S/3700e Multichannel Power Amplifier
|Threshold Audio was
founded by Nelson Pass in 1974 -- I remember listening to a Threshold amp in the late
70s, when I was still in high school. Though way out of my price range, it was one
of the nicest-sounding amps Id heard at that time. Almost three decades later, I
hadnt heard anything about the firm for several years and had assumed theyd
gone out of business. Actually, Threshold ran into economic trouble in the late '90s, and
it was purchased by a Texas-based company ran by Kevin and David Lee, who headed speaker
manufacturer Nova Audio at the time. It has since come back strong; the S/3700e
multichannel power amplifier is only one of the new products the revived company has
introduced in recent years.
Price: $3500 USD
Dimensions: 19"W x 7"H x 21.5"D
Weight: 64 pounds
Warranty: Three years parts and labor
- Five channels (standard), expandable to six or seven
- All discrete components
- Direct-coupled, input to output
- Massive toroidal power transformer
- Military-spec precision resistors, computer-grade
capacitors, military-grade glass-epoxy circuit boards
- Isolated power reserves for voltage and current gain stages
- Gold-plated RCA jacks
- Swiss-made XLR connectors
- Cardas gold-plated binding posts
- Intelligent 12V DC trigger for remote startup
- Soft-start turn-on
- Modular construction
- Rack-mountable design
- Attractive polished silver-anodized aluminum front panel
- Hand-assembled in the US
A formidable presence
To look at the Threshold S/3700e ($3500), you might assume
its the typical 200Wpc powerhouse that seems to be all the rage these days in home
theater. At 19"W by 7"H and 64 pounds -- a good 20-30 pounds more than many
competing designs -- its one of the larger home-theater amps Ive had in the
house, and its 21.5" depth meant that it didnt quite fit the equipment rack in
my smaller theater room. But while the S/3700e is built like a powerhouse, it puts out
From the front, the S/3700e is simple but attractive, with
a slightly sculpted silver aluminum front panel that allows for rack mounting. The rear
panel sports heavy gold-plated RCA jacks, Swiss XLR connectors, and Cardas speaker binding
posts. Also on the rear are a 12V trigger input and output and a standard IEC connector.
Like several other amplifiers Ive recently auditioned, the S/3700e is a modular
design. Five channels are standard, but open sixth and seventh slots will accept
additional amplifier modules at $500/each, should the need arise.
The removal of 20 screws let me peel off the black aluminum
top plate and view the S/3700es innards. Ive peered inside my share of amps
over the years, and few have looked as neat and orderly as this one. Each module is on a
self-contained circuit board of military-grade glass epoxy, the only external connections
being power taps and a few short wires to the binding posts. Output is provided by two
matched pairs of Motorola ON Semiconductor complementary NPN-PNP bipolar power transistors
per channel, cooled by large heatsinks. Up front is a large toroidal power transformer
with a 1039VA primary tap and a 990VA secondary. Between the transformer and the amp
modules are two Nippon 80V, 33,000µF filter capacitors. Threshold states that all
resistors are metal-film and noninductive metal-oxide. There are no capacitors in the
signal path, and those in outlying circuits are high-quality film and silver-mica caps. In
short, theres nothing inside to complain about and plenty to applaud. The S/3700e
has what I want to see when I open up an amplifier: a clean layout, quality construction
and parts, and short signal paths.
Setup was straightforward, as youd expect from a
modern solid-state amplifier. I first connected the Threshold to an Outlaw 990
preamp-processor and five Snell Series 7 speakers I had in for review. Later, I replaced
the Outlaw with my own Anthem AVM 20 and the speakers with my reference Magnepan MC1-CC3
system. Both processors and the Threshold offer balanced connections, but I have very
short cable runs and decided to stick with the RCA connections for consistency over the
series of tests I was working on at the time. I also used the trigger connection to
remotely control power cycling from the processor.
The S/3700e elicited a soft flutter from all speakers
during power on and off, but nothing loud or potentially damaging. Though the amp never
got anything more than moderately warm during my testing, Threshold recommends connecting
the channels in a specific sequence for improved heat dissipation. Other than that, the
only thing you have to pay attention to during setup is to select between the balanced and
unbalanced inputs for each channel.
My Magnepan speakers arent the most difficult loads
to drive, but they arent the easiest either, and theyre fairly inefficient.
Some amplifiers dont drive difficult loads to high levels all that well, but this
was never an issue with the Threshold S/3700e. During The Bourne Supremacy, the
louder I pushed the system, the more it opened up. Only when the volume level was high
enough to be painful did the sound become harsh or compressed. The dynamics of the
apartment explosion in chapter 9 were the cleanest and loudest Ive ever heard from
this system, including with some 200W amplifiers that I doubt could have done better.
Dynamics are great, but Ive always contended that the
best surround systems are those that handle subtle sonic cues with the greatest finesse.
In Gladiator, the creaking of the carriage, the rattling of gear, and the sound of
hooves outside as Commodus and Lucilla near the battlefield, were all around. For me,
its the subtle placement and level of detail of such sounds that separate merely
good systems from the truly spectacular. With the Threshold, my Anthem-Magnepan system
entered the latter realm.
The performance with movies was fine, but it wasnt
until I began listening to music that I began to fully appreciate the S/3700es
potential. One of the first discs I spun was Monty Alexanders My America
[Telarc SACD-63552]. Its a nicely mastered SACD, though I sometimes think the
surround channels are used too heavily for this material. A point in case is "Summer
Wind": I find the bongo in the right rear channel horribly distracting. Still, My
America gets a thumbs-up from me for its otherwise excellent sound and ambience. On
"Honky Tonk," the Threshold S/3700e allowed the Magnepans to really open up and
sing at higher volume levels, with no hint of compression, distortion, or harshness.
For something a little different and just for fun, I
dropped disc 1 of The Bill Wyman Compendium [Koch 8056] in the player. If you can
listen to this CD without tapping your feet or bobbing your head and smiling, seek help.
Early in "What a Blow," Wymans vocals sort of swim around the front
soundstage a bit, but Id never heard quite the eerie, ethereal quality I heard with
the Threshold in the system. The soundstage and imaging were more reminiscent of what I
hear from my reference analog system, which is high praise indeed.
The S/3700es noise floor was nearly nonexistent.
Threshold doesnt publish signal/noise ratios, so, in an admittedly unscientific
test, I turned my preamp-processors volume all the way up while the source was in
Pause. With my ear only 3" from a front speaker, I heard only a barely audible hiss.
Because this hiss would also have included any noise from my preamp and/or source, I think
its safe to say that the S/3700e is as close to electronically silent as is
A surprising discovery
At 140Wpc, the Chiro C-300 ($1500) is rated to be
marginally more powerful than the Threshold, though it never sounded like it. Driving my
Magnepan MC1-CC3 theater system to high volumes, the Chiro began to show signs of strain.
In comparison, the Threshold S/3700e produced clear, open sound all the way up to the
limits of any kind of marginally comfortable sound level. In fact, the Threshold smoked
the Chiro in every important performance category.
What was more telling was that I began to favorably compare
the Threshold S/3700e to the modified Cayin TA-30 tube amp ($899) in my reference analog
system. This rare event was quite unexpected. Both amps have a basic purity of sound that
cant adequately be described in words, but that I suspect has to do with the minimal
number of components placed directly in each amps signal path. The Threshold even
managed to retain much of the expansive, swirling soundstage thats appealing in so
many tube amps -- without the owner ever having to bias a set of tubes.
A not-so-surprising conclusion
If youve read this entire review instead of just
skipping to the end, it should come as no surprise that Ive grown very fond of the
Threshold S/3700e in the last few months. If I hadnt completely blown my equipment
budget building a new dedicated theater and reviewing space, the Threshold S/3700e would
easily qualify as a keeper. Boxing it up to ship it back to Threshold will be difficult.
The Threshold S/3700e is a solid value for those looking
for a high-end multichannel power amplifier. Its built to last and handles difficult
loads with ease. While its not the most powerful amplifier in its class, it seemed
impossible to fluster or strain under extreme conditions during my testing. More
important, the S/3700e has a purity of sound when playing music that was unlike any other
solid-state amplifier Ive heard in recent memory. For all those reasons, I highly
|Speakers - Magnepan MC1
(mains, surrounds), CC3 (center); Snell M7 (mains), K7 (surrounds), LCR7 (center),
Basis 300 (subwoofer)
- Anthem AVM 20, Outlaw Model 990
|Amplifiers - Rotel RB-976,
Chiro C-300, Cayin TA-30
- Pioneer DV-563A DVD player, Sony SAT-HD200 DirecTV receiver, Hughes DirecTV HR10-250 HD
|Cables - Analysis Plus,
Audio Magic, Monster Cable, Straight Wire
- Hitachi 46F500 rear-projection HDTV