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Sophia Electric S.E.T. Music™ Baby Amplifier

Sophia Electric's Baby Amplifier, Small in Size, Big in Sound

[Sophia Electric Baby Amplifier]
Sophia Electric S.E.T. Music Baby Amplifier
[Italian version]

Product: S.E.T. Music™ Baby Amplifier
Manufacturer: Sophia Electric
Approx. price: $899.99 USD ($799.99 with standard binding posts)
Reviewer: Richard George - TNT USA
Reviewed: June, 2003

A few decades ago, after solid state amplification had risen to preeminence based on vastly superior distortion measurements, audio magazine recommendations, and heavy advertising, I went completely against then-current audio wisdom and replaced a perfectly serviceable and socially acceptable Marantz Model 1030 integrated amplifier with a Dynaco PAS-3X preamp and a pair of Dynaco Mark III, 50-watt monoblocs. No one would listen, though some would smile with the condescending smirk of true believers watching a poor, deluded soul go astray. One friend listened to my setup once, for about five minutes, with an odd look on his face, then finally declared that the 'mid-range distortion' was so bad he didn't know how I could stand it. Comparing the solid state amp I had (and a good one it was) to the Dynaco tube equipment, I was amazed at how sweet and musical the Dynaco sounded. I decided at that time that I would always choose equipment based on the sound of it, rather than specifications or a predetermined decision based on which was supposed to be better.

Move ahead 25 years. My original Dynaco amplifiers were stolen, but have been replaced with a Stereo-70, although it isn't my primary amplifier. Some things never change, but some things do - vacuum tube equipment is back in fashion. Despite superior measurements of low- and mid-priced solid state compared to competitive valve gear, the present renaissance of tubes has not abated, in fact it appears to be accelerating. Why else would we have valve preamps and power amps, valve output CD-players and DACs, and, recently, a computer motherboard with onboard sound card that uses a vacuum tube output?

Currently, much attention is paid to single-ended triode amplifiers (SET) and the quality of sound output that has made them so desirable. However. Since SETs typically only put out a few watts (or less), they require very efficient loudspeakers to get adequate performance. Another established route to better performance would be the use of a more powerful amplifier. To this end, a push-pull arrangement would deliver substantially more power than a comparable single-ended design.

While vacuum tube gear still hasn't penetrated the hallowed halls of electronics supermarkets, numerous manufacturers and distributors of vacuum tube equipment can be found by a cursory search on the Net. Sophia Electric, based near Washington D.C., is not a particularly well-known name brand. While they have been making tube amplifiers as an OEM supplier for years, Sophia Electric has begun to market equipment under its own name. They have several high quality valve amplifiers under the Sophia Electric name, and a line of Sophia-branded vacuum tubes, including a 2.5v mesh-plate 300B tube that is currently being evaluated. While most of Sophia Electric's products are relatively expensive, they recently introduced their new entry level amplifiers, the S.E.T. Music™ line. It should be noted here that the name, "S.E.T. Music™" has nothing to do with amplifier design, but rather seems to be a reference to the intended sound quality - both amps in this line are push-pull designs. The subject of this review is the smaller of the two, the Baby Amplifier.

What is the Sophia Electric Baby Amplifier?

As implied by its name, the Baby Amplifier is quite small, 18cm wide, 23cm deep, and 13cm high (7in x 9in x 5in), and weighs about 7kg (15 lbs). The Baby Amp is rated at 10 watts per channel with distortion listed as less than 1% at full rated power. More important than distortion ratings, the specifications claim the frequency response of the Baby Amplifier to be an astounding 6Hz to 80KHz at 3dB (12Hz to 45KHz at 0 dB) and a signal to noise ratio of -95dB. These specifications are achieved using a Class A, push-pull circuit with output tubes wired in pentode mode and using minimal, global negative feedback. Solid state diodes take care of power rectification. Nominal speaker impedance should be 8 ohms.

[Tubes for the Baby Amp]
Sophia Electric Baby Amplifier Tube Complement

The quad of output tubes are Russian military 6P1T pentodes, treated by Sophia for low noise. While the 6P1T is similar in dimensions and outward appearance to the EL84 family of tubes, they are not interchangeable due to significant electrical differences. A visual comparison with an EL84 reveals that the 6P1T has substantially more robust construction. The input/phase splitter tubes are American-made, NOS 5670, medium mu, 9-pin miniature dual triodes. The brand of the 5670s was unknown as there were no markings on the tubes.

Sophia Electric has designed the Baby Amplifier to be as inexpensive to produce as possible, while maintaining the fine sound quality of their more expensive amplifiers. To this end, the chassis and printed circuit board have been outsourced, but voicing and final assembly of the amplifiers is done by Sophia Electric. The tube sockets, which are mounted on the PC board, are located just below the top surface of the amplifier chassis. Unlike some PC board mounted tube sockets, the Baby Amp's sockets have a solid feel when installing or removing tubes. The transformers are located beneath a slotted metal cover at the back of the chassis.

The back panel contains the RCA input pair, the IEC power connector, and four speaker binding posts. The upgraded, high-end Sophia Electric speaker binding posts on the sample were gold plated and covered with protective clear plastic. Such a design would make accidental shorting by improperly secured speaker cables far less likely. The standard binding posts are simpler, gold-plated units. The binding posts were laid out in a line with the positive posts in the middle flanked by the negative posts.

[Baby Amp Back Panel]
Sophia Electric Baby Amplifier Back Panel

The exterior of the chassis is a simple and aesthetically pleasing design. Several people who saw it made very positive comments about its appearance - the WAF (wife acceptance factor) of this unit is quite high. The chassis and transformer cover were painted with a matt black finish. Paint on the sample, a pre-production model, had a dull finish. While the sample was quite attractive, Sophia Electric has since upgraded the paint to a crinkle black finish. A gold-colored plaque in the top center of the transformer cover was inscribed "Sophia Electric S.E.T. High End Audio".

Located near the front of the chassis, the quad of power tubes are set in a shallow arc just behind the pair of input/phase splitter tubes. A curvaceously cut, brushed stainless steel, sheet metal accent surrounds all the tubes and bends over the front of the chassis to contain the gold-plated volume knob. Unit power is controlled by a single toggle switch on the left side of the front panel. Short pieces of carved hardwood (which appear to be cherry) are used as accents on the sides of the amp near the front panel. The Baby Amp sits on four, soft rubber feet.

How Does It Sound?

The sound quality of the Baby Amplifier is at once clean and clear, with quick transient response and potent immediacy. It is more aggressive sounding than most SET amps, but without the harshness or added grit of most solid state offerings, especially those in the same price range. The Sophia Electric Baby amp has greater impact and slam to the sound combined with more power for increased dynamic range, again, compared to typical, flea-powered SET amps.

The rated frequency response is phenomenal, listed by Sophia Electric as 6Hz to 80KHz at 3dB. No measurements were taken, but the Baby Amplifier delivered everything within the audible range with clarity and strength. The little Sophia had strong, deep bass within the limits of all suitable speaker systems tried. Highs were clean and crisp, with no trace of grit, harshness, or odd, sibilant artifacts. Too often with inexpensive amplifiers, bells and chimes aren't recognizable, they simply don't sound like what they are. This is not a problem with the Sophia Electric Baby Amp - bells, triangles, and other high-frequency tones are easily recognizable (provided the recording is of decent quality!). Mid-range is clear and smooth, though it doesn't quite measure up to the liquid-smooth middle frequency sound of SET amps, particularly those with directly-heated triode (DHT) output tubes. The Baby Amp seems to have a very well-balanced frequency response, but compared to many SET amps, the Baby amp is a bit bright, due largely to its excellent upper frequency extension. As with any amp that has a very lively high end, this may make use with overly bright speakers an issue, especially in a live listening room.

Another pleasant aspect of the Sophia Electric Baby Amplifier is the large soundstage. The soundstage, with suitable speakers, extends slightly beyond the speakers to the sides. It also extends well behind the speakers, taking up space that isn't actually present in the room. The result is that the room sounds larger than it is, simply because of the size of the soundstage. Holographic imaging is also very good, allowing precise lateral placement of instrument locations to be easily perceived. However, while lateral location was easy, depth placement was not as precise. Imaging in the third dimension was still quite good, but didn't have the three-dimensional focus of some amplifiers.

Unfortunately, no modern push-pull amps were available for comparison, so an ancient Dynaco ST-70 was pressed into service. The ST-70 is a push-pull stereo amp that uses EL34 pentodes and 20dB of negative feedback to get 35 watts per channel output. While switching back and forth between the ST-70 and the Baby, several things were very, very obvious. While the 35-year-old ST-70 still gives a very satisfyingly musical presentation, it is relatively harsh in sound, and details are obviously veiled compared to the little Sophia. Combined with, or perhaps because of the veiled details, imaging with the ST-70 was only fair compared to the Sophia. While the ST-70 had noticeably stronger bass, particularly when using sub-92dB speakers, perceived bass was slow and somewhat flabby sounding, while the Sophia's bass was quick and well-controlled. The Sophia's highs were much more extended, had greater clarity, and superior definition. Of note is that the Baby Amplifier is nearly dead quiet, while the ST-70 hums audibly, a victim of its low-cost, 1960s design and construction. The one aspect of performance in which the ST-70 had the advantage was output power. Quite simply, the ST-70, with nearly four times the power, can satisfactorily drive any speaker I had available. With only 10 watts, the Sophia could not. For best results, speakers over 90dB sensitivity, and with relatively simple crossovers (or none) will help get the best from the little Baby amplifier.

Next, came a comparison between the Sophia Electric Baby Amplifier and one of my favorite amplifiers, the Decware SE84C-Select, a 1.8 wpc single-ended amp that uses SV83 pentodes wired in pseudo-triode mode. In this comparison, there was much greater parity of sound quality, though they were still very different. The Decware did have some advantage in detail, 3-dimensional imaging, and mid-range tonal characteristics, especially when listening to female vocals, such as Jacintha's captivating Harlem Nocturne, or anything by Mary Black or Sarah Brightman. However, the little Sophia was more forward and aggressive, lending a more immediate and palpable presence to less ethereal vocals - music such as the Pretender's Learning to Crawl LP was simply more fun and engaging with the Sophia Electric Baby amp than the little Decware. Part of the difference comes down to one of power - the Sophia has at least a 6dB headroom advantage over the SE84C-S. This allows the satisfactory use of a much broader variety of speakers than can be used with an amp that has less than 2 watts per channel. Another part of the difference is that Sophia Electric's Baby Amp has much stronger and deeper bass than the Decware, which is an important consideration with many types of music. Pulling out an old LP of Stravinsky's "Firebird Suite" provided a clear reminder that additional power can really help bring some music to life. Even when using the Omega TS1 speakers (96dB efficiency), the Decware sounded a bit thin and overworked, while the Baby Amplifier provided sufficient dynamic range and full, rich sound for much greater appreciation of this classic recording.

[Baby Amp, back quarter]
Sophia Electric Baby Amplifier, view from back quarter.

One final amplifier comparison seems in order, that is, comparing the Baby Amplifier to an SET amp that uses a directly heated triode (DHT), in this case, a Fi X 2A3 with the stock complement of tubes. First and foremost, the Baby costs only two-thirds as much as my Magnequest-equipped Fi X. Frequency response was very, very different between the two. The Sophia clearly had more extended high frequencies that were sharp and clean. While the Fi X highs were clear, they were somewhat rolled off and seemed slightly less detailed by comparison. The little Sophia Electric amplifier was also quicker, with a more agile sound than the X, particularly in the lower bass. Again, there is a power disparity, as the Fi X makes a whopping 3 watts, leaving the diminutive Sophia with over three times the power. Despite the disparity in price, the only real advantage to the Fi X was in the mid-range, where the sweet, compelling sound of the 2A3 held a clear advantage over the Sophia Electric Baby Amplifier.

Because the Sophia has its own volume pot, it can be used as a standalone amplifier with a single input, provided the input source has sufficient voltage to adequately drive the Baby Amplifier. Used by itself with my primary digital source, a nOrh CD-1, the Sophia displayed exceptional clarity and detail. However, the CD-1 and the Baby Amplifier seemed to be somehow mismatched as the soundstage seemed flattened and the overall sound was somewhat thin and bright with a bias toward the high end. Switching interconnects and moving speakers around changed the sound, but didn't affect the expected sonic improvement. When the Sophia was connected directly to a Pioneer DV525 with an ART DI/O DAC, the combination worked very well, illustrating once more that component synergy is crucial to final sound quality. Not only was the Pioneer/ART combination as clear and detailed as the CD-1, but the sound was richer, fuller, and simply more musically satisfying - normally, the opposite is true with the CD-1 sounding more musical than the Pioneer/ART.

[Baby Amp, side view]
Sophia Electric Baby Amplifier, view from side.

Using a preamp with the CD-1 as a source seemed to be the best solution. When trying an IRD Purist preamp, which was being evaluated at the same time, the little Sophia had a fuller, richer sound, but it also took on a more aggressive and forward presentation. This certainly was not a bad combination and, it may be the best depending on speakers, room, and preferred music. The best combination for my listening room used my reference preamp, a Decware ZTPre tube preamplifier. The Sophia amp will work very well directly connected to a source, but for some inexplicable reason, it didn't work overly well with my CD-1 except in combination with a preamp.

The Sophia Electric Baby Amplifier worked well with a variety of loudspeakers, but it showed some distinct preferences. Two pairs of speakers with sensitivity below 88dB were tried, and both worked poorly. There simply was not enough available power from the Sophia to overcome the lower efficiency and to feed the passive components of the relatively complex crossover networks. In addition, while the Baby Amp worked very well with a pair of B&W DM602 speakers, the same cannot be said of a pair of Reynaud Twins. Both speakers are rated at 90dB, but the Reynauds are only 4-ohm impedance. With speakers of only 4-ohm impedance, the Sophia became somewhat sullen. Instead of a quick, agile, and highly detailed presentation, the Sophia was soft and slow sounding, with dulled, veiled highs and blubbery bass. Using a pair of ZERO Autoformers to increase impedance to 8 ohms made a huge difference, allowing the Reynauds and the Sophia to work very well together. Other speakers that worked well in my listening room included Omega TS-1s and Hornshoppe Horns.

Positive Impressions

The combination of sound quality, frequency response, clarity, soundstage, and imaging of the Baby Amplifier is exemplary for a sub-$1000 power amplifier.

[Baby Amp, wood and stainless steel accents]
Wood, Stainless Steel, and Gold Knob, Accents on Front of Baby Amplifier

The little Sophia strikes an excellent balance between its sound, power, and price. Printed circuit boards in power amps have developed a bad reputation in recent years among some audio enthusiasts. While it is widely accepted that poorly done PC boards can adversely affect the sound of an amplifier, properly done, they should not significantly degrade its quality. After all, the very best solid state amps use printed circuits, and their sound quality is top rate. The real advantage to the use of PC boards in the design is that it allows Sophia Electric to bring this product to market at a much more reasonable price.

The Sophia makes 10 watts per channel. To solid state fans, this seems like a miniscule and laughable amount of power. In reality when using reasonably efficient speakers such as many B&Ws, Klipsch, Polk, or similar products in the price range of the little Sophia, the power output of the Baby Amp is more than adequate. In reasonably sized rooms at normal listening volumes, the Baby Amplifier will deliver sufficient sound with adequate headroom to keep most people happy. Compared to flea-powered SET amps, the little Sophia has a 4dB to 6dB headroom advantage. Even compared to some higher-powered SET amps, such as those powered by the 300B, the Sophia delivers somewhat more power.

The Sophia Electric Baby Amplifier has first rate build quality. Just picking it up, feeling its solid construction and considerable heft gives the impression of quality. Turning the volume control reveals its motion to be silky smooth, and it is completely quiet in operation. From the flawless matt black finished transformer cover to the rubber feet on the bottom, there nothing cheap or cheesy about the build quality of the Sophia amplifier.

The Baby Amplifier has a classy design that uses brushed stainless steel, gold, and wood accents. It looks much more expensive than it is. In fact, it is easily aesthetically more appealing than most competing valve amplifiers. As is often the case with valve amps, operating the little Sophia at night provides a delightful light show. The 6P1T pentodes have a pleasant glow from top and bottom, but the 5670s not only have the usual dual-triode glow, but they also have a reddish glow from the bottom of the tube. These contribute to the unique appearance of the Sophia in a darkened room.

This is a simple amp that appears to be easy to use and easy to maintain. The tubes are neither rare nor expensive. When the time comes to retube it, an entire set will cost about $60USD. In addition to all the standard features and the optional, higher quality binding posts, the Baby Amplifier may also be ordered with many custom features, including a custom chassis. Premium component options for custom Baby Amplifier orders include Jensen Copper/paper-in-oil capacitors, and Blackgate power supply capacitors. No pricing was available for this kind of customization.

[Baby Amp, Tubes Lit]
New paint on Baby Amp - shown with tubes lit. Photo courtesy Sophia Electric

Negative Observations

The Sophia Electric website states the required break-in time of the Baby Amplifier is 50 to 100 hours. Believe it. When first set up, the sound of the little Sophia was a little harsh, gritty, and surprisingly brittle. Prior to hooking up the Baby Amp, I had been working with a well broken-in 2A3 amp that delivers liquid smooth sound. When I first hooked up the Baby Amp, I thought something was wrong with it. After reading the break-in time recommended on the Sophia Electric website, I set up the Baby Amp in my home entertainment system to be used as much as possible in order to break it in. Since two weeks of frequent use allowed the Sophia to sound much smoother and more relaxed, I had to conclude that this unit had never been properly broken in. This is a case where patience will be rewarded.

All connectors on the Sophia Electric Baby amp are well-marked and easily identifiable. However, because of the diminutive size of the case, connectors on the back are rather close together. In fact, the RCA inputs are so close together that some high-end, oversized, clamp-type RCA connectors may not fit well. The speaker binding posts are also close together, which is no problem when using banana plugs, but can make connecting unterminated wires to the posts somewhat tedious. In addition, the Sophia posts are small enough and close enough together that people who prefer the use of garden hose sized speaker cables will have difficulty.

Power was listed as a positive attribute of the Baby amplifier when compared to typical, flea-powered, SET amps. However, with only 10 watts per channel, the Sophia Electric Baby Amplifier is not a powerhouse. Care must be used to select properly matched speakers for the room size, intended music type, and listening volume, or the audio quality will suffer. With a pair of 90dB speakers played at an average 85dB, there is about 15dB headroom, which will be sufficient for most music, but when the Baby amp bumps into its maximum output, it does not clip as gracefully as some tube amps. Sound compresses badly and distortion increases radically as its limit is reached. To get ample headroom for ordinary listening, 90dB speakers will work well, but for loud sessions, 95dB or greater efficiency speakers are highly recommended. During testing, I never ran out of headroom while using the Omega TS-1 speakers (96dB, single-driver), but crashed hard into the power ceiling with the B&W and Reynaud speakers.

The Sophia Electric Baby amplifier does not work well mis-matched impedance loads. This is not really a 'negative', but is something that must be taken into account when selecting this amplifier to power an existing set of speakers. If your speakers are 4 ohms or lower, the Sophia will not deliver the type of performance of which it is capable - if your speakers are 16-ohm impedance, the Sophia Electric Baby amp will probably sound thin, bright, and unpleasant. As with any components, it must be properly matched with the system if it is to work well.

[Sophia Electric Plaque, Top of Transformer Cover]
Sophia Electric identification plaque, from the top of the transformer cover.


The entry-level audio market used to be populated with mid-fi gear that performed adequately, but left its purchasers wishing for more. This situation is, of course, advantageous to the equipment builders, as they have plenty of higher-priced gear to fulfill the needs imposed by the dreaded audiophile affliction, 'upgrade-itis'. Increasingly, we are seeing products in the 'entry-level' price range that have amazing performance - performance that is out of character with the price. Sophia Electric is now making just such a unit, the S.E.T. Music™ Baby Amplifier, with production beginning as this review is being written.

Sophia Electric has entered the sub-$1000 amplifier price range with a vengeance, serving notice of their intentions with a completely new amplifier designed, as their website says, "to be the world's finest amplifier." While that stated goal may be a bit optimistic, especially in light of higher priced Sophia Electric products available, the fact remains that the Sophia Electric Baby Amplifier is certainly among the finest in its price class - and beyond. With decent, usable power, impeccable sound, superb build quality, and very pleasing visual aesthetics, the littlest Sophia is pleasing to see, and wonderful to hear. With any luck, they will be able to continue to offer the Baby Amplifier at a low price for a some time to come.

Many thanks to Richard Wugang, Managing Director for US and European Markets for Sophia Electric, for providing background information and the sample used in this review.

© Copyright 2003 Richard George - www.tnt-audio.com

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