors, Is The Type of Actual Cable Different w/ Balanced Headphones?
Yes, the cable must have at least four conductors to get the proper balanced signal to the
headphones. HeadRoom uses our signature 'Fat Pipe' cabling which is made especially for
HeadRoom by Cardas, one of the finest cable manufacturers in the world, and is internally
structured to provide shielding and separation of the left and right channel pairs to reduce crosstalk.
Most Importantly, What Does Balanced Drive Really Sound Like?
This cannot be answered in a single sentence, but expect to be completely flabbergasted and
sonically wowed with an expansive soundstage and a full, rich, 'open-toned' sound never before
heard on your headphones... and if you've ever been flabbergasted by familiar music you've heard a
million times before that suddenly sounds fresh and brand-new again, then you know what a
huge thrill that can be!
Article I- Balanced Drive vs. Unbalanced Drive
We really didn’t know what was going to happen when we
introduced the world’s first balanced headphone amplifier, the
HeadRoom BlockHead, in 2001. We didn’t know if getting rid of the
common ground on headphones would make much difference. We
didn’t know how many headphones could be successfully re-cabled
to a balanced configuration. We didn’t know if balanced headphone
drive was going to sound better---or even if it would sound good. We
just knew it could be done and that we had to try. Man, are we glad
we did; balanced-drive headphones sound great! It is a new idea
though, so we thought we’d help you understand what we’re talking
about.
A normal headphone cable plug has three connections on it: the tip is left; the ring is right; and the
sleeve is ground. The tip connects to a wire that goes to the positive (+) lead of the left headphone
driver coil; the ring connects to a wire that goes to the positive lead of the right driver. The sleeve
connects to a wire that goes to both negative (-) terminals of the drive coil; this wire usually has a
solder joint in the “Y” or in the earpiece where ground wire from the plug splits into separate wires
that are connected to the negative terminals of the driver coils.
Bold lines indicate common return of both left and right channels
The most important thing to note here is that as the left and right channels of the headphone
amplifier drive the left and right driver coils, the return current from the drivers gets joined together
and travels some distance before returning to the amp’s audio ground. This common pathway has
some- possibly significant- electrical resistance from the wire, solder joints, contact resistance at the
plug/jack, and so on, which causes a common signal to appear at the negative terminal of both
driver coils. This common signal (a low-level summation of the left and right channel) will generate
low level cross-talk and distortion in the sound heard on headphones. Just how low depends on the
quality of the whole headphone/amplifier system (and, of course, we do a lot to minimize the
problem with our amplifiers and re-cabling services), but it will always be there. There is, however,
a way to completely get around the problem: balanced headphones.
Balanced headphones are just
regular headphones that have been re-cabled in a special way. The normal three-conductor cable
with the common ground connection is replaced with a cable that has four conductors: right positive
and right negative conductors to the positive and negative connections of the right driver coil; and
left positive and left negative conductors to the left driver coil. The cable is terminated in two XLR
male connectors, one each for the left and right channel. A special headphone amplifier is used that
has “balanced” outputs where each channel has a normal audio drive signal and a mirror image
inverted drive signal. The trick here is that there is no “ground” to the headphones anymore, so
there is no opportunity for the crosstalk distortion described above.
Well … there’s actually another trick: an amp that makes perfect mirror imaged balanced signals to
drive balanced headphones.
Article II- What's the Difference Between Balanced Transmission and a HeadRoom Fully
Balanced Headphone System?
So you've learned how re-cabling headphones for balanced drive (a service that HeadRoom
provides for certain high-end headphone models) can significantly improve headphone audio
performance by getting rid of the common ground shared by the left and right headphone drivers.
But there are other sonic advantages to be gained by driving headphones in balanced mode.
Unfortunately, “balanced” drive has a number of subtle nuances and meanings that need to be
explained to fully understand what we are trying to accomplish.
The most common use of balanced audio signal transmission has actually little to do with driving
headphones in balanced mode. In many professional audio applications, signals are routed from
place to place via balanced cables in an effort to reduce common mode interference from radio
frequency (RF) noise sources like fluorescent lights and motors. Because the voltage developed on
the transmission line from RF interference is identical on both normal and inverted signal
conductors, and because the balancing transformers only allow current flow when the signals are
opposing, the common interference signal is cancelled out (fig.1). This problem is not typically an
issue even with single-ended headphones because the low output impedance of the power amp
prevents a significant RF interference noise voltage from ever developing. But there are other
excellent reasons to drive headphones with a particular type of balanced amplifier.Certainly, there
are a number of amplifier designs that are single-ended internally, but use transformer coupled
outputs (fig.2); these amplifiers improve headphone performance largely because of the removal of
the common ground as described in last month’s ad.
However, there is an entirely different approach that can be used to get significant and measurable
performance improvements at a lower cost than would normally be available against the
diminishing returns curve of component upgrades. Often called “fully balanced” designs (fig.3), this
type of amplifier has completely separate and matching electronics circuits for all four (left normal
and inverted, and right normal and inverted) audio signal paths. The advantage of this design is that
there are two power amps driving each coil; each amp effectively drives half the coil, with a virtual
ground or zero voltage point halfway into the coil. Since each amp is only driving half the load, a
significant improvement in control can be achieved, and because the voltages are in opposition, an
effective doubling of slew rate (volts per second the amp can swing) is realized compared to the
normal slew rate of either amp by itself. In other words, by doubling the amount of electronics
circuits, a two-fold performance increase in some critical areas can be achieved with only a 50%70% increase in cost. Normally, a doubling of measured performance would easily cost much more
to achieve.
Next, we will continue by describing how we get a balanced signal to begin with, and how
HeadRoom balanced amps, in particular, help you get it right between your ears.
Using a Balanced Source, such as Phono Source or a Computer
If you’ve been reading along and have absorbed the gist of our balanced headphone articles, you’ll
know that re-cabled, balanced headphones and fully balanced headphone amplification will get you
killer bang-for-the-buck audio performance ---but you have to use a fully balanced source. There
are two we really like.
Vinyl Sources
Sure, digital has gotten very good (and we’ll get to that in a minute) but vinyl is organic and liquidsounding, and just happens to be a very cost efficient way to get a balanced source -- not to mention
it provides hours of platter picking pleasure at indie record stores, too. The coil in a phono-cartridge
is naturally balanced, and if you run it to a balanced phono amplifier, voila, you’ve got a truly
balanced source. (Tape heads make great naturally balanced sources, too---but if you thought vinyl
was obscure try finding source material on 15-inch reels!)
Digital Sources
The proper way to get as close to perfectly balanced digital source as possible is to create the
inverted channel by flipping while it’s still in the numbers stage. Normally, DACs (Digital to
Analog Converters) run with 0000… giving a low voltage to 1111… giving it’s maximum voltage.
In this case the output with digital audio is non-inverted (or improperly but commonly called, “inphase”). But with a simple toggle of a pin, the DAC inverts its word sequence and runs from
0000… giving the maximum output to 1111… giving it lowest voltage, which inverts the audio
signal---pretty much perfectly.
In our latest generation of HeadRoom balanced headphone amplifiers you’ll find a numbercrunching sweetheart of a balanced digital front-end for our fully-evolved balanced headphone amp
circuits. We use two Cirrus Logic’s flagship CS4398 stereo DACs, each running a channel and
creating a normal and inverted audio signal, followed by discrete hand-matched circuit paths which
allow our DAC boards deliver exquisitely matched pairs of balanced stereo signals to all four
channels of our balanced amps. The result of this pure and very short path to your ears in
HeadRoom balanced headphone systems is audio performance that can only be equaled by
supremely hyper-expensive speaker-based systems.
We could end right here with you thinking about how your noggin can be transformed
into a world-class listening room for a mere couple of thousand bucks, but there’s
something else. Our DAC boards have USB inputs, as well as digital TosLink optical
and digital co-axial inputs. That means your laptop could be a perfect digital source for a high-end
listening system; that means your Airport Express or Squeezebox is a perfectly good front-end
anywhere in your home or office... That means most anywhere you are, you can be perfectly
balanced, Right Between Your Ears.
To get the most out of your balanced headphone system, it’s
important to use superb audio gear that provides true differential
'balanced drive' signals. Our HeadRoom Ultra Desktop DAC is
just such a device. The advantage of this balanced method -- first
released by HeadRoom in 1999 -- goes far beyond simply
reducing induced noise; amplifier slew rate is doubled, most THD
harmonic distortion components are suppressed, and a doubling of
voltage output power is realized resulting in a supremely accurate
and smoothly open-toned sound not possible with standard headphone systems.
With typical 'unbalanced' audio connectivity, the audio signal is carried on a single conductor, while
a shield or ground conductor is provided for the return current path. A differential balanced drive
system uses two audio signals: a normal audio signal, and a perfectly matching but inverted
[positive/negative] audio signal. A ground conductor may be used as a shield, but is technically not
required in these topologies.
Balanced drive has long been used to reduce interference on long cable runs with microphones and
pro audio componentry, for example. But while some gear may offer balanced XLR connections
externally, they are often single-ended devices internally, which are either transformer-coupled or
use complex phase splitters to create their so-called balanced signal. These methods invariably
result in the normal and inverted audio signals acting as slightly imperfect, fluctuating mirror
images of each other, and in reality only serves to degrade
the full acoustic performance potential.
In a true fully differential balanced drive system, a source of
perfectly matching balanced signals is followed by
identical, highly-matched signal paths. In the HeadRoom
Ultra Desktop DAC the signals are perfectly created by
painstakingly paired sets of DACs that are running in
normal and inverted positive/negative modes and therefore
create, again, perfectly matched output signals.
Interestingly, a balanced LP turntable phono stage could be
used by taking the signals of either side of the LP cartridge
coil and running the signals through identical RIAA equalization curves and output driver channels!