Review: Yaqin MC13S Stereo Integrated Amplifier

Review by Colin McKay

In some ways, the Yaqin MC13S stereo integrated is a paradox. It is playing music in my system where, normally, a several thousand-dollar integrated amplifier should be. The paradox is that I am soundly satisfied with the music I am hearing. I can live very happily for a long time with this amp in my system before I even feel the itch to invest in a costlier upgrade. I am certainly not saying this is the integrated amplifier that you must rush out and purchase immediately. Rather, let me introduce the reasons I believe that this amplifier occupies a unique niche in the more frugal-minded tube amplified market. As well as a few cautions to those considering its purchase.

Let’s start with some hard to find facts about the company we know as Yaqin. From their website we learn that the company was founded in 1994. Its products are mainly exported to Japan, North America, and, Europe. It now owns a 5000-square-meter production facility. Moreover, this facility houses workshops for metal chassis stamping, CNC machining, circuit board printing, and transformer production. All the research and design, quality control, and assembly are done within Yaqin’s own walls. These are truly “in house” products.

The amp weighs a hefty 22 kilograms. It measures 47 cm in length, 31.5 cm in width, and 17.5 cm in height.

Many of the circuit components are of audiophile grade, produced by well-known Japanese, American, and European companies. Solen, Philips, Siemens, and Thomson capacitors are quoted as being used through their circuits. As well, the volume controls used are from ALPS, the well-known Japanese company. The vacuum tubes Yaqin uses are from reputable Chinese manufacturers such as Shuguang. The Yaqin factory has received Chinese 3C, and European CE certification.
The stated specifications that Yaqin gives for the MC13S stereo integrated specifications are:

Output power: 40 watts + 40 watts at 8 ohms;

Distortion: ≤0.9% measured at 28 watts;

Signal to noise ratio: ≥85 decibels (A-weighted);

Two speaker output impedance posts rated at 8 ohms or 4 ohms;

Four switchable line inputs;

Power consumption: ≤220W; and,

Input Sensitivity: ≤0.26 volts.

The Yaqin MC13S has a very minimal and straightforward circuit. Bells and whistles found in more expensive integrated amplifiers are not there. If you want an auto-mute circuit, a tube auto biasing circuit, a remote control, or even a protective grill, you will need to look elsewhere. At a significantly higher price, Yaqin offers amplifiers that do include the above items.

However, there is a silver lining to be found here. The somewhat bare-bones circuitry of this amplifier does deliver a very high-quality sound. The circuitry is based on a time tested, ultra-linear push-pull design that made the sound of an EL34/6Ca7 based integrated amplifier the mainstay of frugal tube amp audiophiles while we weathered the rise and triumph of the new solid-state transistor world order. Our hats are off to David Hafler, Dynaco, and many others on this point. The moral of the story here is that if it is a tried and true audiophile circuit that has won over so many hearts, why play with it? Well, I guess we cannot resist the urge to do so. But without any minor modifications, this amp’s circuit design is the first guarantee that the MC13S will deliver a quality audiophile sound.

The second guarantee to such sound is the high quality of this amplifier’s components. The Yaqin uses audiophile-grade resistors, coupling capacitors, and volume controls. Yes, they do make another big contribution.

Of all the components used, there is one that stands out the most. The MC13S is equipped with excellent iron. Both the input and output transformers are very high quality. It starts with the oxygen-free enameled copper used in the windings for the transformers cores. It ends with the use of 35-millimeter Japanese steel sheet employed in the building of the laminated stacks surrounding the core windings.

It’s worth noting that output transformers are the highest cost and most labor intensive part of a vacuum tube amplifier to make. Each of output transformers takes a lot of time to slowly wind the cores, and assemble the steel sheets for the stacks. They are then heated, dipped in resin and baked. Once done, they then need to be cleaned and painted. Their external leads and connecting caps are lastly fitted for final assembly on the chassis. The number of hours involved depends on the size of the output transformer. Yaqin then adds substantial metal covers to their transformers in order to increase their magnetic isolation. Again, these transformers are designed and fabricated in Yaqin’s own production facility.

The complement of vacuum tubes used are four EL34-B, two 12AX7, and two 12AU7. There is no tube rectification provided. Instead two diode based bridge rectifiers are employed. One is used for high voltage needs. The other is used for the bias voltage needs. I won’t get into the debate here, of which avenue of rectification is better. Having extensive experience with both, I know that each has its unique sound qualities.

The chassis is very well made. You can choose to love it or hate it on your own. It is not steam-punk enough for me. The four line inputs, and six spade/banana speaker plugs are first rate, as are the volume control and input switch. There is no phono pre-amplifier fitted.

The MC13S was tested in a system composed of Focal 836 VW speakers. Audio components employed for CD playback were the Mytek 192-DSD DAC, and the Toshiba HAD-2 as a transport. A Toshiba Satellite laptop A660 OT4 was used for DSD playback through the Mytek.

Vinyl was played back on the Well-Tempered Turntable and Arm. The arm has been rewired with Van Den Hul silver wire. A Roksan Chorus served as the pick-up cartridge. Cartridge amplification and RIAA equalization were done by the Yaqin MS-12B preamplifier and phono stage.

I could happily live with the stock tubes that the Yaqin MC13S is supplied with. However, I have an extensive new old stock (NOS) collection of just such tubes. The 12AU7 tubes are the first ones that I changed. These tubes are employed in the amplifiers push-pull driver stage. It is with these tubes that I heard the biggest improvements in the musicality of the amplifier.

You may ask, “Why the push-pull driver stage?” To drive a pair of EL-34s to their maximum power rating, the balanced signals coming from the preceding 12AX7-B voltage pre-amplification stage need to be increased to a higher level. The 12AU7 driver provides the dynamic gain each of the positive and negative phases of the signals.  That means the tubes are often called on to provide a five to ten-time voltage increase to realize the EL34s full power output.

At lower levels the 12AU7 contributes no distortion. When the tube begins to reach maximum level, slightly before the EL34s do, they will dynamically clip. Of course, this clipping will be further amplified by the EL34s in the power output stage. We all tend to drive our tube amplifiers to clipping levels. It just nice basking in that glow of “tube warmth”. It is sometimes described as quality to listen for. However, it is still distortion; and, as such, should be reduced as much as possible.

I replaced the stock 12AU7’s with a pair of Canadian-made Rogers 12AU7A MQ (for military quality). The MQ labels were reserved for the closest-matching internal triodes. Most likely they were made during the 1970’s. I bought a sleeve of them in Toronto during the early 1990’s. For reference purposes, they look exactly like a Mullard 12AU7A made in the UK. The Rogers tubes improved the sound by audibly cleaning up the dynamic transients or the ‘attack and decay’ of the music. They removed a layer of grain from the music in all its forms. They are also quieter. Details in the music became more evident. Complex passages were rendered more understandable. The speakers drew less attention to themselves.

I then swapped the 12AX7-B drivers for some Telefunken-branded Phillips ECC83’s made in Holland. These ECC83 long plates are etched with codes from the Heerlen factory. These were manufactured in 1972, using Mullard tooling that Philips acquired when they bought Mullard in 1965. These came as stock tubes in the Scottish-made Grant G60S, of which, I purchased two examples in the mid-eighties. Barry Falcon of Falcon Audio imported and serviced these beautiful handmade integrated amplifiers. Ironically, the Dutch-made tubes are much rarer than the Hamburg-made Telefunken ECC83 long plates.

The ECC83 offered an audible improvement over the stock 12AX7-B tubes. The background was rendered more intelligible, and allowed more detail to be heard. Bright upper frequency transients, especially harsher sibilants, became much less irritating. This was especially appreciated when listening to various digital recordings.

In addition, as both triodes are used in the 12AU7A and the ECC83, it is essential that these triodes be as closely matched as possible. I use my Mercury 990 tube tester to ensure that my tube pairs are as closely-matched as possible.

I decided to keep the stock Shuguang EL34-B power tubes in place for the duration of the review. For comparison purposes, I did roll some NOS KT-77s, 6CA7s, and EL34s. Yes, they all offered various improvements to the musicality of the Yaqin. However, I found that I could live very happily with the stock power tubes. They were quiet enough. They faithfully produced the bandwidth of the music played. And, they were quite good at producing the micro and macro dynamics of all the genres of music that I had listened to. Their tonality had little to find fault with. So, they stayed in the system.

I manually biased the tubes starting at 30 millivolts. I found the music a bit restrained, especially in the lower spectrum of the bandwidth. Bringing the bias up to 35 millivolts brought the lower spectrum back in line with the medium and higher spectrums. At 40 millivolts, I felt that the imaging began to suffer a bit. I brought the bias back down the 35 millivolts. The Yaqin is biased for class AB1 operation.

Now, let’s get on to some musical examples.

As noted, the MC13S has no onboard phono stage. Although I played many vinyl samples during this review, I’ll cover vinyl playback in the sequel to this review. That’ll be the review of this amp’s soulmate; the Yaqin MS-12B preamplifier and phono stage.

I decided on a challenging start to the evaluation of the Yaqin’s musical abilities. It is Rachmaninov’s Piano Concertos Nos. 2 & 3 with Yefim Bronfman; Esa-Pekka Salonen conducting the Philharmonia Orchestra. This is an excellent Sony Classical recording made in 1990. It was produced by Gary Shultz at the Abbey Road Studios in London, England.

The Concerto for Piano and Orchestra Nos. 3 in D minor begins with Yefim playing a rather folklorique melody on the grand piano. The piano was situated a fair distance from me. It was if I am sitting somewhat in the center of the venue. The amplifier manages to capture the dialectical delicacy and dynamism of the piano. The attack and decay of each note played exhibited the Yaqin’s ability to reproduce subtle micro dynamics. As the string section responded to the piano, all the instruments were clearly presented. When the wind section joined in, the interplays between the flutes, clarinets, and oboes was delightful. As intended in the recording, the brass and percussion sections remained ever so subtle.

The stage was wide. It extended across my room. It was deep. As it should, the orchestra enveloped Yefim’s piano. I smiled when the first movement reached one of its many climaxes. I expected the amplifier to exhibit some compression, and chase the music back into the boxes of the speakers. Rather, everything stayed in its place on the stage. The Yaqin expressed the full dynamic swing of the climax with grace and finesse. Of course, I was listening at my habitual listening levels. I could get it to compress by cranking it to ear-bleeding levels. But in general, that would be considered abusive to your ears, and to your equipment.

The 2014 album “Mini World”, is French-born Indila’s recording debut. Recorded in the Davout Studio in Paris, this is one of the better musical offerings I’ve experienced in the last few years. This electro-pop effort is definitely not in mold of the typical productions of this variety. Thanks to co-writing, recording, and mixing efforts of Scalpovich, the production levels are at an equal level to Indila’s musical talents. In 2014, the album reached number 1 on the charts in France, Belgium, and Poland.

Indila’s style is difficult to translate into English. Almost always, she sings in an ascending scale. She has a poetic lilt that can only be identified as Parisienne. She is, in the old Argo expression, a true môme following in the footsteps of Edith Piaf. Forget the google translations. With a cup in their hand, a môme was the traditional name for the sidewalk huskers who sang the popular melodies of the time. If they were good they were invited to sing inside the cafés and bistros of the neighbourhood. This is Indila to me. She sings the modern day gestalt of the streets of Paris; and, she sings them in her (and Scalpovich’s) own creations. By the way, they are married.

The video of the first song of the album explains exactly what I mean:

Track four is entitled, “S.O.S”. It opens with a Indila singing solo. At first her voice is somewhat synthesized, but as an acoustic guitar begins to accompany her the synthesizer is faded out. The Yaqin captures the nasal subtleties of her voice. The details are there as well. Perhaps, due to do nervousness, her mouth is dry. I can hear her tongue licking her pallet to provide it with moisture while she inhales. The acoustic guitar in right stage behind the speaker is clearly delineated. As the second verse opens, a synthetic bass line opens to envelope the stage in an aural embrace that plumbs to the very depths of my system. In the left of center backstage, the drummer begins a tambourine like rhythm on his high-hat cymbal cascading into a classical pop drum beat. I am impressed with the depth of the image. The drummer is not stacked on or under Indila’s singing, but is placed behind her.

The synthesizer through the Yaqin does not have the authority of more powerful amplifiers that I use in my system, but it gets the basics done right. It does not project a point source emanating from the speakers. In my rather large listening room, the Yaqin manages to envelop it with the lower octaves of the song, thus completing the soundstage. With the proper associated equipment, it is capable of providing a very satisfying experience.

Not only in this track, but throughout the entire recording, there is one mentionable negative character in Indila’s voice. There is an ever present hint of hardness or sheen in the leading edge of her voice. This hardness blurs ever so slightly her subtlety. My first suspicion was the recording of the album. It is a Redbook recording. I needed to clear my doubts with a different recording resolution.

I could think of a no better choice than Amanda Martinez’s second album entitled “Amor”.   This is an album devoted to well-known Spanish language love songs that span several decades, and, come from at least two continents. I am familiar with several of the songs, and, yes, there are a few songs she sings here that bring tears to my eyes. She lives in Toronto. When she is not busy enchanting us with her beautiful voice, she is hosting the CBC series called Panamania.

The album has been mixed from the analogue tapes to single and double rate Direct Stream Digital (DSD). It was mixed here in Montreal by René Laflamme in his studio called 2xHD. The effort was realized by the legendary Quebecois producer André Perry. I am very grateful to René and André. Finally, we can begin to download a good selection of DSD recordings in Canada. The studio is just a few blocks from my humble abode. I am planning to pay him a visit. I am also planning to be at Amanda’s performance at the National Arts Centre (NAC Studio) in Ottawa on May 26, 2016.

So, will a higher resolution recording cure me of my harshness blues? I tried a double rate DSD. The audio tapes are sampled at 128 times more than that of regular CD. Read on.

The sixth song of the album is entitled “Alma Mía”. Sung in the traditional Bolero style, Amanda’s voice is presented without that hint of hardness. The subtle intonations of this classic song are presented with insight and ease. This is where the Yaquin shines its brightest. This amplifier will draw you into such a voice. It is presented with hardly a fault. Again, the soundstage is accurate. The imaging has gained in resolution. All the instruments are more clearly delineated than the previous album. In, fact I was quite happy this time to hear the gentle hiss of the analogue tape in the start, and at the end of the song. It was somewhat pronounced for my tastes. Yet, it left me with the impression that I was listening to these songs on a fine studio grade reel to reel tape machine.

And where did that hardness go? I am not sure, but it is no longer there. What remains in the music here is only a very small reminder that we are listening to a digital recording. There is a missing level of macro and micro-dynamic finesse that I have only heard in good analogue recordings, be it played on reel to reel or on a turntable. I can hardly blame this amplifier for adding any additional hardness. In fact, I should thank it for furthering my understanding of the limits of digital playback, whether it be Redbook PCM, or double rate DSD.

In terms of a conclusion, I would like reiterate my first statements. Simply stated, the Yaqin MC13S does not fail when taking the place of an amplifier in a system where you would budget anywhere from two to five thousand dollars for such a piece of equipment. It is certainly not at the same level of my Grant G60s when it comes to plumbing the depths of music. It does not project the same size of soundstage. But then again, the Grant’s 2 watt, 10 ohms, 1% non-magnetic tantalum cathode resistors cost $22.75 Cdn each to replace. And the Grant uses 1% non-magnetic tantalum resistors throughout the whole integrated amplifier. The resistors are available from Audio Note UK Ltd.

The Yaqin is an integrated amplifier that gets all the fundamentals right. I feel it excels in tonal accuracy. It is able to reproduce detail without excessively exaggerating artifacts, digital or otherwise. It has a balanced dynamic bandwidth, and presents it with a realistic stage. I highly recommend the Yaqin MC13S.

Follow my tube upgrade path. Purchase a voltmeter, and adjust the EL34B bias to your ear. Just remember to respect Yaqin’s power tubes’ bias limits. I personally would not push it beyond 40 millivolts. Already, that is a hot biasing. Start with replacing the 12AU7 with a superior one of your choice. It does not have to be NOS. You will hear the big improvements here. Next, replace the 12AX7-B. You will hear more improvements. Remember, you already have a great deal of “audiophile” quality components already used in the amp.

Above all, you have top notch input and output transformers. These transformers are the principal reason this amplifier sings so damn well.

There are a few cautions that I wish to address. Yaqin does not have an established walk-in dealer or distribution network in Canada or the USA. It is impossible to audition unless you know someone who owns one. If you do experience reliability issues, it will be more difficult to have the repairs done under guarantee. I purchased this amp on eBay. It is presently priced around $750.00 CAN plus shipping and applicable taxes. Though I bought my example for much less over a year ago, in my opinion, the price of the amplifier is still reasonable. I would happily order another one today. (Editor’s Note: as of 2021 the MC13S is still available to purchase for $850 Canadian from Lee’s Electronic in BC)

For comparison, I’ve compiled a list of EL34 integrated amplifiers that share similar characteristics: the Yarland M34-IV-EU ($1,499.00 CAN); the Jolida JD 202BRC ($1139.00 CAN); the AudioSpace AS-3i -EL34 ($2100.00 CAN); the PrimaLuna ProLogue Classic ($2300 CAN); the Antique Sound Lab AQ1003 MARK II DT ($1600 CAN); and, the Line Magnetic LM-211IA El34 ($2200 CAN). If I were to do a comparison review of any of these EL34-based integrated amps, I wouldn’t hesitate to throw the Yaqin MC13S into the evaluation.