A U D I O... P A P E R


 MAY 2003
by Steve Deckert

In our support forums, each member has a moniker that usually includes a little tag line. Mine says "If the first watt sucks, why continue?" suggesting a somewhat favorable opinion of low power SET amplifiers... So it might be easy to assume that I'm going to come from a singular perspective when I offer my observations on what makes great sounding playback systems, but...

Over the years I have learned that for every assumption about audio there are exceptions that could lead one to conclude the exact opposite. This ďlaw of exceptionsĒ encompasses every facet of audio, from cartridges to loudspeakers and all the cables and components in-between.  

Most people, for example, would a assume a 2 watt Single Ended Tube amplifier wouldnít have what it takes to get out of itís own way... let alone control a loudspeaker to a dynamic conclusion! You would hear them say (as they stare at the 2 watt amp), "It couldnít possibly have any real bass, but we hear the midrange is to die for."

Many might also assume the only way to hear any dynamics from a flea powered amplifier is to use big nasty horn speakers (and we've heard those are suppose to suck) so really what is the point?

All of these assumptions could be a side effect of the general direction that high-end audio took since the 1960ís. By the late 1960's solid state was exploding onto the marketplace promising superior sound and performance. Solid state has made high power affordable for everyone and as a result the loudspeaker industry has responded by making speakers smaller (more salable) and consequently less efficient to both reduce their size and flatten the frequency response for better marketability.

Despite popular belief, you don't need horn speakers to use or enjoy a good SET amplifier. And if you look around, you can also find many good horn speaker designs that sound wonderful, better than wonderful in fact, so the question then becomes this:

What are the advantages are to using SET amps with high efficiency speakers?

To answer this, lets start with the advantages of a SET amplifier over any other type. A Single Ended Triode is the simplest circuit design there is, using the least number of parts. Typically this is a driver stage coupled to a single output device. Triodes do not require negative feedback, something found in most all push-pull circuits, solid state or tube in which negative feedback is used to lower distortion and in solid state keep the transistors from exploding all over the inside of your amplifier case. So is negative feedback a problem?  Well, if you donít mind the time smear it creates and the resulting 2 dimensional sound stage with almost no depth, then no I guess itís probably not an issue.  ;)

Aside from the SET amplifierís superiority thru simplicity, there is a more profound reason for using SET amplifiers. The magic that 95% of ALL high end audio gear misses is missed because it predominately lies in the first watt. By magic I mean inner detail and most of the dynamics. For example, a pair of 96dB speakers playing with one watt of power against the average noise floor in your listening room (55dB) is 40 dB of dynamic range.  (96 Ė 55 = 41 dB) Adding a second watt of power from your amplifier only increases the dynamic range by another 3 dB. And for every additional 3 dB you have to double the power. So if you think about it, there is over 10 times the dynamic range in the first watt as there is in the second and it dwindles from there.

This brings us directly to loudspeakers.  A typical loudspeaker today is 86 dB efficient with 1 watt.  It also usually has a complex crossover that attempts to keep the frequency response and the impedance seen by the amplifier as flat as possible. The crossover alone can dissipate a significant portion of the first watt as heat never to reach the drivers in the loudspeaker.

So lets compare the 86dB speaker with one that is 96dB. To reach the same loudness level as the 96 dB speaker the 86dB requires over 8 watts! If we used 2 watts on the 96 dB speaker the 86dB would require 16 watts to keep up. If we used 4 watts on the 96 dB speaker the 86dB speaker would require 32 watts to keep up.

The problem here is beyond the obvious... volume.  The problem here is really resolution.

If you canít hit a usable listening level with the 1st watt, youíre not likely to hear whatís happening in the 1st watt. For a driver to achieve a high efficiency itís moving parts must be low in moving mass. That makes it dramatically faster or put another way, more accurate (or more linear) than a speaker with heavier moving parts. If you like inner detail and want to hear all of the textures and layers of a good recording you need speakers that are fast, efficient, and have the resulting linear accuracy required to reproduce realistic sound.

A good SET amp combined with a single full range driver with no crossover or a simple 2-way using minimal crossover parts on the tweeter only, has a purity and depth that you simply donít find in more conventional multi-way systems. It is a benchmark for coherency, and noted for its ability to create a hauntingly real and holographic sound stage. Bass and dynamics with this combination usually sound more realistic due in part from the tremendous speed and in part from the linearity.

Iíve consulted many people about their audio systems, and the most common complaints include: "Dry somewhat fatiguing sound with a fairly boring sound stage followed by the realization that it simply doesnít connect you to the music emotionally like you hoped it could.

Experience has taught me that by far the easiest way to get a liquid sound that becomes holographic with stunning clarity and detail, something that excites the listener, is to set him up with an SET and a simple pair of efficient speakers. It also usually ends up being the least expensive solution since a speaker with only one driver, perhaps two, is likely to cost less in the retail market.

A great conformation of this becomes evident when you look at how many phone calls we have gotten over the years with the same basic story... They complaing about owning several hundred watt systems built from many thousands of dollars invested in show winning audio gear only to find themselves still looking for audio gear! You have to ask yourself, why? Why didn't that high dollar investment of magazine cover audio gear sound good?

These same customers after trying Decware gear will the report that even our 2 watt SET amplifier paired with efficient speakers has better dynamics and weight than their high power solid state multi-way system had which they find simply amazing. It's the exact opposite of the the propaganda that claims more power is better. If youíve ever observed how audiophiles rotate through audio gear during their lifetime you might also find it interesting that the ones who finally land on SET amps and good pair of simple speakers seldom find anything they like better or simply never look because until they hear something better the hunt is over!

The bigger is better mentality is directly connected to more expensive is better and this is certainly a handicap that stunts most audiophiles from discovering truly high fidelity sound because you run out of funds before you get there.

By now you might be imagining yourself explaining to your friends how your new 2 watt system sounds so much better than your famous brand name electronics...  I had the same issue when I stumbled across this low power amp approach. It was the most profound audio experience I had ever had since getting into the hobby and wanting badly to share it with anyone... the fellow audiophiles in town were the first to get the call.  Sadly none of them would come over since the amp in question was only 2 watts.

I soon learned after letting some pass, to lie and claim I had the latest brand X amplifier with special upgrades and was only going to be able to audition it for 3 more days before I have to give it back. It cost's upwards of $100,000.00 so do you want to come over and hear it? Naturally everyone attended... anxious to hear the holy grail each of them held in their mind, so I gave it to them in a cardboard box.

Sure enough as each local audiophile made his way over to the house for a secret listen to this new yet to be released model they were each puzzled to see a large cardboard box on the floor between the speakers with speaker wires and various cables leading to it. "Where's the amp" was predictably the first question as they entered the room, and I would say "There it is, under the box!" To which they would look at me like I was crazy so I followed with "It's the new model X and the rep was in town last night and will be here until Monday so after a few beers I talked him into leaving it here so I could listen to it. He will be here shortly to get it, so you're luck you got here when you did!

"No you're not allowed to see it, it's a secret until the big release" I said and motioned for them to sit down." Armed with speakers that were crossoverless and 96dB efficient I had no issues with playing it loud, but the beauty of it was this amplifier didn't need to be turned up to bloom, it had the detail and dynamics and weight at literally any volume from the lowest to the highest making it easy to listen at more modest levels. The more modest levels reduced distortion from room acoustics and set the stage for liquidity with slam that made most solid state sound soft. That was on reflex speakers not horns, Horns would have taken it yet another level, but it's pretty hard to hide horns under a cardboard box.

Each and every one sat there and listened to music reproduced with a level of finesse and uncanny resolution that frankly the experience truly tested the boundary of "Real vs. Memorex" as each listener was turned to stone by the sound quality until I pressed pause. Then after letting the dust settle a bit, I asked if they wanted to peek under the box!  As I lifted the cardboard box from the floor and they saw a small toaster sized device with 4 tubes on it and no fancy chrome or machined parts they each looked as if they were going to need a minute to process it and most had to reboot. 

Even after hearing it, at least half couldn't accept it was two watts on crossover-less speakers, viewing both as simply inferior and a waste of time.  So as you might have predicted I am no longer bothered by the local audiophiles who I have systematically managed to piss off with just such demonstrations.

Anyway the point is clear, you need the low part count in the signal path that SET offers combined with the lack of negative feedback to achieve the resolution of the recording. To reproduce the resolution you need speakers that are high in efficiency and low in complexity.  The amp will make a simpler speaker vanish in a vast arc of sound without effort.


-Steve Deckert



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