Help choosing capacitor value?
 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

 Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

 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
 Thread Tools Search this Thread
 27th April 2006, 06:52 PM #1 sbelyo   diyAudio Member   Join Date: May 2004 Location: East Coast Help choosing capacitor value? I'm gathering the parts for this OTL Headphone Amp: My question is on C1 and C2. The minimum value for C1 is 10uf. How whould I determine the right value to get the best frequency response? My headphones are 48, 55 and 250 Ohms
 27th April 2006, 07:06 PM #2 dsavitsk   diyAudio Member     Join Date: Jan 2005 Location: Hartford You are probably going to want a 470uF cap which is going to be an expensive part as you'll need a pretty high voltage. For how to figure this out, see my article here: http://www.ecp.cc/cap-notes.html
 27th April 2006, 07:41 PM #3 sbelyo   diyAudio Member   Join Date: May 2004 Location: East Coast That article explains a bunch for me. Just so that I can see I'm using the formula right F = 1/(2 * pi * C * R) what is the value obtained if C = 10uf and R = 250 Ohms
 27th April 2006, 07:58 PM #4 fragman56 diyAudio Member   Join Date: Jun 2002 Location: Denver, CO f=63.66 cps about 64 hz
 27th April 2006, 07:58 PM #5 dsavitsk   diyAudio Member     Join Date: Jan 2005 Location: Hartford It's about 64Hz (10uF is .00001F). Really, your caps are probably going to cost more and sound worse than a couple of cheap output transformers. I don't get the OTL thing in general, but I don't think it is particuarly appropriate for headphones, at least not low impedence ones. One option might be to use the small cap, and add an impedence matching transformer -- something with a 10K primary and a 32 ohm secondary -- after the cap. Or, you could put a solid state buffer after the output cap. These tend to have a very high input impedence which would allow you to get away with a little cap -- something like 0.1uF perhaps?
 27th April 2006, 08:03 PM #6 sbelyo   diyAudio Member   Join Date: May 2004 Location: East Coast Thanks a bunch... I'm begining to understand
 27th April 2006, 08:07 PM #7 sbelyo   diyAudio Member   Join Date: May 2004 Location: East Coast pi=3.14 right? I got it now
 27th April 2006, 08:22 PM #8 sbelyo   diyAudio Member   Join Date: May 2004 Location: East Coast Now the real question is how low can I actually hear? I should get my ears cleaned and hearing checked anyway!
 27th April 2006, 10:18 PM #9 cerrem   diyAudio Member     Join Date: Jun 2005 Location: San Diego, CA To calculate the cap size for a given low frequency response.. You need to know two R values... The (2*pi*R*C) is an ideal equation that assumes you have an ideal source, which is never the case... You need to know the equivelent impedance looking back into the amplifer from before the cap...and then ahead of the cap which you already know as you headphones.. I would use the smallest headphone impedance for the calculation, since anything higher is gravy... Keep in mind you typically use a -3dB frequency much lower than 20 Hz, the reason is that in audio you are concerned with phase shifting.... Since the Phase shift at -3dB for a -20db/decade slope is 45 degrees, not really good for audio... Drop the freq then examine the phase shift until it is satisfactory.. I personally design for 6Hz or lower to obtain least phase shifting at 20Hz.. Chris
 27th April 2006, 11:07 PM #10 cerrem   diyAudio Member     Join Date: Jun 2005 Location: San Diego, CA Did some number crunching... The output Z of the circuit is roughly 220 ohms..... Driving a 48 ohm load: You would need a 100uF to get a -3dB at 6Hz.....roughly... Driving 250 ohm load: You would need 57uF to get the same -3dB at 6Hz.... Since they don't sell 57uF, you can parallel caps or use a 68uF that will bring you to -3dB at 5Hz... Using 6Hz as your -3dB point will roughly bring you in to 12 degrees of phase shift.... Chris

 Thread Tools Search this Thread Search this Thread: Advanced Search

 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 alexmoose Tubes / Valves 19 7th September 2014 11:08 PM candi.hansen Multi-Way 2 27th January 2009 11:47 PM mindless_bg Chip Amps 8 4th May 2004 12:22 AM Michael Rothacher Pass Labs 5 25th March 2003 08:06 PM

 New To Site? Need Help?

All times are GMT. The time now is 01:35 AM.

 Home - Contact Us - Advertise - Rules - diyAudio Store - Sponsors - Privacy Statement - Terms of Service - Top - Opt-out policy

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki