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This is the 33rd in a series of reviews dedicated to the concept of 32Ohm Audio as embodied by the store of that name in downtown Portland/Oregon and described here - Ed.
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Reviewer: Srajan Ebaen
Financial Interests: click here
Sources: Ancient Audio Lektor Prime, Apple iMac 1TB (AIFF files up to 24/192), Weiss DAC2, iPod Classic 160GB (AIFF, ALAC), Sieben Technology dock, Onkyo NS-D1 iPod digital-direct dock
Headphones: ALO Audio recabled Audez'e LCD-2, Sennheiser HD800, beyerdynamic T1 and AKG K-702; stock audio-technica W5000; stock Grado PS-1000; HifiMan HE5LE with optional silver wiring and grill mod; Hifi Man HE-6 [on review]
Headphone amps: Trafomatic Audio Head One; NuForce HDP; Woo Audio Model 5; Burson Audio HA-160; Meier Audio Corda Concerto, Schiit Asgard [on loan]
Headphone stand: Sieveking Sound Omega
Cables: ASI Liveline interconnects and power cables, Furutech GT2 and WireWorld Starlight 5² USB A-to-mini-B cables [on loan], LaCie and Entreq Firewire 800 cables, Entreq USB cable, Black Cat Cable Veloce S/PDIF cable
Review Component Retail: $349
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If you've reached this page directly, rewind to the real beginning on Schiit the company and their first product,
the Asgard Fet/Mosfet amp. This will avoid unnecessary repetition and paint the complete picture -
including
plenty of photos from a 'remote viewing' session of the Schiit facilities. - Ed
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As Schiit's Jason Stoddard would confirm, neither the $249 Asgard nor the $349 Valhalla are truly universal headphone amps. The Asgard is distinctly happier with low impedance loads. The OTL or output-transformer-less valved Valhalla—there's the name's tie-in—prefers high impedances. Both share identical enclosures and layouts. It's no big surprise that some cut 'n' paste would net Schiit's third product. The $449 Lyr combines—kinda*—Valhalla genes with Asgard chromosomes by wedding a two-tube voltage gain stage to Mosfet outputs. This hybrid combo makes a whopping six watts per side. That's studly peak-to-peak swing of 40 volts into 32Ω. By design it caters to hard-of-hearing HifiMan orthodynamics and other designs hungry for power. Yet Stoddard insists that the Lyr "still drives the piss" out of 400Ω statement cans like Sennheiser's HD800. Sure, if you start with such a—for a headphone amp —surplus of power into 32Ω, you'll definitely have enough left once you reach 600Ω for beyerdynamic's T1. But back to the Valhalla first.
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* "Lyr is actually *quite a bit more* than just a Valhalla with Asgard outputs. It's running what we call a 'dynamically adaptive' output stage which is Schiit slang for a neat current-sensing topology that runs pretty much single-ended Class A into high-impedance loads (or at low volumes), then gradually shifts to push-pull Class A, then finally into Class AB as current demands increase. It allows Lyr to run a little cooler than Asgard despite having 6 x the power output. It also uses ECC88 tubes and is rollable for all 6DJ8/6922/ECC88 types. It'll most likely ship with JJs though we're still evaluating options.
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Valhalla is a classic SET sans feedback. It runs a single non-inverting voltage gain stage with two 6N1P (6Н1П in their original Cyrillic and 9-pin medium-gain twin triodes) and two equally twinned 6N6P triodes in the output stage (also Russian, there spelled 6Н6П
and related to the ECC99 and E182CC).
Because these 6Н6П couple directly to the 6.3mm output, Valhalla—there's that name again—is as close as it gets to plugging valves directly into yer pink bits.
Zin is 100KΩ, Zout 20Ω. Amplification factor is 8 for a gain of 18dB. That works out to 100mW into 50Ω, 200mW into 100Ω, 500mW into 300Ω and 300mW into 600Ω. For such RMS ratings (not peak), the inefficiency of class A operation draws 40 watts from the wall.
Unlike the Asgard whose Mosfets bolt to the right end of the C-shaped aluminum profile and really sink heat into it—hence my recommendation to orient that amp upright, volume control on top—the Valhalla's exposed tubes are air cooled. The chassis gets a little less toasty.
My kitchen table photo shows how everything goes together. What seems like an inner box is nothing but an empty frame-up job. Very clever.
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This makes it impossible to extricate the circuit board without unbolting it. Nudie shots are by definition odd then. It's not as though the top came clear off. Still one sights a quality Alps pot; six good-size caps (four along the front panel, two in the back); four smaller Wima between the ceramic tube sockets with silvered contacts; and two power transformers. "We chose to go dual for two reasons.
1, with a very simple tube amp the only variables really are tube choice, power supply and passive parts. We wanted the beefiest power supply possible so we overbuilt.
2, it allows us to separate the heater from the high-voltage supply. Because of our chosen tubes, the heater current is significant—about 3A—so it was best to treat it to a separate transformer. The heater transformer is the smaller of the two.
The larger transformer is dedicated entirely to the HV supply, which along with almost 2.000uF of filter capacitance gives us a nice stable power supply with a lot of reserves."
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A quick glance at the published specs nets a
frequency response of 10Hz to 200kHz (-3dB)
for unexpectedly excellent 'anti-tube' bandwidth while THD of <0.5% from 20Hz-20kHz into 1V is full-on expected 'tube'. Unlike the Asgard's iron which hummed very noticeably—at the end of its review Jason had promised a solution from supplier MCI plus a decoupled mounting scheme to quelch any bad vibes—the Valhalla's trafos leashed to the same power strip and power cord were text-book quiet. An all-American all-glass all-quiet amp for all of $349? That's surely a lot of 'all' in one short question - actually answer since it's all true!
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