It seems that ampsandsound‘s Justin Weber is a fan of vintage equipment – Klipschorns, single-ended tube amps – and now wants to spread a somewhat modernized vision to a new generation of audiophiles. Although their offerings include designs based on tubed output stages, the power supplies are solid-state and point-to-point wiring is eschewed for PCB’s. The subject of this review is their relatively affordable headphone and integrated amp, the single-ended Mogwai.
The Mogwai has a classic look about it that’s not too far removed from the amps you’ll find from Border Patrol or Bottlehead’s DIY kits. The sides of the chassis are made of wood panels with the bottom and top panels in steel. The labeling on the top panel seems to be laser etched and stands out clearly. All controls and connections are made from the top panel: the volume knob and power switch are located along the front with a pair of single-ended inputs, headphone output socket, speaker output binding posts, and power inlet taking up space in the rear. Tube sockets aren’t labeled but the input tube socket is oriented differently from the output sockets to prevent folks from accidentally inserting the wrong tube. Four stout rubber feet keep the amp from sliding around.
You can roll the output tubes to the 6L6GC, EL34, KT66, KT77, KT88, 6550, or KT90 without batting an eyelash. The input tube is limited to the 6SL7 and its equivalents. The tube complement for this review included a pair of Apex-matched JJ 6CA7’s and a NOS RCA 6SL7GT. The output tubes are wired in triode mode.
Headphones can range in impedance from 32 – 300 ohms but speakers are limited to 8 ohms nominal. The manual states that baseline specs for loudspeaker listening is 87 dB sensitivity and an impedance that doesn’t dip to 4 ohms. Unfortunately, that meant that hooking the Mogwai up to my Vandersteen 3A Signatures was out of the question.
The amp is straightforward to connect and turn on. It’s also powerful. Even when used with the Sennheiser HD 600’s and listening to SACD’s on my Ayre C-5xeMP (which outputs a signal that’s 6 dB lower than with PCM material), I never reached 9 o’clock on the volume knob. The Mogwai is a beast, at least for the headphones I had on hand.
At times, there were some audible pings from the output tubes as the amp warmed up. I also found the Mogwai somewhat susceptible to microphonics – I could hear light tapping on the amp’s chassis through the headphones and it even amplified light knocking from my desk. There was also a very low-level intermittent noise in the right channel. Justin assured me that these were all due to the miles that the amp has covered in its travels and that normal production samples would be quiet.
I listened to the Mogwai using my Audeze LCD-XC’s and the aforementioned Sennheiser HD 600’s. Through both sets of cans, the amp exhibited eminent control over the audible frequency spectrum. This was particularly noticeable in the bottom octaves where it might have been a little too iron-fisted. Images possessed an athletic quality to them: well-defined and taut with a piquant tonal balance. The Mogwai sounded clean and the midrange was finely textured.
As I listened to track after track, clarity and resolution were words that kept coming to mind. On tracks like The National’s “Demons” (CD, 4AD, CAD3315CD), Tegan and Sara’s “White Knuckles” (24/96 FLAC, HDTracks), and The Yeah Yeah Yeah’s “Little Shadow” (CD, Interscope, B0012735-02), vocal and instrumental textures were readily apparent and drum kits were tight. Distorted guitars sounded, well, distorted. Images were appropriately dense, though the bottom octaves lacked some heft. The Mogwai seemed to hit its stride on classic rock. On “Done Somebody Wrong” from The Allman Brothers’ The Fillmore Concerts (CD, Polydor, 314 517 294-2), Doucette’s harmonica took on a slightly wailing quality. Vocals, percussion, and guitar all telegraphed clean and clear across the ages. The Mogwai did an equally fine job on Cream’s “White Room” from The Very Best of Cream (CD, Polydor, 31452 3752-2). Its incisive approach to Baker’s drumming and Clapton’s wah-wah’d guitar riffs showcased its low-level resolution chops.
Lateral spatial resolution was stable and the soundscape seemed to be projected outward. Images never wandered. During complex passages in classical material such as the finale of Schumann’s Piano Concerto (CD, Sony, SK 64577) or Saint-Saëns Organ Symphony (SACD, Telarc, SACD-60634), the amp remained poised and firmly in control. Yet a convincing portrayal of depth seemed to elude the Mogwai. Performers and instruments seemed to generally exist on the same plane throughout. Images were focused, but I sometimes got the sense that they tended to be a cardboard cutout of the real thing.
Transients never lacked snap and it commanded dynamics of the micro and macro variety. On the Cold War Kids’ “Go Quietly” (CD, Downtown, DWT70397), the Mogwai captured the sharp report of every snare hit. The same went for Rilo Kiley’s “Silver Lining” (CD, Warner, 189372-2) – the drum kit sounded tight, though the kick drum and bass line were a bit lower level than I’m used to. On acoustic fare such as “Al Vaivén de mi Carreta” from AfroCubism (CD, Nonesuch, 525993-2), guitar sounded clean from the initial pick through the subsequent decay of the string tone. Background percussion possessed a tactile quality that served the sinuous rhythm of the song. On Holst’s “Jupiter” (CD, London, 289 560 606-2) the initial crescendo was intense and the finale was equally stirring.
I felt the Mogwai was within a whisker of ultimate timbral realism and naturalness. Perhaps part of the cause could be traced to the somewhat dampened bass response. That might have robbed the sound of a bit of warmth, lending a slightly more forward nature to the presentation. Whatever the case, massed strings sounded just a touch dry and I missed a small degree of airiness from symphonic works. The instrumental solos in “I’m Old Fashioned” from Blue Train (24/192 FLAC, HDTracks) seemed to lack a smidge of vitality and glow. It took my mind a bit more effort to suspend disbelief and simply flow with the music.
I normally switch between two amps when listening to cans: the Donald North Audio (DNA) Sonett 2 and the HeadAmp GS-1 with Dynalo+ modules. The former is an all-tube SET topology utilizing a 5AR4 rectifier and a pair of 6H30’s with their twin triode sections paralleled for more power output. The latter is a solid-state design with a venerable history.
The Sonett 2 added some heft back to the lower registers along with a sensible dollop of warmth to vocal and instrumental timbres. To my ears, it sounded more organic and better balanced next to the Mogwai, though its sound field was less intense with a mid-hall perspective – even when volume levels were matched. The DNA amp also sounded a touch smoother through the midrange and treble at the expense of some texture and images possessed more dimension.
The GS-1 split the difference between the Sonett 2 and the Mogwai. It too was a little more even in its frequency response and posted slightly more natural sounding images with a similar perspective to the Sonett. I also felt it projected a more dimensional and layered soundscape than the Mogwai or the Sonett 2, but didn’t quite reach the realistic timbre of the latter nor the detailed and textured sound of the former. Like the DNA amp, the GS-1 offered up more bass quantity without sacrificing quality in the process.
The Mogwai’s vibrant nature and generally excellent command over the frequency spectrum is ripe for some serious system matching exercises. It truly was a shame that I didn’t have loudspeakers with the right specifications on hand for pairing with the Mogwai. Music lovers looking for an amp with an intense sound and a laser-like focus take note: this amp may be the perfect match for you.
Headphones – Audeze LCD-XC (2016 drivers), Sennheiser HD 600
Sources – Ayre Acoustics C-5xeMP, Ayre Acoustics QB-9 DSD
Amplification – Donald North Audio Sonett 2, HeadAmp GS-1 w/ Dynalo+ modules
Cabling – Blue Jeans Cable LC-1 and 1800F interconnects
Power – Bryston BIT-15, ZeroSurge 8R15W-I
Volume levels were matched using pink noise from Audiocheck.net using a Radio Shack analog SPL meter (model 33-4050) on C weighting, slow response.