- Category: Full-Length Equipment Reviews
- Created on Wednesday, 01 September 2010 01:00
- Written by Vade Forrester
For a long time, the model for a high-end, two-channel hi-fi system has included a separate preamplifier and power amplifier, which makes sense: separates let you put the heavy, hot amplifier section away from your equipment rack, with a lightweight, cool-running preamp sitting high on the rack, where you can reach its controls. Today, however, more and more integrated amplifiers (an amp and preamp in a single chassis) are appearing on the scene. There’s no functional reason an integrated amplifier can’t work just as well as separates, thanks to one of the most convenient technologies: the remote control. Having the amp and preamp in the same chassis saves an expensive interconnect cable and power cord, and should offer quieter operation due to superior grounding. Given the minimalist designs of today’s preamps, it’s not as if there are a lot of controls to worry about. Which brings us to the subject of this review, Musical Fidelity’s AMS35i integrated amplifier ($8999 USD).
The 62.3-pound AMS35i could be a challenge to insert into an equipment rack; its dimensions of 19"W x 5.875"H x 18.75"D would be a tight fit on many shelves. Given that heft, you may be surprised to learn the AMS35i is claimed to put out only 35Wpc into 8 ohms. Why so little? The AMS35i is a class-A design, which are typically substantially heavier than equivalently rated class-AB or class-B amplifiers. At first, I thought it odd that Musical Fidelity, who strongly believes that the more power, the better, should bring out a lowly 35Wpc model. Then I recalled that MF has been building class-A amplifiers a long time. And if you have sensitive speakers -- say, 95dB or higher -- then 35Wpc may be all you need. The AMS35i sure didn’t break a sweat driving my 103dB-sensitive horn speakers; in normal use, I didn’t turn the volume knob higher than 9 or 10 o’clock. I haven’t always been a fan of the styling of Musical Fidelity gear, but I think they got it right with the AMS35i. It looks very elegant, is exquisitely finished, and comes in two colors: black (the review sample) and titanium (a metallic gray). Each version has a name badge of stainless steel. Like most MF designs, the AMS35i is quite simple: there’s a single central knob for the volume, with a nearly invisible notch to indicate the setting; everything else is controlled by small, silver buttons. The faceplate isn’t obscenely thick, but substantial enough to tell you that this is a quality piece of gear.
Starting at the left of the faceplate and working right: The first button is the On/Off switch; a small blue LED tells you the amp is on, and a brighter red LED tells you when it’s muted. The AMS35i goes into mute when it’s turned on; about ten seconds later, it unmutes and is ready for action. Next are the tape monitor switch, the volume knob, and five source-selector buttons: Balanced Input, CD, Tuner, Aux, and Tape. Each input has a blue LED that tells you which input is selected. I was disappointed that there was only one balanced input (I have several balanced sources) and no balance control; in my experience, it’s often necessary to make minor, and sometimes not so minor, adjustments to a recording’s balance to get a good soundstage. My speakers are placed asymmetrically for uniform front-wall loading; a balance control is useful to center the image when I sit in the center of my couch.
On the rear of the chassis are the speaker terminals. Between them are the unbalanced input jacks and preamp output jacks (all RCAs). The latter is useful for driving subwoofers. I would have appreciated balanced output jacks, since that’s the preferred connection for many subs; and as the AMS35i’s internal circuitry is balanced, it would require no adaptation. The balanced input jacks (XLR) are under the speaker terminals and toward the center, and at the right is an IEC inlet for the power cord. The cord that shipped with the AMS35i looks like a computer-grade cord.
The AMS35i’s input impedance is 40k ohms, which should cause no trouble for any competently designed source component. Its damping factor is 130, which means that while the amplifier will provide ample control over the speaker, it shouldn’t overdamp the bass and make it excessively lean.
The massive remote control is machined from an ingot of aluminum. It looks impressive but has several design flaws. First, its sharp corners will damage whatever the remote is dropped on: amplifier, coffee table, toes, etc. However, it does have small plastic feet on the bottom to keep it from scratching whatever it sits on. Nearly all the controls on the front panel are duplicated on the remote, except for the most important one: On/Off. If you, like me, place the AMS35i on your rack’s bottom shelf to give this very hot-running amplifier maximum ventilation, it’s a pain to have to go to your rack and bend over nearly to floor level to turn the amp on or off. What’s the point of a remote control if you have to operate the amp manually? I could have put the amp on a higher shelf, but none of those provided as much ventilation.
Another gripe about the remote concerns the volume control, which is implemented with two buttons: upward- and downward-pointing triangles to raise and lower the level. I renamed these Too Loud and Too Soft. I couldn’t find a setting that would provide anywhere near the volume I wanted. So once again, I had to trudge over to the rack and manually turn the volume knob. And would it have been too hard to paint a dot or a stripe on that knob, to make it easier to tell from your listening chair what setting you’ve chosen? On the black model, at least, I couldn’t see the notch. I finally trimmed a Post-it into a triangle and stuck it on the front of the volume knob to act as a pointer to tell me where the volume was set.
When I placed the AMS35i on the bottom shelf of my Billy Bags equipment rack, I learned just how sharp the edges of its heatsinks are. From then on, whenever I lifted the amplifier, I used well-padded oven mitts.
The AMS35i’s four feet have some sort of soft rubber central part that seemed to want to come off but that actually adhered to the shelf; that should provide unusually good isolation from vibration. Connecting the speaker cables and interconnects was straightforward; I used both balanced and unbalanced interconnects. The speaker cables had spade-lug connectors, which worked fine.
I tossed the stock power cord back in the box and did what most audiophiles would do: use an aftermarket cord, in this case a Purist Audio Design Venustas ($1000), which has never failed to substantially improve the sound of power amps. I realize this somewhat limits the universality of the review, but I wanted to realize the AMS35i’s full potential -- and it’s not that goofy to pair an $8999 amplifier with a $1000 power cord.
My review sample of the AMS35i was a demo unit that had already had about 100 hours’ use, which reduced the burn-in period (hooray!). But while it was never unlistenable, I gave it another 200 hours of burn-in. Some audiophiles reject the need for burn-in, but my experience has shown me that most equipment benefits from it, and most manufacturers will tell you the optimum burn-in time for each component. Like many other class-A amplifiers, the AMS35i needs to reach thermal equilibrium before it sounds its best, and that can take nearly an hour.
To get experience using the MF’s preamp output jacks, I connected a pair of JL Audio Fathom f110 subwoofers and set them up using my real-time analyzer, which took about five minutes. The AMS35i drove the Fathoms superbly, indicating that the amp has the requisite low output impedance. But the MF produced large pulses through its pre-out jacks when I turned it on and off, which prevented my using the subs’ automatic turn-on/off feature. Fortunately, there were no pulses through the speaker terminals. Still, that’s not the kind of behavior I expect from an $8999 amp. To assess the AMS35i’s bass performance, I didn’t use subwoofers during my listening tests, though I normally use them when listening to music.
Before I start talking about how the AMS35i sounds, a short comment about how it didn’t sound. I placed an ear right next to the sensitive Feastrex driver of one of my Affirm Audio Lumination speakers and heard . . . absolutely nothing. No other component in my experience has been so utterly quiet. That’s good.
The AMS35i lived up to Musical Fidelity’s reputation for making electronics that have exceptionally pure, extended high frequencies. While not at all peaky, the highs were very evident. That made the AMS35i a good match for my speakers, which slightly roll off the treble. On Jennifer Warnes’ "The Panther," from her The Well (CD, Sin-Drome SD8960), the high-pitched chimes came through as if someone had switched in a supertweeter. A speaker with a hotter high end might sound too bright with the AMS35i. This isn’t to knock the MF; it’s just a reminder that you need to carefully match a system’s components to get the flattest response.
At the other end of the spectrum, the bass was tight and punchy, and fuller than I had experienced with other solid-state class-A amps. I attribute that to the AMS35i’s medium damping factor of 130; the last class-A amp I tried had a super-high damping factor of 5000, which made the bass lean and a tad too damped. For many speakers, the higher damping factor would result in better woofer control and tighter, faster bass -- but horn speakers such as mine are pretty much self-damped. Bass extended as low as I’ve heard my speakers go.
The midrange had remarkable clarity and detail. Timbres were very well fleshed out -- musical instruments sounded unusually realistic. Instrumental attacks demonstrated excellent transient speed without overemphasizing it. As is typical of class-A amplifiers, the tonal envelope of instruments was fully presented, so in this way, too, instruments sounded unusually realistic. One of my few 24-bit/192kHz recordings is a collection of Mozart symphonies performed by the late Sir Charles Mackerras and the Scottish Chamber Orchestra (FLAC, Linn Records). The sound of the strings was drop-dead gorgeous -- this is one of the best digital recordings I’ve heard in any system.
Concurrently with the AMS35i I was reviewing the Esoteric D-07 DAC, and for that I exclusively used digital files from my computer music server. Perhaps the most distinctive attribute of high-resolution music files is an extremely palpable soundstage, in which a sonic image of each performer seems to be painted in space with reach-out-and-touch-it precision. The AMS35i depicted hi-rez soundstages neatly and accurately; it neither overemphasized them nor grafted its own version of space onto the recording -- performers never seemed too separate, or as if they were sitting in isolation booths (though some of them probably were). Instead, the MF presented an impression of musicians performing within an appropriate environment, whether a small club or a large concert hall.
The AMS35i’s dynamic response was rapid and accurate at all levels, from microdynamics (very small volume changes) to macrodynamics (very large volume changes). On my fave test cut for dynamics, Folia Rodrigo Martinez, from Jordi Savall’s La Folia 1490-1701 (CD, Alia Vox AFA 9805), the volume continuously changes as the performers proceed through this rollicking piece, and the AMS35i precisely tracked those changes. Some components make the volume sound as if it’s changing in discrete steps; not so the AMS35i.
My Atma-Sphere S-30 Mk.3.0 has much in common with the AMS35i -- it’s a 30Wpc class-A stereo amplifier -- but unlike the AMS35i, it’s a power amplifier only. And there’s another major difference: the Atma-Sphere is tubed. However, unlike most tube amps, it doesn’t use output transformers, so it has more extended frequency response than amplifiers with transformers. And because output-transformerless (OTL) amplifiers produce more power into higher impedances, the Atma-Sphere puts out 45Wpc into my 16-ohm speakers. The Atma-Sphere’s 16 tubes made the heat output of the AMS35i feel positively cool.
I used my Audio Research LS26 line stage to drive the Atma-Sphere: a combined cost of $9945, or only $946 more than an AMS35i. (Of course, that price doesn’t include the $1000 power cord and $1200 interconnects I used.)
The ARC/Atma-Sphere combo immediately reminded me why tubes have a reputation for soundstaging. It sounded more open, with even more solid spatial definition than the AMS35i. The combination didn’t manufacture a bogus soundstage, but showed me that the MF hadn’t completely fleshed out the three dimensions of space. I never felt the AMS35i was lacking while listening to it, but when the tubed combination was returned to the system, I immediately realized its superior soundstaging prowess. (To be fair, the ARC/Atma-Sphere combination has surpassed several combinations of tubed gear, too.)
Its lack of output transformers means that the Atma-Sphere has quite deep bass response that was the equal of the AMS35i’s -- and not only deep, but punchy and detailed as well. But both amplifiers had excellent bass; the AMS35i’s was tighter and perhaps a bit leaner, but not by much. The Atma-Sphere’s bass is close to ideal for my speakers: dynamic, detailed, and deep. If I had ported speakers instead of horns, I think the AMS35i’s higher damping factor would have given me better control over the woofers and produced tighter bass response. That’s important to keep in mind; there aren’t that many horn-loaded bass speakers out there. The Atma-Sphere had most of the dense tonal color and palpable soundstage of a single-ended triode (SET), but without the high levels of second-harmonic distortion those amps sometimes exhibit. Highs were extended, with no additional emphasis. Perhaps I slightly preferred the information density the Atma-Sphere packed into its sound, but I do mean slightly. And as I finished up my comparisons, a tube in the Atma-Sphere began to make noise, which necessitated ordering new tubes. What a pain!
Finally, the Audio Research LS26’s remote control is everything the AMS35i’s is not. Light plastic with no sharp corners, it won’t wound you if you drop it on your foot -- I know, I’ve tried it. From Off to full On, its volume adjustment has 103 steps, which lets precisely set the loudness you want. And a large numeric readout on the LS26’s front panel shows me the exact volume setting. I can also turn the ARC on and off from the remote control -- which also has a balance control. As far as I’m concerned, this is as good as a remote control needs to be.
Who should be interested in the Musical Fidelity AMS35i? Someone who loves the sound of tube amplifiers but not the hassle of maintaining them, who has reasonably sensitive speakers (95dB or higher), and who listens to unamplified music (classical or jazz) at less than ear-splitting levels. I suspect that such a person will find the AMS35i class-A integrated amplifier’s rich, pure, transparent sound extremely appealing. Its extended high-frequency response lights up the treble, and its bass sounds considerably more powerful than its specification suggests. I suspect that the AMS35i is very conservatively rated, and will probably surprise you with its ability to drive speakers of average sensitivity -- but if your speakers are inefficient, try before buying.
While I found some ergonomic problems with the AMS35i, that’s a personal reaction that’s somewhat system-dependent. If your speakers are less sensitive than my 103dB horns, the volume-control increments may suit you just fine. And if you don’t use the AMS35i’s preamp outputs, it won’t matter that they emit turn-on/off pulses.
I loved the sound of the Musical Fidelity AMS35i in my system, and could easily live with it long-term. If you’re shopping for an amplifier at or around $9000, I urge you to add it to your audition list, even if you’re a dyed-in-the-wool tube dude. It could be your ticket to listening nirvana. Highly recommended.
. . . Vade Forrester
- Speakers -- Affirm Audio Lumination, JL Audio Fathom f110 subwoofers (2)
- Preamplifiers -- Audio Research LS26 and PH5
- Power amplifiers -- Audio Research VS115, Atma-Sphere S-30 Mk.3.0, Art Audio PX-25
- Analog source -- Linn LP12 turntable on custom isolation base, Graham Engineering 2.2 tonearm, van den Hul Frog cartridge
- Digital sources -- Meridian 508.24 CD player, Sony SCD-XA5400ES SACD/CD player, Apple iPod Touch and Wadia 170iTransport, Hewlett-Packard DV-9205us laptop computer, Benchmark DAC1 Pre DAC, Auraliti PK100 digital music player, M2Tech hiFace USB-to-S/PDIF converter
- Interconnects -- Audience Au24 e, Blue Marble Audio Blue IC, Clarity Cables Organic, Crystal Cable Piccolo, Purist Audio Design Venustas, TG Audio High Purity Revised
- Speaker cables -- Audience Au24 e, Blue Marble Audio, Clarity Cables Organic, Crystal Cable CrystalSpeak Micro, Purist Audio Design Venustas
- Digital cables -- Wireworld Starlight USB and Gold Starlight 6 S/PDIF
- Power cords -- Audience powerChord e, Blue Marble Audio Lightning, Clarity Cables Vortex, Purist Audio Design Venustas
- Power conditioner -- Audience aR6-T
Musical Fidelity AMS35i Integrated Amplifier
Price: $8999 USD.
Warranty: One year parts and labor.
Musical Fidelity Limited
24-26 Fulton Road
Fulton Road, Wembley
Middlesex, England HA9 0TF
Phone: +44 (0)20-8900-2866
Fax: +44 (0)20-8900-2983
North American distributor:
Tempo Sales & Marketing
P.O. Box 541443
Waltham, MA 02454-1443
Phone: (617) 314-9227
Fax: (617) 336-3486