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Post by metaldaze on Jun 29, 2020 12:48:34 GMT -5
Say a solid state amplifier is biased to have a fixed point of operation in class A to a certain unit of output, before transition into A/B.
Lets say that point is 6 watts/ch into 8 ohms before transition. So 12 watts total into 8 ohms.
If the impedance is halved to 4ohms - the amplifier (although rated for less to keep THD down) can double its power into half the load. As shown by professional review & measurement.
What happens to the Class A operating point?
The way I understand it, the bias point is fixed regardless of impedance loading, and must obey Ohm's Law.
So at 4 ohms the class A output will be halved to 3 watts/ch. Or 6 watts total before the transition to A/B.
Is this correct?
Corrected answer from manufacturer:
'I just wanted to tag back into this thread. I spoke to a nice gentleman from Parasound today & he stated that while there may be a little less class A power into 4 ohms vs 8 ohms - its not that drastic or as dependent on impedance as I thought. The bias point basically is what it is.
If approximately 12 watts is class A into 8, ~10 into 4 will be class A before the slide beings into A/B.
*note: this is per channel. '
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Post by garbulky on Jun 30, 2020 18:19:38 GMT -5
Say a solid state amplifier is biased to have a fixed point of operation in class A to a certain unit of output, before transition into A/B. Lets say that point is 6 watts/ch into 8 ohms before transition. So 12 watts total into 8 ohms. If the impedance is halved to 4ohms - the amplifier (although rated for less to keep THD down) can double its power into half the load. As shown by professional review & measurement. What happens to the Class A operating point? The way I understand it, the bias point is fixed regardless of impedance loading, and must obey Ohm's Law. So at 4 ohms the class A output will be halved to 3 watts/ch. Or 6 watts total before the transition to A/B. Is this correct? I believe that’s right |
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Post by metaldaze on Jul 2, 2020 18:06:12 GMT -5
Say a solid state amplifier is biased to have a fixed point of operation in class A to a certain unit of output, before transition into A/B. Lets say that point is 6 watts/ch into 8 ohms before transition. So 12 watts total into 8 ohms. If the impedance is halved to 4ohms - the amplifier (although rated for less to keep THD down) can double its power into half the load. As shown by professional review & measurement. What happens to the Class A operating point? The way I understand it, the bias point is fixed regardless of impedance loading, and must obey Ohm's Law. So at 4 ohms the class A output will be halved to 3 watts/ch. Or 6 watts total before the transition to A/B. Is this correct? I believe that’s right Thank you garbulky. Cheers & Happy 4th of July weekend! |
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Post by metaldaze on Jul 13, 2020 21:39:32 GMT -5
I just wanted to tag back into this thread. I spoke to a nice gentleman from Parasound today & he stated that while there may be a little less class A power into 4 ohms vs 8 ohms - its not that drastic or as dependent on impedance as I thought. The bias point basically is what it is.
If approximately 12 watts is class A into 8, ~10 into 4 will be class A before the slide beings into A/B.
*note: this is per channel.
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Post by Deleted on Jul 14, 2020 23:49:00 GMT -5
I just wanted to tag back into this thread. I spoke to a nice gentleman from Parasound today & he stated that while there may be a little less class A power into 4 ohms vs 8 ohms - its not that drastic or as dependent on impedance as I thought. The bias point basically is what it is. If approximately 12 watts is class A into 8, ~10 into 4 will be class A before the slide beings into A/B. Appreciate your followup. Your findings give me confidence in my own listening observations and resulting conclusions. I rarely if ever surpass 7 watts nonetheless 10 watts of power per channel from my Parasound A31 during listening. I find the Parasound to be smoooooooooooooth. Just love the fidelity. |
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Post by metaldaze on Jul 15, 2020 15:52:08 GMT -5
I just wanted to tag back into this thread. I spoke to a nice gentleman from Parasound today & he stated that while there may be a little less class A power into 4 ohms vs 8 ohms - its not that drastic or as dependent on impedance as I thought. The bias point basically is what it is. If approximately 12 watts is class A into 8, ~10 into 4 will be class A before the slide beings into A/B. Appreciate your followup. Your findings give me confidence in my own listening observations and resulting conclusions. I rarely if ever surpass 7 watts nonetheless 10 watts of power per channel from my Parasound A31 during listening. I find the Parasound to be smoooooooooooooth. Just love the fidelity. It's funny you chose the word smooth because I was contemplating a small write up on here, just my own findings of experience. And that is the EXACT word I was thinking if I could describe the sound in one word. Its not rolled off, just smooth and very natural sounding. Very pleasant to the ear. I find myself much more involved with the music, rather than just listening. I also remarked on the phone that it sounded almost as if I had added a subwoofer. Not in a bad way, not boom-y or over exaggerated. Just the lower octave and below from what I had before is filled in and so damn punchy. Every bass drum kick a reminder of the amount of current and storage behind the drivers. And he followed up with that they rate their amplifiers at full power down to 5Hz. I believe Emotiva does this as well so I'm not sure the difference, maybe its the Class A. But yeah a whole new level of very satisfied  I lastly asked him about leaving the equipment on, as I usually do with the Gen 3 XPA. (PS audio has a whole thing about leave it on) Since the xpa is so efficient and low heat I may still leave that on unless I go away for more than a little while, then its all triggered to be off normally for safety. I have the A21+ well ventilated with a fan pulling air up, the amp gets warm. Sometimes the fins are hot if I go nuts but its mostly just warm to the touch. But he said he would definitely not leave the equipment on while not in use. After the first 100 - 150hrs of 'burn in' its not green and will only keep the amp "at the ready all the time. But with the soft start/warm up circuitry after burn in, the amp is warm & good to go after about 7-8 mins." Considering it uses 160 watts just at idle I'll believe them. |
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