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KingRex Preference Pre amplifier

[Kingrex Preference pre amplifier]

Out of this world? - Two Reviewers Decide...

[Italian version]

Product: Product name: KingRex Preference.
Manufacturer: KingRex
Cost: 1195 UKP (1500 with phono). (YMMV)

Reviewers: Nick Whetstone - TNT UK and Geoff Husband - TNT France
Reviewed: January 2010

By happy chance KingRex sent samples of the Preference to both Nick and Geoff - read on to see what both of them thought...

The inclusion (or exclusion) of a pre amplifier in a system can and does have a profound influence on the sound of that system. Some swear by leaving it out altogether, or at least using what is called a passive pre, ie one with no active electronics. A lot depends on the source component, and the power amplifier of course, but I tend to favour an active stage and have investigated many options, both commercial, and ones that I have built myself. The KingRex Preference, is by quite a way, the most expensive that I have tried in my own system and I was obviously keen to see how it acquitted itself.

Kingrex Preference in packaging. If first impressions are anything to go buy, the Preference certainly gets off on the right foot. Inside the outer packaging is another cardboard box but nothing like the standard brown stuff used to protect it during transit. Instead, a black satin finish (with chrome silver printing) gives an impression of luxury that is maintained when you open the box and find the Preference, and its dedicated power supply snugly accommodated in black packing foam. A nicely produced instruction book (albeit in 'Far-east English') is included, as is a mains cable and the umbilical lead that goes between the PSU and Preference.

That impression of luxury is continued as the Preference is removed from the foam insert. It is finished beautifully in Satin black with quality satin silver control knobs. I'll be honest, my own preference with cases is not to have any fasteners on show but those on the Preference case are so neat that it doesn't really detract from what is a classy looking piece of equipment. The case of the PSU is finished to match the Preference and a nice touch is the use of locking XLR connectors to connect the umbilical between both units. Both pre amplifier, and power supply unit, are half width size.

The Preference is built around a high quality op-amp and diamond buffer using the BUF134 and OPA627. A current booster has been added to the output of the amplifier stage to enhance 'drive-ability', and a DC Servo circuit has also been implemented to remove the need for coupling capacitors. The separate power supply is another classy touch, and boasts more audiophile components.

In use, the luxury feeling is continued with the silky-smooth controls of the Preference. Both the attenuator knob, and the source selector knob move so smoothly that you feel that you could almost turn them by blowing on them. The source selection is slightly unusual in that the knob can be turned infinitely in either direction. As it moves from stop to stop, one of four blue LEDs lights up to indicate which source is selected (via a relay). A fifth blue LED in the centre of the other four is the power indicator. In my main listening room I didn't find these LEDs too bright, but in my smaller room where I was sitting about a metre closer to the Preference, they were a bit OTT. I guess that it will also depend on the ambient lighting in the listening room, and personal preference (or is that tolerance?) as to whether people will find the LED's too bright or not.

One issue that I did notice with my review sample and that was the source selection defaulted to the number 2 input when the unit was powered up. A minor annoyance if you want one of the other inputs. And while I am having a moan, I would have liked to have seen remote control for at least the volume control on a pre amp at this price. I appreciate that adds extra cost to production but with so many of us using PC based sources of music these days, and with even cheapish hi-fi now coming with remote control facilities, I think that we have to expect the same from the more up-market gear too. That said, the operation of the Alps Blue potentiometer is silky smooth and perfectly quiet in use.

On the plus side, KingRex are offering a degree of customization with the Preference. It's possible to change some of the opamps to tweak the sound. I quite like the OPA627, and didn't have anything to hand that I thought I may prefer. It's also possible to change the level of gain by moving a couple of jumpers. You need to remove the top cover to do so and then change a pair of jumpers. This should make the Preference compatible in almost any system, and less dependent on the gain in the power amp, and the efficiency of the speakers. It's interesting to try different gain settings when you have the option. As I said, much depends on the other components in the system, but it is clear that different gain settings, in different parts of the system, do make more of a difference to the sound than increasing, or decreasing, the volume level!

[Kingrex Preference pre amplifier interior]

The sample that I received for review had no phono stage partly because KingRex were short of modules, and also because I don't currently have a turntable set up anyway. So my review is about the Preference used as a line-level pre amplifier.

Kingrex asked me to give the Preference a long burn in time and I obliged by running it for a few weeks before I got down to serious auditioning. I then put it straight into my main system, SB3, Monica3, Preference, amps, Hawthorne Audio Duets. I'm going to say straight away that how you will like the Preference depends much on the type of power amplifier that it is used with. I started off with a Virtue V1 that has its pot bypassed, making it essentially a class-T power amplifier. With the V1 the Preference shows its transparency, and what I consider to be a gentle handling of the signal, ie what goes in, pretty much is what comes out. That results in a wide variation of tone and micro detail, and a subtlety that is both engaging and musical. There is layer upon layer of detail with the Preference. For instance, it is easy to hear a duet as two voices rather than a single 'sound'. It's the same with something like a guitar duo. Everything is well controlled and 'accurate', and while the Preference gives the impression that it has the music in a vice-like grip, it appears to be using velvet gloves that allow all the nuances and macro-details to come through unscathed. All in all, it's very enjoyable but there was something not quite 'right' with the Preference/V1 combination. If I had to say just what, I would say that it sounded too 'solid-state'!

In fact, when I moved the Preference to a system using another class-T amplifier, eg Charlize or Trends 10, the results were the same. Very impressive, and nothing really to write down as a negative. But again not quite right. In my experience, these amplifiers sound much better with a valve pre amp or buffer, and that gave me the clue to take out the Virtue V1 from my main system and put in the Yarland FV-34C valve amplifier. And the result was that the good points of the Preference were still very much in evidence, but the balance was also 'right'. But it was much more than that. The tone (for me) was perfect, neither too warm nor too cold. The bass was tightened up, and the already very good timing that the FV-34C is capable of seemed even better. There was no doubt in my mind, the FV-34C with the Preference in front of it is much better than when connected directly to the DAC. In fact it was one of those combinations that you feel is 'made in heaven'. I was a little disappointed not to have a valve power amp to hand, ie one where the signal is not passing through another pot, but the combination was still highly addictive to listen to. The results were very similar with the Miniwatt valve amplifier as well, although it seemed an odd combination from a cost point of view with the Preference costing so much more than the valve amplifiers. I suspect that a more up-market valve power amplifier would be the perfect partner for the Preference. I've heard valve power amplifiers with a very good valve pre amplifier but I would suggest to anybody running valve power amps that they try the Preference as they may get quite a pleasant surprise.

[Kingrex Preference pre amplifier rear view]

All of which is a little strange as Kingrex don't produce a valve amplifier. I have not heard their own power amplifiers but as the T20U is a Tripath 2020 based amp, I have a good idea that it would not make the ideal partner for the Preference. That's not to say that they don't have a 'right' to produce what is a very high quality pre amplifier of course, just strange that they don't have a matching amplifier, at least at the time of this review.

Perhaps hi-fi happiness is rather like a sandwich where solid state is the bread, and valves the filling (or vice versa)! Certainly some of the solid-state power amps benefit from a valve stage before them, and although many owners of valve power amps also turn to valves for the pre, the performance of the Preference in my system(s) indicates that they would do well to audition it against a valve pre amplifier.

I won't go so far as to say forget the Preference if you have class-T amplification (or class-D) because you may like the combination, and of course, the speakers will make a difference too. And there may be solid-state power amps that sound excellent with the Preference, a lot depends on personal taste of course. But if you have good quality valve amplification I can strongly recommend that you try the Preference if you are looking for a pre amplifier that will pass the signal from the source in a manner that will show the power amps at their best. Aside from the lack of remote control, I would certainly recommend the Preference to anybody looking for a serious pre amp. It looks good and it sounds even better (with the right power amplifier).

© Copyright 2010 Nick Whetstone - www.tnt-audio.com

A second look by Geoff Husband

A couple of months ago I was delighted to learn that as well as sending their new pre-amp to me, Kingrex had also sent one to Nick. Now this is rare, but I really like such opportunities as not only does it give the reader an idea of how two different reviewers see an item, but also perhaps how it works in two completely different systems. From a personal point of view it's also interesting to see if what I hear is remotely what another reviewer is hearing.

As Nick got his copy out first I get to dodge the boring technical stuff (most of which I don't understand) and really concentrate on what the thing does, but by way of introduction the amp is neat and sexy in that miniature hi-fi way, and works just fine.

Ah! But there is one think Nick missed – in every sense. His pre-amp came without the built in phone-stage that graced my sample. This is a flexible, fully featured stage with variable load and gain controlled by DIP-switches just like a Lehmann stage. These switches are accessed by sliding back a panel on the top-plate, unusual and very easy. Besides that Nick and I were hearing the same thing, though our systems are very different...

When something is delivered I always give it a quick check – it's not normally a time when I take notes, but in the case of the KingRex the thing jumped out at me so immediately that I was compelled to sit down and make a load of preliminary notes so forgive the scrappy nature of the 'Part 1' but it offers an insight into my first impressions.

Listening Notes Part 1

Yesterday a delivery man handed over a box containing the KingRex PREference. As usual I plugged it in to make sure it all worked, nothing is worse for a manufacturer than to send a component and then after the reviewer has sat on it for a month, to get an email that their baby is dead...

Anyway I plugged it into my main living-room system rather than the more usual review system as it was convenient.

It replaced a rather fine, and rather expensive valve pre-amp and thus ended up driving the Yamamoto A-08s Single-Ended, 45 valve amp. So a small transistor pre-amp powering a real 'hair-shirt' 2.5 Watt amplifier, which in turn provided current for my own full-range Loth-X Polaris horns. If you were going to throw a transistor pre-amplifier into the deep-end this is just the sort of system you'd choose, and it's the last combination you'd imagine would work together!

So what follows are my initial, spur-of-the-moment, unedited, rambling impressions over a whole variety of records, Jazz, Classical, rock and female vocal I've heard over about 6 hours. That I've spent so much time, so quickly, on such a selection of music will give you a clue as to why I felt these initial impressions so important. As I write I have no idea how much the KingRex costs, no idea what is inside those two black boxes (or whether you could build a clone for 50 Euro + P&P from Maplins) and I didn't expect the combination to be a match made in Heaven.


Good on CD, in fact very transparent, big detail, lovely drum kit on 'Take Five' sax a bit thin but very clear and not at all harsh, very tuneful. Lovely brushed cymbal, piano a little further back in the mix but great drive.

Time for a record. Set the phono stage for Moving-Coil (MC), maximum gain and 100 ohm loading for the DRT-1s. Hmmm, pretty noisy, still I guess it's asking a lot to replace the ESE Nibiru. But hang on, moving the power-supply as far away as possible made it much better, no way should they sit side-by-side. Put on 'King James' (always a safe bet) damn the turntable's running fast. Get up to adjust it, but no it's actually running slightly slow. This little pre injects so much pace!

Holy Moly! Just listen to all that metal being bashed in the percussion. This thing loves cymbals! They are pushed forward in the mix, prominent strikes but followed by a real sense of 'tinny' body. Not as full and rounded as the valve pre it replaced, but not in any way distorted or harsh. Lots of depth to the image, in fact imagine pretty exceptional all round. The chapel that 'King James' was recorded seemed to have harder walls, the drum kit more isolated. Dynamics good without quite the clout of the valve pre. Lots of detail coming through; Madonna's 'Till Death Do Us Part' clearly showing the detail of the second voice, the various electronic noises very clear.

This is starting to impress me an awful lot, huge transparency, it's lifted the Yamamoto up to the level of the Ayon Crossfire in this area. The result isn't quite the same! The KingRex+Yamamoto pairing being a little thinner and with this incredible pace dominating everything.

Incredible feeling of Deja-Vu, the Roksan Xerxes turntable has exactly the same effect on the system, how very strange...

Bass powerful and tuneful, perhaps a little thudding with kick-drum, but may be the recording, must investigate further.

Handles the opening organ in 'Zarathustra', very clean and working the REL sub hard, though not quite the scale it could have. Climax well handled without getting edgy. Really, really impressive for a built-in phono stage; as good as many 500 Euro stages I've heard. Doesn't seem to have an RIAA roll off (thankfully), any 'anti-rumble' being very gentle if there at all.

Sheesh this thing makes everything sound exciting/interesting, for these jaded reviewers ears there's always the risk of 'different' being seen as 'better', but the pre doesn't do anything badly, it doesn't irritate me. I spent all evening listening to Jazz without my wife complaining once so it is pretty glitch free. Not sure it's going to be so happy with an incisive transistor amp, really needs the purity of SE valves, or maybe the warmth of a 'class-A'. Using it with a Xerxes would probably give me a heart attack, but it'd liven up an LP12 a treat:) Not something that would match small, bright, bandwidth limited speakers either, the Loth-X's just love the presentation though, no crossover or dodgy tweeter to get pushed into edginess. How on earth can a transistor amp match the SE amp so well!

This is something that I need to spend a lot more time with and really get to know, but right now it's making music fun and that's worth a lot...


So now lets calm down and take a long hard look at the performance over a couple of months.

Listening Notes Part 2

After the surprising synergy with the Yamamoto A-08s SE amplifier it was natural to continue for much of the review with this combination. This is high praise! Few items remain in my living-room system, because generally I don't like messing around with it as it's perfectly balanced for the room, and I like to leave the inevitable disruption to the specific listening room. But in the case of the KingRex, even after prolonged exposure, the little pre-amp continued to make some very sweet music with the Yamamoto.

So first lets look at what it doesn't do. It doesn't work very well with the KingRex T20power amp! In fact I tried it with several of the new breed of digital amps and in every case it left them feeling a bit grey and hard, lacking soul and flow. Of the one's I had to hand the Lehmann Stamp was the best match, it's a noticeably sweet example of the breed, but even here it's well behind the Yamamoto. It also didn't sound like the Kingrex pre-amp I reviewed a couple of years ago - an amp that matched the T20 rather well.

The problem is that the Preference is simply too transparent. It doesn't add any warmth or gloss to the signal; in fact (and I don't say this lightly) it's the most transparent pre-amp I've heard. The way it exposes the slight greyness of digital amps is a prime example. To be fair to KingRex, Christine (my contact there) did suggest that the pre-amp wasn't at its best with their own amps and advised something like a Class A. That's quite an admission, and I can only look forward to the moment when they do produce a matching amp.

Following this advice I did try the Preference driving the Jungson Ja-99. Obviously the Jungson is an integrated and so doesn't really need a pre-amp, but it was interesting in that using the Preference into one of the Jungsons's inputs (set to max) showed practically no change at all in the sound, again showing the lack of artifice of the Preference. Sadly the Jungson doesn't have a pre-in so in effect the signal was going through two pre-amp sections, but at least the Preference didn't screw the sound up, and the warm powerful character that I liked so much in the Jungson remained.

But whatever I tried, and no matter what Christine told me, after each experiment the little amp (which was easy to move of course!) was put straight back into the living room system to be paired with the Yamamoto, I was finding it hard to live without.

In my original review of the Yamamoto I praised it, but I was convinced that one of the reasons the Ayon Crossfire (which is an integrated) was more transparent was down to the pre-amps I had to partner the Yamamoto A-08s. The KingRex confirmed this, because it made all the pre-amps I had to hand (more expensive pre-amps) sound as if they were slugging the sound. With the KingRex the Yamamoto really showed it's true colours and in combination the pair got very close to the Ayon in the areas of detail, transparency and sound staging, lagging behind only in the areas of macro dynamics and really low bass control.

Which brings me to the one part of this review where I have to fly solo; the phono stage. What can I say? All the comments above originate primarily from my listening to vinyl. At first I used my Nibiru Phono stage into one of the Preference's line inputs, but with all the swapping, and also out of interest I began to increasingly use the Preference's on-board stage.

I've had many phono stages here over the last ten years. Of course they vary, but only one has a significant lead over the little Preference's stage and that is my own Nibiru. The Nibiru costs twice what the Preference does, and it's lead, primarily in weight, power and the sheer size of players in the soundstage, is gratifying, but ultimately not so great that I felt irritated or short-changed when using the Preference solo. Like the rest of the amp, the phono stage shows an openness and clarity to shame some stages up to 500 Euro, all without a hint of grain. In fact it reminded me strongly of the Lehmann Black Cube SE and that means a lot.


I grew to appreciate the way the selector didn't have a stop position but could just be rotated, but others might not like it. The size (not the sound or build) won't impress your friends for the money. As mentioned above, the phono stage picks up noise from the power supply, and so though the two look neat next to, or on top of each other, the power supply really needs to be as far away as the power cable allows.


The Preference is an exceptional pre-amp and contains a phono section that would worry most stand-alone stages. With it KingRex have gone from a company making neat budget components to reveal ambitions to do something really special. That a confirmed valve nut is now by preference (sic) using a sand based pre-amp with a Single-Ended power amp shows a lot, but then considering that I also use a transistor phono stage perhaps that's not such a surprise.

So well done KingRex; now go and design a matching power-amp. :-)

© Copyright 2010 Geoff Husband - www.tnt-audio.com

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