The following article is republished on this website with kind permission of TNT-Audio/Lucio Cadeddu. All rights remain resereved at TNT-Audio/Italy.

Phono preamp Lehmann Audio
Black Cube

 Lehmann Audio (Entec) is a new German HiFi Company with ambitious plans: design and build hi-end level components at an affordable price. Norbert Lehmann, the man behind the project, isn't totally crazy though. He is an electronic engineer with an incredible know-how and who has understood that time was come to shake the Hi-end market with some top-level products at prices as low as possible, saving everywhere BUT in the sonic quality of its designs. So aesthetics, finish and attractiveness of his designs are optimized to reduce the production costs. In other words what NAD and Rotel (and others) have been doing for years in the low-end of the market. More or less the same ideas behind the old Audio Alchemy project.

Norbert Lehmann has hence designed some products, a phono preamp and some digital converters (DACs), rather ugly to see but, as we will discover later on, a pleasure to the ear (and to the wallet :-) ).

The Black Cube is the solid-state MM/MC phono preamp under test: an ugly small black box (11 x 10 x 4 cm, more or less the same size of three piled CDs) with no switches, no chrome finishes, no gold knobs, nothing that can attract your eyes. Outside.

 

Everything changes on the inside of the box: a top-quality construction which makes use of top-notch passive and active components and a precision that is simply stunning.
The project, with respect to the RIAA equalization network, has been based mainly on the paper On RIAA Equalization networks by Stanley P. Lipschitz, published by the AES journal.

If you dare to judge this preamp from the outside you start wondering why this product is quickly becoming a MUST for every serious vinyl addict. It seems that after the Black Cube has started to be distributed in the US, the Company has been literally buried by requests of 110 V models.

The Black Cube has also an ugly separated power supply, one plastic black box that reminds those of the external modems and similar stuff. Even the cable between the power supply and the preamp seems poor and cheap. At a first glance. Then you soon realize that it is a hi-quality shielded cable, instead. It is 2 meters long so that the power supply can be placed very near from the preamp itself. Uhm, you just begin to understand.
And you begin to understand that for 695 $ this preamp shoud have something special inside. The price isn't exactly low (there are separated phono preamps that are way cheaper) but then you should consider that the Black Cube isn't just an affordable preamp, it is an Hi-end level ambition preamp. Hence, when compared with the prices of some hi-end preamps, its price can be considered incredibly low, IF AND ONLY IF :-) its sound is of hi-end level. We're going to prove this.

Some technical data

As already pointed out, the Black Cube is a MM/MC phono preamp which can be adapted for every cartridge in the market, just by means of some switches easily accessible from the inside of the box. If you prefer, a custom version for your needs can be requested to the Company.

The capacitance is a standard 220 pF and the MM gain is of 40 dB while the MC stage gain is 60 dB. The output impedance is less than 100 Ohms and the channel separation is greater than 85 dB.
The RIAA frequency response plot is simply impressive: even with an enlarged scale the two channels graphs are coincident, a fact that explains the accuracy of this preamp.

This is actually one of the pluses of the Black Cube project: an accurate top-level construction in order to deliver state-of-the-art musical performance. The RIAA equalization network is entirely passive and makes use of top-quality WIMA MKS 5% caps and low-noise metal film resistors. The board is two sided and the RIAA passive network is placed between two active input and output stages which make use of top-quality op amps by Analog Devices.

The RCA connectors are gold-plated. The power supply section is quite sophisticated: it contains several anti-RFI stages to minimize noise and spikes from the mains. Once the *cleaned* voltage reachs the preamp board it is filtered once again, before the input stage and one more time before going into the output stage.
The designer admits that a good part of the sonic performance of his Black Cube is due to this highly sophisticated power supply section for, in order to achieve the best performance from the active/passive circuits, one needs to feed them with the best clean and regulated voltage available. The Black Cube has no on/off switch so it has been designed to remain permanently connected to the mains. Its power consunption is 0.7 VA.

The Sound of the Cube

The Black Cube is a solid-state preamp but nothing of its sound reminds you of the worst *solid-state* sound nor it is *tube-like* in its worst meaning, i.e. slow and extremely smooooth.
It is like it should be: absolutely neutral. And let me add that its sound is a clever mix of the best solid-state precision and of the best tubes charm.

The frequency response is well extended in the bass, so extended that it is hard to believe, if one looks at the size of the preamp.
Audiophiles tend to associate a good bass response to the size of the component. If it is huge and heavy it should have a excellent bass response :-)

Clearly the Black Cube knows how to extract bass information from the grooves of your vinyl while the in-board subsonic filter has no effect on the audible range. Thumbs up.

The bass range reminds the best solid state amps, fast, tight, well extended and articulated. The first things that hits you is how fast can sound the bass range of this preamp: the electric bass lines are so easy to follow that even when the musical program is complex you can still hear every single note and the same applies to the left hand part of the piano: deep, articulated, and powerful.

Or, when the electric bass and the kick drum beat at the same time, you are always able to distinguish the metallic note of the string and the sound of the skin of the drum. This bass has something of the best tubes, too: it has breath and life, some organ pedal tones remain *in the air* and you can nearly touch them with your fingers.

This is the breath of the real Music: nothing too sharp with unnnaturally fast decays. Fast attacks and fast decays only when and if needed. As I said before, a clever mix of fast solid-state sound and tubes breath and charm.

Going up to the mid range, it is very difficult to find a fault: it is so clean and detailed that sometimes it seems slightly behind the rest but you are aware this is a well known psychoacoustic effect: when the midrange is so clean and free of every harshness it seems slightly *on the tame side*, since we are often used to harsh, distorted and forward mids.

And you begin to understand how are the mids of this preamp once you listen to the female voices: sexy and warm or aggressive and harsh, every singer's personality is respected by the Black Cube, it knows pretty well when to sound smooth and warm and when to be aggressive. The same happens with the reproduction of a drum: you can hear the *skin* and the *shape* of the drum (dear prof. Kac, please forgive me :-) ).

Even with complex musical programs you are always able to hear every single beat of the drum kit, well defined, powerful, fast and very, very realistic.

Take the right hand of the piano as another example: you can hear the metallic sound of the notes, with an amazing richness of the harmonic components of the fundamental notes.
When reaching the high range this behaviour remains the same, the high range is so coherent and precise that every tiny information is brought to you with a natural sense of grace, no excesses and no contraints.

A tasty cocktail of solid-state precision and of tubes warmth which is very difficult to not fall in love with.

This preamp is so coherent that if the Black Cube was a loudspeaker I'd say that the cross between the tweeter and the woofer is acoustically invisible. It is not warm and slow or fast and dry...it sounds warm and fast, almost a contradiction, indeed, but very, very close to the real thing.

Dynamics

Here's where the solid-state soul takes the lead: you wouldn't believe how dynamic can sound your vinyl unless you listen to it by means of a serious phono stage. The Black Cube is one of these. Fast, tight, dynamic and explosive like the best preamps in the market, clearly a top-level performance. It doesn't matter if you listen to audiophile or commercial LPs, the Black Cube will make them sound at their best, if when poorly recorded you'll be able to hear the details and the liveliness you though it was lost in the years.

Pace, timing, swing: it's all in there, inside this tiny, ugly black box. It will surprise you record after record, song after song, opera after opera. It will bring new life to your old LPs, no matter how bad they are. This impressive liveliness and dynamics shouldn't be thought as a unnatural hurry. The Black Cube knows when to slow down, when to use its velvet touch instead of its explosive punch.

3D imaging

One of the big pluses of the Black Cube, definitely. The most impressive aspect of this performance is the depth of the virtual soundstage. The rear wall does no longer exist, literally destroyed by a 3D stage so deep that you wouldn't believe to your ears, a soundstage crowded by virtual objects each one of which has a well defined position inside of it, both with respect to height and width.
This happens even with poorly recorded LPs, those with very few soundstage informations. The Black Cube extracts them and builds a virtual image that is stunning for precision, focus and realism.
The accuracy of the construction and of the components used pays its dividends here and the Black Cube performance is really top-class: something that many recording engineers should hear to understand how properly (or poorly) the recording place informations have been transferred into their discs.

From an audiophile's point of view, the Black Cube allows to discover every fault of the recording, a singer as tall as a dwarf, guitarists that play inside the kick drum or violins that play inside the timpanis :-)

This was the designer's original idea: to give to the hi-end crowd a component so precise and accurate to be considered of studio-quality, at a price as affordable as possible.

Some advice

The Black Cube is a very user-friendly device: just plug in the cables and enjoy it. Before judging it leave it connected to the mains at least one week or, if you listen to your system just over the weekends, leave it permanently connected, the power consumption is low and the circuits will thank you and reward you with a top-class performance. An omni-comprehensive owner's manual will tell you how to properly configure the Black Box for your cartdrige otherwise you could have the Lehmann Audio guys doing the job for you. You should place the Black Cube as near as possible to the turntable in order to use the shortest path from the cartridge to the phono preamp.

Just to point out one more time how much attention has been given to this project, Lehmann Audio makes a version of the Black Cube that can be placed right inside some turtables (ask them for more details). Otherwise place it over a vibration-free shelf (no, not the subwoofer :-)) and the Black Cube will reward you with a performance that is insensitive to the kind of shelf you're using, not like many other hi-end components that have some idiosyncrasy for some tables. The Black Cube isn't a *prima donna* if you know what I mean. It will give its best without driving you crazy.
Clearly not only its circuits but also its mechanical construction is well-thought too.

The obvious (forgive me) final advice is to connect it to a line input (CD, tuner, aux) of another preamplifier: the Black Cube has no volume control and your preamp phono input won't appreciate much the high voltage that comes out from the Black Cube ;-)

Conclusions

When Hi-end becomes affordable and clever. This would suffice to describe the Lehmann Audio philosophy. The Black Cube has an ugly body and a wonderful heart, all you need to enjoy your LPs for the years to come. I hope to see more of such clever designs, we don't need brass knobs, gold plated cabinets, just plain serious good sounding Hi-end components that don't cost an arm and a leg.
Kudos to Norbert!

Thanks to Norbert Lehmann for having sent me the Black Cube for reviewing. More infos on the Lehmann Audio (Entec) products can be found on the Lehmann official Web site

Copyright © 1998 Lucio Cadeddu