- SURROUND SOUND
- Digital Delay Unit For Surround Sound, Reverb, Echo & PA
- How to Phase Your Speakers
- Audio Delay Module
- PT2399 Basic Surround Delay Circuit
SURROUND SOUNDThis surround-sound decoder is based on the 'Hafler' principle, first discovered by David Hafler sometime in the early s. The original idea was to connect a pair of speakers as shown in Figure 1, for use as the rear speakers in the surround setup. There is also no way to control the level reproduced, since it will always simply be the difference signal between left and right channels. If the signal is mono, then the signal in both channels will always be more or less identical, and there will be no output from the rear speakers at all. This circuit works by allowing the rear speakers to reproduce only the difference signal between the left and right outputs. All stereo encoded material has some difference between left and right channels if it didn't, it would be monoand it is this difference signal that is reproduced by the rear speakers. It is important to ensure that the connection between the rear speaker negative terminals is not earthed, or they will simply be in parallel with the main speakers. So, if you want to use separate amps for the rear speakers, basically you can't - unless you get sneaky. The first circuit in Figure 2 is completely passive, but requires that a suitable transformer is available. A suitable transformer means a line level, 10k impedance unit with a ratio - these are scarce, but are available after a search. You might be able to get away with a Ohm unit, but because of the impedances you need, its performance will be very ordinary, with an extreme lack of bass there is not enough inductance for a Ohm transformer to work satisfactorily at high impedances. Loading the transformer will give back some of the bass, but the preamp is unlikely to be very happy with the resulting impedance. Having said this, I have used telecommunications transformers for this application ohms and they seem to work fine. The circuit shown is not a bad compromise, although the impedances are too low for anything other than a solid state preamp preferably using opamps. Using a telephony transformer Ohmthe loss overall is about 3dB, with a low frequency -3dB point around Hz. This will vary depending on the quality of the transformer used, so experimentation will be needed. Although Ohm telephony transformers are reasonably readily available, some of them are pretty ordinary. My tests were on a really good one, built by an Australian company called Transcap. I think I can say with some certainty they will be rather unwilling to sell one-off quantities. Another manufacturer of really nice transformers is Midcom in the US, but you will have the same problem with them. These manufacturers are set up to deal with large orders from other companies, not the likes of you and me wanting one "You want As a result you will have to take whatever you can get. Since it is unlikely that this will be viable for most constructors, the alternative is to go active, using a dual opamp to perform the functions. This is described next.
Digital Delay Unit For Surround Sound, Reverb, Echo & PA
How to Phase Your Speakers
Audio Delay Module
The RC delay element is a way to create a time delay in your circuit by connecting a resistor and a capacitor. And very useful. A capacitor is kinda like a tiny little battery. You can charge it with a voltage. And you can use this voltage for a short time until the capacitor is discharged. A capacitor with a higher Farad value can store more energy than one with a smaller value. Therefore it also takes more time to charge a high-value capacitor versus a small-value capacitor. If we connect the capacitor directly to the battery, there is no restriction on the amount of current that flows through the capacitor other than the batteries own maximum current capacity. The task of the resistor is to reduce the flow of current to the capacitor to slow down the time it takes to charge it. It gives you the time it takes for the voltage to rise from zero to approximately Skip to main content Skip to primary sidebar Skip to footer The RC delay element is a way to create a time delay in your circuit by connecting a resistor and a capacitor. The time it takes for the voltage to rise across the capacitor becomes our time delay. The more current that flows, the faster it charges. So a lot of current flows, the capacitor charges really quick, and the delay becomes very small. Social: Facebook Twitter YouTube.