Jolida SJ-101A Amplifier Review

It wasn’t so terribly long ago that pretty much every hi-fi amplifier looked a lot like the Jolida SJ-101A. In those dimly remembered days most amplifiers were very nearly as simple, too. A heavyweight sheet-metal chassis, a couple of knobs, a handful of tubes, and three hefty transformers were about all you saw, and that’s precisely the pattern followed by the Jolida design.

If you think I sound nostalgic, you’re right — I have a soft spot in my heart for tube amps. It’s not for any mystical ability to make audio signals sound “sweeter” or “more musical” than they might otherwise. Instead, I love tube amps because I can pore over their innards (and schematics) and tell you with reasonable accuracy what each and every blessed component in there is doing, something I most assuredly cannot do with even the simplest A/V receiver in these days of microprocessors and digital surround.

Jolida is a small Maryland-based firm whose mission is to bring tube sound, if not exactly to the masses, at least to a wider population of serious music listeners (already a fairly select group). And at $499, the SJ-101A is astonishingly low-priced for a tube amp — any tube amp. Yet this exceedingly simple integrated amp will do everything a minimalist, aspiring tube-head hi-fi buff needs: amplify signals, adjust volume and balance, and accept two line-level inputs, period.

And the SJ-101A delivers all the power an HO-scale audiophile could demand — assuming that he or she listens at modest levels in a near-field layout (with speakers within a few feet of the listening position) or uses high-sensitivity speakers. Jolida rates the maximum 8-ohm output of the SJ-101A as 25 watts per channel at 1 kHz and 20 watts from 20 Hz to 50 kHz. Total harmonic distortion plus noise (THD+N) is given as less than 1.75 percent from 39 Hz to 9 kHz at 15 watts into 8 ohms.

The amp’s Lilliputian output is derived from four EL-84 (6BQ5) tubes, one pair per channel, an ultra-compact design originally developed some years ago for efficient operation in small radios and the like. The tubes are deployed in a push-pull (Class AB1) pentode circuit, with a single 12AX7 dual-triode tube for each channel performing input/driver-stage chores. Overall, the SJ-101A is rather nicely made and finished for its modest price, especially in view of the cost of tubes these days; you’d pay about $40 for its tube complement alone.

Unpacking and hooking up the SJ-101A was simple and straightforward. Three pairs of RCA jacks on the rear edge of the chassis are marked CD, aux, and line out. The last is a simple preamp output, after the volume and balance controls, presumably for connecting an auxiliary amplifier. (Jolida’s rather sketchy, inconsistent, and occasionally inaccurate manual makes no mention of a line output. Instead it shows three inputs. Come on, guys.) The CD and aux inputs mix together, presumably via passive, resistive loads, so you will hear both sources simultaneously if both are playing. This arrangement is certainly simple enough, and does save the cost of a stereo switch (and the circuit complication of buffer amps), but it seems a bit kludgy to me. In addition, you might inadvertently be adding noise to the signal path, and the impedance-loading effects of the paralleled components are unpredictable. If the SJ-101A was permanent in my system, I'd use only one input at a time and terminate the empty jacks with shorting plugs.

Following tube-amplifier practice since time immemorial, Jolida provides both 4- and 8-ohm speaker outputs by way of a banana/binding-post trio for each channel. These correspond to different taps on the dual output transformers. Misloading a transformer-coupled tube amp like the SJ-101A can affect frequency response fairly dramatically, reducing usable power somewhat as well, and it isn’t all that healthy for the output trannies, either.

In keeping with the spirit of Jolida’s design, I did the bulk of my listening in a near-field layout in which the amp’s 8-ohm outputs drove a pair of NHT SuperOne compact two-way speakers. The speakers were placed at ear level, about 4 feet apart and a similar distance from my head. The audio source was a Marantz CD-17 CD player connected directly to the amp’s CD jacks (I shorted the aux input jacks as mentioned earlier).

Jolida indicates no special requirements for warm-up or break-in other than suggesting that users wait a half-minute or so for the tubes to become more or less linear. While EL-84s are quite fast in this regard, I still played the SJ-101A for several hours at solid levels before doing any serious listening. My experience with EL-84s (mostly with guitar amps, but a tube is a tube) is that they assume their true nature only after a few hot hours, and infant mortality is not exactly unknown.

But the Jolida amp’s complement of EL-84s lit up and played cheerfully from day one, no problem. The manual recommends that you check and fine-tune power-tube bias — the idle current drawn through a tube to “bias” it into linear operation. A screw-trim and probe-point (to check voltage) are provided for each of the four output tubes, though you have to supply your own digital multimeter (about $50), something any self-respecting tube-o-phile is going to want in the toolbox anyway. It’s a simple procedure, which Jolida says will not require repetition until tube-replacement time — several years down the road with typical usage. My inspection revealed the need for very slight adjustments to two of the four tubes’ bias, though I can’t say that I heard any difference before and after.

The Jolida SJ-101A did a fine job driving the NHT speakers, which have a typical sensitivity of about 86 dB. The amp’s affordable price cast no reflection on its performance. Much as I expected, it did not play terribly loud. Output before audible clipping was sufficient to reach very satisfying levels with dynamic musical material, but no more. Like most tube amps, however, the SJ-101A clipped quite gradually, making the onset of audible distortion a bit of a moving target. This takes some getting used to if you’re habituated to solid-state gear — transistor amps usually clip hard and fast when they run out of gas, making their limits easier to identify. That said, the SJ-101A provided plenty of level for serious auditions, giving reasonable punch and impact to pop and rock recordings. While the little amp did not have quite enough oomph to deliver a near-field concert hall-level orchestral experience, it did play loud enough for enjoyable, intent listening.

Did the SJ-101A evidence any intrinsic “tube sound?” Well, to my ears it had a distinct sonic “signature.” The sound was warm, slightly punchy, yet undeniably extended and airy, with excellent ambience and depth. Transient speed and sparkle were not quite as etched as I’ve heard from the finest amplifiers I’ve tried in my system. Bowed strings — especially in fine chamber-music recordings — sounded gorgeous. Bottom-octave reproduction was very solid and “rich,” with the kind of natural-acoustic roundness so often associated with tube amplifiers — maybe even a slight surplus. String bass sounded particularly beguiling; is there perhaps good reason that so many tube nuts are jazz fans — and vice versa?

Most of these sonic elements — all of which were, by the standards of normal folk, decidedly subtle variations on “plain old” accuracy — can probably be illuminated by Hirsch-Houck Labs’ bench tests, which revealed typical El-84 results: a slight top-octave droop in response (-0.3 dB at 15 kHz) along with rising distortion at both ends of the spectrum, with 15 watts producing 2 percent THD+N at about 25 Hz and 13 kHz; mid-band distortion and noise was typically a few tenths of a percent below the clipping level. The Jolida delivered about 16 watts per channel at clipping level in the midrange, which is excellent for an El-84 pair but proves the maker’s spec of 25 watts per channel “maximum” to be rather, ummm, optimistic.

Although noise measured -70 dB at 1 watt output — decidedly mediocre by modem solid-state standards — the Jolida SJ-101A “sounded” much quieter than that. Much of this might be explained by its being a low-gain design. Its line inputs require solidly more than 1 volt to reach full output, which means that your source component will need ample output capability.

It should come as no surprise when I say that the Jolida SJ-101A will not suit the average music listener’s needs for flexibility, power, and multipurpose amplification. It has strictly limited output, lacks effective source-selection options, and omits tone controls, signal-routing for tape-dubbing, remote control, and a dozen other features that are all but universal among affordable amps and receivers nowadays. The SJ-101A supplied to me also lacked a protective “cage” to guard its tubes from damage and inquisitive fingers from burns, though one that covers the entire top of the amplifier is available as an option. Nevertheless, for the budget-challenged audiophile yearning to examine the whole glass-audio thing firsthand without making a punitive financial commitment, the SJ-101A is truly unique.

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