Lehmann Audio DAC+ Digital-to-Analog Converter

by Frank Alles

From the designer of the Entec/Lehmann Black Cube phono stage, Norbert Lehmann, comes a new digital product designed to compete with the creme de la creme of high-end DACs, all for the low-low price of $1995. Enter the Lehmann DAC+. Because the name Entec is already owned here in the US, the German-based Entec company will market all of its products imported into the US under the Lehmann Audio moniker.

Features

What puts the plus in the DAC+? Well, the designation implies that the DAC+ is more than a mere DAC, and it is. In this case, we have an onboard volume control and switching for one auxiliary input. Additionally, there are three types of digital outputs, TosLink, coaxial, and AES/EBU, and choice of four digital inputs, AES/EBU, two coaxial, and one TosLink. With the DAC+ you can dub digitally while listening to an analog source via the auxiliary input selector. Front-panel features include LEDs to indicate power on/off, choice of auxiliary input or digital inputs 1 through 4, "Lock" of the signal from the transport to the input receiver, "Pro" which indicates selection of a professional source (e.g., hard-disk recorder or professional DAT recorder) and finally "DE" which signifies that the recording was made with pre-emphasis and that the built-in de-emphasis filter is active. (This feature is important only for older CDs when pre-emphasis was used with the first digital recording processors.) There are a series of five push buttons to facilitate input selection and a Noble potentiometer with a black-chromed brass volume knob rounding out the package.

Speaking of features, the one feature that I would like to have seen on the DAC+ but was nowhere to be found, was an absolute polarity reversal switch. Call me crazy, but I’m one of those people who claim to be able to hear sonic differences when absolute polarity is inverted (as it often is). Two of the most obvious differences I usually focus on are an increase in treble energy combined with a more repressed midrange. Also this converter does not employ HDCD decoding, which I can’t always say I miss.

On the rear apron are the digital inputs and outputs, the power switch, and one pair of single-ended analog outputs. There is also a pair of RCA jacks for the auxiliary input. A female IEC receptacle allows for easy power-cord swaps.

From an aesthetic perspective the DAC+ is somewhat nonplused. It is your everyday basic slim-line rectangular black box. The push-button labels are engraved into the faceplate and are hard to read from virtually any distance. In practice, it might make the most sense just to familiarize yourself with their layout and commit it to memory, as Norbert Lehmann suggested to me. (There are those of us with poor recollective abilities, and I must confess that I forgot what Mr. Lehmann suggested.)

In addition to the external control features, the DAC+ contains several options for its internal configuration. Removing the cover, you will see three sets of jumpers on the main audio board. These are tiny plastic-covered clips that push onto the jumper posts. J1/J2 allows bridging the volume control, J3/J4 allows the +6 dB buffer stage to be bypassed, and J5/J6 bridges the output capacitors for a DC-coupled output stage. I will elaborate more on the effects of the various settings further along in this review.

Under the cover, high-quality parts and construction are the rule. A Crystal CS 8412-CP input receiver is used in conjunction with a high-grade CS 4329-KP Crystal DAC chip, with 20-bit resolution. All standard sampling rates are supported (32kHz, 40,056 kHz, 44.1kHz, 48kHz). The analog section uses op-amps by Analog Devices, select relays, a metal shielded Noble volume pot and WIMA MKS output capacitors. Heavy-duty gold-plated RCA jacks are employed as well as Neutrik XLR connectors with gold-plated contacts. The DAC+ has a maximum rated output of 2V, or 4V if the +6dB buffer stage is engaged, with the volume control rotated fully clockwise.

System

Initially I used my Parasound C/BD-2000 transport feeding the DAC+ via a Wireworld Gold Starlight III AES/EBU digital cable. The amplifiers were Clayton Audio’s M-70 class-A monoblocks which were linked to my Paradigm Reference Studio 100 speakers with a biwired 10' run of Wireworld’s Equinox III speaker cables. The interconnects were Full Spectrum Audio Signatures. A Parasound D/AC-2000 Ultra converter and Krell KAV-250cd CD player were my alternate digital references.

Later on I tried running the DAC+ through different preamps, including my AHT (tube) linestage and a home-built passive unit. I also tried my Radio Shack CD-3400 portable CD player as a transport with a DH Labs coaxial digital cable. Other speaker systems included my Acoustat IIIs, driven by custom direct-drive (tube) servo-charged amps, and the InnerSound Eros electrostatic hybrids, using the Clayton M-70s on the electrostatic panels.

Setup

Over a period spanning several months I’ve had ample opportunity to acquaint myself with the virtues of the Lehmann DAC+. This has been a pleasurable and positive experience in that the performance of DAC+ is easily on par with that of my reference Parasound DAC in most parameters and is actually a bit better in certain areas. As stated previously, the DAC+ has several different modes of operation depending on how you configure its three pairs of internal jumpers.

Although I did not perform extended listening tests with every possible combination, some clear patterns emerged. To me the direct-coupled mode of operation sounded slightly etched and artificial, so I tended to stay capacitor-coupled throughout my listening. Capacitor coupling places a capacitor in the signal path, which makes it impossible for any DC offset to be present in the output of the DAC.

As convenient as it was to have an integral volume control on this unit, the sound in my system was actually a bit more transparent without it, so I normally left it bridged out of the signal path. If you do opt to use the onboard volume control, keep in mind that this will allow you to connect the DAC+ directly to your amplifier inputs with no need for an additional preamp, be it active or passive. This option worked out best when used in conjunction with the +6dB output line buffers because the sound was simply too thin and anemic when using the internal volume pot sans buffer stage. This brings us to our third variable.

There is an analog line buffer stage that adds 6dB of gain to the outgoing analog signal and lowers the output impedance, which means the output stage will be better able to cope or interface with the input impedance of a given amplifier. The benefits of this, in addition to the extra 6dB of gain, are an increased sense of liveliness or dynamics and a bit more extension and power, especially in the low frequencies. However, for me this was a double-edged sword. Although I thought the line buffers added a touch more snap and slam, I found that the unbuffered mode offered a greater degree of overall transparency and added a little more air, ambiance and depth to the soundstage. In my particular system the difference in dynamics and bass was more subtle than severe. However, this is an area that could go either way depending on the user’s preference and his or her associated gear. So experiment -- that’s the name of the game.

This said, be aware that most of my listening tests were performed capacitor-coupled, with the volume control and line buffers bypassed. This was my preferred modus operandi on most occasions. What I found was that with the +6dB buffer stage engaged, the lower treble appeared more prominent and the midrange was a bit thinner -- which mimicked polarity reversal. So when I whipped out my copy of I Don’t Wanna Go Home by Johnny & The Jukes [Epic EK 34180], which I have marked as sounding more natural with the polarity inverted. I got the full double whammy -- an extra dose of bright and thin, that is. To say that this recording didn’t sound harmonically accurate (or akin to the way I’m used to hearing it) would be a fair statement. Fortunately this wasn’t a big problem with most material, but it was one more reason that I elected to eschew the use of the line buffer stage.

But I know what you’re thinking: Why pay extra for a volume control, switching facilities and a line buffer stage if you’re not going to use them? My answer is that this unit is the only one I know of that allows the user the flexibility to tailor the sound and features of the DAC to suit individual needs. In the end, you may prefer different choices than the ones I made. Used in a different system with other gear, my own preferences could vary as well.

Listening impressions

This is the good-news part of the review because I’m here to tell you that when all is said and done the Lehmann DAC+ is one outstanding-sounding piece of audio gear.

First off I noticed that the DAC+ had a deeper and punchier bottom end than my reference Parasound DAC. Playing bass-heavy material such as Paula Cole’s "Tiger," from This Fire [Warner Bros. 9 46424-2] or Copland’s Fanfare For The Common Man [Telarc CD-80339], the DAC+ offered up all the lower-frequency oomph one could reasonably ask for, and then some. It seemed to add a half an octave of extension to my Paradigm Reference Studio/100s, and with the InnerSound Eros electrostatic hybrids it exhibited authority that was most impressive and stimulating.

The bass was not only extended, it was also taut and tuneful. Runs on acoustic bass on tracks like "It’s Like That" from US3’s hand on the torch [Blue Note CDP 0777 7 80883 2 5] burst forth with all the agility and body one could hope for. The electric bass and kickdrum on Erykah Badu’s "Rimshot" from Erykah Badu Live [Universal/Kedar UD-53109] couldn’t have been much more convincing. With regard to bass performance, there is little doubt in my mind that the DAC+ would be ranked as one of the top performers in its price category.

For speed and transient snap try a recording like Cecilia Barraza’s "Canterurias," from The Soul Of Black Peru [Warner Bros. 9 45878-2], which features Barraza’s vocal accompanied by some fearsome licks on Spanish guitar and backed up by high-level Black Peruvian percussion. Here the Lehmann DAC+ provided all the transient snap and bite of the actual instruments without sounding hard, etched or artificial. This is a cool recording -- a collection of Black Peruvian music by various artists selected and compiled by head Talking Head David Byrne, who also performs the last song on the album, "Maria Lando." Highly recommended.

While I do consider the bass and transient reproduction of the DAC+ to be consistent with the very best units I’ve encountered at the $2000 price point, the upper frequencies ain’t slackin’ either. There is a focus and precision to the DAC+’s treble presentation that sets it apart from lower-priced units. In comparison to my Parasound D/AC-2000, the high frequencies of the DAC+ were rendered a bit harder but with more precise focus. Or, if you prefer the inverse, the Parasound sounded a bit softer and slightly more diffuse. I would hesitate to pick a clear winner here because depending on the program material, you could make the case either way. Suffice it to say that the treble performance of the DAC+ is certainly very good. It’s not fatiguing or nasty-sounding and doesn’t call undue attention to itself, except that at times one can’t help but be impressed with its precision and fine detailing.

As for soundstaging capability, I found the DAC+ to present the greatest degree of layering and imaging with the most air and stage depth in its non-buffered mode sans volume control. I have no complaints about the width of the soundstage, and the DAC+’s uncanny ability to lock vocalists and instruments into precise locations in three-dimensional space was most impressive.

One aspect of performance that might have been lacking was that of providing ambiance and air. While the DAC+ did show some ability in this regard, it seemed that my Parasound DAC was a bit better in providing a sense of ambiance out to the far reaches of the recording venue. To cite one example, "Emmeleia" from Dead Can Dance’s Into The Labyrinth [Warner Bros. 9 45384-2] has always provided cushions of air between the multi-layered church-hall vocals with the Parasound DAC. With the Lehmann DAC+, the recording still enjoys a good sense of layering and the hall perspective, but it’s missing a small degree of echo and bloom. Recently I had the chance to try the new Krell KAV-250cd single-box CD player in my reference system, and I found that it too eclipsed the Lehmann (and possibly the Parasound as well) in this area. Indeed, the baby Krell conjured up such an expansive and airy soundstage with the InnerSound Eros electrostats that my observation of the Lehmann’s lack of upper frequency air was clearly confirmed.

As I’ve mentioned, features lacking on the DAC+ are an absolute-polarity inverting switch, which I felt should have been included, and HDCD decoding, which was not missed. I found that HDCD-encoded recordings sounded every bit as good through the DAC+ as they did through my Parasound D/AC 2000, which features HDCD decoding.

Conclusion

While I find many DACs a touch too aggressive, particularly in the upper midrange, which can lead to listener fatigue, I would not count the DAC+ among them. Though it can sometimes lean that way when the buffered line stage is used, for the most part it is a very precise, clean, controlled, and detailed unit that also happens to be intimate, harmonically virtuous and musically satisfying. As noted, however, there was a slight loss of upper-octave air and ambiance which acted to give a dryer sense of acoustic space to certain recordings. This was not particularly bothersome and was mainly observed in relation to my reference D/A converter and the Krell KAV-250cd player.

Add to this a generous amount of control flexibility in the form of a buffered line stage, a volume attenuator, and a switchable auxiliary input (meaning an additional preamp isn’t necessary) and you have a very excellent start on setting up a minimalist high-end system. Just add a decent power amp and a nice set of speakers and, presto, you’ve arrived. Then you’ll have the option of adding a phono preamp and a turntable system if that is where your fancy leads you.

The simple truth is that the Lehmann DAC+ is one serious piece of audio gear. It sounded great with each of my transports and when paired with several different combinations of amplifiers and speakers. Accordingly, I recommend that you test drive a DAC+ just to see how good a sub two-Gs D/A converter can sound.

...Frank Alles
frank@soundstage.com

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