Potentiometer volume vs. db reading

[Shadow_Ferret]

OK. Now on my old receiver, I turned the volume knob up to 11 and knew that I had maxed it out. Basically, I knew that at the halfway point it was pretty loud but not in danger of distortion.

In other words, I had a knob that gave visual and solid feedback as to how loud I wanted it without causing damage to anything.

My new one?

What the heck is -10db? Or 0db? or 10Db?

What is the comfortable halfway point? At what db level am I going to cause damage to either the unit or the speakers?f

What was wrong with a potentiometer everyone understood how to use?

I have a feeling Spinal Tap wouldn't be anywhere near as funny if he'd said, "the amp goes to 25db."

 

[MDS]

The numbers are a scale between minimum and maximum and despite looking odd with negative numbers are the same as using all positive numbers from 0 to whatever. The negative number system is known as 'relative' volume display whereas the all positive number system is known as 'absolute' volume display.

If you calibrate the receiver so that 0 dB on the volume display results in a specific SPL then when the display reads -10 dB the SPL is 10 dB below that calibrated level; if the display reads +5 dB then the SPL is 5 dB above the calibrated level. In other words, the volume number indicates the SPL relative to the calibrated level ('reference level').

The same exact principle applies if the receiver uses the absolute volume display. The difference is simply that it is not as convenient. If the range is from 0 - 100 and you use 80 as the reference level then when the display reads 70 you have to think '80 - 70 = 10' so I'm 10 dB below the reference level.

Onkyo is the only receiver brand I know of that allows you to choose absolute or relative on some models (you can switch back and forth at any time) and the manual actually tells you that 0 on the relative scale is the same as 82 on the absolute scale.

 

[Shadow_Ferret]

I'm very old school electronics. I'm not sure I understood that.

Let me see if I can explain myself better.

On the old potentiometer knob, if the amp goes to say 80 wpc, and you crank it all the way until it won't turn any longer, theoretically, that is 80wpc. Granted you don't want to run it that way because you'll blow something up.

So at the halfway point, we can assume we're running 40 wpc. 3/4 is 60wpc.

See where I'm going with that? How do I make that determination using db, especially since the new knobs have no stopping point? Theoretically you could spin that thing forever.

I assume at some point (I just got the receiver over the weekend) now I'll have to buy an SPL meter, but that still doesn't explain when I'll know I'm at the receiver's clipping point.

 

[MDS]

The half way point is half of the range. If the scale is -80 to +20 there are 100 steps and the half way point is -30.

I wouldn't be too hung up on the half way point. The receiver won't be anywhere near clipping at half way and probably won't clip at 0 dB either. If the receiver is calibrated to Dolby Reference Level, 0 dB is pretty unbearably loud.

 

[Haoleb]

The reading on the volume knob is for the most part irrelevant to the amplifiers power and the point at which distortion starts and things can be damaged (including your hearing) While the db level reading may be more usefull for Home theater enthusiasts with OCD I really wouldnt give it much thought in the big picture. Just turn things up until they are as loud or as quiet as you want them

With seperates you can have a preamp that will overdrive an amplifier with its volume halfway up or you can turn it up to max and still not be close to maximum amplifier power. Single box components are in essence the same way. Although I would certainly hope that the preamp and power amp stages are matched for one another that doesnt mean they all are.

 

[Midcow2]

dB is a logrithmic measurement

OK. Now on my old receiver, I turned the volume knob up to 11 and knew that I had maxed it out. Basically, I knew that at the halfway point it was pretty loud but not in danger of distortion.

In other words, I had a knob that gave visual and solid feedback as to how loud I wanted it without causing damage to anything.

My new one?

What the heck is -10db? Or 0db? or 10Db?

What is the comfortable halfway point? At what db level am I going to cause damage to either the unit or the speakers?f

What was wrong with a potentiometer everyone understood how to use?

I have a feeling Spinal Tap wouldn't be anywhere near as funny if he'd said, "the amp goes to 25db."

The actual setting doesn't mean as much the difference between settings. newer power scales are in a logrithmic dB scale which corresponds closer to speaker SPL (Sound Pressurelevel) increase also in dB. dB s an abbreviation for "decibel". One decibel is one tenth of a Bel, named for Alexander Graham Bell. The measurement quoted in dB describes the ratio (10 log power difference, 20 log voltage difference, etc.) between the quantity of two levels, the level being measured and a reference. To describe an absolute value, the reference point must be known.

Sound Pressure Level

The definition of dB SPL is the 20 log of the ratio between the measured sound pressure level and the reference point. This reference point is defined as 0.000002 Newtons per square meter, the threshold of hearing. However, the threshold of hearing (and sensitivity to level) changes by frequency and for soft and loud sounds, as discovered by Fletcher and Munson in 1933.

Sounds dB SPL
Rocket Launching 180
Jet Engine 140
Thunderclap, Air Raid Siren 1 Meter 130
Jet takeoff (200 ft) 120
Rock Concert, Discotheque 110
Firecrackers, Subway Train 100
Heavy Truck (15 Meter), City Traffic 90
Alarm Clock (1 Meter), Hair Dryer 80
Noisy Restaurant, Business Office 70
Air Conditioning Unit, Conversational Speech 60
Light Traffic (50 Meter), Average Home 50
Living Room, Quiet Office 40
Library, Soft Whisper (5 Meter) 30
Broadcasting Studio, Rustling Leaves 20
Hearing Threshold 0

An increase of 3dB is actual a doubling in power/sound.

 

[Shadow_Ferret]

I knew what db stood for and I knew what a decibel was. I didn't know it was named for Alexander Graham Bell though.

Thanks everyone for the responses.

And yes, maybe I do have a bit of OCD when it comes to wanting to know what the maximum db number my receiver puts out before it blows.

And no, I'm not going to experiment to find out.

 

[Haoleb]

And yes, maybe I do have a bit of OCD when it comes to wanting to know what the maximum db number my receiver puts out before it blows.

And no, I'm not going to experiment to find out.

Not so much that but people who set the volume according to what the display says and according to their SPL readings vs simply what just sounds right to them. That is, If those two things are different. I dont know for sure but im Pretttyy positive they exist...

 

[Shadow_Ferret]

Well, I do just set it for how it sounds. And that's often louder than my wife would like.

I was just curious if there was a maximum db each receiver can go to before it blows. I'm assuming though, that that number is different between manufacturers and maybe even models.

Whereas with the old volume knob, you knew you were at full volume when you couldn't turn the knob any further.

 

[Midcow2]

Newers AVrs have protection.

Well, I do just set it for how it sounds. And that's often louder than my wife would like.

I think that is just their nature

I was just curious if there was a maximum db each receiver can go to before it blows. I'm assuming though, that that number is different between manufacturers and maybe even models.

Whereas with the old volume knob, you knew you were at full volume when you couldn't turn the knob any further.

Receivers and speakers and everything else have come a long way. The olderones were as was indicated earlier basically a potentiameter or a rheostat; in simple terms a variable resistor. Most speakers were stereo only; 2.0 systems and were full range at 8 ohms. So at full clockwise, you go the maximum out of the system and albeit it was typically 30 or so RMS.

Newer systems have much more advanced circuitry and speakers are more dynamic and it depend on how many speakers you hook up in how many room and the load of each speaker and how the combine load affects the power. Speakers can also be 8 ohms, 6 ohms, 4 ohms and some even as low as 2 ohms. The power out put is higher typically 80-150 RMS into 7 channels on an AVR and even higher with dedicated power amps. There has also been a significant improvement in protection cicuitry; very few AVRs made in the last 5 or so years do not have both theram land well as amperage protection cicuitry. While , I wouldn't compeltely rely on it; iit is very difficult to overload a newer AVR. You still need to be careful in wiring speakers , because even a whisker hair short can overlaod a AVR.

 

[MDS]

Whereas with the old volume knob, you knew you were at full volume when you couldn't turn the knob any further.

The volume knob is infinitely variable now but there is still a maximum - the last number on the volume scale.

 

[Shadow_Ferret]

The volume knob is infinitely variable now but there is still a maximum - the last number on the volume scale.

So what you're recommending is I crank it up until the db numbers stop changing and then I'll know the maximum output?

OK, I'll check back in when I'm done.

 

[MDS]

So what you're recommending is I crank it up until the db numbers stop changing and then I'll know the maximum output?

Not exactly. I think your idea of 'max' is the point at which the amp starts clipping. That may or may not be the maximum value on the scale. If you crank it up and it starts to get distorted or smoke comes out of the top, you'll know you went too far.