Parasound - Next Media

EQUIPMENT REVIEW
Parasound
P3 Preamplifier & Halo A21 Power Amplifier
It is my personal view that the world
has too many hi-fi brand-names already, so
I am a bit peeved that a company with the
street-cred of Parasound seems hell-bent on
increasing that number. After more than 25
years in business as plain old ‘Parasound’,
this Californian-based company seems to
have decided to use different ‘branding’ to
differentiate between its different ranges, so
the top-line Parasound equipment will be
known as ‘Halo’ and the second-string line as
‘NewClassic.’ And if that wasn’t enough, Parasound’s rack-mount models are known as its
‘ZCustom’ line.
But if you look closely at the Halo logo,
you’ll see that Parasound is playing it safe by incorporating (in smaller type) the words ‘by Parasound’. Likewise, although the NewClassic line
is advertised as ‘ParasoundNewClassic’, when
you get to look at a product in the flesh, the
front panel bears only the word ‘Parasound.’
What has not changed is that the famous
John Curl is still a part of the design team
at Parasound. If your memory needs a little
jogging, you may recall that Curl became
famous around the world as the designer of
the original Mark Levinson JC-2 preamplifier,
which at the time—and for a good number
of years afterwards—was widely acclaimed as
being the best pre-amplifier in the world. Curiously enough, Curl’s most recent preamplifier design for Parasound recycles the famous
JC-2 model number (the Parasound JC-2).
Curl also designed the Halo by Parasound
A21 power amplifier that is the subject of this
review. (It’s my understanding that although
he certainly played a significant part in the
design of the P3, this preamplifier is ‘not all
his own work.’ )
The Equipment
The Halo by Parasound A21 is rated at 250watts per channel into 8-ohms and 400-watts
into 4-ohms in two-channel mode. If you
want even more power, you can bridge the
two channels of the A21 and operate it as a
32 |
Australian Hi-Fi
mono amplifier, in which case it’s rated to
deliver 750-watts into a single 8-ohm load.
Although the circuitry is entirely solid-state,
Curl has managed to avoid the ‘hard’ sound
quality usually associated with high-power
solid-state amplifiers by using metal oxide
field effect transistors (MOSFETs) to drive four
pairs of 60MHz/15-amp Sanken bipolar output transistors. This odd coupling completely
removes odd-order harmonic distortion components while at the same time extending
the amplifier’s frequency response to beyond
100kHz. Ahead of these, Curl uses matched
pairs of discrete JFETS in a dual differential
cascade configuration. This means very low
noise and that circuit operation is in no way
reliant on the output impedance of the source
component. Rather than use blocking capacitors or trim controls to prevent unwanted
direct current (d.c.) from appearing at the
speaker terminals, Curl instead uses a fast d.c.
servo. This enables speakers to move around
their exact midpoint, rather than an arbitrary
offset position. It also effectively immunises
the circuit against the deleterious effects of
age, so that unlike conventional designs that
uses trim controls, which allow d.c. drift over
periods of time, the A21’s d.c. offset will always be exactly 0V. There are three other layers of protection built in: relays, fuses, and
current sensors. As with all high-end designs,
Curl uses a linear power supply, at the heart of
Reprinted from Australian Hi-Fi magazine
which is a massive 1kVA toroidal power transformer and four 22,000µF Elna electrolytics,
each of which is bypassed by small-value
polypropylene capacitors.
Curl has also elected to include balanced
inputs. These are becoming increasingly common on audio components. I must admit that
I find this a bit puzzling. While I am a confessed fan of balanced connections, this is primarily because I much prefer the convenience
of the larger, three-pin XLR connector, which
I think enables superior terminal mating than
standard RCA connectors. I also like the fact
that if you experiment with making your own
cables (which I do… regularly), XLR connectors are far easier to wire up, and you can easily replace various components in the XLR
plug, such as pin-blocks, shells, screws and so
on. What I don’t agree with is that balanced
connectors ‘sound’ better than unbalanced…
though I’d add in a caveat that this is only
true if you are not experiencing any problems
with induced noise or hum that results from
your unbalanced leads picking up stray interference. If this is the case, balanced lines
are by far the best way to go because their
design completely eliminates the possibility
of any noise or hum inveigling its way into
your system. The way this happens is a bit
technical, so here’s my ‘Idiot’s Guide’ take on
it: A standard unbalanced line has only two
conductors, signal and earth (or, if you prefer, [+] and [–] ). This means that if the wires
carrying these signals pick up another signal,
it simply superimposes on whatever’s there
and manifests as hum or some other type of
interference. A balanced cable has three conductors, signal positive (‘hot’), signal negative
(‘cold’) and earth, but most importantly, the
signal positive conductor is 180 degrees outof-phase with the signal negative conductor.
When a component receives a balanced signal, it looks only for the voltage differences
between the two signals and sends only these
signals for further amplification. Since any
hum picked up in the line along the way will
be identical on all three conductors, it will
simply be ignored by the differential circuit.
Looking back, I guess such a long discussion is likely a bit over the top in view of the
fact that Parasound is not actually asking you
to choose between balanced and unbalanced
connections, but offering you both. Sure this
means you’re paying for the balanced option even if you don’t use it, but in the great
rack. The speaker terminals are standard goldplated multi-way types that will take stripped
wire, bananas or pretty much any standard
speaker connector.
Parasound P3 Preamplifier
Someone has gone to a great deal of trouble
with the layout of the controls and display
on the front panel of the P3. Is it a sort of
electronic Feng Shui? Do consumers identify
more strongly with preamplifiers that have
“Curl has also elected to include balanced
inputs. These are becoming increasingly
common on audio components. I must
admit that I find this a bit puzzling.”
scheme of things, I can’t see that this would
impact too much on the RRP. You could almost make the same case for the bridging
option. This, too, adds to the manufacturing
cost of the A21, yet my guess is that very, very
few people will ever use the bridging option.
Why? Firstly, the A21 is already sufficiently
powerful for 99.99 per cent of users and secondly, because using it means you’d need to
buy a second A21 and bridge that to drive
your other channel—and that doubles the
price of your amplification!
Obviously, you need to be able to switch
between balanced and unbalanced operation,
and between bridged mode and stereo, and all
these switches are provided on the rear panel,
along with gold-plated RCA and XLR (female)
inputs. There are also volume controls (one
for each channel), a ‘loop’ output, so you
can run the input signal to another amplifier if you want, a ‘Ground Lift’ switch, and
a switchable and fully adjustable ‘Automatic
Turn-On’ circuit if you plan on positioning
the amplifier remotely from your equipment
symmetrical control layouts? All questions to
which I doubt anyone will have any answers.
But it sure looks good, so there’s both rhyme
and reason in it.
The photograph accompanying this review should be large enough to see what controls are fitted, but if not… Either side of the
central display are bass (to the left) and treble
(to the right) controls. They’re electronic, so
as you press either the ‘Up’ or ‘Down’ buttons, you’ll see a read-out in the display as to
the amount of boost or cut you’ve dialled in.
Very nice. If when you press these buttons,
nothing happens, you’ll need to first press the
‘Tone’ button just under and to the right of
the Bass > button. To the left of this ‘Tone’
button is the source selector control. There
are six sources to choose from, plus two input/output loops, one of which is identified
as a ‘Record’ loop and the other simply as
‘External.’ Obviously, if you’re using external
processing of some sort, you’d use this latter
loop, while you’d connect a CD-R recorder to
the former loop.
Parasound P3 Preamplifier
& Halo A21 Power Amplifier
Brand: Parasound
Model: P3 Preamplifier & Halo A21 Power Amplifier
Category: Pre & Power Amplifiers
RRP: $1,695 (P3)/ $4,295 (A21)
Warranty: Three Years
Distributor: Network Audio Visual Pty Ltd
Address: Unit 6B, 3–9 Kenneth Road
Manly Vale
NSW 2093
T: (02) 9949 9349
F: (02) 9949 6972
E: sales@networkav.com.au
W: www.networkav.com.au
Reprinted from Australian Hi-Fi
magazine
Australian
Hi-Fi | 33
Parasound P3 Preamplifier & Halo A21 Power Amplifier
Parasound has provided extraordinary
flexibility with its inputs. There are two ‘Direct’ inputs, which both by-pass most of the
internal circuitry, to give the purest signal.
One of these (Direct 1) can be driven by a balanced or an unbalanced source (selectable via
a switch on the rear panel). There is a phono
input, but if you have no need for it, you can
quickly and easily change it to a standard
auxiliary input, again by means of a switch
on the rear panel.
Once you have selected your source, you
can adjust volume via the front panel control
on the far right, or via up/down push-buttons
on the infra-red remote control. This remote
also adds a Mute feature that’s not available
from the front panel but that’s about all. Most
of the 35 buttons on the remote can only be
used to control Parasound’s T3 AM/FM tuner.
Outputs are also flexible, with your choice
of balanced or unbalanced. Actually, there’s
not really a choice as such, you can use either or both… if you can think of an application! There are also external remote jacks
(input and output) and 12V triggers (input
and output) plus and RS232 port. The fit and
finish of the P3 was extraordinarily good, but
I did notice that the surface of the right-most
balance push-button on my sample had some
very slight imperfections, as if there were tiny
‘bubbles’ under the surface of the anodising.
Since my review sample had obviously ‘done
the rounds’ before I got it, it’s entirely possible this was not a manufacturing fault but
the result of poor handling or outright abuse
(at least one hi-fi reviewer of my acquaintance
has been known to apply heat to determine
whether a finish is metal or plastic!)
Listening Sessions
I couldn’t wait to fire up the Parasound combo,
and was pleasantly surprised right from the
get-go by the attractive blue-coloured LEDs
that are behind all the knobs, which contrast
nicely with the red-illuminated ‘P’ logo. The
display is also a bright blue colour, with dotmatrix style lettering. Making tone and balance adjustments is straight-forward, though
the display in the ‘balance’ mode is basic in
the extreme, looking for all the world like an
old ‘Space Invaders’ game from the DOS days.
Given all the buttons and lights, not to mention the dot-matrix display, I was surprised to
find that there doesn’t appear to be an indicator to show whether or not the tone controls are in-circuit or defeated. Maybe I just
missed something. I regret that I made a note
to double-check this, but by the time I re-read
my note about the need for double-checking,
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Australian Hi-Fi
I’d already returned the amps. It’s of no real
consequence—if you’re not sure you can simply press the ‘Tone’ button—but it does seem
odd. By contrast, if you press the ‘Mute’ button on the remote, the word ‘MUTE’ is writ
large in the front-panel display, leaving you
in no doubt as to why there is no sound! I
was thrilled to find that switching to a different source does not cancel the mute, and
that touching either the volume controls on
the remote or the front-panel volume control
instantly cancels the mute function. This is
exactly what should happen, yet few manufacturers manage to get it right. One thing I
am not sure Parasound has got right is the
headphone socket on the front panel. It’s
a 3.5mm phone socket instead of the more
usual 6.5mm one. I know that it looks neater,
and that because of the iPod, more and more
headphones are now being supplied with the
smaller plug rather than the larger one, but
it’s not as if there wasn’t enough room on the
front panel, is it?
You’ll be pleased to hear that this is where
my carping ends, because when it comes to
the operation and sound of this duo I could
find absolutely nothing to criticise. The controls all operate perfectly and precisely and
the sonic performance is just out-and-out
stunning! In the end I did end up using the
balanced connections (and in the case of my
CD player, right from the source) for almost
all the listening sessions… though I did, of
course, end up using unbalanced connections for my turntable listening (so far as
I know, no-one has yet developed a phono
cartridge with a balanced output!). So, needless to say, hum and induced noise were not
a problem. Indeed I’d go so far as to say that
I think this is the quietest pre/power amplifier
combination I have ever auditioned, and this
Reprinted from Australian Hi-Fi magazine
Parasound P3 Preamplifier & Halo A21 Power Amplifier
“the sound issuing
from the Parasound P3
and A21 was as clean
as a whistle.”
36 |
Australian Hi-Fi
particularly important when you’re playing
back at the relatively low volume levels that
are more common in domestic living rooms.
I did actually check the noise levels when using unbalanced connections and though I
couldn’t do an instant A–B comparison, what
I did hear convinced me that noise levels
were just as vanishingly low with the unbalanced connections as they were with the balanced, so self-evidently the circuitry has been
designed for low noise levels right from the
outset.
I seem to recall that the ultimate ‘amplifier’ is a straight wire with gain and from what
I heard from this Parasound combo, they’d
come very close to this ideal, because not only
could I not hear any noise behind the signal, I
also could not hear any signal distortion. This
proved to be the case not only when listening to music, but also when I listened to specially prepared test signals designed to reveal
the presence of harmonic distortion, should
it exist. No matter what I tried, and irrespective of the volume level, the sound issuing
from the Parasound P3 and A21 was as clean
as a whistle.
I should say that when I say ‘irrespective
of volume level’ I don’t think that in any of
my auditions, despite using a variety of speakers of varying efficiencies, I ever came even
close to approaching the A21’s maximum
output power—not even close! The A21 is an
incredibly powerful amplifier; of that I have
not the slightest shadow of a doubt. My own
amplifier is rated at a shade over 120-watts per
channel and the A21 just blew it away. Not
so much in sheer volume—as I said, I didn’t
even begin to approach full volume—but in
terms of dynamics. I could be playing both
amplifiers equally loud, but when it came to a
crescendo, or even a savage attack on a kickdrum, the A21 handled it so much better, delivering a free-er, far more ‘natural’ sound. I
can only liken it to driving a small-engined
car up a steep hill. You can be travelling quite
nicely, and it seems as if you could easily go
faster, but when you put your foot down, you
find that absolutely nothing happens—the
car doesn’t speed up at all. Ever had that feeling? Now imagine you’re driving a powerful
V8 up the same hill at the same speed. If you
put your foot down now, the car will rocket
up the hill with a vengeance. It’s the same
with Parasound’s Halo A21.
This power does not come at the expense
of subtlety. I took particular care to listen
carefully to the very tiniest details of performances, right down to the whisper of pages
being turned by performers, faint sounds in
audiences, even the breathing of singers not
singing at all, but simply awaiting their entrance, and I could detect no difference in
these details between the P3/Halo A21 and
the same signal played through headphones…
yes, these Parasounds are that good.
Conclusion
Sometimes I think Parasound is harbouring a
death wish because despite the fact that it is
building state-of-the-art components, its retail prices are consistently so low that many
audiophiles don’t even ask for an audition. I
should tell Parasound’s execs the true story of
a start-up here in Australia that entered the
dry-cell market by trying to sell very highquality alkaline batteries at half the price of
the two ‘biggies’ (Eveready and Duracell).
The company bombed, because no-one even
tried their batteries because they seemed too
cheap. The company then re-invented itself
and re-entered the market with exactly the
same batteries, under a different brand, but
this time priced just a few cents below the
premium brands. Success was immediate and
it’s now in a three-way tussle for the No 1 spot
in the AA and AAA categories. So my message
to Parasound regarding its P3 and A21 is that
these are truly great products and you’d be
selling a lot more of them if you set the retail
prices a lot higher than you have. My message
to you, dear reader, is that you only have a finite amount of time up your sleeve before the
good folk at Parasound read this review!
Jutta Dziwnik
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Reprinted from Australian Hi-Fi magazine
Parasound P3 Preamplifier & Halo A21 Power Amplifier
TEST RESULTS
Test Results
Power output was massive! As you can see from
both the tabulated figures and the bar graph
results, the A21 exceeded its rated power at all
test frequencies and into all loads, registering
its highest output (808-watts/29.0dBw) when
driving a 1kHz test signal through only one
channel into a 2Ω load. When driving a both
channels into standard 8Ω loads, Newport Test
Labs measured a minimum output (at 20kHz)
of 268-watts per channel, 18-watts higher
than specification. Under the same conditions, the A21 delivers 276-watts at 1kHz.
Measured into 4Ω loads with both channels
driven the Parasound Halo A21 exceeded specification by a minimum of 41-watts (at 20kHz)
and by 50-watts at low and midrange frequencies. It delivers nearly 500-watts into 4Ω with
only a single-channel driven, which is an indicator of the headroom available under dynamic conditions. Driven into 2Ω, the A21 comfortably delivered nearly 700-watts per channel
at all frequencies except in the extreme bass,
where the amplifier’s internal protection activated at an output level of 450-watts.
Graph 1 is a spectrogram showing the total harmonic distortion (THD) present in the
output of the Parasound P3/A21 combination, at a level of one watt. You can see that
there’s a second harmonic at –100dB, a third
harmonic at –110dB and a fourth at –112dB.
These components are all far below the realms
of audibility, either singly or in combination.
Look, too, at the noise floor, which is sitting
at –120dB above 1kHz and for the most part is
more than 100dB below reference below 1kHz.
Reducing the load impedance to 4Ω has a very
small effect on the harmonic distortion components—such as they are!—with the most
significant being an increase in the level of second harmonic distortion to –90dB (equivalent
to a distortion level of 0.003%). This is shown
in Graph 2. Overall THD+N at one watt was
measured by Newport Test Labs at just 0.006%.
Distortion increases significantly at rated
output, as you can see in Graph 3 (which
shows the distortion spectrum at 250-watts
output into 8Ω) and Graph 4 (400-watts into
4Ω). Although you can now see harmonic distortion components stretching out to the 13th
and beyond in the 250-watt/8Ω graph, the second and third components at 2kHz and 3kHz
are both in the order of 90dB down (0.003%),
the fourth and fifth components are in the
order of 100dB down (0.001%) and all other
components are even further down again. At
400-watts into 4Ω, the second harmonic is at
–80dB (0.01%) and the third and fourth have
increased slightly in level. More significantly,
the structure of the distortion components
has changed from being evenly distributed
between the odd- and even-order harmonics
Continued on page 100
38 |
Australian Hi-Fi
Reprinted from Australian Hi-Fi magazine
Parasound P3 Preamplifier & Halo A21 Power Amplifier
Continued from page 38
to favouring the odd-order harmonics. Also,
you can see from the sidebands down around
the fundamental (1kHz) and stretching up to
4kHz, that the power supply is finally running
out of puff. This is hardly surprising: dropping
400-watts of power across 4Ω means the A21
is delivering a continuous current of 10 amps.
Note also that because of the increased power
output, the noise floor is even lower again, almost down at the –140dB limit of the graph.
Despite appearances, summing all these distortion components and adding in the noise
still gives a THD+N figure of just 0.005% at
rated output, which is an order of magnitude
better than most high-power amplifiers, including high-end designs.
The Parasound P3/A21’s frequency response was outstanding. Newport Test Labs
measured it as extending from 1Hz to 59kHz –
1dB and from 0.5Hz to 105kHz –3dB. Remember that most manufacturers quote frequency
response specs separately for the pre and
power amplifiers. This measurement includes
both! The response within the audio band is
shown in Graph 5. The black trace shows the
response into a standard laboratory test load
(a Dale 8Ω non-inductive high-power resistor). You can see that it’s incredibly linear, and
only 0.04dB down at 7.5Hz and 0.14dB down
at 20kHz. Using the normal 20Hz to 20kHz
criteria, the frequency response of the P3/A21
would be within 0.07dB. The other trace on
the graph shows the frequency response into
a load that simulates that of a typical two-way
loudspeaker system. This normally causes the
frequency response of most amplifiers to deviate well outside their specification, but in
this case the Parasounds still returned a result
of 20Hz to 20kHz ±0.07dB. Notable is the fact
that the red trace for the most part does not
deviate from the black trace by more than
0.02dB! Indeed, in order to show up such
a vanishingly small difference, Newport Test
Labs had to expand the vertical (dB) scale
of this graph to 0.04dB per horizontal division, which means it’s far more ‘zoomed-in’
than you’ll normally see in this (or any other)
magazine. The more usual graph presentation
is shown in Graph 5a, which has horizontal
divisions of 0.2dB. As you can see, only the
non-inductive response is shown because at
this magnification, it would overlay the other
response anyway!
Channel separation was excellent, with
a best result at 1kHz of 90dB, reducing to 84B
at 20Hz and to 70dB at 20kHz. Remember,
these tests are with both the P3 and the A21
being tested as a single entity. Even better was
channel balance, which came in at 0.028dB.
This would be good in a high-end stereo integrated amplifier, and is unheard-of in a pre/
power combination.
100 |
Australian Hi-Fi
“The Parasound P3/A21’s frequency response
was outstanding. Newport Test Labs measured it
as extending from 1Hz to 59kHz –1dB and from
0.5Hz to 105kHz –3dB.”
Reprinted from Australian Hi-Fi magazine
TEST RESULTS
Parasound Halo A21 Power Amplifier - Test Results for Power Output
Channel
Load (Ω)
20Hz
20Hz
1kHz
1kHz
20kHz
(watts)
(dBW)
(watts)
(dBW)
(watts)
20kHz
(dBW)
1
8Ω
294
24.7
294
24.7
285
24.5
2
8Ω
271
24.3
276
24.4
268
24.3
1
4Ω
490
26.9
495
26.9
484
26.8
2
4Ω
450
26.5
454
26.6
441
26.4
1
2Ω
450
26.5
808
29.0
760
28.8
2
2Ω
450
26.5
690
28.4
684
28.3
Note: Figures in the dBW column represent the output level, in decibels, referred to one watt output.
Parasound P3 Preamp and Halo A21 Power Amplifier - Test Results
Graph 5b simply shows the boost and cut
action of the P3’s tone controls. You can see
that boost is restricted to around 7–9dB and
cut is bang-on –10dB. The boost is quite properly shelved, so using the tone controls won’t
mean you are overdriving your tweeters at
ultrasonic frequencies (or overdriving your
bass drivers at infrasonic frequencies!), which
is what happens if there’s no shelving. Using
the controls does have a very slight effect on
the response at midrange frequencies, but it’s
difficult to tell what it is from this graph because it appears to me that whoever ran the
test at Newport Test Labs failed to properly
calibrate the ‘flat’ response at precisely 0dB,
and I doubt that boosting the controls actually results in there being less level at 1kHz!
Intermodulation distortion was almost
completely non-existent, as you can see from
Graph 6. The two test frequencies of 19kHz
and 20kHz are towards the right of the graph,
and are reproduced at the correct level. There
are two unwanted sidebands appearing at
18kHz and 21kHz, but they’re at –95dB, or
0.001%, so would be inaudible and inconsequential. As for the main purpose of this particular test, I can’t see any unwanted signal
regenerated at 1kHz at all, which is a fabulous
result (for the A21 in particular). The small
spikes in the noise floor at the extreme left of
the graph appear to be power supply-related,
Test
Measured Result
Units/Comments
Frequency Response @ 1 watt
1.0Hz–59kHz
–1dB
Frequency Response @ 1 watt
0.5Hz–105kHz
–3dB
Channel Separation
84dB / 90dB / 70dB
(20Hz/1kHz/20kHz)
Channel Balance
0.028dB
@ 1kHz
THD+N
0.006% / 0.005%
1 watt/rated o/p
S/N Ratio (unweighted/weighted)
91dB/97dB
dB re 1 watt output
S/N Ratio (unweighted/weighted)
109dB/115dB
dB re rated output
Input Sensitivity (CD input)
104mV/1.6V
(1 watt/rated output)
Output Impedance
0.025Ω
OC = 2.8447V
Damping Factor
320
@ 1kHz
Power Consumption
28.0/143.0 watts
Standby/On
Power Consumption
405 watts /753 watts
1-watt/Rated O/P
Mains Voltage Variation
231–252 volts
Min–Max
with some 50Hz at –97dB and the others more
than 100dB down.
You can see that noise is low on the graphs,
so the tabulated figures should be no surprise,
with the A-weighted S/N figures coming in at
97dB referenced to 1-watt and a stunningly
good 115dB referenced to rated output.
I think a signal-to-noise ratio of 115dB is the
best I have ever seen from any amplifier. Sure
this figure is given a boost because of the very
high output of the A21, but it’s still a magnificent achievement for Parasound. The
frequency response into a simulated speaker
load should have given you a hint that the
A21 had a high damping factor, and this indeed proved to be the case, as you can see
from the table, with the A21 scoring a result
of 320 at 1kHz.
The power consumption figures show that
the duo draws quite a lot of mains power at
stand-by (28-watts) and a significant 143watts when the two are switched on but doing nothing at all. Consumption increases to
405-watts when the amplifier is delivering
just one watt to your speakers and to 753watts when it’s operating at rated power, so
it’s not an overly ‘green’ amplifier and this
will certainly be reflected in your electricity
utility bill!
Tested with square waves, the Parasounds
came though with all guns blazing. The 100Hz
square wave shows not a skerrick of tilt (indicating an extended low frequency response)
and no ‘curve’ to the top (showing no phase
shift). Indeed it’s almost indistinguishable
from the 1kHz square wave, which has such
a good shape that it would be easy to swear on
a bible that it came straight from a function
generator, rather than via the P3/A21 combo.
The 10kHz square wave has a rounded leading
edge, which is due to the frequency response
starting to roll off above 59kHz; otherwise, it’s
excellent. The final oscillogram, which shows
square wave performance when the amplifier
is loaded down with a parallel capacitance, reveals that the A21 will be unconditionally stable into any loudspeaker load and in particular will drive electrostatic models with ease.
There’s a tiny single-cycle overshoot visible
that rises to less than a quarter of the overall
wave amplitude, and a complete recovery after the second cycle.
If I had designed Parasound’s Halo A21,
I’d be mighty pleased with myself, so Curl
deserves an enormous pat on the back, and
Parasound is to be commended for managing to deliver such superlative performance at
such a low price, but I shouldn’t neglect the
P3, which more than played its part in achieving these results… superb performance from
both components.
Steve Holding
Reprinted from Australian Hi-Fi
magazine
Australian
Hi-Fi | 101