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Sanders Preamplifier Review

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Sanders Preamplifier

Slide rules and pocket protectors

In the subjective audio universe, where gross amounts of 2nd harmonic distortion, horrendous phase shift, and totally inadequate frequency response gets euphemistically labeled “bloom” and “harmonic richness,” the purveyors of audio accuracy must hide their devotion to truthfulness like it’s a cardinal sin. “Zero phase shift?! Grab the matches and gasoline, we have a scientist in our midst.” There are negative connotations to marketing with specifications. Anyone old enough to have heard the first transistor amps will agree they sucked, regardless of what the specs said. Engineers in the ‘60s, ‘70s, and ‘80s, with their use of feedback as a blunt-force-instrument, forever tainted integrated circuits, feedback, and solid state. Though the equipment measured good, it sounded bad. Real bad. In a way, we should be thankful the big corporations made bad sounding equipment. Had they not, we wouldn’t have the audio underground and cottage industries that sprung up to satiate the appetite for good sound.

So, what’s wrong with electronics that have no audible distortion, no audible phase or frequency response issues, no oscillations, no noise and no problem driving any set of cables or amps or speakers? Nothing. Nothing is wrong with that. Are you so hung up on tube rolling and tweaking that you reject the hypothetical existence of an integrated circuit that would do a better job, and keep doing it the same way for 20 or 30 years? Are you that afraid of your music collection?

Though I admit to enjoying tubes, analog, open reel tape, and single driver loudspeakers, I will be the first to admit that there are significant limitations with all the above. If the primary job of an audio system is to be truthful, then does the current crop of high performance digital, and high performance integrated circuits deliver the goods? Increasingly, the answer is yes. We are advancing the state of the art in baby steps. Some of the advancements come from improved manufacturing techniques, giving us higher performance through better matched transistors and purer materials. Some of it has been new ways to accurately measure distortion, or the discovery that the ear can hear things that are hard to measure with simple harmonic distortion analyzers. Some of it is trickling down from medical, aerospace and military technology. The same circuits used to hunt down submarines or find tiny tumors have applications in audio. Billions of dollars have been spent to beat the competition, whether it is another chip manufacturer, stage IV cancer, or enemy combatants.

For all audio, I ask a few simple questions. Is the frequency response wide enough, and flat enough, to allow us to hear all the fundamentals and overtones, and in the correct relationship? Is there audible distortion? Does it have enough power to avoid clipping? After those criteria are met, can it recreate an acoustic space (imaging)? Finally, is it reliable? Those criteria are hard to satisfy, and when a piece meets the criteria, it usually satisfies musically. Sure, there are very subtle nuances, almost impossible to measure, that are the difference between the good and the great, but I have a hard time hearing those nuances over audible harmonic distortion and hum. Almost all the equipment I’ve reviewed had issues, usually minor ones, in one or more categories. Some people don’t mind scads of harmonic distortion, limited power or limited bandwidth, and you know who you are. I do mind, but there is a niche product for everyone.

Sanders Preamplifier

The Goal

So, what has that to do with the latest preamplifier from Sanders Sound Systems? Everything. Roger is an actual engineer, in an industry with many “gurus” and copycats. Let me offer a few interesting excerpts from the Sanders website in the following:

“Our previous preamps (line stage and phono) were $4,000 each, for a total cost of $8,000 for our customers who needed a phono preamp. Since both preamps are now combined, customers who need a full-function preamp can now save several thousand dollars as the new preamp sells for half the price of the previous two.

The goal of a true audiophile grade preamplifier is to offer gain, switching, and other conveniences, while at the same time passing the original signal downstream without adding distortion, noise, or a sonic signature of its own. The Sanders Preamp does exactly that but includes many ergonomic features for convenience and ease of use that are not available on even far more expensive preamps.

The levels of each individual input can be adjusted to get them all matched so that you don’t get “blasted” or have to turn up the main level each time you switch sources. A stereo/mono switch remains standard equipment. The overall gain, individual gain between devices, and channel balance can be adjusted in precise, 1 dB increments. Muting by remote control is standard. A video readout makes it easy to monitor the levels.

… Front panel controls are done through micro-touch electronic switches. Internal switching is done by miniature, sealed, gold relays. Conventional rotary volume controls have channel matching error of around 20%, which causes the left/right balance to shift as you change the level. To solve this problem, some preamp manufacturers use discrete, precision resistors on a multi-step switch.

While this solves the channel tracking problem, they introduce new ones. Specifically, they have very limited resolution due to too few steps (typically 31 steps of 2 dB each). These “stepped attenuators” produce very annoying switching transients at each step.

The Sanders Preamp solves these problems by using the “volume control” knob to drive an optical comparator circuit. The optical circuit operates a microprocessor that controls an electronic gain system. This controls the level using one hundred, one dB steps, with precision of greater than 0.1% between channels.

The microprocessor monitors the signal voltage and waits for it to cross the zero voltage point between waves before switching to the next level. This prevents any switching transients. The volume control knob has detents at each 1 dB point and it rotates continually. So it as an infinite number of detents and you can feel each 1 dB change in level.

There is a digital display with beautiful, blue, light emitting diodes (LEDs). The display continually shows the output level of the unit and switches automatically to show level differences between channels, when you adjust the balance, or when you adjust the input levels. You no longer have to guess at the levels or try to see fine gradations on a knob to know the levels, since you can see them from several feet away.”

 

3 Responses to Sanders Preamplifier Review


  1. Excellent, I already bought the Sanders amp and have a used pair of Magneplanars 20.1, It took me loans to afford those two, but since nirvana is near I decided to be in debt by making a deposit on the Sanders preamp, the review has made me realized that when all of them will be together I will not be leaving my living room at all for quite some time. I was convinced that tubes will give you pure sound but after listening to the Sanders amp with my unbalanced YBA preamp, I disagree, totally! Thanks!!

  2. phillip holmes says:

    It takes a lot of power to make the Maggies sing, so I’m glad you got the big amp. The Sanders preamp is a commendably neutral piece, with none of the traditional transistor limitations (dark sound, lots of IM, etc..).

  3. Deaghlan says:

    Amp/preamp on early 2016 buy list. Can’t wait!!!

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