DDMF phi-L Audio Tube Preamp v2.1.2电子管前置放大器 x64 x86 VST VST3 AU AAX WiN MAC

流云高飞 · 发表于 2022-5-27 20:00:00

该管前置放大器仿真是Philipp Bulling作为论文工作开发的。Philipp在自己的网站上以VST格式提供该插件已有一段时间了。他现在已经进入了新领域一段时间了，但不想让他的用户失望。因此，DDMF接管了代码，并将继续作为免费软件提供该插件，目的是进一步改进它，并可能在将来添加更多的功能。

This tube preamp emulation has been developed Philipp Bulling as a thesis work. Philipp has been offering the plugin in VST format for some time on his own website. He has now moved on to new areas for some time already but didn’t want to let down his users. Hence, DDMF took over the code and will continue to offer the plugin as freeware, with the intent to further improve it and maybe add some more bells and whistles in the future.

The plugin is very unique in the sense that it gives you full control over all aspects of the modelled circuit. All values of all the capacitors, resistors etc. can be tuned by the user. Here is what Philipp had written on the original page.

该插件非常独特，可以让您完全控制建模电路的各个方面。用户可以调整所有电容器、电阻器等的所有值。这是菲利普在原页上写的内容。

Abstract

摘要

Since the sound of an analogue tube amplifier has always exerted a strong fascination, electrical circuits with tubes play a certain role in the world of audio engineering up to now. On the other hand, audio technology becomes more and more digitised. In many cases, digital models emulate real devices in such a way that differences in sound are hardly audible. In this work a model is developed which is able to emulate the typical sound of a tube amplifier on digital devices. Here the main focus is on preamplifiers with triodes, since they have a particular influence to the sound.

由于模拟管放大器的声音一直具有很强的吸引力，到目前为止，带管的电路在音频工程领域发挥着一定的作用。另一方面，音频技术变得越来越数字化。在许多情况下，数字模型模拟真实设备的方式几乎听不到声音的差异。在这项工作中，开发了一个能够在数字设备上模拟管放大器典型声音的模型。这里主要关注带三极管的前置放大器，因为它们对声音有特殊的影响。

Based on the physical properties of real tubes, a tube model is developed first. This mathematical model includes results of theoretical studies as well as analysis of data sheets. The model is then used to implement an entire amplifier circuit. In addition to the tube itself amplifier circuits contain several passive elements. In the domain of digital signal processing the latter are described by finite difference equations, which are solved recursively.

根据实际管材的物理特性，首先建立了管材模型。该数学模型包括理论研究结果和数据表分析。然后利用该模型实现整个放大器电路。除了管本身，放大器电路还包含几个无源元件。在数字信号处理领域，后者由递归求解的有限差分方程描述。

The resulting algorithm is finally implemented as an audio plugin in order to examine its tonal properties. The behavior of the digital model corresponds satisfactorily to real amplifier circuits. Important sound effects of analogue tube amplifiers can also be attested to the digital model.

最终将生成的算法实现为音频插件，以检查其音调特性。数字模型的行为令人满意地符合实际放大器电路。模拟管放大器的重要音效也可以用数字模型证明。

Diode model

二极管型号

The first step was to develop a triode model, based on the characteristic curves of real tubes. In theory, the characteristic curve of a vacuum tube is described by Langmuir-Child’s law. However, it was quickly realised that compared to real tubes, this law is not accurate enough. So a new model has been developed. This model describes a triode as a mathematical function. With the model, it is possible to compute the plate voltage (Upc) as a function of the grid voltage (Ugc), depending on the working resistor (Ra) and the supply voltage (Ub).

第一步是根据实际管的特性曲线建立三极管模型。理论上，真空管的特性曲线是用朗缪尔-Child定律描述的。然而，人们很快意识到，与真正的管子相比，这条定律不够精确。因此，开发了一种新的模型。该模型将三极管描述为一个数学函数。利用该模型，可以根据工作电阻（Ra）和电源电压（Ub）计算板电压（Upc）作为电网电压（Ugc）的函数。

The following graph shows this function for a 12AU7 triode with Ra = 10k and Ub = 250V:

下图显示了Ra=10k和Ub=250V的12AU7三极管的此功能：

DDMF phi-L Audio Tube Preamp v2.1.2 x64 x86 VST VST3 AU AAX WiN MAC [FREE] screenshot

DDMF phi-L音频管前置放大器v2.1.2 x64 x86 VST VST3 AU AAX WiN MAC[免费]屏幕截图

Circuit modeling

电路建模

Based on this model, a plate follower stage was implemented.

在此模型的基础上，实现了一个板式随动台。

DDMF phi-L Audio Tube Preamp v2.1.2 x64 x86 VST VST3 AU AAX WiN MAC [FREE] screenshot

DDMF phi-L音频管前置放大器v2.1.2 x64 x86 VST VST3 AU AAX WiN MAC[免费]屏幕截图

Cathode biasing

阴极偏压

In this circuit, cathode biasing is used to adjust the bias point of the tube. This is realised by a resistor (Rc) and a capacitor (Cc), placed between the cathode and ground. The effect of cathode biasing can then be modeled by a simple first order RC low pass filter, with Ic*Rc being the input of the filter, and the cathode voltage (Uc) being the output.

在该电路中，阴极偏置用于调整管的偏置点。这是通过放置在阴极和接地之间的电阻器（Rc）和电容器（Cc）实现的。然后，可以用一个简单的一阶RC低通滤波器模拟阴极偏压的影响，Ic*RC是滤波器的输入，阴极电压（Uc）是输出。

If the input signal jumps for example from 0 V to 5 V, the cathode voltage follows quite similar to the step response of a RC-low pass filter:

如果输入信号从0 V跳至5 V，则阴极电压与RC低通滤波器的阶跃响应非常相似：

DDMF phi-L Audio Tube Preamp v2.1.2 x64 x86 VST VST3 AU AAX WiN MAC [FREE] screenshot

DDMF phi-L音频管前置放大器v2.1.2 x64 x86 VST VST3 AU AAX WiN MAC[免费]屏幕截图

Signal limiting

信号限制

There are two reasons for signal clipping in this circuit. The first one is caused by the tube itself. If there is a high peak at the negative half-wave of the input signal, the tube can’t amplify the signal anymore since the flow of current is completely cut-off. Thus, the positive half-wave of the output is clipped. This effect can be intensified by a more negative bias point.

此电路中的信号限幅有两个原因。第一个是由管子本身引起的。如果在输入信号的负半波处有一个高峰，由于电流被完全切断，管子就不能再放大信号了。因此，输出的正半波被剪裁。这种影响可以通过更负的偏置点来加强。

Here the bias point of an 12AU7 is at around -12 V:

此处12AU7的偏置点约为-12 V：

DDMF phi-L Audio Tube Preamp v2.1.2 x64 x86 VST VST3 AU AAX WiN MAC [FREE] screenshotThe second reason for clipping is caused by grid current. High peaks of the positive half-wave of the input signal make the grid voltage positive compared to the cathode voltage. In this case electrons are attracted by the grid. The grid current causes a voltage drop at the internal resistance of the previous stage, which limits the input signal. The following figure shows the effect. The grid voltage is obtained by shifting down the input signal (Uin) by the cathode voltage (Uc). In the upper picture the maximum grid voltage (Ugc) is ~ 0 V compared to the cathode. Hence, there is no grid current. In the lower picture the input signal has an amplitude of 10 V. At the positive peaks of the input signal the grid voltage rises above 0 V (compared to the cathode). The grid current begins to flow and clips the grid voltage.

DDMF phi-L音频管前置放大器v2.1.2 x64 x86 VST VST3 AU AAX WiN MAC[免费]屏幕截图剪切的第二个原因是由电网电流引起的。与阴极电压相比，输入信号正半波的高峰值使栅极电压为正。在这种情况下，电子被栅极吸引。电网电流在前一级的内阻处引起电压降，从而限制输入信号。下图显示了效果。栅极电压是通过将输入信号（Uin）向下移动阴极电压（Uc）获得的。在上图中，与阴极相比，最大栅极电压（Ugc）约为0 V。因此，没有电网电流。在下图中，输入信号的振幅为10 V。在输入信号的正峰值处，栅极电压上升到0 V以上（与阴极相比）。电网电流开始流动并阻断电网电压。

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