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REVIEW: Applied Research and Technology SLA-1 Amplifier (SS)

Model: SLA-1
Category: Amplifier (SS)
Suggested Retail Price: $300 USD
Description: 100 Watt Amp: unbalanced TRS/balanced XLR inputs, bridgeable, ground lift,,variable sensitivity
Manufacturer URL: Applied Research and Technology
Model Picture: View

Review by PeAK (A) on June 18, 2003 at 07:16:38
IP Address: 209.50.91.70
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Background


I've been thinking about the amp end of things for a while. I looked at the AKSA kit amplifier and had my ear to the ground hearing about the Samson Servo 170. The 55W/Ch AKSA kit does not include chassis or a transformer costing about $385 Canadian verus the SLA-1 at $300 even. The immense success of the DI/O in my playback system persuaded me to become a repeat customer.

The guys/gals designing at ART are turning out some pretty decent stuff (DI/O for one) these days with great price/performance ratio. Hinting stronly to my wife, I recieved a belated BD gift in the form of a SLA-1 over the weekend. I was tuned into the Audiogon SLA-1 infomercial thread prior to it being deleted and am aware of some of the underhandeness going on with regard to false pseudonyms posting about their own companies. Regardless, I sensed something very real underlying all of this. I have the original post that mentions the SLA-1 in the same breath as Mark Levinson and Pass amplifiers.

The specifications on ART's home page show the ART SLA-1 to have high power and low distortion.
The one indpendent review found was one of the SLA-1 and partnering SLM-1 speaker. Being down under, the price premium for shipping this product there is quite steep. There is a PDF available. The manual is currently not available.

1.0 Initial Links


1.1 Impressions/Evaluation


Any component evaluated needs to be taken within the context of the system it is evaluated in. This section covers short term and longer term impressions of the SLA-1. The latter section will be updated over time and as the SLA-1 is evaluated in different systems.

My long term reference has been the integrated amplifier that I have used for the last two decades. It is not perfect. Its imperfections to me are known and I can to some degree filter them out when comparing components ahead and behind it...to some degree. To a large degree, the changes that I have wrought on the 3020 are very similar to how the SLA-1 comes in stock form: No tone controls, simple gain path from line level to to amplifier input circuitry. The NAD has the benefit of the following: Seperately regulated predriver for the amplifier output stage, Boutique caps (Wondercap), Updated internal wiring with Kimber 8TC, DC coupled preamp output, ALPS potentiometer and most impotantly a host of subtle mods/cap types to tune it to my system over time...most of which I have forgotten. Out of the box, the SLA-1 has some of the NAD "sound/imperfections" removed and this has encourage me to listen to some CDs which I have not listened to in a while. The balances are close but I'll have to wait until I compare it to my friends 50W reference Tube Soundtech amplifier based system to sort out
the signature of the SLA-1. From what I have heard to date, the designers at ART have done their homework. I could live with it for quite a while.

1.1.1 First Listen


I presently run a highly modified NAD 3020 that is the equal of more costly amps in terms of the first Watt (probably more) of amplification. It has served very well in the role of a microscope to sort out deficiencies in upstream cables and sources. Out of the SLA-1 box, last night, I still find the 3020 to win in terms of information retrieval and overall balance. The SLA-1 sounds surprisingly close, though. From turn-on, the 3020 normally takes about an hour or two to warm up to its sonic splendor.

Within 1/2 hour, I opened up the top, disabled the fan and gave it more of a listen. Updating the power cord to an Belden 83802 based unit gave a bit more resolution. The next morning it sounded somewhat better after having been left on all night. I'm not sure if it sounds better with or without the ground "lifted". It sounds promising. I do not know if it beats 95% of the amps out of the box (as claimed by Don) but it sure has potential at this early stage. Perhaps my little 3020 beats 96% of the amps

The amp is stable driving 2/3 Chris Venhaus CAT5 loudspeaker design.As these cables are fairly capacitive, the fear of the output stage blowing up and frying my speakers was in the back of my mind. I tested this first on my "cheaper" Radio Shack LX5 speakers before moving onto my Axiom M22ti.

1.1.2 Middle Term Evaluation


The urge to unplug it has not hit...which is a good initial sign. I am beginning to listen to CDs from start to finish (always a good sign) at this early stage.

Using a wider variety of music over the last few days shows me that it is getting better as I leave it plugged in. I did not expect my jaw to drop on the first day but good systems have a way of proving themselves worthy over time.

On the construction side, I noticed internal construction details to ease/lower cost of construction related to the snap on connections between the power tranformer outputs and the full wave rectifier and the connections between the Attenuator controls and the main amplifying stage (read mod potential).

I will adding further comments to this section from within mostly the context of my system with specific references to how it fairs with different types of music.
Stay tuned. I'll might organize subsections to reflect this chronological updating of the evaluation. This might be week to week, month to month and include discussion from the various other parties who are also evaluating the unit. I will also try this amp in another system and report back but the basic rule of thumb for this evaluation is to use the unit "as is" with few to no mods. Section 2.2 will address the long term finessing/modding of the unit and resultant gains from doing so.




1.1.3 Preliminary Conclusions


Note: See the link above that describes a tweak...it turned my system on its ear and most of the criticism leveled at the SLA-1 has been lifted. The following summary pertains to it prior to Day 8's changes and listening).

It is still early. Some of the early adopters/reviewers (3 so far) have the relevant experience and ears to make an assessement of the SLA-1 within the context of their systems and tastes.

The positive comments are:


  1. Speed and transparency
  2. Engaging snap and drive...this I take to mean dynamic
  3. clarity/clean sounding
  4. delineation of "space and time"...soundstage/separation
  5. Not cold and not sterile or embarass itself in much more expensive systems. Mostly the sins of omission.

The negative comments are:


  1. lack of "deep authorative bass" and "some congestion"
  2. mid to upper midrange forwardness with a tradeoff to overall integration
  3. Lack full round organic tone (also referred to as "poor tonal quality" compared to the best). This has been described as "tonal thin" and "upwardly balanced" leading to carefulness in system matching in both upstream and downstream paths.
  4. Some solid state "hash and grit". The "highs are nothing special".

The summary above is my attempt to group "common" observations into a succinct summary from each of the three reviews. There is a slight filtering upon my part which I will address below. .

Some of the statements above come from user's with very extended LF speakers and tastes. For me, #1 is not so much an issue providing everything above the last octave is tight, controlled and fast. The smallish filtering in the power supplies is sometimes eclipsed by competing 100W amps by as much as 7x (ie. 35,000uF versus 4,700uF). This might lead to some of the comments regarding congestion and deep bass at loud volumes. LS3/5a users need not worry or comment. Issues #2 and #3 were not so much an issue with Danny's dac but were noticeable using my DI/O with the attenuated gain. For me, on femalie voice, it amounts to a slight edge and un-natural sharpness to the pitch and lack of chest/warmth. Issue #4 was made by a tube lover and I can understand his perspective. The high's comment is something I need to ponder as I did not find it particularly hard, bright or spitty...again a case of erring on sin's of omission? I'll pay more attention to these points with more extended listening when my frontend is updated. The overall impression the SLA-1 and Danny's DI/O was that I just listened to one CD after another and took off my analytic hat.

As mentioned above, the strength of the amplifier is mostly that of the sins of omission. If the sonic signature of amplifier in due to the first input stage, then op-amp substitution may very well help SLA-1 on the road to getting a fuller and more round orgainic tone. At the same time it is desirable not to upset positive speed, transparency, and dynamic nature of the stock unit. It is entirely possible that a more a "better" opamp in the voltage gain stage might lead lead to less synergy with the bipolar output stage. The AN6554 and the present passives could have easily done a lot worse.

If the issue are in the second stage, hopefully it does not have to deal with supply regulation and that beefing up the supplies can help. In this case, passive swaps of critical caps and gain setting resistors may address some of the weaknesses. The modification section will capture this as a work in progress. ClaudeG...where are you when I need you.


Product Weakness: Unbalanced inputs are 1/4" phone jacks. Stock power cord. Sound may be a little lean. System matching required.
Product Strengths: Transparency, speed, and soundstage. Price/Performance ratio


Associated Equipment for this Review:
Amplifier: Art SLA-1
Preamplifier (or None if Integrated): None
Sources (CDP/Turntable): Modified Art DI/O
Speakers: Axiom M22ti
Cables/Interconnects: Cardas twin-ax
Music Used (Genre/Selections): Jazz, femail vocal
Room Size (LxWxH): 15 feet x 20 feet x 10 feet
Time Period/Length of Audition: 8 days
Other (Power Conditioner etc.): JR unit
Type of Audition/Review: Product Owner




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Topic - REVIEW: Applied Research and Technology SLA-1 Amplifier (SS) - PeAK 07:16:38 06/18/03 (11)


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