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Sanders Sound Magtech Mono Amplifiers Review

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With the Legacy Audio Whisper DSW Clarity Edition

After the stint with the Comet I decided to build a more traditional system by swapping out the integrated DAC for a dedicated DAC and a proper preamplifier. The new system included the aforementioned Small Green Computer/Sonore front end, Eastern Electric Minimax DAC Supreme, Cambridge Audio Azur 840E Preamplifier, and the Whisper speakers. As a heads up to fans of opamp rolling, I will be writing a follow up to the 2011 and 2012 series of articles published here detailing my experiences with rolling discrete opamps (see below). A new generation of discrete opamps is available, as well as a different genre of component in which to roll them, and I will be chronicling the experience.

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Often, I will pair a more affordable component with a luxurious one in order to see how the two will interact. I reviewed the Cambridge Audio Azur 840E Preamplifier 10 years ago and bought it after the review as a commendable yet affordable preamp that I could use ongoing with reviews. Since that time the 840E has been paired with no less than 8 amplifiers. A surprising and disturbing thing happened when I fired up the system the first time the 840E was connected to the Magtech Monos; one of the amplifiers failed.

This was surprising given the lofty reputation of the Magtech amps and how the 840E had been operationally perfect with all other associated equipment. What went wrong? This allowed me to chat more in depth with Roger Sanders. Roger is a numbers and measurements man who lets the testing dictate procedure and design. Before I move ahead with the resolution of the amplifier failure, let’s look at the design of the Magtech amp, as well as its lifetime warranty.

The Sanders Sound Systems website has, in its Reference Menu, a page featuring several Technical White Papers detailing the methodology and build characteristics of Sanders speakers and amplifiers. Roger explains in the ESL Amp Bias White Paper, “Sanders Sound Systems amplifiers use a very modern, sophisticated, and expensive type of bi-polar transistor made by Motorola that combines very high power capability with an amazingly linear transconductance transfer function. As a result, we are able to reach virtually un-measurable distortion levels with only a trace of bias,” and, “We use a combination of very good transistors, low bias, and low NFB to achieve this performance, while keeping the amplifier running cool.”

In the Magtech Regulated Power Supply White Paper the basics of this unusual design is distilled down to a few lines: “The Magtech uses two power supplies as you would in an up regulator. I call the low voltage one the ‘ride’ supply. It is exactly like the power supply in a conventional, unregulated amplifier. The second power supply is the ‘boost’ power supply. It has a higher voltage and current rating than the ride supply and can add massively more power to the ride supply when needed.” Roger goes into great detail discussing the challenges and advantages of this design, concluding, “When the ESL amplifier modules are combined with a practical voltage regulator, the result is an amplifier with seemingly unlimited power, virtually immeasurable distortion, and the ability to drive even the most difficult loudspeakers with ease. The Magtech offers a truly new level of performance in amplifiers.” I will vouch for the properties of seemingly unlimited power, extremely low distortion and driving difficult speakers with ease.

A most marvelous feature of Sanders Sound Systems amps is the lifetime warranty! These amps are built to be extremely reliable and operate with a vanishing failure rate. What precisely happened with the one amp going down in conjunction with use of the 840E? A thread on Audiogon from 2015 discusses failures of the Motorola 4000 series Thermal Trak transistors that could develop a fault in the thermal sensor. Failure was not immediate, and there seemingly was no way to identify which transistors were affected. This is a good reason to have a lifetime warranty. The thread seemed to die down in 2016, but there seems no easy diagnosis for units in the field that may have such transistors that could go bad.

Roger seemed nonplussed by the event; rarely have I heard a manufacturer so nonchalant about an amp failure. Roger’s analytical nature went to work considering that there may have been a spurious signal sent from the 840E to the amplifiers. I was to return the amp at my cost and it would be fixed, and the review would resume. This was also the first time a manufacturer expected me to return the amp at my cost, given that the cause of the failure was unknown. That’s the downside of this lifetime warranty – the return shipping is on you. As to diagnosis of the problem, Roger thought that the 840E might be the culprit. I could either send the Cambridge preamp for him to test, or I could use my continuity tester to check the output of the 840E. Let’s see, spend more shipping the Cambridge over to him or test it for free. I was going to test it.

The outcome of the testing was that the 840E was putting out some DC in the right channel when started up; the highest intermittent reading using a Voltmeter set on auto ranging was 0.086 V. Roger said that was what would be expected in a potentially damaging output of DC. But then why did the preamp work perfectly with several other amps? I wondered if the nature of the Magtech Monos amplifies, pardon the pun, the potential issues when pairing preamps.

Roger is gracious with his time spent explaining things, and he gave me a tutorial on spurious signals and his amplifiers. Below are some pertinent snippets of the discussion:

All amplifiers can be damaged by dangerous and abusive input signals such as large DC turn on/off transients or supersonic oscillations. All brands and models of amplifiers are susceptible to damage and you will find that all amplifier manufacturers have to deal with amplifier failures and repairs.

Dangerous signals usually cause a fuse to blow in a Magtech amp. But nothing is 100% perfect and occasionally a transistor will be damaged before a fuse blows. We buy the best transistors available (genuine Motorola), but even they have a small percentage of failures. Regrettably, it appears that you have been one of the unlucky users where a transistor was damaged instead of just having a fuse blown.

In summary, this issue is not unique to Sanders Sound amplifiers. So, it would not be fair for you to single out the Magtech amplifier as having a special problem with faulty source components or that it can only be used with certain preamps or sources. The Magtech is fully compatible with all properly operating preamps and sources that are available on the market today.”

4 Responses to Sanders Sound Magtech Mono Amplifiers Review

  1. Dave P says:

    I’ve been thinking about purchasing the stereo version of this amplifier for some time but paused for thought by the documented failures in the past. Now the mono version fails — during a review, no less. I’m not interested in paying God-knows-how-much to ship a heavy power-amp half-way around the world to the US if it’s faulty just after receipt. Mr Sanders has some explaining to do if his amplifiers are to be seen as anything other than great-sounding but unreliable (thus effectively junk for the prices charged).

    • We here at Sanders Sound Systems build Magtech amplifiers from the highest quality parts available. Unfortunately, nothing is perfect, so a small percentage of parts from even the best suppliers occasionally fail, which of course, causes the amplifier to fail.

      Amplifiers contain hundreds of parts, so it is not surprising that you hear of failures. While all amplifier manufacturers suffer failures, the more amplifiers a manufacturer makes and sells, the more failures will occur. We have sold thousands of Magtech amplifiers, so even though our failure rate is very low, you have become aware of some of them.

      Because electronic failures cannot be completely avoided, manufacturers offer protection to their customers in the form of warranties. Because we build our equipment to the very highest possible quality standards, we can — and do — offer a life time warranty on our products. I am not aware of any other amplifier manufacturer who offers such fine warranty protection to their customers.

      It is standard industry practice to require the customer to pay for shipping faulty equipment to the manufacturer for warranty repair. It is the manufacturer’s responsibility to repair or replace the faulty component at no charge. The manufacturer also pays for return shipping. So our warranty shipping policy is the same as any other in this regard.

      However, we are sincerely concerned about the cost and inconvenience warranty repairs cause customers. So we build our equipment in modular format. This makes it possible for us to send warranty replacement modules to customers so that they can fix the problem themselves. This makes it possible for us to give customers — especially our many international customers — the option to get problems fixed in their home without having to ship the amplifier back to our factory. Obviously this saves them time and money. So it is rarely necessary to ship anything to our factory for warranty repair.

      In summary, we offer the best customer support and service in the industry. We genuinely care about our customers and do everything possible to assure quick, easy service should a rare problem occur.

  2. Vladimir Dorta says:

    The 1kΩ balanced input impedance is so abnormally low that I checked the factory website in case this was a typo of your review (it wasn’t). A potential purchaser should make sure to check the compatibility of his preamplifier, or use only the unbalanced outputs.

  3. Charlie Mathews says:

    Hi Douglas,
    Correct me on this doesn’t CODA build the magtecch amplifiers?

    Anyway thank you for all your work that you do reviewing equipment…

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