Pass Labs HPA-1 headphone amplifier Associated Equipment

Sidebar 2: Associated Equipment

Digital Sources: Antipodes DX Reference, Aurender N10 music servers; Apple 2.7GHz i7 Mac mini computer running OS10.9.4, iTunes 12, Pure Music 3.0, Audirvana Plus 1.5.10; PS Audio PerfectWave DirectStream, Logitech Transporter D/A processors.
Headphone Amplifier: Ayre Acoustics Codex.
Headphones: Audeze LCD-X & LCD-4, AudioQuest NightHawk, Master & Dynamic MH40.
Cables: USB: AudioQuest Coffee. Interconnect (unbalanced): AudioQuest Fire. Headphone: Cardas Clear (balanced), manufacturers' own (unbalanced). AC: manufacturers' own.—John Atkinson

Pass Laboratories Inc.
13395 New Airport Road, Suite G
Auburn, CA 95602
(530) 878-5350

ACF's picture

I just hate these glowing reviews from John Atkinson. It's costing me a small fortune.

Steve Eddy's picture

Mu-metal shielded toroidal transformer? Might want to double check with Jam on that. Mu-metal saturates at very low levels and wouldn't be very suitable for the sole shielding on a power transformer. Typically you'd use steel to reduce the levels to the point that you could use Mu-metal to handle the residual.

allhifi's picture

Nelson Pass has a rich history and remains (rightfully) a highly respected guy.

In no way do I feel his choice of (almost entirely?) Mosfet output stage devices (of his amplifiers)are the best choice. In fact far from it.

The amplifiers I (and many others) most enjoy are those utilizing premium bi-polar output (stage) devices.

Consider the splendid amplifiers from respected brands including including M-Levinson, Classe, Bryston, Spectral, SimAudio, Boulder M-Fidelity Luxman's amplifier/Int. amps (some or all?) and (I'll kick myself for forgetting names/brands) others employ this class of device. and for great reasons; the sheer speed/scale, clarity/definition, power/dynamics sounds refreshingly life-like. These qualities are near-immediately recognized in models utilizing this topology. And this, much before I decided to examine "why" in further detail -and come up with the association I now discuss.

Naturally, thre is far more to excellent amplifier design than choice of transistor. Yet, all of my favorite (and others of course) main power amplifiers ALL have this output stage device.

Anyway, I suspect the PASS HPA-1 HP amp also uses Mosfet devices. Yet ,this is not the reason for my reply.

The internal design/build of the HPA-1 reveals that it uses a simple volume pot (of unknown origin/quality. It also appears far more time/money was given to the large volume control/contrasting black chassis/volume styling cues as opposed to the far more important volume attenuation circuit/design employed.

The Sim Audio '430', on the oter hand (similarly priced) uses a far superior resistor/relay type set-up offering far superior performance than any "wiper-based" standard potentiometer.

At the prices of these items, we should all expect the finest parts commensurate with price.

And that would apply to all other products in the hi-fi world -or other worlds. Higher pricing is fine -just ensure the finest circuits/parts are used.