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#12
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__________________
Dan STUDIO - McIntosh C1000C/P, MC2301 (2), MR88, Aurender N10, Esoteric K-01X, Shunyata Sigma spdif digital cable, Sonos Connect, PurePower 2000, Stillpoints, Furutech Flux 50, Michell Gyro SE, Michell HR Power Supply, SME 309, Ortofon Cadenza Black, Wireworld, Sonus faber Amati Anniversario LIVING ROOM - McIntosh C2300, MC75 (2), MR85, Magnum Dynalab 205, Simaudio MOON Neo 260D-T, Schiit Audio Yggdrasil, Aurender N100H, Shunyata Sigma USB cable, Micro Seiki DD40, Ortofon Cadenza Blue, Nakamichi BX-300, Sony 60ES DAT, PS Audio P10, Furutech Flux 50, Sonos Connect, Stillpoints, Wireworld, Kimber, PMC EB1i, JL Audio f113 VINTAGE - McIntosh MA230, Tandberg 3011A tuner, Olive 04HD, Sony DTC-59ES DAT, McIntosh 4300V, JBL 4312A Last edited by jdandy; 09-01-2016 at 09:39 PM. |
#13
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Horses must be freaked out. Mine go nuts in a big storm. Be safe.
Sent from my iPad using A.Aficionado |
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Wind is beginning to pick up speed and some of the down pours are torrential but it appears the eye is going to miss us. Back to the original topic, the new Esoteric integrated amplifiers.
__________________
Dan STUDIO - McIntosh C1000C/P, MC2301 (2), MR88, Aurender N10, Esoteric K-01X, Shunyata Sigma spdif digital cable, Sonos Connect, PurePower 2000, Stillpoints, Furutech Flux 50, Michell Gyro SE, Michell HR Power Supply, SME 309, Ortofon Cadenza Black, Wireworld, Sonus faber Amati Anniversario LIVING ROOM - McIntosh C2300, MC75 (2), MR85, Magnum Dynalab 205, Simaudio MOON Neo 260D-T, Schiit Audio Yggdrasil, Aurender N100H, Shunyata Sigma USB cable, Micro Seiki DD40, Ortofon Cadenza Blue, Nakamichi BX-300, Sony 60ES DAT, PS Audio P10, Furutech Flux 50, Sonos Connect, Stillpoints, Wireworld, Kimber, PMC EB1i, JL Audio f113 VINTAGE - McIntosh MA230, Tandberg 3011A tuner, Olive 04HD, Sony DTC-59ES DAT, McIntosh 4300V, JBL 4312A Last edited by jdandy; 09-01-2016 at 11:10 PM. |
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Be safe. Luckily, our place in Boca seems to have been spared (this time). Look forward to hearing yours and Gus's report in the morning.
Sent from my iPad using A.Aficionado |
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#17
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Marc - I expected that this would be questioned and have been searching for supporting info as you requested. Unfortunately so far I haven't found it, but I know that I've read this several times including once within the last month or so. I will continue my search and when I find it I'll post it here. You are correct that when the Class A output stage goes beyond its limit it switches to Class A/B operation, and that's exactly what happens with Class A amps when operated into lower impedances. Many Class A/B amps operate in Class A for their first few watts and then switch to A/B.
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Still unable to locate the detailed technical explanation that I saw. In my research I noticed that even the Accuphase "Pure Class A" power amps like their A-47 only state Pure Class A operation into 8 ohms. Because of its robust power supply, output stage and overall build quality it does continue to double its output power into lower impedances even going down to 1 ohm (very impressive!) but it doesn't state that it maintains Class A operation into those lower impedances. I believe it would be impossible to do so unless the output stage and heat sinking were sufficient to support 360 watts per channel into 1 ohm which would require a significantly larger and even more massive amplifier.
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Hopefully this isn't considered OT; I think it's alright since it's directly related to the new Esoteric F-03a amp being a Class A design. After extensive searching I was able to find one of the sources which documented the technical explanation regarding power output of Class A amps into impedances lower than 8 ohms. Since it was posted on another forum I know I can't link to it, but I'll copy the basic explanation here for reference.
This applies to solid state push-pull output stages like used in the Esoteric Class A designs as well as those by Accuphase and many others. Single ended output stages are inherently Class A by their nature since only a single device carries the signal. Transformer coupling of an output stage as used by some amps maintains a basically constant output power across varying loads without an increasing power into lower impedances. As power = resistance x current x current , and maximum class A current is determined by the bias current, the class A power is proportional to the resistance. To make it clear a 100W class A amplifier has 50W class A at 4 ohm and 25W class A at 2ohm. This happens for true class A. Some designers have sliding bias schemes to increase bias depending on signal prediction, but IMHO they are creating new problems and can not be considered class A anymore. Bridged amplifiers increase voltage swing capability, but not bias current. Class A power for a bridged amp is the same as that of a single unit even though its maximum output power is much higher. The class A power specification is mainly established by the amplifier bias current . It is specified as the maximum power delivered by the amplifier to a 8 ohm resistor without switching off any of the active elements. The theoretical class A efficiency rating is calculated for an amplifier having a power supply with the minimum power supply voltage needed to deliver that power, ignoring any losses. Most of the time the amplifiers have much higher voltage in the power supply than this value, and can be operated at higher output power outside class A. Hope this helps to clear things up a bit (and not add more confusion!) |
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