Capacitors in a Recording Studio
All kinds of audio-electronic equipment and computers jam pack recording studios. There are lots of capacitors. It’s important for the engineers who operate the recording studios to be familiar with electronics. This will help them attain the best quality sound from their equipment, and ultimately, for their client. We follow this philosophy religiously at Sydney Recording Studio, Crash Symphony Productions.
Capacitors in Analogue Musical Equipment
Analogue equipment is packed full of all different kinds of electrical components. Tube amplifiers, like the famous LA2A levelling amplifier, for example, have within them Electrical components. These include vacuum tubes, transformers, resistors and capacitors, to name but a few. All these components have a their own impact on the sound of the signal passing through them. In this article we will focus on the capacitor. We will look at the role of the capacitor and how this can impact the sound of the signal, and hence, the entire sound of a client’s recording.
Capacitor Physics
Capacitors essentially store energy in the form of electrical charge. They are created by placing two electrical plates at a distance, d, apart from each other. They are separated by a material that is referred to as a dielectric. Different materials have a different dielectric value called the dielectric constant, k. This material prevents the plates within the cap from touching. It stores the charge between them. When the cap has been charged up, much like a battery, it retains the charge and this can then be used at a later time.
Caps and their Role in the Music Circuit
In a circuit, capacitors will block DC current and allow AC current to pass through. Capacitors will smooth out ripple in an AC circuit. AC current alternates back and forth in the circuit. It is electrically manipulated such that only the positive stages of the current is used to power a section of the circuit. Naturally, the sine wave will have bumps. This is where the AC rises to the peak and then falls back to zero. In order to smoothing out this “falling-back-to-zero” the capacitor will release the stored charge at the appropriate time as to fill the void as the AC falls back. This serves to smooth out the AC wave. The System becomes quieter the more smoothly the AC is smoothed out. Capacitor quality has a huge impact on the noise of a device for this very reason.
Capacitors, or “caps” are often the most responsible components in an electronic device for introducing noise into the system. It is highly advisable to have high quality capacitors in very high end audio equipment. Brands like Audience and Mundorf and considered the top end manufacturers of audio capacitors. Often if a device fails or it is extremely noisy “re-capping” the whole device can fix things immediately. It is usually a failed capacitor that causes an electronic device to fail.
Capacitor Types
There are a few different kinds of capacitors. There are oil, polypropylene, teflon, mica caps and many more. All have different electronic, thermal and sonic properties. In the audio world polypropylene and oil caps are the top end capacitors and the most reliable. These give the most pleasing musical and sonic properties. These are ideal for use in recording studio and audio equipment.
Safety
It is important to communicate, as you will see, that when working on audio equipment caps can be very dangerous. They retain their charge for a very long time. Caps can shock or kill you if you handle them without draining their charge first. For this very reason, removing a device from the wall mains is not good enough in regards to safety. Before manipulating a circuit board, one must drain all the capacitors of electrical charge. You can accomplish this by using a grounded resistor or by bridging the poles of the resistor.
Capacitor Ratings in Electronics
Units of stored charge called Farads measure capacitors. The electronic community commonly uses Micro-farads to measure capacitance and symbolises it as uf. Manufacturers provide a max voltage rating after specifying capacitance. This is the limit in which the capacitor can function effectively. A capacitor’s rating may be 0.1uf +/- 2% @ 450V.
Conclusion
Capacitors are really the unsung heroes of the audio circuit. Capacitors can ultimately cause the device to completely fail or become extremely noisy. Good capacitors will give a music device depth and clarity!
