|
|
Implementing a variable idle current usually runs the risk of wildly changing DC operating points, which could lead to dangerous voltage pulses at the output. Using a choke load would help to eliminate many of these dangers, as the DC shifts at the plate would only equal the change in idle current against the DCR of the choke, which is only a fraction of the comparable plate resistor. Shown below is a common-cathode amplifier that allows easy adjustment of the idle current by varying the common cathode resistor's value.
Weight Control: Light and Heavy
The impression of heft or weight is found in the deep bass response of a system and ideally synthesizing sub-harmonic information from the signal might create it. This would require digitally synthesizing these frequencies. A simpler method might be to apply a boost to the lowest frequencies. (A danger with either method is the potential damage to the woofers, as reproducing lower frequencies requires greater watts.)
Rhythm Control: Slow and Fast
Many of us grew up listening to sped up 45s over the radio (it allowed the radio stations to play more commercials I have been told). Today, when we hear these songs they seem slow. So in order to make the listening experience accurate to our history, and not any absolute, a speed control is needed. Ideally, a speed control for either turntable or CD player would be the way to go. Failing this direct manipulation, haven't we all heard amplifiers or oil coupling capacitors that sounded slow? Where does the perceived slowness derive? High frequency phase relationships, maybe? More research is definitely needed.
Temperature
Control: Cool and Warm
No, heating the heaters extra hot is not the answer. But maybe having predominately even-order harmonic distortion gives a warm quality
|
|
|
|
to the sound; just as a predominately odd-order harmonic distortion gives a cool quality? Differential amplifiers eliminate even harmonics, which effectively boosts odd harmonics. And single-ended grounded-cathode amplifiers create a good amount of second harmonic distortion. Selectively blending between these two circuits may be the answer.
Illumination
Control: Dark and Bright
Skewing the high frequency response (above 6 kHz) up or down creates a bright or dark sound. Coupling capacitors can also create a dark or bright sound. For example, to my ears, the red Wima capacitors often sound dark, whereas the MIT capacitors often sound bright (if not a bit metallically clanky). So boosting or attenuating the high frequencies and/or switching coupling capacitors might work well.
Texture Control: Soft and Hard
How do proceed? Solid-state Vs. tube? Different coupling capacitors, resistors, tube types? We all know a soft or hard sound when we hear it, but how do we create it? Is soft the same as blurry because of microphonics? Is hard the same as harsh harmonics such as the 5th and 7th? Or is it something else altogether? My guess is the latter.
Depth Control: Shallow and Deep
This is not the same thing as position control. The issue is not how close are the musicians, but how far back does the hall they performed in go back. Some audiophiles use a second set of subwoofers, situated several feet behind and out from the primary subwoofers. These add readily hearable increase in perceived depth. Possibly, adding a time delayed low frequency signal to the mix could mimic this effect. (Capacitive bucket delay lines would work well, as their high frequency bandwidth limit would not be reached by those exclusively low frequency signals.)
|
|
