Capacitors in a Recording Studio

Recording studios are jam packed full of all kinds of audio-electronic equipment and computers. 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 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 capacitor from touching. It stores the charge between them. When the capacitor has been charged up, much like a battery, it retains the charge and this can then be used at a later time.

Capacitors 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. To explain this as simply as possible, the 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 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 more effectively this AC is smoothed out the quieter the system becomes. 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 capacitors 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 are also the capacitors that give the most pleasing musical and sonic properties, ideal for use in recording studio and audio equipment.

Capacitor Safety

When working on audio equipment capacitors can be very dangerous. They retain their charge for a very long time and shock or kill if they are not drained of their charge prior to handling. For this very reason, removing a device from the wall mains is not good enough in regards to safety. All the capacitors must be drained of electrical charge before manipulation on a circuit board begins. This can be done by using a grounded resistor or by bridging the poles of the resistor.

Capacitor Ratings in Electronics

Capacitors are measured in units of stored charge called Farads. Most capacitors are rated in micro-farads. In the electronic community this is symbolised as uf. On a capacitor a tolerance is also indicated. This is followed by a max voltage rating. This is the limit in which the capacitor can function effectively. For example, a capacitor’s rating might be 0.1uf +/- 2% @ 450V.

Capacitor Conclusion

Capacitors are really the unsung heroes of the audio circuit. They actually have a longer working life when they are being used and have charge running through them than if they lie dormant and do nothing for years. In fact, if a capacitor has been idle for a long time it is more likely to fail than if it had been used excessively. If they are mistreated and fail they can also be the achilles heal of an electronic device. Capacitors can ultimately cause the device to completely fail or become extremely noisy. Good capacitors will give a music device depth and clarity more so than most people will ever realise.