why are avr vol. controls different?

leftwinger57

I think I posed this question my 1st year here and never got a definitive answer. My questions centers around avr volume controls and how they work in a backwards type of way. Someone said it's a logarithmic formula which means nothing to me 1. because I failed at math and 2. that's like saying Google is a search engine but does not say how it works. My Yamaha RX-V665 before mute goes to -80 then down the minus scale to get louder and eventually the plus db side and eventually I clipped the thing 'when I aired it out' and went into protecto mode and thankfully came back. So why can't they just have a volume control like from the 50's that goes from right to left from 0-to 10 ?

mhardy6647

1. Do you understand the concept of decibels? The decibel is a unit (actually, the "Bel" is the unit -- a decibel is a tenth of a Bel, see below) that is actually dimensionless -- the dB exists only as a ratio of two quantities -- the dB must always be referenced to something. That reference point depends on the quantity we're measuring -- and it is why you'll sometimes see things like "dBA" (A-weighted SPL), "dBf" (on tuner specifications, related to 1 femtowatt of signal power), etc. The reference point is kind of arbitrary (we just have to agree on what it is!), but it's important and it defines the "0 dB" level in any "application".

2. Volume controls are attenuators (well, at least passive volume controls are -- on a preamp,the volume control also has attenuation, but the preamp's gain may be such that the zero dB reference point may not be at the 'maximum' setting of the volume control pot).

3. Traditionally/historically, no attenuation (volume control "maxed out") could be thought of as 0 dB of signal attenuation. the attenuation is calibrated in dB; it is negative to indicate attenuation. For example on a power amplifier, if you think of 0 dB as its full output level (say, 100 watts), -3 dB is equivalent to 50 watts output; -10 dB is equivalent to 10 watts output; -20 dB, 1 watt, etc. Relative to this hypothetical power amp, a level of +3 dB would equate to 200 watts output... which our amp simply cannot "do"... unless it has "headroom" of 3 dB, in which case it could (perhaps!) put out the required 200 watts of power for some short period of time (say, perhaps, 100 milliseconds).

4. The logarithmic "taper" of a volume control is important, but it's also unimportant :- ) There's nothing magical about logarithms (even though there can seem to be!)... it's just a way of collapsing a broad range of numbers into a smaller, more manageable range. Our hearing is incredibly sensitive and it has an amazing dynamic range (about 14 orders of magnitude; or a range of 100,000,000,000,000-fold from the softest sound to the loudest). It's inconvenient to use numbers that big, so we compress the scale logarithmically, and express the result as Bels (for sound pressure levels, e.g.). The Bel is inconveniently large, so we just multiply the numbers by 10 and call 'em decibels. The reference point for SPL is essentially the limit of hearing. From there, the SPL numbers go up to about 140 dB (pain, damage, danger... like a jet engine up close and personal). Practically speaking, the logarithmic ('audio') taper of a volume control "pot" is convenient to smoothly distribute its range from soft to loud as one turns the knob -- a linear taper pot would make very little difference across much of its travel, and compress a lot of change into a small "arc" or "throw" of the knob -- which would be hard to use.

5. On an AVR, the 0 dB reference point is...well, whatever it is (I don't "do" AVRs, so I don't know, but the videophile types will!). The point on the volume control that corresponds to that level is calibrated as 0 dB -- levels above that are positive (boosted, relative to the 0 dB reference point); levels below it are negative (attenuated, relative to the reference point). If the signal level fed to the power amplifier section of the AVR is too high, it will start to clip (go nonlinear), with more or less aggravating audible consequences.

To answer (?!?) your question, The AVR volume controls could have used a linear scale, but it wouldn't be "portable" -- it would be unique to the receiver and its controls. Using the calibrated dB reference gives everyone a standardized platform to compare apples to apples for quantitative assessment of signal levels, power output, voltages, SPL, etc.

Does this help at all? :- )
(I hope so)

leftwinger57

Doc Hardy, This was /is the most concise answer that I could possibly wrap my head around. I will reread this about 6x to fully understand it but for such a moron like me I would have thought it had to do more w/ splitting of the power signal in an avr because of the 5.1,7.1 and so factors. I'm actually astonished there's that much involved w/ this and yet avrs still basically suck when you push them to hard.Your actually lucky" you don't do avrs" because I would think you would just throw it out the window. Yes it helps way better than 1 or 2 word answers I got the 1st time around. I need a few Advils after reading this but thank you for going this deep for me....Lew

tonyb

Lew,
Does it matter anyway ? 1-10....0-100....nobody really cares anyway because the best volume dial is your ears. That is if you know what to listen for.

There's just too many variables to determine each individual "safe zone" on the volume dial. It's all system dependent. Instead, you should be listening for when the sound starts to sound congested at higher volumes....when the soundstage starts to collapse. That's the sign to back off the volume dial, but sometimes even then it's too late.

Most avr's have a 0 reference point dividing the + side and the - side. As a general rule of thumb, stay a good 10 points below that 0. So -10 should be the loudest you push that puppy without paying real close attention. The plus side....your asking for trouble.

"Airing out" .....is what kids used to do to see how loud it will go and if it will hurt their ears. Which is also why a kids room is full of blown speakers.

voltz

Lew it makes sense if your DK now me, everything went straight over my head....think maybe that is why I don't have much hair on the top of my head!

Easy Runnin

I’m no expert but I think when you calibrate an AVR (or at least my AVR) the 0dBreference level is when pink noise produces 75 dB of sound pressure at the calculated listening position. I think pink noise is the frequencies between 500Hz and 2000Hz.
My receiver also has a volume display option for relative display (-81dB to +18dB) or absolute display (1 to 99).

BlueFox

They don't mean anything. That is just the current fad now to display the volume. My Onkyo SC5509 has the option to switch volume displays between the -xx to +yy, or 0-100.

The actual volume will be entirely dependent on the speakers used, and the size of the room. Not the volume control. 0db with one set of speakers will be different with another set of speakers.

tonyb

Like I said....system dependent. Mhardy gave a fairly good explanation, but unfortunately one that very few newbies will understand.

Ya know, Google is a tool....use it for more than searching useless information. Learn how to LISTEN to your system/music rather than just trying to see if you can vibrate that picture off the shelf across the room. Once you learn how to listen, volume knobs and their variety are of little concern.

The reason I stress this point is because so many don't listen....continue to bury the volume dial to supposedly "air out" a new piece. Like getting a new Corvette for the first time and then flooring it to see what it can do....without having any feel for the car. That's usually why some youngsters wrap those cars around a tree too. Too many are still under the assumption that the whole volume dial should be of use.

Listening is something you need to learn how to do, but once learned you'll never be likely to blow up a speaker again or send your gear into protect mode.

mhardy6647

^ to which the only benediction that may be added is...

http://youtu.be/N3L4EZwmRrA

Most of my critical listening is done at 80-85 dB (A weighted) SPL at my chair (based on the good old, it is what it is, analog R/S SPL meter)

zingo

A true negative-zero-positive volume scale should have the negative as signal attenuation and positive as signal amplification in the preamp section, but that is rarely case. As stated above, it's just a popular way to show volume, and probably means as much as turning your amp up to 11.

Easy Runnin wrote: »

I think pink noise is the frequencies between 500Hz and 2000Hz.

Nope: Pink noise is a signal or process with a frequency spectrum such that the power spectral density (energy or power per Hz) is inversely proportional to the frequency of the signal. In pink noise, each octave (halving/doubling in frequency) carries an equal amount of noise power.

This is why pink noise sounds softer than white noise.

ken brydson

Polk has been known to go to "11"...

mhardy6647

zingo wrote: »

A true negative-zero-positive volume scale should have the negative as signal attenuation and positive as signal amplification in the preamp section, but that is rarely case. As stated above, it's just a popular way to show volume, and probably means as much as turning your amp up to 11...

Well, yes and no (and... not really to prolong the discussion... I think we scared leftwinger57 off quite a few posts ago!).

In terms of attenuation, yes, of course, that's correct.

But... dB scales aren't arbitrary (at least, they shouldn't be -- when "properly used"). A scale calibrated in dB is always referenced to something -- the reference point doesn't have to be zero attenuation -- I think that's the deal with the AV preamps. Now, SPL would be impossible to standardize for all the reasons enumerated in previous posts. But, a reference voltage (or power level) could be "durable" (i.e., reproducible by a third party "in the field").

For example, the time honored 0 dB reference level of "line level" signals. This dates back to the days of using telephone lines for remote feeds for radio programming. The definition of line level 0 dB (i.e., the reference point) is delivery of 100 mW (millwatts, i.e., 0.1 watt) of power into a 600 ohm load (due to the "milliwatt" reference, this age-old audio standard is known as "dBm"). Even this morphed over the years into a reference of 0.776 V (AC, I'm guessing RMS voltage, but I don't know!) independent of load impedance (source: https://fmsystems-inc.com/index.cfm?tdc=dsp&page=publication_detail&pid=94. But, still, a reference point ( "0 dBm") it is.

It could be perfectly sensible to calibrate the volume control pot on a preamp to the 0.776V reference point. If the preamp could deliver more (say, e.g., 6 VAC at full gain, unattenuated), the top of the volume control scale would then be calibrated as "+ 9 dBm" (6 V is 8.88 dBm "more" than 0.776 V).

but...

"That and a dime'll getcha a cuppa coffee" :- P

tonyb

mhardy6647 wrote: »

"That and a dime'll getcha a cuppa coffee" :- P

Amen bro......lol

zingo

To add the the above point:

The concept of 0 dB and its negative and positive values migrated from the professional broadcasting and recording environment to consumer audio gear. In the old days, Bell Labs and the broadcast networks came up with the concept of “0 VU” (which stands for Volume Units) to standardize electrical audio signal levels between interconnected radio and TV stations sending programming across the country over telephone lines to affiliate stations. The “0 VU” setting was standardized as a certain voltage into a particular impedance, and in a sense it reflected the perceived loudness of the incoming source signal (not quite the same as “0 dB,” but close enough for illustration). The use of the VU meter in broadcasting and recording was to ensure a strong enough audio signal that was well above any noise, yet prevent a too-loud signal that might distort or overload any recording equipment or the input circuits of the control consoles in the other radio stations. So long as the station engineers kept the incoming signal levels at or below the “0 VU” indication, they were likely to broadcast or record a nice clean undistorted signal. In analog tape recording, the 0 VU setting was viewed as the level beyond which the recorded signal might distort or overload the magnetic tape. In fact, 0 VU is 8 dB below a level of 3% harmonic distortion. With recorded peaks hitting 0 VU or slightly below, distortion was kept below 1%, which is generally inaudible with music or programming sources.

mhardy6647

The ballistics of a VU meter (analog) are different than a peak-reading meter -- the VU meter is an averaging meter.

leftwinger57

Mark, scared off no, befuddled, confused, over thy head for sure. As usual Tony's no tech approach in it's simplest form is just to listen for that quality of life sound and not to clip your machine in the process. Lesson here don't over think everything. I got way more responses this time around that tried to explain the avr volume control idiosyncrasies w/ varying degrees of comprehension on my part. My brain is like a sponge, the wrung out part.... lol lol lol

mhardy6647

Well -- I like the both/and.

In my day job I was/am an analytical scientist. I live/eat/sleep/breathe quantitative and qualitative data. I love data and meta-analysis (and even... heaven help me... statistics. It has its place).

But I generally get all right-brained when it comes to hifi. I like what I like, and, as you say, I don't like to over-think it, either. In fact, I like surprises -- like the one I had about 12 years ago concerning high-sensitivity loudspeakers and low-powered amplification.

That said, (and speaking only for myself), it adds some appreciation of the hobby to me to have some understanding of the basic technical underpinnings... that fits in with the scientist piece; I like to understand stuff, not just use it. I have some pretty strong opinions on that topic... but they're pretty much irrelevant to this discussion ;- )

One comment I will make (and then duck and cover!)... I think that the better one understands some basic physics and electronics, the harder it is to be hornswaggled into buying into hyped "technology" that is expensive but fundamentally not grounded in good scientific/engineering principles. I won't mention any examples, as we all have our own shibboleths* ;- )

That said, if you get the urge to 'study' the fundamentals, and you don't mind being challenged a little, but you don't want to be over-challenged, I cannot think of a better introduction to hifi than the three-volume set by Norman Crowhurst called Basic Audio. You can download all three volumes free, thanks to Pete Millett, at his wonderful resource of 'tube books online': http://www.tubebooks.org/technical_books_online.htm#Audio (hi-fi, amplifiers, speakers...)

Now... these books are old, but the concepts (and most of the execution) are timeless. Everything that "we" need to know about hifi reproduction had been worked out, mostly by Western Electric, RCA, and Magnavox researchers, by the mid-1930s! Personally, I find the electronic side of the hobby far easier to understand in the vacuum tube domain -- just because the circuitry is far simpler. Modern solid state circuitry isn't fundamentally any different, though -- Ohm's Law still applies.

Glad you stuck it out! Yeah, don't play it too loud and life'll be grand.

* shibboleth - "a custom, principle, or belief distinguishing a particular class or group of people, especially a long-standing one regarded as outmoded or no longer important."

ken brydson

Dang dude, had to dust off the dictionary to make it through that post...

mhardy6647

My work is done here ;- )

(hey, I even defined "shibboleth"...)

EDIT: besides... real hifi glows in the dark. Everybody knows that! ;- )

meshplate2A3 by mhardy6647, on Flickr