1) Gs: I've never seen anything in Ohm's law that states the following:
"While Ohm's law says this is inevitable, Ohms law also states that the voltage decreases with an increase in power (current). As the load is halved, the PS voltage drops and lessens its ability to keep up the current flow."
The only time voltage will sag or drop is if there is not enough current to be had within the circuit. The "pressure" ( voltage ) within the circuit will remain consistent so long as the "volume of flow" ( amperage ) is maintained. As such, an amp can act as a voltage source ( doubles down in power output as impedance is halved ) so long as the power supply and output stages are capable of passing enough current to meet the demands placed upon them.
When you find an amp like this, you will notice that the clipping power at 4 ohms is almost exactly twice that of what it is at 8 ohms. If it is really a "high current" design, it will produce twice the power output at clipping into a 2 ohm load that it does at 4 ohms.
2) Since there is SOOOO much "fudging" of power output specs and manipulation of numbers for marketing purposes, forget about "rated power" and start looking at what the amp does at clipping at various impedances. This will tell you a LOT more than what they rate the unit at. On top of that, forget about frequency response on a power amp. Look at the power bandwidth. Frequency response is spec'd at 1 watt of output ( typically ) whereas power bandwidth is the frequency response as measured at rated power.
3) As to tubes vs SS, tubes appear to be more powerful than an equivalently rated SS amp for multiple reasons. SS amps tend to clip much harder and sound much worse when running out of steam. Tube amps can be pushed into clipping without sounding nearly as harsh. In effect, this makes them sound like they actually have more headroom since they aren't getting "nasty" sounding yet they are being run at or above rated power output.
4) As to tube amps having a much higher headroom rating than SS amps, that is a pretty broad generalization that i can't agree with. Either design can have a lot of headroom. While most of this will have to do with the power supply of either unit, the transistors would obviously have to be able to pass enough power to do this. While the same is true for tubes, some tubes will do this far easier than others. Tubes with a high Mu are probably more suitable to "peak power" or dynamic headroom than those with a lower Mu with the same power supply / circuitry supporting them. At least that's what we've come to find out with RF circuits. 8417's are a perfect example of a tube that works excellently in an RF circuit and was also used in audio power amps. Too bad these tubes aren't available anymore. 6L6's are another example, but they are nowhere near the tube that an 8417 is.
5) Regardless of all of the above, it is harder to match a bunch of output tubes than it is to match output transistors. This is not to mention that tubes are "born to die" and replacing them at random as needed will surely create greater imbalances / poorer performance over time. As such, most "experts" agree that all of the tubes within one section of a circuit should be replaced at one time. Matched parts should be used when doing this if possible.
6) While i have nothing against tube amps or those that favour them, you should know what you are getting into should you choose to go that route. Tube power amps are SURELY higher maintenance than an equivalently rated SS amp and i don't think that anybody ( tube-head or not ) would argue that point. If you like the sonics of a tube amp enough to put up with the maintenance and expense that is required to keep it running at optimum performance levels, go for it. Sean
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"While Ohm's law says this is inevitable, Ohms law also states that the voltage decreases with an increase in power (current). As the load is halved, the PS voltage drops and lessens its ability to keep up the current flow."
The only time voltage will sag or drop is if there is not enough current to be had within the circuit. The "pressure" ( voltage ) within the circuit will remain consistent so long as the "volume of flow" ( amperage ) is maintained. As such, an amp can act as a voltage source ( doubles down in power output as impedance is halved ) so long as the power supply and output stages are capable of passing enough current to meet the demands placed upon them.
When you find an amp like this, you will notice that the clipping power at 4 ohms is almost exactly twice that of what it is at 8 ohms. If it is really a "high current" design, it will produce twice the power output at clipping into a 2 ohm load that it does at 4 ohms.
2) Since there is SOOOO much "fudging" of power output specs and manipulation of numbers for marketing purposes, forget about "rated power" and start looking at what the amp does at clipping at various impedances. This will tell you a LOT more than what they rate the unit at. On top of that, forget about frequency response on a power amp. Look at the power bandwidth. Frequency response is spec'd at 1 watt of output ( typically ) whereas power bandwidth is the frequency response as measured at rated power.
3) As to tubes vs SS, tubes appear to be more powerful than an equivalently rated SS amp for multiple reasons. SS amps tend to clip much harder and sound much worse when running out of steam. Tube amps can be pushed into clipping without sounding nearly as harsh. In effect, this makes them sound like they actually have more headroom since they aren't getting "nasty" sounding yet they are being run at or above rated power output.
4) As to tube amps having a much higher headroom rating than SS amps, that is a pretty broad generalization that i can't agree with. Either design can have a lot of headroom. While most of this will have to do with the power supply of either unit, the transistors would obviously have to be able to pass enough power to do this. While the same is true for tubes, some tubes will do this far easier than others. Tubes with a high Mu are probably more suitable to "peak power" or dynamic headroom than those with a lower Mu with the same power supply / circuitry supporting them. At least that's what we've come to find out with RF circuits. 8417's are a perfect example of a tube that works excellently in an RF circuit and was also used in audio power amps. Too bad these tubes aren't available anymore. 6L6's are another example, but they are nowhere near the tube that an 8417 is.
5) Regardless of all of the above, it is harder to match a bunch of output tubes than it is to match output transistors. This is not to mention that tubes are "born to die" and replacing them at random as needed will surely create greater imbalances / poorer performance over time. As such, most "experts" agree that all of the tubes within one section of a circuit should be replaced at one time. Matched parts should be used when doing this if possible.
6) While i have nothing against tube amps or those that favour them, you should know what you are getting into should you choose to go that route. Tube power amps are SURELY higher maintenance than an equivalently rated SS amp and i don't think that anybody ( tube-head or not ) would argue that point. If you like the sonics of a tube amp enough to put up with the maintenance and expense that is required to keep it running at optimum performance levels, go for it. Sean
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