Quick questions answered

David Mellor

David Mellor is CEO and Course Director of Audio Masterclass. David has designed courses in audio education and training since 1986 and is the publisher and principal writer of Record-Producer.com.

Thursday November 30, 2006

What exactly is the difference in importance between current and voltage in a microphone as it relates to sound capture and transmission?

There a lots of ways of looking at this question. Perhaps the most significant is that the capsule (the diaphragm and its associated assembly) of a dynamic mic is able to produce enough power to send directly to the mixer. A transformer at the microphone's output converts the impedance to around 200 ohms, which is standard for microphones. There will be sufficient current flow to keep the noise level low, and also make leakages in the cable insignificant. At the same time, the voltage will be high enough to adequately drive the microphone preamplifier. The capsule of a capacitor microphone on the other hand does not produce very much power. The voltage is reasonable but the current is very low. Hence the signal needs to be amplified within the microphone itself. A capacitor microphone therefore requires phantom power so that the internal amplifier can function.

The term 'flat' is often used in relation to recording normally (vocals) and in some contexts highly confusing could you give a precise definition?

In this context, 'flat' means singing below pitch. This is a common problem with singers. Sometimes a singer has poor pitching and will sing either sharp or flat randomly. But flat singing caused by poor breath control is much more common.

I don't understand how the amount of channels on a mixing console influences mixing while overdubbing?

If you have enough channels, then you can allocate a set of channels to the outputs of the multitrack. While you are overdubbing, you can continually refine the mix of the previously recorded tracks. When you have finished overdubbing, the mix will already be well developed for when you start the mix stage itself.

What is a U-Matic video tape?

U-Matic was developed in the 1970s as a domestic video format prior to VHS. In the 1980's it was used in digital audio recording. A stereo signal could be digitized and further processed so that it had the characteristics of a video signal and recorded on U-Matic tape. There are still many U-Matic masters in record companies' archives.

Where remixing is concerned which piece of material is handed over: the final product or the half inch tape. And is it possible to remove instruments from vocals mastered piece. If yes briefly state how?

Everything is handed over to the record company. They generally own the multitrack and stereo masters. It is not generally possible to remove instruments from a mixed stereo recording. The only way this is possible is to invert one channel and mix the two channels together. Any vocal or instrument panned center will cancel. However, what is left will generally sound pretty poor.

What is 'sonic character'?

To give an example, some microphone manufacturers such as DPA strive to make mics that are as accurate as possible. The signal from the mic is therefore a very close replica of the original sound pressure waveform. The mic does not impose its own character on the recording. However, this can result in recordings that sound rather plain. So other microphone manufacturers would allow certain defects in accuracy that give rise to sounds that are 'pleasant' rather than accurate.

What is the process involved in bouncing? Please explain as it relates to analogue and digital systems.

'Bouncing' in tape-based multitrack recording systems means mixing several tracks to one or two tracks in order to free up room on the tape for further recording. For instance, you might have recorded twenty-three tracks on a twenty-four track tape, leaving only one free. But you could perhaps mix four tracks of previously recorded backing vocals onto that last track. Those four tracks could then be re-recorded with other instruments.

In computer-based multitrack recording, bouncing as above can still be done if you are running out of tracks. But also the final mix to a stereo file can be known as bouncing too.

What is meant by homogenous as far as music is concerned?

'Homogenous' means 'pretty much the same'. So a brass section consists of homogenous instruments, as does a string quartet, as does a choir. But an orchestra consists of diverse, or heterogeneous, instruments.

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