换个话题吧!

你到底需要多少钱？

aa amp 2 ac不差的

http://www.soundstagemagazine.com/measurements/tenoraudio_75wi/这台功放阻尼只有10左右，但是国外人用它推落魂的老旗舰、功率也不大（应该是不带变压器的真空管机，当时的价格也两万美金了）

The unbalanced input impedance, specified as being >30k ohms, was a usefully high 46k ohms at low and middle frequencies, dropping inconsequentially to 37k ohms at the top of the audioband. The balanced input impedance was 20k ohms at all frequencies, as specified. The output impedance was high for a solid-state design, at 0.3 ohm (including 6' of speaker cable) at all frequencies. Consequently, there was a slight, ±0.25dB variation in frequency response with our standard simulated loudspeaker (fig.1, gray trace), due to the Ohm's Law interaction between this impedance and that of the load. The NHB-458's small-signal frequency was otherwise flat within the audioband with all impedances above 2 ohms; the bandwidth into 8 ohms was wide, the response being down by <1dB at 200kHz (fig.1, blue trace). As a result, the amplifier's reproduction of a 10kHz squarewave into 8 ohms featured very short risetimes (fig.2), with no trace of overshoot or ringing. Good stuff!
包含6尺喇叭线在内输出阻抗0.3，对于晶体管机来讲有点高。（一般通用的方法是接模拟喇叭假负载!阻抗是恒定的。一般功放实际接喇叭后、测试指标还要差好多！）

Sidebar 1: Specifications
Description: Solid-state monoblock power amplifier. Inputs: unbalanced voltage-mode (RCA), unbalanced Zeel (BNC), balanced (XLR). Output power: 450W (26.5dBW) (850W peak) into 8 ohms, 800W (26dBW) (1700W peak) into 4 ohms, 1000W (24dBW) (1800W peak) into 2 ohms (software limited). Voltage gain (user selectable): 26 or 32dB into 8 ohms. Input impedance: >30k ohms, 5Hz–200kHz (RCA); 50 ohms, ±1 ohm (Zeel); 10k ohms per phase (XLR). Output impedance: <0.28 ohm, 20Hz–20kHz (into 8 ohms). Frequency response: 0.7Hz–700kHz, +0/–3dB; 20Hz–20kHz, +0/–0.2dB. THD: <1%, 7Hz–77kHz. Signal/noise: >115dB, A-weighted, ref. nominal power.
Dimensions: 18" (460mm) H by 11" (277mm) W by 20" (511mm) D. Weight: 154 lbs (70kg).
Serial number of units reviewed: TZ-UA1458.538L/R.
Price: 135,000 Swiss Francs/pair ($144,500/pair at time of going to press). Approximate number of dealers: 9.

http://www.stereophile.com/conte ... lifier-measurements

从评测来讲，动态优秀、但失真一般！

最典型的如dartzeel 458功放，它的阻尼系数在8欧时、只有几十的样子，但是其音乐感就特别好。人也不会再在意它的控制力了。其实用目前现有的物理数据是无法表达听音乐这种复杂的感性认识的，关键还是要听。

功放如果对于喇叭的阻抗变化的跟随能力强的话，对喇叭的推控才自如的多。这比一味地增加功率更重要。

的确如此，当初为了找一台控制好的功放就找阻尼系数大的功放、本以为阻尼系数大就可以推好、其实推出来的效果确实不好。本以为阻尼系数小的功放推不好音箱，以为控制不好音箱，但是推出的效果又很好。我觉着还是一个音箱和功放的匹配问题。这不仅要功率的匹配，而且还有阻尼的匹配问题。有些喇叭适合阻尼系数大的去推、有些却适合阻尼系数小的功放去推。打个不恰当的比喻，如果功放的阻尼大的话、在系统里反映功放的特征就强一些、如果功放的阻尼小的话，那在系统里反映喇叭的特性就强一些！

控制好和推好也只是相对而已。有的时候有的功放控制力很好，但还是推不好喇叭！
musicmad 发表于 2012-11-7 10:29

是否可以这样理解:
后级控制好喇叭--更多是指物理意义上的控制,与音色基本无关.
后级能推好喇叭--更多是感性层面的,指音色漂亮,音乐感流畅.

只有大家明确这些基本概念的定义,才能继续讨论.

电流是后级提供的, 不是前级. 前级只是电压放大.

瓦数是一个不靠谱的指标，对同一对箱子100W的功放推的比200W的功放推的好的比比皆是。最主要的是前级是否提供了足够的电流。打一个不恰当的比方，就如一组水力发电机（10台)安装在大坝上，枯水季节全部开足得到的能量，还不如汛期1台发电机得到的能量多。有的功放放大部分只提供了1ma的电流，功率部分有12对大功率管又有什么用。