As a final test of the Passion I decided to see what my systemsounds like without a pre-amp at all. I use a JVC XL-Z1050 as mytransport, which, besides it fine ability in that capacity, hasvariable analog outputs. So, to bypass the pre-amp I spent sometime listening to it hooked directly to the McCormack. Inabsolute terms the Audio Alchemy DDE v3.0 through the AudibleIllusions L-1 clearly bested the JVC's output (due no doubt tothe better quality output stage in the DDE, among other things,more than making up for the added componentry), but the sound didtake on an appealing immediacy. After several days I put thePassion between the JVC and the McCormack, with the gain set atunity, and continued to use the analog outputs on the CD playerto control the volume. The differences I heard, or rather didn'thear, were the final proof of the Passion's power. What littleeditorial affect the Passion had was so minute that I spent hourschasing one little wrinkle or another, never quite convincingmyself that I captured it. What difference I did find is morethan easily chalked up to the additional interconnect needed toadd the passive to the set up. Impressed? Damn Right!
The "" cable running from the keyboard to the VCA is a signal that sends one of two messages to the VCA: "on" if a key is depressed, and "off" otherwise. When the gate signal is off, or closed, we hear nothing. When the gate signal is on, or open, then the VCA will let the noise from the oscillator to the audio output. The "" cable sends a level to the VCA that corresponds with how fast we hit the key, and controls the volume level of the output. If we press a key very hard, and thus very fast, the volume of the output will be louder than if we pressed the key soft and slow.
"THE PRE-AMPLFIER", I can hear you scream,"he's just nuts! I knew he didn't have a clue what he wastalking about and now he's shown it for everyone to see".Well, not so fast. Traditionally a pre-amp has had 3 tasks. Thefirst is to provide source switching. The second is to give ussome way to control volume. And the third, especially with phono,is to provide additional gain. The decline of vinyl coupled withthe advent of CD, as well as amps of greater power andsensitivity means that today most pre-amps spend the vastmajority of their time performing only the first two of thosetasks. And to do that all you need is a selector switch and agood attenuator. Or, in other words, a passive pre-amp.
When looking for such components I'd say that certain classesof components will have a far more difficult time with this taskthan others. Speakers, for example, which have the Herculean taskof converting an electrical signal into mechanical motion andthen into acoustical pressure, are nothing more than a series ofdesign trade-offs with no real way to win. Like the talking dog,at times I marvel not at what they say, but that they speak atall (I mean no disrespect to speaker designers by this, butrather I mean to indicate my awe at their tremendous successes).But, some components would seem to be disposed to a purity ofreproduction that would allow them to pass on all the detail theyreceive without obscuring it, or adding to it, all whilepreserving the musical message. Wire would be one obviouscategory. Another, not quite as obvious category would be thepre-amplifier.
Correctly called passive control devices, passive pre-ampscombine just source selection and attenuation. Circuit topologyand parts quality are what set passives apart from each other,and in my opinion, play a greater role in determining soundquality with a passive than with an active pre-amp simply becausethat is all they are composed of. A poor design has no place tohide, nor do inferior craftsmanship and parts selection. With itstasked limited, a high quality passive has a chance to be a truestraight wire without gain.
In order to get the most mileage out of our synthesizer, we need a way of controlling each of its components internally. While many synthesizers have myriad knobs and buttons for controlling the sound, most people only have two hands, and it's difficult to accurately twist more than one or two knobs at a time. Fortunately, almost every module in a synthesizer can be controlled by another module. Our imaginary synthesizer does this already: the frequency of the oscillator and the volume level of the VCA are controlled by our keyboard.
So, how do I wrap this up. Simply. The Audio Synthesis Passionis one serious piece of equipment. In the right system it cantake you places no active pre-amp can (I tried it paired with theWarner Imaging VTE-200 amp where it was, if anything, a bettermatch than the McCormack. And the Passion, McCormack,Martin-Logan CLS combo went beyond musical reproduction to almostliteral music re-creation). Detail is presented with purity, butin a musically consonant manner. And while breaking the"Slip Slidin' Away" principle may not bring a Nobelprize like breaking the "Uncertainty" principle would,in my world it's nearly the equal achievement.
Let's add a low pass filter module to our imaginary synthesizer. We'll place it between the oscillator and our VCA. Depending on how we control it, this filter can make all kinds of changes to our synth sound, from gently decreasing the harshness of the high frequencies to making a variety of more intense special effects.
There are some problems with our synthesizer design—not the least of which is that because we have no way of controlling the volume of the oscillator, our instrument is always making sound! In order to fix this problem, we need to add a module called a Voltage Controlled Amplifier, or VCA. The function of a VCA is to raise or lower the volume, often called or , of a signal. Essentially, a VCA is a volume knob. Oscillators and other sound generating modules are always making sound, and VCAs are what keep the level down when you're not playing.
Individual synthesizer components which perform a single, simple function—such as oscillators and filters—are called . A is a synthesizer made by linking together lots of small modules in interesting ways. In the diagrams we use, the lines connecting the modules are like virtual cables, sending signal between them in much the same way an audio cable would in real life.
For every fraction a of a second the envelope generator is active, it sends a control signal that can be used to tell another module what to do. One way to think about envelopes is as maps for automatic knob control. For instance, the envelope pictured above starts by sending out a signal that gradually moves up from zero to one, which is like turning a knob from the far left, lowest position, to the far right, highest position. After that, the signal moves gradually down to about 0.7, which is like turning the knob to the left a little bit, and so on.
Now that we understand oscillators, let's draw a diagram of a very simple synthesizer. This synthesizer will contain a single sawtooth oscillator which sends signal to our audio output, and then to our speakers. The pitch of the oscillator will be controlled by a keyboard.