doubling is 3db analog, 6db digital?
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Solid State Talk all about solid state amplification.

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
 24th March 2011, 09:40 PM #1 perfknee   diyAudio Member   Join Date: Dec 2010 doubling is 3db analog, 6db digital? Can anyone give me a simple explanation for why doubling the power leads to a 3dBSPL increase, whereas doubling the number of bits in digital audio leads to a 6dBSNR increase? This is confusing because I thought dBs were a dimensionless scale that should work the same no matter what property was being measured.
 24th March 2011, 10:10 PM #2 perfknee   diyAudio Member   Join Date: Dec 2010 After reading this page: How to Calculate the Signal to Noise Ratio | eHow.com I think I have an idea of how to answer my question. The reason comes down to the different quantities being measured. SPL measures power, but it's the signal level (expressed in Voltage) that doubling bit depth doubles. The relationship between the two is P=V^2/R, or in other words Power is proportional to Voltage squared. That power of 2 is the reason for the 6db digital versus 3db SPL. Another perhaps simpler way of looking at this is to take an example. Lets compare two systems: System A is a 16 bit system with a max voltage of 1 Vrms full scale. System B is a 17 bit system with a max voltage of 2 Vrms full scale. Both systems have the same quantization error noise level because they both represent values up to 1 volt with the first 16 bits, exactly the same. System B doubles the full scale Voltage, and Quadruples the full scale Power (because Power is proportional to 1V squared in System A, and proportional to 2V squared in system B). The effect where a single bit quadruples the power is the reason for the 6db (not 3db) increase per bit in dbSNR for digital. Yet another thing that helped jog my memory on this is the two formulas: dB in power terms = 10 log (P1/P2) -> doubling increases by 3db for Power dB in Voltage terms = 20 log (V1/V2) -> doubling increases by 6db for Voltage
 25th March 2011, 01:33 PM #3 AndrewT   diyAudio Member   Join Date: Jul 2004 Location: Scottish Borders I have no idea why they adopted the term "power" to specify amplifiers and speakers. Voltages and currents would have done better and avoided all the confusion that has resulted from power specifications. I would love to see a speaker specified as being matched up or requiring an amplifier with a 20Vac to 30Vac maximum continuous output. I would love to see amplifiers specified by their output volts into a range of standard load resistances, eg. 2r0, 4r0, 8r0. And it would be nice to see how long each load can be driven. Better than nice. It would differentiate the good from the bad. __________________ regards Andrew T.
 25th March 2011, 01:58 PM #4 geraldfryjr   diyAudio Member   Join Date: Feb 2008 Location: Jackson,michigan I agree with that point. It gets even more confusing when trying explain how to drive some thing like an ESL load. jer
purplepeople
diyAudio Member

Join Date: Mar 2003
Quote:
 Originally Posted by AndrewT It would differentiate the good from the bad.
And that's the problem. Even people buying cheap gear want to believe they are not getting crap. Maybe not top flight, but not crap. Truly useful specs would force too many manufacturers to decide between making good equipment or marketing crap.

The way it stands, the philosophy remains "caveat emptor".

:)ensen.
__________________
Those who claim to be making history are often the same ones repeating it.

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Aussie Amplifiers         CSS         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post freos Multi-Way 122 24th March 2012 04:50 PM rfarn Solid State 0 13th February 2008 04:24 AM Bazukaz Multi-Way 53 17th July 2006 08:30 AM Blue_Max Digital Source 8 2nd December 2004 07:30 PM Ioannis Digital Source 5 11th December 2001 06:52 PM

 New To Site? Need Help?

All times are GMT. The time now is 10:58 AM.