I've been dabbling in budget versions of high-end audio for about ten years, and was recently able to pick up a pair of refurbed Sennheiser HD-600s at a good price. The problem was that with an impedance of 300 ohms, these were my first cans that really required an amplifier. I read what felt like a hundred reviews, and at some point found an SMSL SAP-II lightly used/still in the box on eBay for about $50. In the spirit of "Why not?" I pulled the trigger, and I'm very happy I did.
The SAP-II is sturdily built with an aluminum chassis. The front features a round metal volume knob with a blue LED backlight, two toggle switches (on/off and input selector), and a 1/4" output jack. On the back there's the AC input, RCA stereo inputs, and a 3.5mm input. I use the RCAs for my turntable and the 3.5mm connects to a passive dock for my iPod.
My setup is an Audio Technica PL120 turntable and a 5.5th gen iPod running Rockbox. I listen to a 50/50 mix of vinyl and digital files when I'm at home, and a broad genre mix-- lots of non-vocal classical, minimalist experimental electronic music, occasional post-punk and indie rock, and sometimes an American musical or two.
The SAP-II is a champ across the board. I tested both with the HD-600s and with a pair of Monoprice 8323s (stock pads replaced with Dekoni leather). With the volume just a quarter of the way up (around 9 o'clock for the HD-600s, and a hair less for the 8323s) I have a full, satisfying experience of volume. The HD-600s, unsurprisingly, have more clarity and detail across the board, but the 8323s are also surprisingly good with the SAP-II, and definitely better than they are without it. A few sample listens:
- Pau Casals, J. S. Bach: The 6 Cello Suites, "Suite No. 1 in G, III. Courante"
One of my all-time favorite recordings, and challenging because it was made in 1938, so even the relatively recent remaster has an audible hiss in the background. The level of detail and clarity doesn't do the hiss any favors, but man oh man, the cello sounds fabulous. I feel like my head is inside the f-holes, if you know what I mean. Especially on the lower end, beautifully sonorous and detailed, and the double stops give me goosebumps. Mid-range is a little muddy with the 8323s, and while high end is clear and lovely without being screechy on the HD-600s, it was occasionally so on the 8323s.
- Anna Meredith, Varmints, "Nautilus"
This track is MASSIVE. French horns and tubas are interlocked in a fight to do the death, as layer upon layer is added to sinister effect. The soundstage is massive-- you feel like you're in a music hall the size of a Super Bowl stadium-- and even with multiple layers of distinct parts happening, they're all relatively easy to locate and separate. Again, overall a bit muddier on the 8323s, with loss of detail at the high-end especially.
- Farben, Textstar, "Live at the Sahara Tahoe, 1973"
A clicky, glitchy, beep-and-boop electronic affair. Lots and lots of detail happening on the production end with this track, and again, it's beautifully conveyed. With the HD-600s, the bass is roundly robust, and the staticky hiccups satisfyingly coarse in the mid-range and high-end. The 8323s are bit too bassy, and it bleeds up across registers, but still decent clarity on the high end. Great stereo separation on the soundstage on both sets of cans.
- Bjork, Medulla, "Triumph of Heart"
One of my go-to tracks for determining level of detail. With a solid setup, you can hear spit moving around in the mouth of the person making the raspberry noises at the beginning. Yep, the spit's here, and once again, I can pick out each individual voice in space. Sounds lovely and melodious, rather than screechy.
Conclusion:
An excellent budget amplifier for stationary listening. No audible hiss, static, or background noise. Relatively flat, faithful reproduction of source material, both vinyl and digital. Great clarity and detail and great reproduction of the sound stage, with accurate stereo separation. Mine is black, and is a minimal and unobtrusive aesthetic addition to my audio equipment. Would highly recommend to anyone looking to amplify a turntable or power some thirsty headphones, but also makes even a cheap pair of on-ear cans sound pretty great.
Note:
I initially did have a little bit of background noise when I plugged this amp straight into a wall outlet, but intervening with a cheap Belkin power strip for both the amp and my turntable fixed this. I live in an older apartment complex, so I find this unsurprising, but your mileage may vary.
