#21
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From an engineering standpoint class AB is not that far off from class A (depicted on a load-line showing percent conduction at various bias points). However the alure of class A is undeniable. Esoteric's F03 (30w class A) is wonderful and fits in this discussion perfectly. My personal choice will always be an AB biased amp. I prefer my equipment left on 24/7 and class A amps simply run too hot.
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System: ML:5206,5302 Serafino's Nordost Lumin U1 RM15 |
#22
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#23
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Crossover distortion in today's amplifiers is over blown!!!!! Modern transistors are much more linear during small signal conditions (the period when the device first begins to conduct)
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System: ML:5206,5302 Serafino's Nordost Lumin U1 RM15 |
#24
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Au contraire. Crossover distortion is still a 'real' problem when transistors in the output stage are not well matched and one of the cost drivers of our high-end solid-state gear. The time & expense of finding good matched sets is non-trivial. Especially when one has a dozen or devices for each channel. Sorting, testing and matching is a expensive.
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Glenn... Canton Reference 9 Clearaudio SM Pro Focal Bathys JLA 10" Dominion Kuzma Stabi S w/MC & MM Magnepan 1,7i McIntosh MA8950 & MR88 Oppo 203 Roon Nucleus Rose Hifi RS150B Shunyata Gemini-4 Sony ST-A6B, TA-F6B, ST-J75 & PS-X75 Sorane SA1.2 & TA-1L Stillpoints LP1v2 WW Pt, Au & Ag |
#25
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The class of operation does not go into AB into impedances lower than 8 ohms at the rated power levels. Rated power levels are all class A. Download the 'technical information from their homepage https://www.accuphase.com/technical_...nformation.pdf and have a closer look at the power specs: The rated class A output power (marked in red) is 30W@8Ω / 60W@4Ω / 120W@2Ω and 150W@1Ω. The maximum output power (marked in orange, class AB) before clipping is 75W@8Ω / 125W@4Ω /190W@2Ω / 220W@1Ω. This means: @8Ω it's up to 30W in class A and from there further up to 75W in class AB @4Ω it's up to 60W in class A and from there further up to 125W in class AB @2Ω it's up to 120W in class A and from there further up to 190W in class AB @1Ω it's up to 150W in class A and from there further up to 220W in class AB Martin |
#26
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Transistors are not BETA (gain) matched to eliminate cross-over notch distortion. They are matched to ensure equal conduction of the pos/neg signals and that no one transistor will conduct more or less than any other in the output stage. Class A and AB are biased "on" enough to eliminate notch issues.
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System: ML:5206,5302 Serafino's Nordost Lumin U1 RM15 |
#27
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Hugh Dean is a hugely respected amplifier designer. He openly admits that he has spent the last 25 years or more trying to design a class AB amp that sounds as good as a well designed class A amp. (He dislikes the inefficiency of class A). Perhaps you should contact him and tell him where he is going wrong. |
#28
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This is common in what are referred to as Pure Class A bias (fixed bias) amps since the output devices and heat sinks cannot dissipate the amp's full rated power into lower impedances. I don't intend to get into a long winded dispute on the topic, so I'll respectfully bow out of the discussion at this point. For the record I love the sound of Accuphase gear having owned one of their Class A amps in the past and have nothing but respect for their design quality and sonic performance. Last edited by audio bill; 02-25-2022 at 08:54 PM. |
#29
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System: ML:5206,5302 Serafino's Nordost Lumin U1 RM15 |
#30
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I don't quite understand these technical descriptions between the Class A and AB versions of Accuphase amplifiers.
What I have been playing with are the E380 (directly to a pair of Amati Traditions) and using the E380 as a preamp to the A48 (again to the Amatis). Source is a dCS Bartok. Wireworld Silver 7 cabling. I definitely prefer the E380 driving the Amatis. There's just better control to me especially of the Amati's bass drivers. Also, the A48s benefit greatly from using the E380 as a preamp. I had the dCS directly into the A48 and it sounded drier and more lifeless. The E380 (as a preamp to the A48) just gave it such a breath of energy and realism
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