Receiver db Volume Question

[JamezHill]

On a receiver when you turn up the volume it says "-30db" or whatever. What exactly is it -30db from? The loudest it can go? I have no idea with this but always wondered.

[poneal]

0db is usually the rated ouput of the receiver/amp. Many companies such as Harman Kardon provide additional power beyond the rated output (usually in the range of 10db or so to handle those brief loud movie passages). If your receiver/amp is rated at 55watts then at 0db, theoritically (did I spell that right?), it should be outputting 55watts. This is where it becomes interesting because some receivers/amps sound really bad at 0db and start clipping or sound really harsh. Quality receivers/amps output clean power at their rated output. I have had my receiver at 0db (only briefly to test) and it was loud and clean. Put it this way, I had to put my ear next to my wifes mouth to understand what she was saying and all this from a 55watt receiver. If it helps, I usually watch DVD movies/concerts (DTS rules) at -20db which is approximately 75db at my listening position.

[Pat D]

0db is usually the rated ouput of the receiver/amp. Many companies such as Harman Kardon provide additional power beyond the rated output (usually in the range of 10db or so to handle those brief loud movie passages). If your receiver/amp is rated at 55watts then at 0db, theoritically (did I spell that right?), it should be outputting 55watts. This is where it becomes interesting because some receivers/amps sound really bad at 0db and start clipping or sound really harsh. Quality receivers/amps output clean power at their rated output. I have had my receiver at 0db (only briefly to test) and it was loud and clean. Put it this way, I had to put my ear next to my wifes mouth to understand what she was saying and all this from a 55watt receiver. If it helps, I usually watch DVD movies/concerts (DTS rules) at -20db which is approximately 75db at my listening position.
It depends on the input level, too. As well, volume controls have different characteristics. Speaker sensitivies are also different, and there are other factors, too. Music and sound track signals generally are constantly changing. So you can't make any valid predictions about the amplifier section's output levels from the position of the volume control. I mean, with no signal input, you can turn up the volume all the way and get very little output, just a little hiss and hum.:)

[jackz4000]

When your amp volume is at 0 db you should be at the maximium rated output. For example, I have an older receiver rated at 100 rms per channel, which I use for music and it has both A and B speakers. If I play some classical music as background it will generally be at -68 db or so. As you increase the volume up the scale the music will become increasingly louder. Sometimes I will listen to music, especially rock at a very high volume. Maybe -18 db. The most I have ever pushed it to was -12 and that was just deafening and probably in the db spl range of damaging ones hearing. Hope this helps.

[depressed]

Just as others said. Simplified, it indicates "how much juice is left".
I listen at aprox. -45 dB level, it gets too loud for me under -40 dB. Medium sized room.
I guess Alexander Graham Bell was deaf, otherwise he would have used a slighlty smaller unit to specify the "loudness" ;)

[skeptic]

This question comes up periodically.

Assuming that the markings are calibrated and not just a decoration, if they mean anything, here's what they usually mean;

The receiver has a rated sensitivity and a rated output into a specific load. Usually 8 ohms is used because that is the nominal rating of most loudspeakers. This rating is given by the manufacturer.

If the receiver is rated at 50 watts per channel into 8 ohms with both channels driven for a 100 millivolt input in the aux or high level inputs then when the gain control is set for 0db, the input is exactly 100 millivolts and the load is exactly 8 ohms, that's how many watts will be delivered from each channel power amplifier stage to the load. All of the other markings are referenced to that so that +3db wold equal 100 watts, -3db would equal 25 watts etc. If the load is different or the input level is different then you get a different output. It doesn't have any relevance to how much noise there will be, how harsh it will sound or other characteristics of the sound, or what will happen if you continue to push the amplifier harder. That depends on the particulars of the circuit design and construction and of course the load.

It is interesting to note that the calibraton of the volume control and of any meters is actually a voltage calibration, not a power calibration. This means that the measured reference is the output voltage necessary to deliver the rated output into the specified 8 ohm load. That is what you are actually looking at. The formula is given by the equation wattage = Voltage squared divided by resistance. For a 50 watt output into 8 ohms, the voltage would be square root of 400 or 20 volts. You can easily see this from the fact that if you have meters, they will continue to swing back and forth even when the speakers are not connected and the amplfiers aren't delivering any power at all.

[kexodusc]

Oh, man, PLEASE bring back those glorious meters on amps/receivers....or at least a crappy digital guage or indicator on the OSD..that alone would end so many myths and half truths about power requirements, sound quality, etc, etc...

Who still has them? I've seen some MacIntosh amps with them still, anyone else?

[paul_pci]

Oh, man, PLEASE bring back those glorious meters on amps/receivers....or at least a crappy digital guage or indicator on the OSD..that alone would end so many myths and half truths about power requirements, sound quality, etc, etc...

Who still has them? I've seen some MacIntosh amps with them still, anyone else?


My friend had an old Technics receiver that had those old school gauge, but to be honest I didn't pay attention to whether it was merely decorative or not, but she did tell me that current Technics receivers still have such gauges.