Specifications

• OUTPUT POWER: 5W (Triode)/15W (Pentode) Frequency responsible 1W: 13Hz- 77000Hz+1dB Frequency responsible at full power: 30Hz- 63000Hz +1dB
• Distortion at 1W: <0.6% Distortion at 5W: <2.5%
• S/N Ratio at full power: >78dB (1.3mV) S/N Ratio at 1Watt 8Ohms: 68dB
• THD at 1Watt: 0.6% THD at full power: 4% Damping factor: 1.38
• Input impedance: 100K Output impedance: 8 ohm
• Power request: 135W MAXIMUM 120VAC Input sensitive: 500mV
• Chassis Finished: anodised alluminium Dimensions W X D X H: 13inx10.5inx9in Net Weight: 13Kg/29lb
• Price: $1100

At the end of the last century, the idea of affordably-priced tube amplifiers was a fantasy for most audio enthusiasts. Amplifiers offered by the tube establishment usually fell within the two to three thousand dollar price range. The audio community held products from companies such as Conrad Johnson or Audio Research in high esteem. Only a handful of audiophiles were willing to make the significant financial expenditure required to own these products. Vintage electronics were an alternative for those individuals capable of restoring a twenty or thirty year old piece of equipment. For instance, the DIY crowd patiently brought many a Dynaco, Heathkit, or MacIntosh amplifier back to serviceable condition. However, audio enthusiasts who lacked the electrical knowledge to restore a piece of electronics were left with minimal options when it came to acquiring a good piece of tube electronics.

Eventually, a new generation of tube audio manufacturer arose from the East Asia. The first product I encountered from Asia was the Golden Tube Audio GT40 amplifier. This product created quite a stir in the audio community due to its unique combination of tube power and moderate price. Another one of the early pioneers of Chinese tube manufacturing is Antique Sound Labs. Some readers may remember a company called ASL-USA, which originally imported parts produced by ASL. This company primarily catered to the DIY and kit audio niche. In 1994, Divertech Technologies became the distributor for ASL in North America. This has been a successful partnership, and the ensuing years have seen a wide array of Antique Sound Lab products gain acceptance in the North American market.

The latest version of the ASL MG SI 15 DT integrated amplifier is targeted to value conscious audio enthusiasts. While more expensive than earlier versions of this integrated, the current amp offers several notable upgrades that have elevated the overall performance of the unit. This integrated utilizes an excellent set of transformers, which are the result of ASL developing a sophisticated manufacturing process for their transformer winding facilities. The power supply section of this integrated has also been improved. ASL has decided to use a choke filtered power supply design, which is very unusual for any amplifier residing in the $1000 price category. This integrated has other notable design features, such as point-to-point wiring, which is usually found in higher quality tube electronics. I removed the bottom cover, and noted that ASL used audiophile grade parts throughout the whole design. Also, the build quality of this integrated is excellent, with neat wiring and solder joints. These upgrades are the main reason why this ASL integrated is capable of providing high end tube sound at a price point is lower than most audiophiles would expect to pay.

There are two other notable design features that I need to mention about the ASL amplifier. First of all, the tube biasing system in this integrated is a breeze to use. There is a switch on the side of the amp that allows the user to select between the two output tubes. The meter on the front panel gives the current bias setting, and shows the acceptable operating range of the tube. A small trim pot is located next to each output tube, and is designed to vary the bias current. As the pot is rotated, the meter signals the change in bias current. Just keep the needle of the meter in the green portion of the meter, and the unit will be properly biased. The biasing system on the MG SI 15 DT is a model of simplicity, and even a novice to tube electronics will be able to properly adjust this amplifier.

This integrated amplifier comes with a welldesigned remote control option that makes this unit extremely convenient to use. The remote does not just control volume, but also gives the user the option of selecting input sources, and muting the output of the amp. What is astonishing is that ASL manages to house the remote control electronics in a nicely finished wooden body. Of course the fancy remote option doesn’t improve the sound of the amplifier, but it does add a level of sophistication that really isn’t found within arena of $1000 amplifiers.

The MG SI 15 DT uses a pair of Valve Art KT 88 output tubes. The pre driver tubes are the Electro Harmonix 12AX7’s. The amp can be configured for either triode or pentode operation. In pentode mode this integrated can produce 15 watts per channel. While triode mode reduces the power output to 5 watt per channel. While the power output in triode mode is quite limited, it is less colored than the pentode configuration. As a whole, I preferred listening to this amplifier in the triode position. The Valve Art tubes are considered to be an excellent sounding modern production tube. However, the same thing cannot be said for the 12AX7’s. I found the Electro Harmonix tubes to be harsh, grainy, and quite brittle sounding. In order to determine the true capabilities of this amp, I removed the E.H. tubes, and installed a pair of RCA 12AX7’s. My tube stash no longer contains a wide variety of 12AX7’s, so the RCA’s were the best substitute that I could quickly lay my hands on. With new pre-driver tubes in place, the sonic character of the ASL integrated became smooth and refined. I would strongly suggest that any owner of this amp should replace the stock pre-driver tubes if they want to experience the true potential of this piece.

It is important to use relatively efficient speakers with this amplifier. With a maximum power output of 15 watts per channel, this amp is not suited to being paired with power hungry minimonitor speakers. I chose to use the Atelier Audio First Horns for my listening sessions with this integrated. The Tube Research Labs modified Sony SCD-595 fed the ASL integrated with a high quality source signal. Audio Magic Extreme speaker cables and interconnects was employed throughout the system. Since I still have the Monarchy Audio AC Regenerator on hand, I used it to provide clean power to the system. During one listening session, I installed an Audio Pro Avantek subwoofer in order to evaluate the subwoofer option on the amplifier. It was a seamless match, and I left it in place for the latter portions of my listening sessions. I placed the amp on a set of Mapleshade Iso-Blocs for isolation purposes. As a general rule, tube amplifiers need isolation devices to minimize the transfer of vibration into the tubes. The transformers in the amp itself are a major source of vibration. Creating a pathway for the vibration to leave the amplifier results in a cleaner sound in the system.

The ASL MG-SI15DT does not sound like a typical budget tube amplifier. I will admit to having a preconceived notion on how this unit was supposed to sound. In my experience, budget tube amplifiers tend to have a warm overall presentation that is easy to listen to, but are not able to reveal the finer points of a musical performance. In triode mode, the ASL amplifier sonic presentation is clear and lean. I dropped a John Lee Hooker disc into the CD player to get a feel for the tonal balance of this amp. “I’m Bad Like Jesse James” [Boom Boom; John Lee Hooker Point Blank V2-86653] sounded great through this amplifier. John Lee’s voice was gritty and raspy sounding, yet it was easy to hear the subtle vocal inflections in his singing. The venue of this recording sounds like a large empty stage. This little integrated did a nice job conveying both the room reflections and echo of John Lee’s foot tapping. The Electra Print 300 DRD amplifiers that normally reside in my system do a better job digging out the finer details of this recording, but the ASL amp is not far behind it’s far more expensive cousin. The overall presentation of this integrated can lean to the analytical side of the audio spectrum. However, this characteristic can be mitigated with careful selection of predriver tubes and cabling. I would recommend a good NOS 12AX7, and solid core copper cables. Perhaps the latest offerings from Tara Labs or ZU cables would give this amplifier just the right touch of warmth and fullness needed for long term listening pleasure.

Since the MG SI 15 DT does not have huge reserves of power on tap, it is essential to match a compatible speaker to this amp. The Atelier Audio speakers have an efficiency rating in the mid 90 DB range, and are an easy load for this amplifier to drive. The perfect speaker for this amplifier will have an efficiency level of at least 89 or 90 DB, and use a simple crossover network. Complex crossover networks use several inductors, and tend to soak up power. With a maximum output of 15 watts per channel, these integrated needs to get every watt it can to the drivers. When the proper speaker is used with this amp, it becomes a mini powerhouse in terms of impact and bass response. George Clinton’s band Parliament has been recognized as the most innovative group in the genre of funk. “Flashlight” [Funkentelechy vs. The Placebo Syndrome; Casablanca 824-501-2] is the crowning achievement of this band. Actually this song is modern jazz masquerading as dance music. Funk music is all about the bass line, and when the ASL amp is set to pentode mode it does a respectable job of laying down the notes in the lower registers of this song. The bass riff in “Flashlight” is quick and clean, and is very easy to follow. The bass portion of the MG SI 15 DT does remain true to its character, which means it does have a slightly lean sound. One evening I decided to test the subwoofer option on this amp by hooking up the Audio Pro Avantek powered sub. The installation and set up were easy to accomplish, and within no time I had a seamless transition between the sub and main speakers. The addition of the Audio Pro sub fleshed out the lower registers of the system, and was the crowning touch to creating a highly capable budget audio system.

This integrated amp is the kind of product that makes high-end audio a fun hobby. If this amplifier is used with the right associated equipment, it is capable of reproducing music with a level of refinement and sophistication that belies its modest price. The ASL amp is also user friendly, and has a set of features that most owners will use on a regular basis. The remote control option works flawlessly, and the tube biasing system is extremely easy to use. Being able to integrate a subwoofer is a great way to expand the capabilities of this amplifier. ASL has done a nice job with the overall build quality of the piece. The MG SI 15 DT controls have a solid feel, and the unit has a tidy and attractive appearance. If you want to hear what a moderately priced tube integrated is capable of, contact Divertech and find a dealer who carries the line. I suspect that you will be pleasantly surprised by what you hear.

external link: Drivertech

Associated Equipment:

• Tube Research Labs Modified Sony SCD-595
• Atelier Audio First Horn speakers
• Monarchy Audio AC Regenerator
• Audio Magic Extreme Speaker cable
• Audio Magic Extreme Interconnects
• Audio Magic Extreme Power Cords
• Audio Pro Avantek Subwoofer

from affordableaudio, By John Hoffman