[ Home | Staff & Contacts | DIY & Tweaks | Listening tests | HiFi Playground | Music & Books ]

Lehmann Audio Stamp power amp and Linear headphone/preamp

Tiny boxes...nice sounds

[Lehmann Stamp power amp][Lehmann Linear preamp]
[Italian version]

Products: 'Stamp' Power Amp and 'Linear' Headphone/Pre-Amp
Lehmann - Made in Germany
Cost, approx: 625/675 Euro
Reviewer: Geoff Husband - TNT France
Reviewed: September, 2007


Of all the companies out there manufacturing hi-fi it was probably Lehmann who was the first to really make a reputation, and ultimately a business by becoming well known almost entirely through the internet. Lehmann's first product, the 'Black-Cube' phono-stage swept to prominence because of the buzz on the net and Norbert Lehmann's willingness to provide samples for internet magazines like TNT at a time when the 'big-boys' saw us as insignificant. The success was entirely justified as the 'Black-Cube' proved to be an excellent phono-stage, and that by cutting visual frills and losing the normal publicity budget, managed to be good value too.

To begin with the company stuck to what it was good at - a range of phono-stages - that is until launch of the Black Cube Linear pre/headphone amp about three years ago, and more recently the Stamp power amp.

Casework is identical for these two products - sort of extended black boxes with a silver (or black) alloy face-plate. As with the first Black-Cube aesthetics are simple, but in this case I find them attractive, and certainly the build quality is hard to fault. They are compact and Lehmann even offer a rack mount kit which allows the pair to be bolted to the underside of a desk or shelf - more on this later. Both are also single box designs - a first for Lehmann who usually use off board power supplies and this too adds to their convenience.

The Linear sports two headphone jacks on the front panel - one cuts the main speakers the other not - round the back are two pairs of phonos - in and out, plus the standard IEC mains cable socket. The only other control is the volume knob controlling an Alps pot, though there is a variable gain DIP switch (0, 10 or 20 dbl) under the unit.

[Lehmann Linear-internal view]

Internally we find a typically neat Lehmann layout on double-sided boards and a decent shielded power supply - 30VA in this case, and it appears to be pretty much dual-mono. Custom caps by Vishay and good quality parts throughout give an impression of a class produce.

The Stamp is even simpler with just two phono for 'in' and two pairs of 4mm speaker sockets (note - not binding posts so banana plugs of one sort or another are obligatory and they'll need to be thin). The amp does have a couple of DIP switches underneath in order to turn the amp into a bi-amping monoblock (speakers need to be bi-wirable), but add the IEC socket and that's it.

Lehmann Stamp - internal view]

The Stamp is a 'digital' amp using Tripath's TA 2020 chipset and produces a claimed 20 watts into 4 ohms, so efficient (87 dbl+) speakers are strongly advised. Once again you're struck by the immaculate layout and care in placing components, with a 60VA transformer and 15000 of Vishay power-supply caps dominating the board.

In Use

The Linear is an oddball. It features one line input and one output and so functions as a single input pre-amp. It is also obviously a headphone amp. To be honest I was a little confused by this - what is the market? Do many audiophiles have just one source? Why then not produce a dedicated headphone amp only, so that people can connect it to their normal preamp? It just didn't make sense, it seemed a terribly niche produce aimed at people with one source and who also used headphones.

Then the penny dropped. The biggest group of users for this product are going to be the growing number of people using their computer as the main music source and/or who want quality music at their workstation. Ah Ha! Is Norbert Lehmann once again getting ahead of the game? With so many people using high-speed connection to download music at ever higher rates, the quality of the components down the chain from the computer have become the bottleneck. Now those clever under-desk mountings for the amps start to make sense. The pairing are going to be spot on for that market.

But sadly I'm not in that market and need every input I can get so I'm not a potential customer (yet!) so in my case the pairing had to perform as the main hi-fi pre/power for the purposes of the review.

As for rest of the usual 'in-use' section, there isn't much to say - you plug them in, little blue lights come on and they work - simple.


The pairing were tried using two speaker systems. The first was my main system driven by the Opera Droplet CD player into my Loth-x Polaris horns, the second pair of speakers were the Trivox Pure S reviewed last month. The latter company actually uses the Stamp during demonstrations and the pairing was recommended to me by Norbert so for once I didn't have to worry about mismatches - the job was done for me.

The inevitable question is of course how does the Stamp compare with the dreaded $30 T-amp. This little wonder is a scary proposition for anyone, but it does have weaknesses. Bass below 200 Hz appears to roll off, and there is a certain sterility to the sound - it's not harsh, just cold.

The Stamp sounded utterly different. In fact I was unprepared for how much more powerful and 'full' it sounded. It's not warm like some valve amps or a Musical Fidelity Class A from the 80's, but it had a weight and purpose lacking in the T-amp. Partly this is down to the Tripath chip the T-amp uses (the 2024), but just a glance at the internals of the two will show we are dealing with a totally different order of construction quality, both in components and their layout. Sadly such time spent of being clever doesn't guarantee success, but in this case the effort is richly rewarded. Personally, though totally awed by the T-amp's abilities at the price I just wouldn't be able to live with it long term in the kind of highly revealing, full-range system I have, the Linear/Stamp is a different-kettle-of-fish...

Take the Pretenders album 'Last of the Independents'. This hugely underrated album has a generally bright and forward mix on CD, and the first track in particular with its opening high guitar and thrash drumming can really make you wince. With some systems I even skip this track or dip the volume so unpleasant can it be The Lehmann pairing kept all its edginess and drive but managed to walk the tightrope of listenability. The album seems to calm down a little after this (perhaps the ears habituate!) and the production can be seen as incredibly detailed and open, with excellent soundstaging. The amp here clearly shows that Tripath characteristic of a huge, wide stage, but also resolves depth better than other digital amps I've tried. The width being better than by own 300b SE monoblocks and the depth similar, if more 'etched'. The danger of such soundstaging is that it can leave much music as disconnected musical units placed in a matrix of ambience - the Lehmanns avoid this by giving the performers more solidity than other digital amps I've tried, so that the whole becomes a sum-of-parts. It's not the 'best' soundstaging in the world, anymore than there is a 'best' wine - it's just one flavour of production and one which this writer is happy with.

Detail retrieval is excellent without pushing small, insignificant details (like breathing and sax mechanisms clattering) to the fore - you get all the music and the frills as well, but don't expect to hear 'the smack of her lips opening' type detail that some aspire to, and which is often the result of emphasising midband detail at the expense of balance and - well music I guess...

Bass performance is tight without being too dry - I like the balance/compromise struck. In some systems you might wish for more weight, but this will depend on system matching as much as personal taste. Certainly the 32 foot organ pipes (16 Hz) from the opening of the 2001 film soundtrack rattled everything in the room, and the almost sub-subliminal Grosse Caisse at the opening of 'American in Paris' tapped your diaphragm, but this sort of trick is hardly relevant to most music... More appropriate is the deft handling of Level 42's bass, and the ambient clues from Madonna's 'I Love New York' during the street scene.

With both speaker systems dynamic swings were well handled, but as both have dynamic abilities in spades and are easy to drive (the Loth-x's ridiculously so) this one would expect. However some amps can sound pushy with such speakers and it's to the Lehmann's credit that they managed to remain smooth through orchestral climaxes and the like. Briefly trying my own Transmission-Line speakers, which are borderline in efficiency, did show up a certain restraint here and in a large room the limit of 20 watts was reached before serious levels, but then this is being a little cruel - every amp has a performance envelope and here I was obviously pushing against it.

More to the point is that the two speaker systems chosen cost 10 times as much as the Stamp, that it wasn't a mismatch is to the amp's credit.

In ultimate terms (i.e. price no object) the soundstage has a certain 'T' shape - the depth being in the centre and the width widely stretched. Compared to expensive SE amps there isn't that silky gloss or sweetness, but in my experience this is one of the very few transistor amps that gets close and obviously has advantages elsewhere - initial cost, running costs (both replacement valves and the electricity bill) and ease of placement.


I know I've ignored the fact that the Linear is a headphone amp as much as a pre-amp. Again I have to plead ignorance of the subject, I've only heard one quality headphone stage (the Graham Slee Solo) and though that design impressed me greatly I'm not going to put it forward as being the be-all-and-end-all by any means - I simply don't have the comparisons to hand. All I can say is that the Lehmann made a very strong case for itself in purely sonic terms. Compared to the Solo the Linear was more open and incisive, the Slee warmer and more powerful. Neither was in any way tiring to listen to and the differences were primarily in presentation rather than ultimate quality. What is different is the way they interface with the system. The Slee stage has two inputs so you could run a system with say a CD player and a Phono stage direct to the Solo to give a two-source, headphone only set-up. Or it could take one input from a preamp and the other from a direct source and so on. The Linear is of course a pre-amp as well, but with only one input it has limited appeal - if you have more than one source you need a dedicated preamp as well so the one 'on-board' becomes redundant.


The Stamp I can recommend wholeheartedly. As long as you are realistic with room/speaker matching it offers true hi-fi sound and because it can be configured for biwiring it allows upgrades and increased power/flexibility as well. It's small, neat, unobtrusive but well made. It's also not expensive for the quality you get. Lastly it's one of those components that I'd recommend blind to someone because it's not fussy in use and seems to have a benign rather than difficult character.

The Linear I find hugely frustrating. The reason is that from my point of view it's an extremely capable pre-amp hamstrung with a single input. Yes the headphone input seems to be well up to driving the very best headphones, but for most people reading this (and me) the single input will just write it off. If you run a single source system, and I'm told some people do, then it's an excellent choice all-round, but it will limit you in the future. BUT (having since talked to him) from Norbert's point of view it is primarily a headphone amp, that because it was easy to do, and the space in the box was there he added a single line level input. So I guess it's unfair me winging on about the single input, but the reason I'm so frustrated is that the damn pre-amp section is so good!

But (again) I can see the letters coming now - 'the future is PC based music' and yes you are almost certainly right. With more and more bandwidth available there's no reason why music downloads shouldn't exceed CD quality and of course the PC will have a CD/DVD drive.

So in a way the Linear has exposed my ignorance of developments in music reproduction - I need a crash course in USB DACs, decent soundcards, high end laptops, recording software and so on. And so, slightly embarrassed by my ignorance, my next 'New Adventure in HiFi' will be to explore the capabilities of the latest generation of PC based stereo reproduction.

Now the really good news - Norbert Lehmann has told me that his next product will be a multi-input pre-amp, and about time too!

systems used

Copyright 2007 Geoff Husband - www.tnt-audio.com

[ Home | Staff & Contacts | DIY & Tweaks | Listening tests | HiFi Playground | Music & Books ]