Melos SHA-Gold headphone amplifier
I could be wrong about the target audience for the SHA-Gold, but I suspect that it's, uh, me. That is to say, audiophiles with some budget limitations who want an essentially uncompromised preamplifier that also offers state-of-the-art headphone amplification. With tubes, preferably. And as long as you're at it, maybe even remote control.
The remote control is an outgrowth of the biggest difference between the SHA-Gold and Melos' original SHA-1 (reviewed in Vol.15 No.10 and still in production, with only minor changes): the "Photentiometer" volume control. Russ Novak described the Photentiometer in great detail in his April review of the Melos MA-333 Reference (Vol.19 No.4), so I'll just summarize here.
Melos' Mark Porzilli maintains that the performance of most state-of-the-art preamps is compromised by "270 degrees of convenience"—their volume controls. He points out that at 9:00, the average potentiometer has low resistance and capacitance and, relatively speaking, high rectification. Turn the control to 12:00 and you increase resistance and capacitance, but reduce rectification. This, of course, has an effect upon the signal. Many designers get around this by utilizing switched resistors, which Porzilli calls "Band-Aids." He claims that they just switch the problem into a different arena.
His solution? A heavy-metal (nickel and chromium instead of the more frequently used carbon), 100k ohm resistor is connected in series with a second, light-sensitive, cadmium-sulphide resistor adjacent to an 8V light bulb. This resistor changes its resistance in proportion to the brightness of the light shining on it. The brighter the light, the smaller the proportion of the signal voltage is sent to the next amplification stage. This "Photentiometer," Melos claims, results in constant series resistance in the signal path and far less variation in capacitance over the control's entire range—and, lacking moving parts, it eliminates the partial rectification effects of switches and wipers.
The output buffer voltage on the SHA-Gold has been increased to 40V peak-peak, up from 8V in the SHA-1, which is associated with an increase in the stage's input impedance—to better than 10M ohms—"effectively 'unloading' the preceding tube amplification stage," Melos claims. This, they say, results in an almost purely resistive load for the two 6DJ8s—which is theoretically ideal. Frequency response has been improved slightly, but the biggest change in the basic circuit is that voltage regulation has been increased "by a factor of about 1000," according to Melos' George Bischoff. (I thought Bischoff was being uncharacteristically vague when he said this, but the 1000-fold figure is repeated in Melos' product literature, so I assume it is accurate—if extraordinary.) The regulators use LEDs as voltage references.
The SHA-Gold doesn't lack for inputs: It has six—including one line-level input marked "phono." (I find this confusing, don't you?) There is also a tape loop, two single-ended outputs—one amplified, one passive—and a pair of XLR balanced outputs. An IEC-style AC plug allows for custom power cables.
It's rack-mountable, 19" wide with mounting slots at the corner. The front panel is striking. From left to right, it sports an on/off toggle switch; an illuminated window containing an analog balance-meter; a gold-plated, motorized volume-control; a gold-plated source switcher; a ¼" stereo phone jack; and a tape monitor/source toggle-switch. In the upper right-hand corner, there is an LED that blinks when the SHA-Gold is muted. Plugging headphones into the phone jack mutes the line outputs.
I popped the lid and looked inside. Once again, I was impressed by the level of craftsmanship, as well as the quality of the parts. You expect a lot from a $2000 component and, in the SHA-Gold, you get a lot. I also wanted to see the light bulb, which was not readily apparent. So I turned off the room lights and looked again. There's a lot of illumination inside the SHA-Gold: a row of red LEDs on the right side of the circuit board, two tubes, the bulb inside the balance meter—but I couldn't see the Photentiometer anywhere. Then, I ran the volume up and down, and there it was, mounted under the circuit board! Turn the volume up and it dimmed; turn it down, and the light grew stronger, shining greenly through the circuit-board, throwing the traces into stark relief. Cool.
The remote control is a simple wand. At the top, it has a large red button, labeled "power." This does not, in fact, turn on the power; it disengages the mute function. Next down the wand is a pair of wedge-shaped controls, mounted one over the other, labeled "channel." These, it turns out, are the balance controls. Below them is another pair of vertically mounted wedges, labeled "volume," which—much to my surprise—actually control the volume. There is also a small button, labelled "mute," which engages (but doesn't disengage) the mute function. Got it? Good—it sure took me a while. I'm sure that Melos is sourcing this remote wand from somewhere—a TV, judging from the labels—but I think they should consider relabeling the functions.
Natus ad gloriam
Other than that, I have no real complaints about the SHA-Gold's performance. It is unquestionably superior to the original SHA-1—as it should be, at twice the price. The SHA-1 sounds darker overall, but also manifests a hardness right in the critical midrange area—I have friends that swore the SHA-1 was as transparent as all get-out, but I could never ignore those two distractions.
Besides, if the SHA-1 was transparent, what would that make the SHA-Gold? Virtually nonexistent? Hmmm, that has a nice ring to it... Because the SHA-Gold—whether because of the Photentiometer or not, I can't say—disappears as completely as any preamp I've ever heard, especially when used with the passive output. As always, with passive preamplification, you trade off some bottom-end authority for transparency, but I found the SHA-Gold traded less than most. (I was using 20' runs of XLO Type 3.1 Signature into a KSA-300S amplifier, which was driving Aerial 10Ts. The Krell KPS-20i/l was my source. Even with the long cables, usually a real no-no with passive amps, I was getting spectacular bass and a fast, limpid top-end, brimming with low-level information.)
If you need to drive less efficient speakers, or a more capacitive cable, you'll want to use the active output—or the balanced, which yields an extra 6dB gain. It's not that big a sacrifice, although it does close down the top-end a tad. Either way, you hear exceptional soundstaging and way, way, into the music. The Paniagua track stood every hair on my body upright, when played through the passive outputs of the SHA-Gold. The drum moved so much air that I could watch dust motes, shining in shafts of sunlight, get pushed out of the way by its passage—and then, the preamp allowed me to wallow in the long, long decay. I heard minor intonation changes on the flute that had passed unnoticed previously, and the forward, almost relentless, momentum of the track's last two minutes was manifest.
"Third Uncle" just slammed. It was harder, better-driven, and solider than I think I've ever heard it. I played it over and over, pogo-ing in the middle of my living room until I was breathless. (Not that it takes that long, these days.)
As a headphone preamp, I've never heard the SHA-Gold's equal. It has control, fast response, unbelievable liquidity, and that glorious, grainless tube spaciousness. I've stated that I miss HeadRoom's AIP and wish that high-end manufacturers would adopt it as a standard, but the SHA-Gold is so transparent and free from electronic artifacts that I wonder if it wouldn't be too revealing for the AIP. I'd love to do an A/B—but until I do, I wouldn't change a thing.
You have no idea what the real limits of your headphones' bass response is until you've heard them on the SHA-Gold, nor have you a clue what those overtones really sound like. All of the drive and transparency that the unit manifests as a preamp are equally obvious when it is used as a headphone amp. It really clamped the Grados under its control, vastly reducing the flabbiness of the bass and improving their articulation of timbre down under. They still sounded rolled-off on top, though. The HD-580 Jubilees always sound taut in the bass, but the SHA-Gold gave them greater body than I've heard them manifest previously. On the other hand, their midrange leanness was thrown into high relief by the Melos' liquidity and transparency. Surprisingly, my HD-580s and the Grado SR-125s sounded the most natural and least compromised through the SHA-Gold.
Melos has a real winner in the SHA-Gold. As a line-stage preamplifier, it is at the very top of the heap. $2000 should, and can, buy a lot of preamplifier—there's awfully fierce competition at that price point. The Melos belongs on any preamp shopper's short-list. But if you listen to headphones and you need a reference-level preamp, I can't think of another choice: It stands alone—way out front.