Re: [RDD] The Great Audio Voltage Debate quick ref chart
On Tuesday 11 December 2012 11:15:41 pm Bill Putney wrote: Various people use various values for 0 dBVU. But zero is such a nice round number ! Truthfully, db being a ratio, is always relative to what ? 0 db can be anything you like, and in most professional gear, is adjustable to much more range than anything in common use. -- Cowboy http://cowboy.cwf1.com CAPRICORN (Dec 23 - Jan 19) You are conservative and afraid of taking risks. You don't do much of anything and are lazy. There has never been a Capricorn of any importance. Capricorns should avoid standing still for too long as they take root and become trees. ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
On Wed, 12 Dec 2012, Cowboy wrote: On Tuesday 11 December 2012 11:15:41 pm Bill Putney wrote: Various people use various values for 0 dBVU. But zero is such a nice round number ! Truthfully, db being a ratio, is always relative to what ? 0 db can be anything you like, and in most professional gear, is adjustable to much more range than anything in common use. Remember, folks, money is power! That's my -17db$, anyway. Rob ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
On Dec 11, 2012, at 23:15 41, Bill Putney wrote: Now we kinda get to voltages. 0dBVU is +4 dBM (1.23V RMS at 600 ohms) in pro systems. 0 dBVU is -10 dBV (.316V RMS). VU is a somewhat different animal, inasmuch as it deals with dynamics (originally defined by Ma Bell in terms of the ballistics of an actual physical meter) as well as absolute level. Cheers! |-| | Frederick F. Gleason, Jr. | Chief Developer | | | Paravel Systems | |-| | A room without books is like a body without a soul.| | -- Cicero | |-| ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
On Tuesday 11 December 2012 08:47:51 pm VE4PER/ Andy wrote: RMS is 0.775 and average is closer to 0.5 so be sure to compare apples to apples and oranges to oranges That one is telephone standard. Actually .7745966692... volts RMS, and that is in 600 ohms, so that is the original zero dbm. The apples to apples thing is SO important in this regard. Most professional audio gear these days has an output impedance that is very low, on the order of 45 ohms, and most pro gear has an input that is greater than 10K ohms, and while there is good reason for that, it also immediately means that our arbitrary db reference needs to be defined. Is it an apple, or is it an orange ? ( the actual output Z of the amps is closer to zero ohms, and the build-out resistors are there to avoid blowing amps ) (( and if you wire it wrong, that output Z can actually go negative !! )) .775V RMS in 600 ohms is exactly the same voltage as .775V RMS in 45 ohms, or 10K ohms, but the power is substantially different, and quite possibly the characteristics of the audio through it. 0db is not the same in 45 ohms as in 10K ohms. Or, is it ? This has little to do with program automation, but can have quite a bit to do with how it sounds. Of course, it's irrelevant when you play MP3's. -- Cowboy http://cowboy.cwf1.com ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
I should have added the caveat that the voltages vs. dBVU numbers are only really true for steady state sine wave single tones. :) Bill On 12/12/12 7:12 AM, Fred Gleason wrote: On Dec 11, 2012, at 23:15 41, Bill Putney wrote: Now we kinda get to voltages. 0dBVU is +4 dBM (1.23V RMS at 600 ohms) in pro systems. 0 dBVU is -10 dBV (.316V RMS). VU is a somewhat different animal, inasmuch as it deals with dynamics (originally defined by Ma Bell in terms of the ballistics of an actual physical meter) as well as absolute level. Cheers! |-| | Frederick F. Gleason, Jr. | Chief Developer | | | Paravel Systems | |-| | A room without books is like a body without a soul.| | -- Cicero | |-| ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
The 0 dBm spec is to make 1 mw into a 600 ohm load. in amplifiers without feedback the amplifiers would only make that level reliably when the source and load impedances matched. Come along the 1960's and integrated circuit amplifiers came into common use and they were almost always operational amplifiers. Early work with the use of solid state operational amplifiers in professional audio being pioneered by Bell Losmandy of OpAmp Labs in Hollywood. Operational amplifiers maintain their output voltage as a function of their input voltage and their feedback network design over a wide range of load impedances. Now it is common practice to spec 0 dBm (or +4) at as a voltage value equivalent to that power level when presented to a 600 ohm load. 0 dB means nothing without a reference point. dB values are logarithmic but the values for different measurements use different log functions (i.e. voltage referenced values are log20 and power referenced values are log10). 0dBFS is always a constant in any digital audio system. It's the highest level that the system can produce. It's the only thing you can count on and that makes it important. It's probably the only value anyone needs to talk about until bits are converted to the analog domain. At our station we don't do that til the audio gets inside a DSP at the transmitter so we don't worry much about all the transformations. The only place it's represented for anyone to look at is at the console VU meters and they are set to read 0 dBm when a constant level single tone sine wave is present at -20 dBFS on the program bus. Bill On 12/12/12 7:16 AM, Cowboy wrote: On Tuesday 11 December 2012 08:47:51 pm VE4PER/ Andy wrote: RMS is 0.775 and average is closer to 0.5 so be sure to compare apples to apples and oranges to oranges That one is telephone standard. Actually .7745966692... volts RMS, and that is in 600 ohms, so that is the original zero dbm. The apples to apples thing is SO important in this regard. Most professional audio gear these days has an output impedance that is very low, on the order of 45 ohms, and most pro gear has an input that is greater than 10K ohms, and while there is good reason for that, it also immediately means that our arbitrary db reference needs to be defined. Is it an apple, or is it an orange ? ( the actual output Z of the amps is closer to zero ohms, and the build-out resistors are there to avoid blowing amps ) (( and if you wire it wrong, that output Z can actually go negative !! )) .775V RMS in 600 ohms is exactly the same voltage as .775V RMS in 45 ohms, or 10K ohms, but the power is substantially different, and quite possibly the characteristics of the audio through it. 0db is not the same in 45 ohms as in 10K ohms. Or, is it ? This has little to do with program automation, but can have quite a bit to do with how it sounds. Of course, it's irrelevant when you play MP3's. ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
On Wed, 12 Dec 2012, Jay Ashworth wrote: Lots of non-pro gear interfaces with a 0 VU of, as you note, -10 dBV, which is, as you imply, *not* 14 dB lower, because the baselines are different - one is a power measurement which depends on the impedance; the other a voiltage measurement which does not. My understanding is that dB is always a measure of power ratio. 10 dB down means 1/10 the power. I think what's confusing is the use of dB to measure differences in voltage level. It's not meaningful unless the impedance is the same. For example, 1 volt RMS across 100 ohms is the same level as 1 volt across 1,000 ohms, but the ratio between the two cases is 10 dB. But bridge a high-impedance mixer input across either, and the meters will read the same (or close to the same; the addition of the input impedance in parallel with each resistor will change the ratio slightly). Maybe it's time we actually start calling a volt a volt. Rob ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
Nope, there are many cases were the relationships between voltages are expressed in dB (the consumer line level -10 dBV being just one) dB ratios for voltages are Log20 though. Bill On Dec 12, 2012, at 12:19, Rob Landry 41001...@interpring.com wrote: On Wed, 12 Dec 2012, Jay Ashworth wrote: Lots of non-pro gear interfaces with a 0 VU of, as you note, -10 dBV, which is, as you imply, *not* 14 dB lower, because the baselines are different - one is a power measurement which depends on the impedance; the other a voiltage measurement which does not. My understanding is that dB is always a measure of power ratio. 10 dB down means 1/10 the power. I think what's confusing is the use of dB to measure differences in voltage level. It's not meaningful unless the impedance is the same. For example, 1 volt RMS across 100 ohms is the same level as 1 volt across 1,000 ohms, but the ratio between the two cases is 10 dB. But bridge a high-impedance mixer input across either, and the meters will read the same (or close to the same; the addition of the input impedance in parallel with each resistor will change the ratio slightly). Maybe it's time we actually start calling a volt a volt. Rob ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
On Wednesday 12 December 2012 03:19:28 pm Rob Landry wrote: My understanding is that dB is always a measure of power ratio. 10 dB down means 1/10 the power. NOT true ! A db is a ratio of magnitudes. Can be voltage, current, power, magnetic field strength, sound, lumens, whatever. Anything that has a magnitude. Could even be water pressure, though I know of no one who's ever used the terms that way. For example, 1 volt RMS across 100 ohms is the same level as 1 volt across 1,000 ohms, but the ratio between the two cases is 10 dB. Again, not the case. The voltage ratio is the voltage ratio, in this case 0 db. The power ratio in this case is 10 db. Maybe it's time we actually start calling a volt a volt. And in too many cases, I wish we would !! Using terms not fully understood by the people involved leads to misunderstandings, and truths that are not. Too many assume that db means the same as voltage, when it's no such thing. -- Cowboy http://cowboy.cwf1.com ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
On Wed, 12 Dec 2012, Cowboy wrote: NOT true ! A db is a ratio of magnitudes. Can be voltage, current, power, magnetic field strength, sound, lumens, whatever. Anything that has a magnitude. Could even be water pressure, though I know of no one who's ever used the terms that way. If the decibel were merely a measurement of the ratio of generic magnitudes, then why should 10 dB not reflect the same ratio in volts as in watts? My understanding is that the decibel was defined as a measurement of power ratio, and the only meaningful use of it for a voltage ratio derives from comparing the corresponding powers. Otherwise, if the Boston Red Sox beat the New York Yankees 23 to 2, then how many dB down are the hapless New Yorkers? Rob ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
On Wed, 2012-12-12 at 09:09 -0800, Bill Putney wrote: The 0 dBm spec is to make 1 mw into a 600 ohm load. absolutely in amplifiers without feedback the amplifiers would only make that level reliably when the source and load impedances matched. Strongly disagree! Any number of pre solid-state amplifiers produced enough output to show 0dbm: Our standard GP amp [2 x ecc83 / 12aux7] delivered better than +10dbm at less than 0.1 % thd. Yes they had negative feedback, and bias correction as the tube aged. They ran for years without failure. If they started to sag they were picked up on the monthly checks. Source and load impedances need to be matched to get maximum transfer of energy. If you terminate a 600 ohm line at either one or both ends with some other impedance you introduce losses. So amps were built with 600 ohm output transformers, and plugged into lines which may be local studio lines, or telco lines and terminated by equipment that presented 600 ohms to the line. This gives maximum energy transfer. The critical issue was noise. The 0dbm level was the transmission level for phone lines, and the gear the telco used to relay over long distance ran at this level. Because of the clever stuff that jammed 50 calls on one carrier, and split our 10k audio over 3 circuits that 0dbm level had no margin. The noise floor was about -40 on a good day. The telco local lines had margin, you could feed them at +20 to get over line losses to the tx. Crosstalk was then the issue. Feeding them at 15 ohms made the line equalisation at the far end a lot easier. It also attenuated the crosstalk. It is true that modern equipment has all manner of impedance input and output, and this does cause level issues. These go un noticed because there is usually enough gain hanging around to solve the problem and noise is not such an issue. However impedance mismatch often produces a change in frequency response because input/output impedances are not always purely resistive. Try explaining that to someone who has spent rather a large amount of money on a sound installation in which the components don't match up, and the supplier/installer has no idea about the math of ohms law. All that stuff which the old guys drilled into us hasn't changed, and it's frustrating to see that people in the industry somehow believe it has. Sorry to grump but the mythology of audio transmission creates huge problems which I often get called to fix! Robert Jeffares Big Valley Radio Thames The Wireless Station Hawkes Bay ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
On Wednesday 12 December 2012 05:20:27 pm Robert wrote: All that stuff which the old guys drilled into us hasn't changed, and it's frustrating to see that people in the industry somehow believe it has. Who you callin' old ? You wanna step outside, and I'll show you who's old ! mumble mumble my glasses mumble mumble my cane mumble mumble :) :) :) -- Cowboy http://cowboy.cwf1.com ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
Who you callin' old ? You wanna step outside, and I'll show you who's old ! mumble mumble my glasses mumble mumble my cane mumble mumble :) :) :) __Ha Ha!! Listening to all this has my radio school 1st Phone study tests flashing though my mind! In addition to theory, we had our own five sets of practice tests. Most of it stayed with me, but my path led elsewhere in terms of practice, so thanks for the refresher course! Steve _ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
[RDD] The Great Audio Voltage Debate quick ref chart
Noticed lengthy discussions on normalization and found this chart that might be of interest http://www.google.ca/url?sa=trct=jq=0%20dbmsource=webcd=4sqi=2ved=0CD4QFjADurl=http%3A%2F%2Fwww.tecmag.com%2Fpdf%2Fdbm_v.pdfei=fN_HUK2TGIaE2gXlxoCgAQusg=AFQjCNEY25QxasGndqL5ZAXkYDCgFaB4KQcad=rja also this explanation I found useful http://en.wikipedia.org/wiki/DBm Audacity shows a scale with 1.0 as a max usually but that is PEAK only and is actually 2.0 VAC Peak to Peak RMS is 0.775 and average is closer to 0.5 so be sure to compare apples to apples and oranges to oranges I have a portable oscillator for aligning my mixer board and all other audio sections including the PC's but only have a standard digital multimeter and or a standard analog mutimeter neither of which are calibrated to read in db, dbv or dbm unlike a lot of pro audio test sets are so these relationships help to be able to use the basic meters to calibrate my systems; but one has to be very aware of the relationships and not to confuse, peak, peak-to-peak, average and RMS values in order to maintain a maximum peak range between -8 dbm and -12 dbm and still retain a further 4 db of additional headroom for protection. ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
1.0 in Audacity is 0 dBFS. This has nothing to do with voltage. It has only a tenuous relationship to 0 dBVU. Various people use various values for 0 dBVU. Usually it's -18 (EBU recommendation) or -20 (AES recommendation) down from 0 dBFS. Now we kinda get to voltages. 0dBVU is +4 dBM (1.23V RMS at 600 ohms) in pro systems. 0 dBVU is -10 dBV (.316V RMS). Bill On Dec 11, 2012, at 17:47, VE4PER/ Andy ve4...@aim.com wrote: Noticed lengthy discussions on normalization and found this chart that might be of interest http://www.google.ca/url?sa=trct=jq=0%20dbmsource=webcd=4sqi=2ved=0CD4QFjADurl=http%3A%2F%2Fwww.tecmag.com%2Fpdf%2Fdbm_v.pdfei=fN_HUK2TGIaE2gXlxoCgAQusg=AFQjCNEY25QxasGndqL5ZAXkYDCgFaB4KQcad=rja also this explanation I found useful http://en.wikipedia.org/wiki/DBm Audacity shows a scale with 1.0 as a max usually but that is PEAK only and is actually 2.0 VAC Peak to Peak RMS is 0.775 and average is closer to 0.5 so be sure to compare apples to apples and oranges to oranges I have a portable oscillator for aligning my mixer board and all other audio sections including the PC's but only have a standard digital multimeter and or a standard analog mutimeter neither of which are calibrated to read in db, dbv or dbm unlike a lot of pro audio test sets are so these relationships help to be able to use the basic meters to calibrate my systems; but one has to be very aware of the relationships and not to confuse, peak, peak-to-peak, average and RMS values in order to maintain a maximum peak range between -8 dbm and -12 dbm and still retain a further 4 db of additional headroom for protection. ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
Re: [RDD] The Great Audio Voltage Debate quick ref chart
http://www.sengpielaudio.com/calculator-db-volt.htm On 12/12/12 04:15, Bill Putney wrote: 1.0 in Audacity is 0 dBFS. This has nothing to do with voltage. It has only a tenuous relationship to 0 dBVU. Various people use various values for 0 dBVU. Usually it's -18 (EBU recommendation) or -20 (AES recommendation) down from 0 dBFS. Now we kinda get to voltages. 0dBVU is +4 dBM (1.23V RMS at 600 ohms) in pro systems. 0 dBVU is -10 dBV (.316V RMS). Bill On Dec 11, 2012, at 17:47, VE4PER/ Andy ve4...@aim.com wrote: Noticed lengthy discussions on normalization and found this chart that might be of interest http://www.google.ca/url?sa=trct=jq=0%20dbmsource=webcd=4sqi=2ved=0CD4QFjADurl=http%3A%2F%2Fwww.tecmag.com%2Fpdf%2Fdbm_v.pdfei=fN_HUK2TGIaE2gXlxoCgAQusg=AFQjCNEY25QxasGndqL5ZAXkYDCgFaB4KQcad=rja also this explanation I found useful http://en.wikipedia.org/wiki/DBm Audacity shows a scale with 1.0 as a max usually but that is PEAK only and is actually 2.0 VAC Peak to Peak RMS is 0.775 and average is closer to 0.5 so be sure to compare apples to apples and oranges to oranges I have a portable oscillator for aligning my mixer board and all other audio sections including the PC's but only have a standard digital multimeter and or a standard analog mutimeter neither of which are calibrated to read in db, dbv or dbm unlike a lot of pro audio test sets are so these relationships help to be able to use the basic meters to calibrate my systems; but one has to be very aware of the relationships and not to confuse, peak, peak-to-peak, average and RMS values in order to maintain a maximum peak range between -8 dbm and -12 dbm and still retain a further 4 db of additional headroom for protection. ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev ___ Rivendell-dev mailing list Rivendell-dev@lists.rivendellaudio.org http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
