Review Summary Sound Very powerful and able to control the woofers of even tough speakers; "the ability of this amp to represent spatial relationships and depth is remarkable"; "about as transparent as solid-state amps get" too. Features Direct-coupled, truly balanced stereo amplifier that offers 250Wpc; "uses premium components, such as military-spec precision resistors, computer-grade capacitors, military-grade glass-epoxy circuit boards, and a custom toroidal power transformer." Use "This amplifier needed some serious break-in time" -- at least "100 hours of constant play," after which it will undergo "nothing short of a sonic transformation." Value "It's difficult to overstate how great a value the Threshold S/5000e amplifier is."

When I received word from Marc Mickelson that my next review was to be of a Threshold amplifier, I didn't even realize that Threshold was still in business. In a sense, I was correct. The company begun by Nelson Pass in 1974 had fallen on hard economic times and operations were temporarily halted, but the company name and designs were resurrected by the principals of speaker maker Nova Audio. I was then informed that this Threshold amplifier was a 250Wpc stereo powerhouse, the S/5000e, which sells for $2500 USD.

Just the same, my first thought was not a positive one. How can a company, especially one with the Threshold name, build a good-sounding high-power amplifier for $2500? Perhaps the best answer to this question is that for the time being Threshold Audio sells factory-direct -- no dealer markup. Thus, this $2500 amp directly from Threshold would likely sell for $5000 through a dealer. And for added convenience, Threshold offers a 30-day money-back guarantee, so you can try before you buy.

The S/5000e amplifier is a rather plain-looking piece of audio gear. This can be a good thing -- chassis can be very expensive depending on how elaborate they are, and for $2500, I would hope most of the build costs were put into the internal parts of the amplifier. The S/5000e measures 19'' W x 7'' H x 10.75'' D and tips the scale at 38 pounds. Threshold rates the S/5000e's nominal power output from 20Hz-20kHz at 250Wpc into 8 ohms and 400Wpc into 4 ohms. Frequency response is stated as DC-50kHz, with 0.05% distortion at 1kHz at rated output power. Voltage gain is 28dB. The S/5000e has both RCA and XLR inputs. Input impedance is 22k ohms for the RCA inputs, and in keeping with the Threshold way of doing things, 600 ohms via XLRs. Input sensitivity is 1.80V RMS for full power output.

Parts quality and design of this Threshold amp are quite good considering the amp's relatively low price. The amplifier is both direct coupled and truly balanced from input to output. Threshold uses premium components, such as military-spec precision resistors, computer-grade capacitors, military-grade glass-epoxy circuit boards, and a custom toroidal power transformer. The amp is fitted with gold-plated RCA jacks, Swiss-made XLR connectors, and Cardas gold-plated binding posts. The circuit design features minimal feedback, but the amp has a high-current output stage that should easily drive low-impedance reactive loudspeaker loads. And to top it off, the amp is assembled in the US of A.

Initial listening

Contrary to standard reviewing methodology, I like to listen to new audio components cold out of the box. Some people let components burn in before listening to them, but I like to know what a component sounds like cold, so I know how far its sound has progressed during break-in. This way I can tell if the same piece in a different system is actually broken in or needs more playing time.

I connected the Threshold S/5000e to my Krell KRC-HR preamplifier using the XLR inputs. Truly balanced amplifiers theoretically sound best using balanced inputs. I began to play some of my favorite music and prepared myself for anything.

My first reaction was that this amplifier needed some serious break-in time -- or a complete sonic overhaul. Some components sound great out of the box, but this was not one them. The soundstage lacked depth, the bass was a bit mushy, and the top end sounded rolled off. Overall, the amp sounded very dark, and I was wondering what I had gotten myself into with this review. So I began to put some time on the amp, hoping that the S/5000e would make an extreme sonic transformation after a few days of constant playing.

The little amp that roared

After about 100 hours of constant play, it became apparent that this Threshold amp gets a bit toasty. I am not talking about OTL, "roast your favorite meat" toasty, but the Threshold S/5000e seemed to be only a little shy of Plinius SA-100 Mk 3 in terms of the heat it produces. The Threshold amp runs very warm to the touch and requires about an hour of operation to reach this temperature level.

With 100 hours of playing time and one hour of warm-up time behind me, I put on one of my favorite CDs and my jaw was immediately inseparable from the floor. The S/5000e underwent nothing short of a sonic transformation during break-in. It was as if I were listening to an entirely different amplifier. No longer did it sound even remotely dark, dimensionless, and rolled off. I certainly wouldn't classify the S/5000e as having tube-like sound (as some solid-state manufacturers claim for their products). Its sound is easily recognizable as solid state, but that of really, really fine solid state. I'll probably sound like an audio snob for saying it, but I couldn't believe I was listening to a $2500 amplifier.

Sonically, the first trait that caught my ear was the S/5000e's ability to dominate my Vienna Acoustic Mahler loudspeakers. The Mahlers' bottom end is difficult to control -- and this may be a kind assessment. If every link in my system is not great at controlling the bass, my Mahler speakers can completely come apart in the lower frequencies. This is especially the case at higher listening levels. I was listening to "Hotel California" off of the Eagles' Hell Freezes Over live album [Geffen 24725], and I noticed the amazing dynamic impact the Threshold S/5000e was able to achieve during the drum beats at the beginning of the album. At live volumes I could almost feel the floor of my house flexing reactively to the beat of the kick drum on this track. No matter how high I cranked this amp, it seemed to have nearly unlimited power still in reserve.

The next noteworthy quality of the Threshold S/5000e is the way it portrays a three-dimensional soundstage. The ability of this amp to represent spatial relationships and depth is remarkable. Once again, I would only expect this kind of imaging ability from amplifiers costing two or three times the price of the S/5000e. On Chesky’s The Persuasions Sing the Beatles [Chesky JD220], the four singers are all standing in a semi-circle around a single microphone. I could tell exactly where each singer was in the semi-circle. Furthermore, another subtle sonic quality I noticed was that I could now get some sort of idea of what each signer was doing with his hands and feet. This is an a cappella recording; however, the singers are not completely stationary while belting out their songs. Sometimes the singers tapped their feet or snapped their fingers or moved their arms and bodies to the music. These subtle sounds were able to shine through with the S/5000e, giving the music energy it was lacking in the past on my system.

Next I popped in Chesky’s Ultimate Demonstration Disc [Chesky UD095]. This recording has a wide variety of music on it and an informative announcer who describes how each track is supposed to sound. The music is not what most people listen to for enjoyment, but it is useful for dialing in the sound of an audio system. The first musical cut, from Rebecca Pidgeon’s The Raven [Chesky 115], demonstrates how the upper-midrange region should sound. Pidgeon’s voice was so clean, clear, and palpable with the Threshold amp that I could hear it reflecting off of the back wall of the recording studio. The sense of space on this track is again wonderfully reproduced by the S/5000e, especially when the shaker is introduced in the back-right area of the soundstage. I could hear each motion of the shaker taking on its own unique sonic individual character and differing ever so slightly from its previous motions.

I love the solo flutist on Flute Concerto in D from Chesky’s Ultimate Demonstration Disc, and with the Threshold S/5000e amp in my system, I was able to hear a dramatic sense of depth. The flutist was way back in the soundstage, and there was a great sense of texture from the air as it was blown into the flute. I get a goofy smile on my face when I hear such amazing sound.

Moving to different digital front-ends, I found the Threshold to be about as transparent as solid-state amps get. The S/5000e did not seem to affect the pace or timing of music from source to source. Nor did the Threshold amp obscure low-level detail or detail that better sources are able to offer. Interestingly enough, I compared my DIY digital playback computer system through my Krell preamp to the Threshold and then running the computer directly into the Threshold via the XLR inputs. I found that I could easily hear the sonic signature of the Krell preamp on my system’s sound. In the end, I never felt the S/5000e was the limiting factor in my system. This is saying a lot considering most of my components are two or more times the retail price of the Threshold amp.

Comparisons

I have owned a number of solid-state amplifiers in the $5000 price range, including Aragon Palladium monoblocks, a Simaudio Moon W-5, a Plinius SA-100 Mk 3, Gamut D200 Mk 1 and Mk 2 amps, and an Ayre V-5x. All of these amplifiers have their sonic strengths and weaknesses. The Ayre V-5x was the most complete sonic package of the group. It was the last amp I purchased, and I bought it because I liked it better than the Gamut D-200 Mk 2. I still think the Ayre V-5x amp is one of the best solid-state amplifiers under $5000. However, for my application, driving the Vienna Mahler loudspeakers, I have to admit that the Threshold S/5000e does a better job at controlling the speakers than the V-5x. This is saying a lot because the V-5x is a heck of an amp -- a Reviewers' Choice.

The differences between the Ayre V-5x and the Threshold S/5000e are mainly in terms of space and power. The Threshold amp has 100Wpc more than the V-5x, and while the V-5x may seem more powerful than 150Wpc, the S/5000s seems a lot more powerful than 250Wpc. The S/5000e also presents instruments more discretely -- in their own space in the soundstage -- and with more precision and depth than the V-5x. Finally, the V-5x does sound a bit like a tube amp (about as much as solid state ever sounds like tubes), whereas the Threshold S/5000e never really tries to fool you into thinking you are listening to tubes. You just know you are listening to exceptional solid-state amplification.

Summing up

It's difficult to overstate how great a value the Threshold S/5000e amplifier is. I can only think of two solid-state amplifiers under $10,000 that are better. Both the Parasound JC-1 mono amplifiers and the McCormack DNA-500 stereo amp have a special place in my heart. However, both cost nearly two and a half times the retail price of the Threshold S/5000e. Thus, in terms of sheer bang for the buck the S/5000e succeeds, but let's not forget this amp's wonderful sonic qualities -- the sort that $2500 amplifiers just do not generally possess.

The S/5000e is an amazingly powerful and economical amplifier that also happens to sound terrific. Welcome back, Threshold.

...Keith Forrest
keithf@soundstage.com

• Current Issue Equipment Reviews