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Termyn8or -> RE: Cost and simplicity of solar panels continues to fall. (9/29/2011 12:32:53 AM)
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"As for audio, not sure where you are coming from here. Whether tube/valve or solid state, the upper-echelon power amplifiers and preamps' cost is most directly related to ability of the power supply to provide clean as possible DC (and lots of current) to the relevant circuits, the emitter, the filaments, etc."
Let's get in sorts here. For many applications a rock solid flat line absolute constant voltage is desired, but not for audio. the nature of the audio waveform to be reproduced varying in level very significantly makes it more desirable to have peak instantaneous currents stored in capacitors for use during transient peaks suck as the hit of the bass drum and so forth, which then depletes the "rails" which are the DC supply for the output stage. It also dpends on what you listen to, but that semisoft power supply gives an amp what's called dynamic headroom. That is the ability to produce, for a split second, double or more it's steady state output rating. You get to appreciate that without knowing it sometimes. But that's why they don't use a switched mode tightly regulated power supply in most amps. Also, those transformers do not like anything but sine waves so you better forget those cheapo $200 invertors.
The emitter is an element of a transistor (BJT) which has no filament. A filament exists in a vacuum tube. It heats the cathode which is the functional equivalent. However the same applies about the peak power available for transients, except in the case of true class A amps, whether solid state or not. They are quite rare. There are quasi class A amps which are almost as good, but not quite.
But the point is you can look at almost any thing in your house and take it apart, and find a power supply that gives it 5VDC, 12 VDC, 32VDC. -5VDC, -12VDC. -32 VDC and all that. Everything almost runs an DC, with VERY few exceptions. I have a power drill that is one. It's a VSR but it's a powerful MF.
Most VSRs have a chopper controlled by the trigger that works up in the Khz range, which requires a recitfier and filter. Not this one. It's like an 7 amp motor and it does 2,500 RPM. It will break your wrist off. I have had more powerful drills, but never one that did that much RPM in a handheld with that much torque. Well sometimes it starts a bit jerky, because it chops the power at 60 Hz, not at a fast rate. So if you pull the trigger when the AC is at it's crest, it sorta jerks. But pulling that power in that small package they simply didn't have room for an adequate circuit that would do it more smoothly. They used a four quadrant triac. Cheaper too.
I am happy with the thing though, this motherfucker will drill. It takes both hands to hold it if using a paddle bit. With a sharp paddle bit I can cut a two inch hole in a four by four in about 7 seconds. It is that bad to the bone. I don't even use it all the time. Best hundred bucks I spent in a long time.
But the point is, if the power was DC, they could have put the high speed controller in. If fed by DC now, it would be at full speed with the lightest touch on the trigger because of how a triac works.
And triacs don't lend themselves to inverter applications well, you are talking bipolar or FET. More money per watt handled, and drive circuitry.
T^T
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