December 2009

World Premiere!
King Rex PREference Preamplifier And Pop Pulse T150 Amplifier
A very odd mix of pluses and minuses tangled together two at a time.
Review By Ron Nagle
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  Boundless curiosity definitely has a down side. My on line product research led to so many side branches that if it they were laid out on paper it would resemble a highway map. The hook was baited for me in Montreal at the 2009 Salon Son & Image show. The Salon show is primarily a dealer-oriented event held every year at Montreal's Le Centre Sheraton Hotel. At this show I found myself a stranger in a strange land and everything looked strange (French) to me. It seems that up in the Far North some of our Canadian Cousins were and are into some exotic flavors of high-end audio. Specifically speaking, it was the components on display in Salon 7, the Obad Imports demonstration room. Obad is an on line direct marketer that operates out of two Countries, Langley, British Columbia and in the U.S. from Blaine Washington. The proprietor Sasha Obad specializes in importing novel audio components usually difficult to find outside their home countries. When entering their demo room my first impression was that they were getting some very nice sounds from some very tiny Chinese black boxes. One in particular caught my attention it was the King Rex PREFerence Preamplifier it had much to my surprise an optional Phono Stage circuit board. Note: The odd spelling is exactly the way the King Rex Company writes the word preference.

Preamplifier Configuration
The KingRex Technology Co. is based in Taipei City, Taiwan. The supplied user's manual is written in Chinglish. The PREference preamplifier contains a high quality Op-Amp and a "Diamond Buffer" also a "Current Booster" and a DC servo circuit to avoid coupling capacitors. Note: There is no further technical explanation on the web of what the heck comprises a Diamond Buffer or the Current Booster. The preamplifier is divided into two parts. "The less distortion than a switching power supply" is separate from the control and active circuits. Both units are housed in substantial black anodized aluminum enclosures and both measure 7.25 x 5.5 x 2 (WxDxH in inches). There is an on/off switch at the back of the power supply and an IEC style power cord receptacle and a 3-pin XLR connector on either end of the cord sending power to the preamplifier. Of great interest to me is the access cover on top of the preamplifier. If you slide it back you have access to dual left and right 5 position Dipswitches. These switches allow the preamplifier that is equipped with the optional plug in Phono Stage to adjust cartridge loading and gain. There is a list of all the switch settings printed under the top cover. My review sample came equipped with this Mm/Mc cartridge step up circuit board. There are three voltage gain settings, listed on the manufactures site, 7, 14 and 20 dB. Additionally there are three cartridge resistive load settings, 100, 220 and 47 kOhms and two capacitive load options, 0 and 100 pf.

The front panel of the KingRex control preamplifier is simplicity itself. A source knob on the left selects one of the four inputs and at the right is an Alps RK 27 volume control knob. In the center between the two knobs is an array of five blue LED's the center LED is on when the unit is powered up. Forming a square are the four remaining blue LED's they are on when the corresponding input signal is selected. Note: All of the four pairs of RCA inputs on the rear and front panel are numbered from one to four with roman numerals.  Now looking at the rear panel there are the four pairs of co-axial RCA input jacks plus one additional pair labeled preamp output. If the preamplifier is equipped with the optional Phono Stage the number four pair of RCA's is then used for the cartridge input. Two things remain on the rear panel, a grounding post for the turntable cartridge and a three-pin XLR female connection for the DC power supply. In a separate box there are eight cone-shaped feet and eight disks that are placed under the pointed feet. That is four disks under the power supply and four disks placed under the preamplifier.

The Pop Pulse T150 Amplifier
This is a Class T digital audio integrated amplifier.  The PP T150 Power amplifier was a last minute suggestion made by Sasha Obad to link up with the PREference preamplifier. As a consequence when it arrived I really had hardly a clue about what made it tick.

Other than the obvious physical construction of this amplifier and the fact that it was a Class-T design, no explanatory literature came with it. The Pop Pulse appearance is of a black painted sheet metal rectangle measuring, 6.25 x 10 x 2.5 (WxDxH in inches) and weighing approximately 9 pounds. The front panel has a blue power on LED and a large volume control knob. At the rear there is the usual IEC power cord socket and an On/Off switch. Additionally there are four insulated speaker cable binding posts and two left and right channel RCA preamplifier input jacks. Oddly there is only one XLR output socket on the back panel.  I believe that this single XLR female input socket on the rear panel is used only if you use two PP T150 amplifiers in a mono configuration, one amplifier for each speaker.

This dearth of information necessitated more surfing on the Internet to fill in some of the blanks. In April 25, 2008 the Tripath Company declared bankruptcy. The intellectual property was sold to Etelos and then in a back merger with Cirrus Logic. Now it is Cirrus Logic who produces the Tripath circuits. Gathering data on line I can now tell you the Pop Pulse amplifier was manufactured in Hong Kong by Wickin Development Ltd.  Apparently my sample was upgraded and uses a higher power Tripath Ta-2022 circuit. It is rated at 75 wpc and it may be bridged to produce 150 WPC. Another site tells me that the volume control can be bypassed but nowhere does it tell you how to do it. There is something you should be aware of. Some specifications given by manufactures from Asia do not always follow U.S. guidelines. As an example the power rating might be listed as 150 watts but that's a combined total for both channels. Additionally it may be listed at 4 Ohms with no mention of the RMS specification.

Listening
Note: All my listening was done with Kimber 8TC speaker cables and my Aurum Cantus Leisure 2 SE speakers.

In spite of some confusion about specifications the bottom line is as always to ENJOY THE MUSIC (sorry they made me write that). Installing the PREference and the Pop Pulse in my system was straight forward, the small size and lightweight made everything much easier. The preamplifier as received was a show demo and I had been assured that it was broken in. However the Pop Pulse amplifier was new. But as it turned out the Pop Pulse amplifier never seemed to require any time to break in, the sound essentially remained the same for as long as I had it in my system.

From the very first the combined PREFamplifier and Pop Pulse T-150 power amplifier exhibited what they can do and do very well indeed. And that presentation is comprised of lightening fast transient attacks painted over a dead quiet background. This is in combination with deep bass and slightly bright treble that seems to be more prominent as I listened to my reference CD's. The sound in stereo is the width of the two speakers and extends about five or six feet back where it flattens as if against a solid wall. In this space there is image location and a modicum of height information. My reference CD recording is Basia-Time And Tide, [Epic EK40767]. On this recording the subjective bass boost is not in any way offensive as a matter of fact it just might get your toes tapping to the tunes.  This bass prominence was the single most noticeable characteristic for as long as I kept these two components playing in my system. Which one of these two components is responsible for this bass sound? OK, let us find out. I connected the PREFerence Preamplifier directly into my reference Sanders ESL power amplifier via: 1.5 meters of Audio Research Litzline coax. Consequently with the Sanders amplifier in the system the sound was far more frequency flat from top to bottom. Obviously the low bass prominence was mainly coming from the Pop Pulse T150. At first you might miss the excitement of the bass beat that compels you to tap your feet. But after awhile you realize what your hearing is a closer approximation of what's on the recording without the added bass.

Phonograph Follies
With both the PP T-150 amplifier and the PREFerence back in the system I Installed a Shure V15 V-MR phonograph cartridge on my SOTA turntable and Grado Signature arm. My reference, The Shure V15 Moving Magnet cartridge came with a very impressive individual test print out listing the cartridge output as 3 mV at 1 kHz. Also the frequency response is within 1 db across its entire range. Now we get to the feature that originally ignited my curiosity. Think about the optional add on phono stage and some of the possibilities. We have a small preamplifier with an Mm/Mc phono input that allows you to adjust the gain along with the resistive and capacitive cartridge loading. After installing the Shure high output cartridge I thought the preamplifier gain at 12 db was still to darn low. And so for all further cartridge tests I set the preamplifier gain to the Moving Coil maximum setting of 18 db. The resistance was set at 47k and the capacitance to the maximum100pf. First vinyl up on my SOTA table was a mint two dollar formally owned Tri-fold album titled America Homecoming [Warner 0598 BS-2655] circa 1972. The first cut on side one is my favorite, Ventura Highway. As I listened the excitement is back, driven by the elevated Pop Pulse bass and fast transient treble from the lead guitar. However all is not well; something is missing, there should be a bit more lower midrange information. The same sonic symptom can be heard on another great used two dollar chunk of Rock and Roll vinyl, the Eagles Greatest Hits, Asylum 60305-1. It sounds as if the RIAA compensation network is not totally accurate. Let me mention one last album I bought at the 2009 RMAF show. It is a brand new Boz Scaggs double album Speak Low [Decca 80012025-01]. This is a quiet vocal arrangement of classic pop songs with a piano accompaniment carrying the melody. Listening to this album there is not much low frequency information and therefore the midrange sounds just fine. 

Reconnecting the PREFerence Preamplifier directly into my Sanders ESL amplifier and playing the same vinyl recordings with the Shure 15 V-MR cartridge. As you would expect the overall frequency response is far more even from the bass up to dog whistle levels. Removing the Pop Pulse amplifier from the system ameliorates/flattens most of the elevated bass. But even with far less boom in my room there still needs to be more lower midrange information coming through the PREferenc preamplifier. As an added benefit there is a noticeable lowering of vinyl groove noise when listening with the Sanders amplifier. Now one last factoid: the Sanders power amplifier does not have as much gain/volume as the combination of the PP T150 power amplifier and the PREFerence preamplifier.

Evaluation
What a very odd mix of pluses and minuses tangled together two at a time. This story ran me down more than a few side alleys as I tried to divine who did what to whom. First notable finding is that the PREFerence RIAA phono compensation is not completely accurate when used as a stand-alone vinyl preamplifier. Even with a line level signal this preamplifier subtly elevates the bass and treble response. Now what follows are two characteristics endemic to my system. The preamplifier gain is lower than I would like it to be with the Sanders Amplifier. In addition I did not use my Alpha 1 moving coil cartridge because the cartridge voltage is under 1 mV. Also the preamplifier load settings are limited and do not approximate my cartridge manufacturers specifications. However if you have a music system built around CD or some other non-vinyl higher-level sources some of my nit picking preamplifier comments will not apply to you. And finally I do have a problem with the $1600 PREFerence price tag. There is just too much competent competition out there for that kind of money.

However, Obad Imports lists many affordable hi-fi goodies on their website and their $379 Dollar King Rex Pre-Amp is certainly worth taking a long look. The Pop Pulse power pumper is a strange beast, a mixture of sonic zing and what was that? OK, maybe it is not exactly neutral but certainly a lot of fun to listen to? And so at this juncture I should ask, what kind of music do you like to listen to? Do you play your music loud and do you like big bass? You could use it to bi-amp the woofers of stereo speakers or to power a separate AV subwoofer. All things considered I think the Pop Pulse T150 amplifier is most certainly an unequivocal steal at $260 Dollars.

Semper Hi Fi

Foot Note
To wrap up this story up let me wax philosophical for just a moment. It is about the combined effect of these two components and the performance channeled through them. The relevant comments some might make would be to compare their performance to the sound of tubes or the best qualities of solid-state electronics. But in this instance that would not be an exact fit. These auditions made me think that in the future we might have to make room for a third audio analogy. It would not be just about digital circuits but encompass all compact integrated circuit designs and the sounds they reproduce. I believe that in the future audio may need a new yardstick based on a different set of strengths and tradeoffs, and of course everything involves tradeoffs. Everywhere else outside of two-channel audio this is what is driving technology. At this point does any of this new chip off the old block technology bring us closer to the sound of live music? Hell no, but curiosity compels me to wonder what is over the next hill. 

Reference System
Sanders ESL Power Amplifier, Audio Research SP 9 MK 3 Preamplifier,

Marantz DV 8400 Universal CD player, Cambridge Audio Discmagic-1 CD transport, Cambridge S-700 Isomagic HDCD D/A Converter fed into ART Audio DI/O Tube D/A and A/D processor Up sampling output to 48/96, Magnum Dynalab FT101a tuner and Dynalab Signal Sleuth. Aurum Cantus SE2, Sota Sapphire 2, Grado Signature arm with Shure V15 V-MR.

Three meter Kimber Cable 8TC, 3 meter RCA, 3 meter, Wire World Eclipse-2, RCA, 1 meter Chord Silver Siren, 1 meter and Wire World 10 gauge IEC power cord, Audiobhan 0.5 meter unbalanced digital

System Power conditioning inclues the Richard Gray 20 ampere Substation, Islatrol Industrial 20amp ac line conditioner, Alpha Core Balanced Transformer Power Supply, Audio Power PE-1 power enhancer, Triad 2-ampere isolation transformer, VPI Magicbricks, Argent Room Lens system, Room Tunes Panels, and a comfortable chair.

Specifications
Rex PREference Preamplifier 
Inputs: Four via RCA stereo pair
Outputs: RCA stereo pair
Gain: 7,14 and 20 dB selectable
Frequency Response: 5Hz to 80 kHz (+0~-1.0dB)
Maxium Input Level: 9 Vrms (@0dB)
Maxium Output Level: 9 Vrms
THD+Noise: <0.0005% @ 1 kHz
Input Sensitivity: 1.1V For 2.5V Out @ 7dB gain
SNR: 126 dB
Channel Separation: 112dB @ 1 kHz, 92dB @ 10 kHz
Price: $1599

Pop Pulse T150 Amplifier
Type: Class T Digital Audio Integrated Amplifier
Frequency Response: 15Hz to 80 kHz (-1dB)
Power Output: Output Power: 77 wpc stereo or 150 mono
Inputs: Stereo pair RCA and one balanced via XLR 
Protection: over-current and over-thermal
Volume Control can be bypassed 
SNR: 88dB 
THD: 0.05% (1 kHz) 
Audio Input Sensitivity: 200mV
Weight: 10 lbs.

Company Information
Obad Imports
Langley, BC Canada & Blaine, WA

Voice: (415) 692-5401
E-mail: sasha.obad@gmail.com