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目前一副高档耳机的售价并不亚于一对中档音箱,用高档耳机播放音乐具有音箱不能媲美的优势:首先其音场声道分离度好,其次在播放交响乐时其动态表现得淋漓尽致。若用晶体管功放驱动耳机,虽然音色提高不少,但金属声比较明显。因此很多音响爱好者都热衷于制作耳机胆功放。对专用于驱动耳机的胆功放有其特殊要求:除了采用失真小、频响宽、阻尼特性好的功放电路外,还要求其输出功率较小,否则会增大耳机的失真度,甚至损坏耳机。其次要求放大器有极小的静态噪音。本文介绍一款耳机胆功放电路,供音响爱好者参考。该耳机胆功放电路如图1所示。在该电路中,输出级采用美国 MT 管 WE-417A,该管特性与5842相同,其高跨导特别适合宽频带放大器使用,并且具有低噪声特性。前级放大器的 WE-396A 也用于长距离通信语言放大器,具有极高的信噪比,两管特性如附表所示。WE-417A 和5842均采用小九脚封装,因而可以组装成体积极小的双声道胆功放。由于WE-417A 的跨导达24mA/V,因而输出额定功率时只需2Vp-p的驱动信号,在图示电路 WE-417A 的工作状态和负载阻抗为
At present, the price of a high-grade earphone is no less than that of a mid-range speaker. Playing with high-grade earphones has the advantage that the sound box can not compete with the soundtrack. First, the soundtrack has good channel separation, and secondly, the dynamic performance of the symphony is vividly demonstrated. If the transistor amplifier driver headphones, although a lot of sound to improve, but the metal sound is more obvious. So many audio enthusiasts are keen to make headphones bile amp. On the dedicated drive headphone amplifier has its special requirements: In addition to the use of small distortion, wide frequency response, good damping characteristics of the power amplifier circuit, but also requires a smaller output power, otherwise it will increase the degree of distortion of the headset, or even damage to the headset . Second, the amplifier requires minimal static noise. This article describes a headset amplifier circuit, for audio enthusiasts reference. The headphone amplifier circuit shown in Figure 1. In this circuit, the output stage using the United States MT tube WE-417A, the same tube characteristics and 5842, the high transconductance particularly suitable for wideband amplifiers, and has low noise characteristics. The preamplifier WE-396A is also used for long-range communications speech amplifiers with extremely high signal-to-noise ratio, as shown in the attached table. The WE-417A and 5842 are packaged in a small nine-foot package that can be assembled into a very small two-channel bile amplifier. As the WE-417A transconductance of 24mA / V, so the output power when only 2Vp-p drive signal, the circuit WE-417A shown in the working state and the load impedance of