Tube Preamp Reviews

Frontiers
Is the Modulus 3A the finest preamplifier in the world? I don't know. I can say this: when I raved about what I was hearing to Stereophile headquarters in Santa Fe, I was drop-shipped a Class A recommended preamplifier for comparison: the Sonic Frontiers SFL-2 line-stage and SFP-1 Signature phono-stage which are also based on 6DJ8 tube technology. Total cost: close to $5000.

The Sonic SFL-2 offers features the Modulus doesn't—balanced inputs and outputs, for example—and its performance and construction are clearly Class A, certainly in the same league as the Modulus, though I think the Modulus is even more transparent and liquid-sounding.

In my opinion, though, the SFP-1 phono-stage doesn't perform well with low-output coil cartridges: its relatively high noise floor and only moderate gain casts a grayish veil over the soundstage and imparts a sluggish rhythmic quality to music.

I can't square what I hear with the comments in Stereophile's "Recommended Components" listing for the SFP-1. If it is "marginal Class A," then the Modulus's phono performance is Class A+. And its lack of a mono switch is a serious shortcoming for those of us who want to listen to the many outstanding monophonic records available, without putting up with superfluous vertical-groove modulation.

The Modulus 3A: not for everyone
That said, I have to tell you that the Modulus 3A is not for everyone. If you want balanced ins and outs, you're out of luck. If you want to play with both MM and MC cartridges, forget it: once you've had the gold board installed, MM cartridges will overload the input. If you don't want to hassle with dual volume controls, forget it—although I've found them easy to use and no problem at all, especially because they're dead accurate. You can set them physically and the sound will match.

If you want to be able to listen to one source while recording another, you won't find that option on the Modulus 3A. In addition, because the 3A's design values "hot-rodded" simplicity over convenience, if you opt for the gold board, you're warned that "Tube preamplifiers have high DC voltage surges. Although the Modulus was carefully designed to incorporate a safety relay circuit that protects your system, internal circuitry could conceivably be damaged due to DC voltages being amplified by the additional 30dB of gain from the Gold Phono Board during turn-on cycle. Though safety diodes are built in to shunt these voltages to ground, we strongly recommend that you develop the habit of turning the selector switch to one of the line inputs, (ie, CD), prior to turning the unit on rather than leaving the selector on "Phono".

You're warned elsewhere that if you accidentally transpose your "tape in" with your "tape out," you can seriously damage the unit.

I mention these caveats because high performance is only one piece of the product pie. The above is certainly a consideration when choosing a product. On the other hand, a high-performance automobile is more likely to spin out of control than a family sedan. It all depends on what you want, and what you need. Keep in mind that the Modulus's reliability in the field is extremely high, so don't let those warnings scare you away. You just need to exercise some common sense.

Another caveat: Despite selling over 15,000 Modulus preamps, Audible Illusions is still a small, somewhat quirky company. I've heard complaints about availability of product, and about long downtime when repairs are needed. Make sure you buy from an established dealer; don't pay in advance for a unit to be shipped in the future; and work out your own terms if your unit does need repair. I raised some of these issues with the company, and was told new procedures and manufacturing improvements should make these problems a thing of the past.

Conclusion
I own my Modulus 3A and am absolutely thrilled with its performance out of the box. While I may experiment with Marigo Labs dots later, for this review I've run the product as the factory packs it (except for the Marigo power cord). I don't feel I'm missing anything, nor do I feel a need to coax more from the design.

Because of the circuit's simplicity, tube quality has a greater-than-usual effect on the sound. I've been told by Modulus aficionados that certain brands of NOS (new old stock) tubes improve the sonic performance. Perhaps I'll have a chance to experiment later, but for now I'll stick with supplied tubes, which should last for many years and are inexpensive to replace (about $60 to retube the entire preamp).

The Modulus 3A offers the highest level of performance at a bargain price. It even allows you to switch out the line section's bypass caps for even purer sound (that's how my unit was run for this review), and there's a carefully implemented 7dB line-section gain-limiting switch if your digital source has very high output, thus allowing a wider range of volume pot control. If you don't need a phono section (poor you), Audible Illusions' L1 line-stage offers the same performance, plus a neat headphone amplifier, for $1495.

All of this adds up to what is clearly one of the finest-sounding, best-built full-function preamplifiers in the world—and the reviews from around the world reflect that.

The best? With Audio Research's PH-3 phono section waiting in the wings, I'm hesitant to say, but looking at the cost of the associated equipment used in this evaluation, when I tell you that the Modulus 3A is in the same league and costs just $2395, you ought to listen.