Wyred 4 Sound ST-1000 Stereo Power Amplifier
October, 2008

The high-end is dead! Long live the high-end! A paradigm shift is upon us now. In the Wyred 4 Sound ST-1000 stereo amplifier, we have a maturing technology that absolutely changes the performance-to-price expectation for solid-state amplifiers in the $2,000 to $10,000 price range. After listening to this amplifier in a high resolution system, a listener may not find the amplifier’s character to be a perfect fit with his or her personal preferences, but it will be undeniable that a new standard has emerged.

Over the last few years, we have witnessed the introduction of new “digital” Class D amplifier technologies. These usually do not convert the analog input signals to a digital signal such as used by Compact Discs. Instead, they monitor the incoming audio signal and adjust the power supply to provide the instantaneous voltage required to make music. In conventional amplifiers, the audio circuit uses the power supply to let it do its job. In Class D, the power supply uses the audio signal to change its output and drive the speakers. The efficiency of these amplifiers results from not storing the energy required by the audio signal, but by using the incoming AC from the wall only as needed by your music. Bang & Olufsen’s ICEpower technology, which is implemented by PS Audio, Wyred 4 Sound, Bel Canto, Rotel, Jeff Rowland Design Group, and many others, offers efficiency in the >90% range, compared to around 30-40% for typical solid state amplifiers and 5-20% for many vacuum tube amplifiers. This significant increase in efficiency results in far less energy being wasted as heat, a smaller, lighter product, and a decrease in costs for both acquisition and operation.

Cullen Circuits, maker of the Wyred 4 Sound products, is a company recently coming into the radar for many audiophiles. Cullen Circuits has been in business since 1990. Rick Cullen designed and modified many PS Audio products, including their ICEpower-based power amplifiers and has been responsible for the design of other manufacturers’ products as well. In doing so, he developed some further improvements and now offers a range of ICEpower amplifiers under his own brand. The stereo amplifiers include models offering 150 Watts per channel @ $999, 250 Watts @ $1499, and the 500 Watts per channel ST-1000 @ $1999. All models include both RCA and XLR inputs. There are also monoblock versions if you prefer that configuration. Manufacturers often buy the complete amplifier modules from B&O, add an enclosure and connectors, and sell a plug-and-play product. Some, like Cullen Circuits, make significant changes to the stock modules. The Wyred 4 Sound stereo amplifiers have a completely custom balanced FET input stage that raises the input impedance from 10k Ohms, which is a difficult load for some preamplifiers, to 60.4k Ohms. Other modifications are also made before your purchase.

The review system was really unfair to the ST-1000 (shipping weight 25 pounds) since there was nothing anywhere near its price (or weight) in-house for comparison. The closest was a Halcro MC20 that cost 2.5 times more. Also either on-hand or recently departed was a $7,000 BAT VK-250SE, $7,500 Pass X250.5, $9,000 Manley Neo-Classic 250 tube monoblocks, and $15,000 solid state Marantz MA9S2 monoblocks (see image on right). Sources include a SOTA Cosmos turntable with TriPlanar VII tonearm, Miyajima Shilabe and Air Tight PC-1 phono cartridges, Manley Steelhead phono preamplifier, the wonderful Marantz SA7S1 and Cary 308 Professional CD/SACD players (reviews in progress), PS Audio DL III DAC with Cullen Stage 4 Mod, modified Audio Research LS22 preamplifier, all providing great musical signals to Dali Euphonia RS3 speakers with a pair of JL Audio Fathom f112 subwoofers, and Dali Mentor 5 loudspeakers from the HT system. Interconnects are Mogami. The speaker cables are Audience Au24 E single wire, with Audience PowerChord E, some DIY, and Audioquest NRG-2 power cords. This system permitted operation of the amplifier in fully balanced mode from the CD player or DAC to the amplifier.

I have auditioned several different ICEpower-powered amplifiers during the past two years and have found them to have these common traits:
1. No sense of harshness or brightness. Very smooth.
2. Great dynamic power with no feeling of stress or strain at high output levels.
3. Powerful and deep, if somewhat soft or tube-like bass.
4. Excellent soundstage/imaging with an uncanny ability to keep complex music sorted out, clear, and detailed even at high levels.
5. Less than ideal extension in the upper treble, although with very good harmonic clarity.

The Wyred 4 Sound ST-1000 changes my observation regarding ICEpower for #5: less than ideal treble extension. In the song “Pathway to Glory”, from Loggins and Messina Full Sail LP (Columbia PC32540), the cymbals are recorded on the hot side and can quickly sound splashy and lose their metallic sheen. The ST-1000 occasionally passes this character to the loudspeakers. The 7.5 times more expensive Marantz MA9S2 mono amps barely holds on to the cymbals to keep the sound in good order. The BAT VK250SE does not fare as well on this difficult cut, nor does the Pass X250.5 sound as pure if it is driven over its 15 Watt Class A limit.

Low level resolution is often amazing. On the same Loggins and Messina LP, the sound of dripping water at the beginning and end of the song Sailin the Wind is visceral. I felt as if I reached out my hand towards the speakers, it would get wet! And the sound of creaking wood in that cut is absolutely and completely believable. Very nice!

The guitar and violin interplay on “Steamer Lane Breakdown” from the Doobie Brothers Minute By Minute CD (Warner Bros 3193-2) shows the amplifier’s great clarity and realistic warmth. The plucked guitar strings have a reach-out-and-touch texture and are very present in the room. There is excellent physical separation of individual players, even at high volume levels. The ST-1000 has excellent micro-dynamics that provide the listener with an easy ability to track very small changes in the power and nuance of a subtle performance.

In the bass, the ST-1000 does a very good job with the leading edge of bass notes to provide the impression of speed and agility in the lowest octave. Only in the lower level resolution is it sometimes apparent that the ST-1000 is not up to the performance of much of the solid state competition. However, the bass performance was more akin to the very satisfying character of the Manley Neo-Classic 250 mono tube amps. And this is the one area that if it could be improved, as Cullen as done so ably for the treble range, we would have a line of amplifiers that would destroy the under-$10k competition. Before the Wyred 4 Sound amplifiers, we could not buy this level of sonic sophistication from a solid-state amplifier at two, four, or even five times the cost.*

The Wyred 4 Sound amplifier two real strengths:
1. It does very little wrong. Where the ST-1000 falls short in sonic refinement relative to anything I have heard under $10,000 is due to omissions. This competition actively offends in one way or another, but the ST-1000 is so even handed and smooth that while I sometimes want more of this or that, I never want LESS of anything in the sonic picture. This is significant because it is precisely what a component does wrong that eventually makes us replace it.
2. It is an extremely high-value amplifier. You got a LOT of performance for your money, and more than any other amplifier I can name. In other words, you will pay a lot more to get an across the board improvement in sound quality.

The ST-1000 offers a very balanced sound - not bright or laid back, nor forward or recessed. Resolution in the treble is much better than other ICEpower amplifiers that I have heard. The bass is very deep and powerful, if more on the tube-side regarding resolution. Dynamic impact can be startling. The sound stage is very well presented. I keep listening to this lightweight and cool running amplifier, enjoying LP after LP, CD after CD. I know that there are better amplifiers in the world. My own Marantz MA9S2 monos are one example. But I never get tired of listening to the Wyred 4 Sound ST-1000 stereo amplifier. Every other solid state amplifier under $10,000 has driven me away over a period from one evening to several months by their offenses*. Even the Halcro MC20, with a trace of dryness or harmonic thinness in the upper frequencies, met its match with the big Marantz amps. The ST-1000 is not perfect, but it never actively offends, either. This technology sounds somewhat differently than either tube or solid state, but after a short period of adjustment, it just sounds right. It certainly belongs on your radar if you are looking for an excellent sounding amplifier that just happens to offer exceptional value.

Overall Rating: 9.5 LPs