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What's real quiet? A church mouse? A tomb stone? Outer space? Your system with all power cords unplugged? Whatever you pick, that's how quiet the Aleph H is. Terry's amp cleared the first hurdle without even noticing. Not too many headphone amps on the market can drive my AKG K-1000s. That's due to their extreme inefficiency of 74dB (a spec whose figure obviously changes in typical headphone proximity to the ear but still requires a lot more output voltage than normal headphones). So I just had to try 'em for shits and giggles. Instead of the typical speaker-level connection, I have a spare custom cable leg with the necessary 1/4" plug. In plugged the K-1000s to the Aleph H.


Considering that the amp is set for unity gain, the mere 6dB boost of the transformer-attenuator Music First Audio passive magnetic preamp shouldn't have worked. However, it did. Zero attenuation equated to sufficient volumes though things especially in the bass got a bit thin and lightweight. Under the circumstances, that was expected. Still, I was pleasantly surprised that it worked at all. Terry's power supply did what it's supposed to do - provide drive even in a worst-case scenario. Encouraged, I now added appropriate drive by way of my ModWright SWL 9.0SE 5687-fitted hybrid active preamp, as the sort of preamp this amplifier was designed to tango with.

Switching to my reference Zanden front-end, I now only had a 1V out. The ModWright's a medium-gain preamp at 16dB. Of course I couldn't play much louder than before (+6dB above 2V unity). But I instantly graduated from black'n'white to full color and max attainable levels were louder than necessary even on classical recordings with a low median level.

Son de la Frontera [Nuevos Medios 15 856] is a fabulous back-to-the-roots Flamenco album. It features fret board duels between Raul Rodriguez on Cuban tres and Paco de Amparo on Flamenco guitar surrounded by palmas and fiery dancer's footwork. Having listened to this album at length on the big rig, I had a pretty high standard for how to expect reproduction of the foot stomps on the opening "Buleria Negra Del Gastor". At times, that baile work fully loads the floor below the dancer to perfectly telegraph you seeing the event. It's spooky. Your whole nervous system recognizes it - not just a struck heel but how it sets off a deep low resonance that's over in a flash but completely different from the hand claps or other less violent foot stomps.

Being nearly exclusively percussive, this CD is a showcase for speed and articulation, for crisply defined leading edges and the very different timbres of the bright, at times nearly nasal tres and the more guttural darker guitar.


The Austrian earspeakers, when properly powered, major in very fast reflexes due to their drivers' ring magnets - sometimes to the extent of being nearly too zippy and relentless. In that sense, they're amp eaters. Especially transistor amps. The AKGs make most such amps sound bad. Mind you, that's not the amps' fault at all. But in a backwards way, these headphones are an acid test by how brutally they highlight an amp's lack of body at the expense of leading-edge slicing and dicing.


The Aleph H passed that test with flying colors. Son de la Frontera blistered with brio and vigor but my ears never recoiled nor did any subliminal ringing betray exaggerated high frequencies. Since you may not know this CD, you can't fully appreciate how impressed I was. I love the Ks but am fully aware of their shortcomings. They're very demanding of just the right ancillaries. High-maintenance babes "totally worth it" if you know what I mean.
Unlike sealed cans, the Ks will never be the final word in bass grunt and slam, especially when they're winged out to enhance soundstaging and cross-channel effects. While sheer low bass quantity is thus somewhat compromised, quality can be exceptionally articulate and non-resonant if the driving amp is up to the task. Up to the task? That's why most owners use the speaker-level hookup. They drive these earspeakers with regular speaker amplifiers, meaning 6 watts up to 200. Well, Terry's Aleph H drives them splendidly without ever getting hard. Perhaps I shouldn't have been surprised. Nelson Pass' own 10wpc current-source F1 under the FirstWatt banner does so as well. I kept being fascinated by how the ModWright/Aleph combo neatly sidestepped getting these earspeakers to misbehave. No tripping up their innately hot tonal balance especially since my customary StefanAudio Art wire harness was replaced by the inferior stock cable on the 1/4" jack. The final result was neutral rather than warm which -- considering that these cans are anything but warm -- meant that the amp itself had just enough intrinsic warmth to balance the scales for a neutral end result.


Ultimately, I could have wished for just a skoch more warmth (i.e. actually audible). That could probably be achieved just by raising the amp's gain structure rather than optimizing it for the kind of regular Sennheiser and Grado and Beyer cans 95% of people listen to. Moving on to my personal favorites, the audio-technica ATH-W1000s, the Aleph H showcased that it is indeed slightly on the warm side of things while maintaining the wonderful precision and impact that makes percussive recordings so exciting. I now also became the beneficiary of truly extraordinary image density in the back of my skull and protruding outwards like an airline pillow behind me, i.e. the equivalent of intensified stereo center fill.


As sealed cans, the very bottom end filled in more and became a further contributor to my sense of enhanced warmth, density and spectacular fullness as though every atom of the soundstage was pulsing with equal intensity. It didn't take long to conclude that this DIY project with the famous Aleph blood line barks and bites with the big dogs of the genre. Key descriptors revolve around top-to-bottom linearity, explosive dynamics, tight-fisted control and the resultant sense of precision and articulation that removes indecision, blurring and spots either in the frequency response or soundstage that seem less concrete than others. Very importantly, all that control doesn't end up hard or unduly sharp. While transients are subjectively fast and incisive, this quality doesn't dominate and is nicely counterbalanced by timbral body. The end result is neutrality -- as much as such a thing can be determined -- with just a hint of warmth.
The true test -- which I by now predicted the amp would ace like a champ -- were my Sennheiser HD650s. Originally purchased as an in-house reference wildly popular elsewhere, this pair of cans sees little use around here outside of reviews. Why?


Unlike the W1000s which sound stupendous on the hybrid headphone output of the Eastern Electric MiniMax CD player, the Senns demand a real headphone amp to sound their best. I don't own one, hence the Germans collect dust.


Though there's too much spring tension on their cups and the plush velours padding causes my ears to shvitz, the Senns are actually very good 'phones once they're plugged into the right hole.
Enter the Aleph H. Its gain was uncannily chosen to have the volume control on my ModWright sit between 11:00 and 12:00 for the Germans, around 9:30 for the more efficient Japanese - just right in other words. And as the previous detour into wigged-out earspeakers suggested, the Aleph's drive now made the Sennheisers shine. They're a high-resolution design at the end of a long succession of model-to-model refinements and the amp clearly conveyed why they're so popular. They're truly full-range and capable of delicious nuance and -- to a lesser extent than the AKGs -- even soundstaging. The Aleph H demonstrated that latter aspect as good as I've ever heard it from the HDs before and the same was true for low-bass tautness and impact.


The Aleph H -- as it should -- sounds different from the SinglePower MPX3 I reviewed. That telegraphs its use of tubes clearly and unapologetically. Just as unapologetically, the Aleph H is solid-state. Still, it manages its own version of full-on image density, not as a function of thick harmonic distortion but by way of solidity. Images are unwaveringly focused and fully grounded rather than ethereal flotsam. Because noise floor is absentee, leading and trailing edges don't suffer premature eradication. Clarity and accuracy are the result. The more ambient information there is on your recording, the more you hear. Jump factor is first-rate - no dynamic soft-shoeing anywhere. Very much to its credit, the Aleph H doesn't translate these qualities into a grating treble or cold attack mode. While it's essentially a studio monitor device of great honesty, it completely avoids sounding sterile or cold. The old "just the facts" lacks the undermining mockery of "mam".


Anyone who's ever attempted to appease a tube Jones with transistors will know how difficult of a balance that is to strike. While our kind can likely appreciate advances in control and transparency, we're just as likely to complain of a lack of romance and humanity. "Too honest" we grumble as though honesty came in increments. Terry Aben's feat -- with help from DIY friends and a Nelson Pass circuit for an auspicious beginning -- lies in how he doesn't seem to have introduced a lie, yet his amp's honesty raises no complaints from this-here tube hound. Again, the Aleph H doesn't sound like tubes. Period. But I don't care. And that is somewhat of a surprise and my - er, honest compliment for today's DIYer.


Would Terry's personal amp benefit from parts upgrades? Impossible to foretell. Nothing in its performance suggests a need for plastic surgery. That doesn't mean low-mass Eichmann RCAs -- or any other substitutions -- couldn't make a nice little difference which you'd appreciate once heard. But let me put it this way: I'd purchase this amp as is. I like the absence of an attenuator. As is true for most quality preamps, mine offers dual pre-outs. One is just waiting to be put to good use. Running my premium front-end through headphones rather than duplicating it at a lesser level for a stand-alone headphone rig is only sensible. I like the absence of a power LED. I also like that the amp can remain on 24/7 and barely gets warm to the touch. While the case doesn't scream 24-carat gold or 1/4" panels, it's perfectly adequate for the job. So the verdict is clear. Terry Aben's for-personal-use contraption is fully competitive with current commercial equivalents. Whether it'll become commercial on even a very small scale depends on Terry's interest and Nelson Pass' okay. What it'll cost will equally depend. But that's for you to find out should you be interested. In the meantime, I'll find out for myself. I am very much interested.


PS: Because Terry suggested this column in the first place and then became its first participant, I have relaxed our 5-owner rule to cut Terry some slack. But any participants henceforth will have to submit five owner contacts to be considered.
Terry Aben, Senior Engineer
Civil Infrastructure & Alternative EnergyTechnologies
Powertech Labs, Inc.
Canada
terry.aben@powertechlabs.com