Parasound HALO A 23 Stereo Power Amplifier 
Home Theater Power Amplifiers Stereo Amplifiers
Written by Brian Kahn   
Sunday, 01 December 2002

Parasound has been producing high-quality audio components at a reasonable price for over 20 years. The new HALO line represents a dramatic improvement in both appearance and performance for Parasound. The HALO series represents a departure from Parasound’s traditional black box styling and is clad in a silver brushed metal finish. Each component in the series has a groove, forming an accent line across the bottom portion of each unit. The end caps of each front panel are slightly off-color from the panel itself. Each of the HALO components has a red "P" at the top center that lights up when power is present. I give the front panel the utter coolness award for its faint blue light emanating from behind the buttons which forms like its namesake -- a halo effect.

The T 3 retails for $600 and is a full-featured tuner, measuring 17" inches, by four-and-one-eighth inches in height, 13" inches in depth and weighing 15 pounds. Some of its features include RDS, 60 memory presets, IR input and output jacks, wireless remote and RS-232 control. The T 3, as with the other pieces reviewed, impressively provided balanced XLR connections and 12v triggers. Looking inside the tuner, I found a host of features and a nice-looking, well-laid-out design.

The power supply of the T3 is constructed of a large toroidal transformer, housed in an epoxy-filled steel canister. The audio signal path and the switching/control circuits have independently regulated power supplies to reduce interference. The multi-gang front end and discrete multi-stage RF circuits are mounted on a dual layer glass epoxy circuit board. Murata filters are utilized in the IF bandpass circuit and laser-trimmed Burr-Brown OPA 2134 FETs are used in class A operation for nearly all gain functions. The remote control that comes with both the T 3 and P 3 are the same, allowing one remote to control both units. The remote allows for selection of one of station presets, direct access of a frequency, or merely scrolling up and down through the available stations.

The new P 3 HALO preamplifier shares many features with the T 3, including its dual layer glass epoxy circuit boards, 12 trigger jacks, balanced connections, IR relay jacks and RS-232 control. The P3 retails for $800 and is a full-featured preamplifier with a phono section, headphone output, processor loop and the above-mentioned balanced connections and remote control. The P 3 measures 17 inches in width, four and one eighth inches in height, 13 inches in depth and weighs 16 pounds even. Each of the units in the HALO series can be rack mounted using a bracket that is screwed to the chassis behind the endcaps using existing chassis screws.

The rear panel of the unit sports a pair of balanced inputs, six line level inputs, a processor loop for theater connection, a detachable AC power cord, balanced and single-ended outputs - features typically found in more expensive products. There are also several switches, allowing the user to choose input voltage, utilize one of the line level inputs as a MM phono input, and lastly a switch that lifts the ground to reduce hum on my review sample unit. Subsequent models of the P 3 will actually not have the ground lift as Parassound found it was unnecessary for a preamplifier. The P 3 has three "direct" inputs, two line level and one balanced, although only two of the three can be used at a time. The direct inputs bypass the tone controls and record output to provide a purer and cleaner signal path.

The P 3's power supply, like that in the T 3, starts with a large toroidal transformer that is encapsulated in an epoxy-filled steel canister to reduce transformer noise. The audio signal path and control circuitry power supplies are again kept separate. The input signals of the P 3 are run through the Burr-Brown devices with FET input stages as found in the T 3 tuner. The P 3 utilizes analog ICs for volume and balance controls, according to Parasound, these ICs allow for closer level matching than the traditional potentiometer.

The last piece in the HALO trio is the A 23 stereo amplifier. This $850 amplifier boasts 125 watts of THX Ultra 2 certified power per channel via John Curl designed circuitry. This unit measures very similarly to the P 3 at 17.5 inches in width, four-and-one-eighth inches in height, 13 inches in depth and again weighs 16 pounds even. While most amplifiers have little or no features to discuss, the HALO A 23 has several. The front panel shares the same aesthetics as the rest of the HALO line yet at the center of the accent groove are two status lights. These lights glow blue during normal operation and red if a fault is detected. There is a small light to the right of the panel, which lights up red if either channel overheats.

The rear panel of the A 23 has both single-ended and balanced inputs, single-ended loop outputs, detachable power cord, handles for easier handling of the amplifier and 12v trigger jacks. There are also switches to lift the ground, an automatic turn-on mode, mono/stereo and switches to choose between balanced and single-ended inputs. Lastly, there are independent gain controls for each channel.

The A23’s power supply begins with a 1kVA encapsulated toroidal transformer with independent secondary windings for each channel. This John Curl design has a hybrid circuit topology for the A 23, utilizing JFETs, MOSFETs and bipolar transistor. Each stage of amplification is complementary, meaning half the transistors amplify the positive half of the musical waveform and half the negative side of the waveform. Differentially arranged JFETs are used for the input stage, taking advantage of their high impedance. MOSFETs are used in the driver stage, as they are known for generating less odd-order harmonic distortion than bipolar transistors. The output stage utilizes three pairs of bipolar transistors per channel. Bipolar transistors are better suited than MOSFETs for delivering large amounts of voltage and current, as they have a much larger safe operating area. The A 23 has several protection devices, DC offset is maintained by a servo system that operates outside of the audio signal path, current sensing transistors and relays are also utilized in the A 23’s protections scheme.

The Music
After setting-up the HALO components, I tuned in a local FM station on the T 3 tuner and let the system run continuously for three days to allow for break-in before any evaluation. No one can really explain why a break-in period for A/V components is electronically important, yet few experts question it. Some say the gear heats up to its best operating temperature. I am not really sure if that holds any weight, but for me and other reviewers, at a minimum, a good break-in period for electronics provides us some time to get accustomed to the sound of new gear without forgetting what our old components sound like.

I first listened to Elvis is Back (DCC Records) and found that the P 3 / A 23 system was more than up to the task when it came to reproducing intimate recordings. While listening to “Fever,” the HALO components had a sense of rhythm and a smooth midrange. Elvis’ voice was well anchored and sounded clean, detailed and without any signs of chestiness. The instruments were also clear and vibrant, placed slightly behind Elvis and spread laterally across the soundstage.

I then moved to a larger scale performance with Queen’s A Night at the Opera on DVD-Audio (DTS). I used the mix-down feature of my Pioneer DVD-Audio player to export a high-resolution stereo output that was suitable for the Parasound stereo preamp. The increased resolution of the format was readily apparent with this album. The midrange remained smooth but picked up noticeably more detail, leading to much sharper imaging. About halfway through the song “You’re My Best Friend,” I dispelled any and all initial notions that the HALO system could sound too soft. While the system’s midrange was smooth and forgiving, it had no problems kicking it up and getting in your face when the source material called for it. On “Bohemian Rhapsody,” the system’s lateral image was very wide, extending well beyond the outside edges of the speakers, although not razor sharp, were well defined. I experimented with speaker positioning and found that the image depth changed little, if at all. With “Bohemian Rhapsody,” the soundstage was beautifully overwhelming. I cranked the volume in an inadvertent attempt to involve my neighbors and the A 23 amplifier had no problems keeping up. The soundstage was very full, extending beyond the outside edges of the speakers and left no noticeable holes. While auditioning the HALO system, I found some instruments to image better than others did on the Queen DVD-A. The drums and guitars were well defined spatially, but the piano was a bit vague as its exact position on the soundstage was hard to pinpoint. As before, the midrange was smooth in a positive way. I have never heard Freddie Mercury’s vocals sound more believable than this. Both Freddy’s vocals and the background vocals were extremely convincing and liquid. The amplifier had plenty of power to handle the dynamics of the drums and guitar when the pace picked up. The drums had plenty of kick and the guitar track was sharp and energetic. I found the sound to be quick and detailed, even at higher volumes where lower-powered amplifiers typically fail. While the amplifier never seemed to run out of power (at least not at any reasonable level), the high end did get a bit hard at high volumes.

Next, sticking with the DVD-Audio format in stereo, I listened to Missy Elliott’s Miss E. So Addictive (WEA/Elektra). While listening to one of my favorite tracks, “Get Ur Freak On," I found the soundstage to be incredibly wide. The vocals of Miss E and her background singers were clean and well defined, without any signs of sibilance at any volume. While paying attention to the bass, I found that the lower octaves had a bit of unnatural bloom or a bloated sound. In comparison, I found the bass definition to be tighter than on the recently reviewed Rogue 88 Magnum tube amplifier ($1,995), but not as well defined as on my Krell 300iL ($3,500) integrated amp.

While conducting this review a friend stopped by with Nine Inch Nail’s live album on CD, All That Could Have Been (UNI/Interscope), which I was able to appropriate for a few days. There was no doubt that Trent Reznor’s use of synthesizers and instruments would provide a challenge for this system. The HALO system had plenty of energy at louder levels to maintain the dynamics necessary to keep the guitar lively. I found no noticeable dynamic compression, nor any compression of the soundstage at higher listening levels. The guitars, while remaining sharp, never became shrill or offensive. Some of the higher notes on the synthesizer seemed a bit brittle and less detailed at extreme volumes. While listening to the track “Pain,” I found that Reznor’s voice and the guitar track were reproduced with a sense of immediacy and detail.

While in a rocker mood, I reached for Van Halen's self-titled album (Warner) and played “Ain’t Talking About Love." The HALO system had no problems with the quick transients of the brown sound guitar and had plenty of power at moderate and slightly above moderate listening levels to hand the dynamics of this classic album. The sound was on the forgiving side and thankfully missing the harshness that less expensive solid-state systems can inflict upon you. Higher volumes did not affect the midrange, but again, I found the higher frequencies to become slightly hard and lose some of their depth and detail.

The T 3 tuner also performed admirably. It consistently performed at a higher level than my reference tuner, the discontinued Yamaha TX-950. Magnum Dynalab provided their ST-2 antenna ($99) to help me pull stations in, which worked well with the HALO tuner. The local station played a lot of Sheryl Crow and John Mayer. Having become fond of the latest Sheryl Crow album, I was able to listen to the song “Soak Up The Sun” on both tuners and 16-bit CD. The T 3 tuner sound had more body and fullness throughout the midrange than the Yamaha tuner. I also found the T3’s soundstage to open up a bit more and provide imaging that I had not previously heard through my reference tuner. The solidity of the soundstage through the T 3 was not at the level of the CD as expected, but very good nevertheless. The biggest difference I found was a sense of palpability through the T 3 that was missing on my older tuner.

Tuners in general have many hurdles to overcome now that radio is available over cable, satellite and the Internet. These other technologies can overcome the problems caused by terrain, and let's not forget that tuners still have commercials. My location, which is nestled in the hills, limits my listening to only a few stations. Listeners who live in areas that are more open will likely enjoy many more stations and the virtue of hearing cutting-edge music at it arrives on the scene.

Perhaps the future lies in a new digital technology that may have just extended the functionality of tuners. In mid-October, the FCC announced the approval of a new digital technology that is said to greatly improve signal quality, and is compatible with traditional tuners such as the T 3. This new technology can be pressed into service as early as January 2003 in major markets. Stay tuned to Audio Revolution’s news section for updates.

The Downside
Although the HALO system made music sound seductive, it did not provide the highest level of resolution that you would expect from products costing many times the price. The system sometimes sounded overly smooth to me, as I am used to my Krell integrated amp. This smoothness is something that music lovers will likely relish, but die-hard audiophiles might feel is a bit on the soft side for their tastes. The soundstage was extremely wide but wasn’t as deep as what I heard when I had the Rogue Audio amp in my rig.

This system is well suited for anyone who wants a higher build quality and improved sound over mass-marketed electronics. At $2,250, this system costs a bit more than most chintzy-looking A/V receivers and you definitely get what you pay for. The look gets a “10" from even the Russian judges and the sound for stereo music reproduction is better than any A/V receiver I have heard in my system by leaps and bounds. The T 3 tuner is one of the lowest-priced full-sized tuners on the market and sounds great to boot. The A 23 / P 3 combination has plenty of power, is well-balanced and free of many of the maladies that plague lower-priced solid-state systems.

This system reproduced every piece of music I threw at it with a sense of coherence throughout the frequency range, with little to no noticeable harshness or other intrusive artifacts. The downsides of the system -- the lack of ultimate low-resolution detail and high-frequency hardness at high volumes -- did not get in the way of me thoroughly enjoying the music. The HALO system is limited to two-channel reproduction, so those who are interested in using their playback system for theater or surround music in the future may be better off waiting for the introduction of the HALO surround processor. For the price, you would be hard-pressed to find a system with better build quality and aesthetics. This system is major league, at a minor league price.
Manufacturer Parasound
Model HALO A 23 Stereo Power Amplifier
Reviewer Brian Kahn

Like this article? Bookmark and share with any of the sites below.
Digg!Reddit!!Google!StumbleUpon!Yahoo!Free social bookmarking plugins and extensions for Joomla! websites!
Joomla SEF URLs by Artio