HEADPHONE PREAMPHeadphone preampliﬁer with balanced in/outputs
Made by: Aurorasound Inc, Japan
Supplied by: Pure Sound, UKTelephone: 01822 612449
Web: http://aurorasound.jp/english; www.puresound.info
Price: £2000

Aurorasound HeadaThis bulky, balanced output headphone ampliﬁer from Japan is proof that the bestthings don’t always come in small packages – or are the most tastefully wrapped
Review: Keith Howard Lab: Paul MillerW

hen I reviewed the Teac
HA-501 headphone ampliﬁer[HFN Apr ’14] I described itas ‘a Japanese product of theold school, with the type of no-nonsense
looks that appeal more to male thanfemale eyes’, and I contrasted it with thecompact, svelte Meridian Prime reviewed
two months previously.
Well, the same description applies to
the Aurorasound Heada which, with its
wooden sleeve, little toggle switches andexposed fasteners securing the three XLR
sockets on its fascia, looks even more
obviously retro. With the Preda preamp[HFN Nov ’14] Aurorasound appeared tohave taken a stride towards more modern
industrial design, whereas the Heada (likethe Vida phono preamp too) has thus far
escaped a makeover.
But just as 20th century looks did
no harm to the Teac when assessed asa purveyor of aural rather than visualdelights, so it is with the Heada. If you are aseeker after out-of-the-ordinary headphonesound quality you’d be unwise to scrub
it from your shortlist on the basis of its
utilitarian appearance.

The Heada provides two inputs on theback panel, selectable by the top of two
toggle switches towards the left of thefascia. Input 1 provides for balanced input
via 3-pin XLR sockets or unbalanced input
via phonos, while input 2 offers unbalanced
input only. The Through Output sockets
and an IEC mains input socket complete
the rear panel connectivity.
Around the front, to the left of the
fascia is the volume control with a scale
comprising constant-diameter dots but nonumbers, which makes precise resetting
difﬁcult. Immediately to its right is theinput selector toggle switch above asecond which selects between low andhigh gain. Next comes the ¼in jack socketthat provides the conventional unbalanced
headphone output (the owner’s manual
warns against plugging a mono jack intothis), followed by three XLR female sockets
which offer balanced connection forheadphones that support this option. AnFOR HEADPHONES ONLY
Like the Teac and the recently reviewed
Auralic Taurus MkII [HFN Jan ’15] the Heada
is a pure headphone ampliﬁer, not a DAC/
headphone amp hybrid. It has analogue
inputs and analogue outputs, and that’s it.
It doesn’t even double as a simple preamp.
Yes, there is a pair of phono sockets on therear labelled ‘Through Output’ but that isa literal description: the signal on theseis that downstream of the input selector
switch, with no volume control or output
buffering applied. So you can’t connect
the Heada directly to a power ampliﬁer for
speaker replay, it has to be to a preamp or
an integrated ampliﬁer – something with again control.
RIGHT: Internal layout is neat with the PSU
board to the right (viewed from front) and four
modular amp boards to the left. Volume control
is a high-precision conductive plastic type

REPRODUCED FROM HI-FI NEWS | www.hiﬁnews.co.ukon/off toggle switch has a red LED above
which lights when the unit is powered.
The wooden sleeved aluminium casehas enough circuitry to ﬁll much of its
internal volume. Combining bipolar andJ-FET devices, the four ampliﬁer modules
are unusual in eschewing low output
impedance. Says the designer, Mr Karaki,‘For headphone drive, high damping factor
cannot make good sound. I discovered thisfact by testing a lot of headphones during[the] Heada circuit design.’
Speciﬁed output power, unbalanced, is1W into 40ohm, equivalent to 6.3Vrms –more than enough to accommodate thetransient peaks of high dynamic range
music at sensible (or even excessive)
replay volumes [see Lab Report, p59].
In balanced mode, as you’d expect, thisdoubles to 2W. Despite this ample output
voltage capability, Aurorasound speciﬁes
compatibility with headphones of 16 to600ohm impedance, suggesting that

current capability may be an issue withimpedances below 16ohm, not that they
are common. I experienced no issue here,
though, as I will describe.

A MAGICAL COMBINATION
For the listening I drove the Heada
exclusively via unbalanced signals froma Chordette QuteHD, fed S/PDIF from aMac Mini via FireWire connection to a TC
Electronic Impact Twin. For most of thelistening I used the Sony MDR-MA900 [HFN
Oct ’12] because, rarely, it has the nearneutral tonal balance and explicit midrange
essential for hearing what headphone
ampliﬁers are up to.
The Sony is right at the lower end of
Aurorasound’s speciﬁed impedance range– in fact, with a minimum impedance of
13.9ohm it dips below 16ohm for muchof the audible spectrum. But I heard noevidence of the Heada struggling, although
it might have at extreme output levels
beyond those at which I listened.
In fact the combination of the MDRMA900 and the Heada was magical,
despite the former being limited to using

the latter’s unbalanced output. The Headareminds me of the Teac HA-501 in thatits sound has an all too rare combinationof natural, uncontrived warmth alloyedwith a searching clarity that never leaves
you feeling short-changed in resolution ormusical engagement.
So listening to it is pure, self-indulgent
pleasure, my only concern being that withless honest, less revealing headphones, thebalance could tip towards
it sounding a little too
lush. If that happens it’s
likely to be a commenton the headphone rather
than the Heada, although
it should be borne in mind
that the Heada’s relatively
high output impedance
may result in undesirable frequency
response changes with ’phones that havehighly variable impedance.
Once I’d established the general natureof the Heada’s sound, I lined up a feast of
hi-res tracks via which to enjoy it. I’ll run
through just three of them speciﬁcally:‘Take Five’ from Sabina Sciubba andABOVE: Small toggle switches alongside thevolume control select between the two inputs(top) and high or low internal gain. Balancedoutput is provided on both 4-pin and 3-pin XLRs

Antonio Forcione’s Meet Me In London[Naim Label 192kHz/24-bit download]; theAdagio from Robin Ticciati’s acclaimed
interpretation of Schumann’s Symphony No2 [Linn Records 192kHz/24-bit download];and Dire Straits’ ‘OnceUpon A Time In TheWest’, converted to88.2kHz/24-bit from arip of the CommuniquéSACD (Japanese import).
With words to thefamous Dave Brubeckmelody, ‘Take Five’ is a
showcase for Forcione’s guitar work but,above all, the seductive, elastic voice ofSciubba, who could charm birds from thetrees. Her laughter before she sings sets
the tone – she is enjoying herself here andsoon puts a smile on your face too.

‘I really couldn’t
ask for “TakeFive” to havesounded better’

DAMPING FACTOR
This is the second headphone amp to come our way from Japan that includes
deliberate manipulation of damping factor (DF) – the ratio of load resistance tooutput resistance. In driving loudspeakers it is normal for the ampliﬁer output
resistance to be low (DF high) in order to ensure effective electromagnetic
damping, particularly of the loudspeaker’s fundamental bass resonance. As
this damping effect depends on current ﬂow through the voice coil resistancein series with the amp’s output resistance, though, it’s arguable whether any
practical beneﬁt accrues when the latter is reduced below, say, 5% of the former(a damping factor of 20). Why a reduced DF should be of beneﬁt to headphones,as Aurorasound’s Mr Karaki suggests, is far from clear. But the audible effect, tojudge from the variable DF control on the Teac HA-501, is obvious enough. As thedamping factor is reduced, the sound becomes smoother, less ‘etched’, an effectunlikely to be explained simply by the changes in frequency response.

MUSICAL DELIGHTS
I really couldn’t ask for this to soundbetter: the sense of studio acoustic
was convincing, you could clearlyhear Sciubba’s quiet, staccato breaths
emphasising the rhythm after her ﬁrst
‘just take ﬁve’, and it was obvious that thecentre-placed guitar was recorded more
drily than that to the right. But above all it
was a sheer musical delight.
Ticciati’s chamber-like account of
the Schumann relies for its un-showy,
stealthy charm on precise delineation of
the string harmonies in particular, and aclear exposition of this recording’s ﬁnesense of acoustic. The Heada delivered
both, allowing this triumph of unhurried
exposition to weave its calming magic.

www.hiﬁnews.co.uk | REPRODUCED FROM HI-FI NEWSLABREPORTAURORASOUND HEADAABOVE: Input 1 offers balanced or unbalanced connections while Input 2 isunbalanced only. ‘Through Output’ bypasses the volume control, so the Headacannot serve as a preamp with a separate power amp

From my days of owning
the LP, I’d always thought thatCommuniqué was the best soundingof the early Dire Straits albums,
certainly much better than Making
Movies, but never felt that I’d reallyextracted the best from it. With therecent arrival of the DSD-layer-only
SACD from Japan I feel I’ve ﬁnally gotthere: as close to the master tape as
I’m ever likely to get.
It’s by no means an audiophilerecording, of course – there’s nodeep bass and the cymbal soundis the usual indistinct buzz of theperiod – but, via the Heada, the leadand rhythm guitars and the voiceat last realised the clarity I’d always
suspected was buried there.

THE BALANCED OPTION
But what of unbalanced output
versus balanced output? The Heada
arrived while I was in the processof converting a second pair of theSonys so that they can be usedeither way – quite a major job as
it involves rewiring the capsulesinternally and installing connectors.
But as I couldn’t ﬁnish the task intime for this review I took up theoffer from importer Pure Soundto borrow its Sennheiser HD600s,
complete with balanced cables.
The ageing Sennheiser, if lessthan ideally spritely in its SQ, has
the advantage of high impedance(nominally 300ohm), which should
prevent any signiﬁcant alterationin frequency response occurring
as a result of the Heada’s output
impedance changing according towhether one or two of its ‘damping
factor control’ stages are in circuit.
Concerned not to do too muchplugging and unplugging of the twoleads, bearing in mind Sennheiser’s
warning of old that the two-pin
connectors on the HD600 and
HD650 were never intended for thistype of use, I restricted myself tomaking the unbalanced/balanced

comparison on just one track – theSciubba/Forcione ‘Take Five’. Indeed,that was all I needed to hear thatthe balanced connection wasbetter: the guitar sound was crisper,
Sciubba’s creamy vocals clearer, thewhole performance more energetic
and engaging.
Still, I hesitate to conclude thatthe balanced output option isbetter per se, assuming that you
have headphones to exploit it. Two
reasons: ﬁrst, my concern about thefrequency responses being different
in unbalanced and balanced
operation, because of changes insource impedance, may well berealised when the Heada is usedwith lower-impedance ’phones.
Secondly, the cabling in PureSound’s unbalanced and balanced
cables is different, and having
owned an HD650 myself for manyyears, during which I bought one ofRuss Andrews’ aftermarket cables forit, I know that this in itself can makequite a change in sound quality.
So I reserve judgment as towhether balanced connection
is generally an improvement –but there is no question, in thecircumstances described, that it
made my tail wag.

Despite being based around the same ‘Aurora-AMP’ discrete
bipolar/J-FET op-amp modules we saw in the Preda preamp[HFN Nov ’14], the conﬁguration used in Aurorasound’s Heada
headphone amp exhibits slightly different response/distortion
characteristics. In practice, I think the differences are due tothe transformer-coupled volume control used in the Preda
versus the conductive-plastic type employed here, the upshot
being the Heada offers a far ﬂatter LF response (0.0dB/20Hz
down to –3dB/1Hz) with a more uniform LF distortion (0.0004%/1kHz down to 0.0002%/5Hz). Neither is there any appreciablechange in response or THD under load [see Graph 2, below].
Distortion is actually 10x lower than Aurorasound’s spec. upto a 1W power output although the maximum 1.45W/25ohm
is slightly lower than might be anticipated from Aurorasound’s
rated 1W/40ohm [single-ended – see Graph 1, below]. While
this is also lower than the 5-10W/40ohm we’ve measured
from some of its high-end competition [HFN Sep ’14 and Jan’15], this and the maximum 13V (high gain mode) voltage
output will be sufﬁcient to drive all headphones in the Heada’s
speciﬁed 16-600ohm range. Keith talks about Aurorasound’s DF
control circuit in our review [see boxout, p57], realised in theHeada by its high (by headphone amp standards) 9.3-9.9ohm
source impedance. The value is about 0.8ohm lower in highgain mode but both will represent a ~2.7dB loss into a 25ohm
load and invite system response variations with low/variable
impedance ’phones. Readers may view a comprehensive QC
Suite test report for Aurorasound’s Heada headphone preampby navigating to www.hiﬁnews.co.uk and clicking on the red‘download’ button. PM

ABOVE: Continuous, single-ended power output
versus distortion into 25ohm ‘headphone’ load

HI-FI NEWS VERDICT
Equipment reviewing would beunalloyed pleasure if only every
item of equipment gave as muchlistening pleasure during itstenure. Partnered with a neutrallybalanced, transparent headphone
the Heada is capable of some of
the best, if not the best, sounds
I have heard from between
capsules. Its alluring warmth ismatched to great resolution,
making for a musical experience
as welcoming as it is informative.

Sound Quality: 88%
0-------- 100

ABOVE: Freq. resp. from 5Hz-100kHz (black) and into
25ohm (dashed) with distortion versus frequency(red, 1V; shaded, 40mW) from 5Hz-40kHz

HI-FI NEWS SPECIFICATIONS
Maximum output (re. 1% THD into 47kohm)

13.0V

Max. power output (re. 1% THD into 25ohm)

1470mW

Output Impedance (20Hz-20kHz)

9.31-9.90ohm

Maximum gain (low/high, balanced input)+5.64dB / +13.8dB

A-wtd S/N ratio (re. 0dBV)

96.7dB

Frequency response (20Hz-20kHz/25ohm)+0.0dB to –0.12dB

Distortion (20Hz-20kHz, re. 40mW)

0.00019-0.0031%Power consumption

12W

Dimensions (WHD) / Weight

260x100x250mm / 3.5kg

www.hiﬁnews.co.uk | REPRODUCED FROM HI-FI NEWS