hum attenuation
 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

 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
 2nd July 2006, 08:01 PM #1 AndrewT   diyAudio Member   Join Date: Jul 2004 Location: Scottish Borders hum attenuation Hi, if I have a low pass single pole filter feeding a voltage reference, how do I calculate the attenuation of the ripple before the filter, that appears after the filter. Let's suppose we have 2Vpp of 100Hz ripple from the rectifier/smoothing caps. Then 10k feeding a 10uF cap into a zener type (shunt) reference. The RC time constant of the filter is 100mS (-3db@1.6Hz). Do I just add 6db of attenuation for each octave above 1.6Hz until I reach 100Hz i.e. 6octaves =36db of extra attenuation below the -3db starting point? total -39db below the 2Vpp supply. What happens if two RC filter stages are cascaded? say 5k1 in each half each with 10uF of capacitance. This would seem to give -33db + -33db = -66db below the 2Vpp supply, about 1mVpp . Does this make any sense? __________________ regards Andrew T.
 2nd July 2006, 08:59 PM #2 moamps   diyAudio Member   Join Date: Oct 2002 Location: Croatia Hi: Yes, your math is OK. But, you also need to consider DC attenuation on the series resistors. In your example with just 5mA drawing into the current reference, the DC attenuation on the resistors would be 50V! Regards, Milan
 2nd July 2006, 09:05 PM #3 AndrewT   diyAudio Member   Join Date: Jul 2004 Location: Scottish Borders Hi Moamps, I don't know why you chose 5mA and 50V as an example. My rough supply will be 64V and the Vref is 10V. Hey presto 5.3mA to reference and leakage thro' the electrolytics and amplifier base input. Thanks for the confirmation. __________________ regards Andrew T.
moamps
diyAudio Member

Join Date: Oct 2002
Location: Croatia
Quote:
 Originally posted by AndrewT I don't know why you chose 5mA and 50V as an example.
Hi,

I just assumed that the current was 5mA. It follows that serial resistors with the total resistance of 10K would burn 50V. Actually, I wasn't that far off when you think about it.

Regards,
Milan

 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 ailouros6 Digital Source 14 15th October 2008 06:20 PM KOL69 Everything Else 1 24th April 2008 11:10 PM argonrepublic Analog Line Level 5 23rd August 2005 07:22 AM june Parts 2 20th July 2004 04:07 AM Nappylady Multi-Way 3 18th February 2003 12:07 PM

 New To Site? Need Help?

All times are GMT. The time now is 06:34 AM.