Please note that a head unit will reach its maximum output level (clipping) well before the volume control reaches the upper end of its range (usually at a point of 85-90% of its maximum range). This is especially true of tape decks, not because the audio section is of lesser quality but because some tapes are recorded at lower levels than others and the manufacturer must design the deck to be able to produce a sufficient output level with virtually any tape.
Note: The red arrows (near the volume controls) in the following drawings are showing you the position of the volume control which will produce the maximum (without clipping) output voltage. The test signal would be a tone recorded at its maximum level. This first section principally applies to tape decks. The diagram below shows the approximate position of the volume control which will drive the amplifier to reach its rated power. Notice that the gain controls are set at 5vrms. The head that only produces 1.5vrms cannot drive the amplifier to rated power. The head unit rated for 9vrms drives the amplifier to its rated power with its volume control at approximately the '10 o'clock' position (which will make it difficult to adjust the volume precisely). This would not be an acceptable gain setting for either head unit. This diagram shows the gain control set to 9vrms. The head unit capable of producing 9vrms would be able to drive the amplifier to its rated power. The 1.5 volt head unit wouldnot be able to drive the amplifier to its rated power. This would be a good setting for the 9vrms unit but would NOT be good for the 1.5vrms unit. This diagram shows the gain control set to 1.5 volts. At this gain position, the 9vrms head unit will drive the amp to rated power at a very low volume control position. The 1.5vrms head unit can drive the amplifier to rated power and would be an acceptable gain position for the 1.5 volt head unit. Note: This demo assumes that the test signal is a sine wave recorded at the highest level possible (0dBfs). It also assumes that all tone controls are set flat and the loudness coutour is switched off. This is essentially how a system should be set up. The head unit should be able to use most of its range before the amplifier is driven into clipping. Again, if the gains are set too low, the head unit won't be able to drive the amplifier to its maximum output level. If the gains are set too high, the amp will be driven into clipping at a very low volume level (on the head unit). Clarification of Terminology: Generally, when someone says that you need to 'turn the gains up', you need to make the amplifier more sensitive. When you make the amplifier more sensitive, it will take less input signal to to produce a given amount of power. The confusion comes in when you look at the gain control markings on the amplifier. If they are marked in volts, it's generally the amount of input voltage that it takes to produce full power. When you turn the gains 'up' you turn the gain control to a 'lower' (smaller) number. For example, the gains are higher at 2 volts than they are at 4 volts. And to show it in another way... At the risk of being redundant, the following diagram shows how the output of the amp relates to the output of the amp at different gain settings. |
This is another gain control calculator. It's fairly self-explanatory. One note... If the tops and bottoms of the amplifier sine waves go out of view, the amp is clipping. The right negative is inverted because the amplifier is bridgeable (as are most amplifiers on the market) and the signal output is on the right negative. The bridging terminals for many amplifiers are the left positive and right negative. |
No comments:
Post a Comment