jaddie
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Quote:
Well, no, not exactly. Not quite a meaningless term, it's an actual measured parameter.
Many amplifiers can produce very steady-state maximum power vs short-duration peak power. In fact, it's part of the THX Ultra 2 spec., and required. Older, and many current solid state amps have stiffly regulated supplies. When the output swing hits the supply rail (minus transistor drop, if any), that's it, it clips. However, it's possible to provide that same steady-state clipping level yet with proper power supply design allow for as much as 3dB of headroom above that level, but for very short durations. Tube amp power supply designs tended to be softer, high voltage, low current designs, which often were just plain unregulated. Large value filter caps at high voltages were hard to make years ago, so they went smaller, just enough to keep ripple down. That meant you you couldn't sustain the same power level continuously as you could for short peaks where the supply had a chance to completely recover and charge the filter cap fully. When the move was made to solid state, we no longer needed high voltage power supplies, and so large filter caps were now possible, which resulted in stiff power supplies at lower voltages. The max was the max, no matter how long the peak lasted. Now, if the supply was high enough and the output devices up to the task, you just ended up with a biggie sized amp with plenty of headroom above normal listening levels. But if you didn't want a product that cost a lot, you'd want to stay around 100 to 140 watts per channel. To keep cost down, you wouldn't want the biggest high-current power transformer, runs cost up. So you could get higher power on a short peak basis using a smaller transformer at higher voltage, save some money, and still deliver high peak power.
The first amp made that used this design, and a couple of other interesting power supply tweaks, was the Apt-Holman Apt 1. Holman wrote an AES paper about it which covered the concept quite well, "New Factors in Power Amplifier Design", presented at the 1980 AES Convention, and published that year also. Paragraph 1. "Load Matching and Dynamic Headroom" begins the discussion. The concept has been adopted by many manufacturers today, and as I said, is required to meet THX Ultra 2 specs.
The point is, even though typical tube amps didn't have the steady-state output power capability of their solid-state cousins, they did manage high enough peak power, where a solid state amp of the same continuously rated power would clip at the same peak level. It was an accidental design point in tube amps, and so was the lack of it in SS amps, until the value of dynamic headroom was better understood, which didn't happen until 1980. SS amps of the 1970s would have zero dynamic headroom.
Well, no, not exactly. Not quite a meaningless term, it's an actual measured parameter.
Many amplifiers can produce very steady-state maximum power vs short-duration peak power. In fact, it's part of the THX Ultra 2 spec., and required. Older, and many current solid state amps have stiffly regulated supplies. When the output swing hits the supply rail (minus transistor drop, if any), that's it, it clips. However, it's possible to provide that same steady-state clipping level yet with proper power supply design allow for as much as 3dB of headroom above that level, but for very short durations. Tube amp power supply designs tended to be softer, high voltage, low current designs, which often were just plain unregulated. Large value filter caps at high voltages were hard to make years ago, so they went smaller, just enough to keep ripple down. That meant you you couldn't sustain the same power level continuously as you could for short peaks where the supply had a chance to completely recover and charge the filter cap fully. When the move was made to solid state, we no longer needed high voltage power supplies, and so large filter caps were now possible, which resulted in stiff power supplies at lower voltages. The max was the max, no matter how long the peak lasted. Now, if the supply was high enough and the output devices up to the task, you just ended up with a biggie sized amp with plenty of headroom above normal listening levels. But if you didn't want a product that cost a lot, you'd want to stay around 100 to 140 watts per channel. To keep cost down, you wouldn't want the biggest high-current power transformer, runs cost up. So you could get higher power on a short peak basis using a smaller transformer at higher voltage, save some money, and still deliver high peak power.
The first amp made that used this design, and a couple of other interesting power supply tweaks, was the Apt-Holman Apt 1. Holman wrote an AES paper about it which covered the concept quite well, "New Factors in Power Amplifier Design", presented at the 1980 AES Convention, and published that year also. Paragraph 1. "Load Matching and Dynamic Headroom" begins the discussion. The concept has been adopted by many manufacturers today, and as I said, is required to meet THX Ultra 2 specs.
The point is, even though typical tube amps didn't have the steady-state output power capability of their solid-state cousins, they did manage high enough peak power, where a solid state amp of the same continuously rated power would clip at the same peak level. It was an accidental design point in tube amps, and so was the lack of it in SS amps, until the value of dynamic headroom was better understood, which didn't happen until 1980. SS amps of the 1970s would have zero dynamic headroom.
