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
 18th December 2016, 03:02 PM #1 merlin el mago   diyAudio Member     Join Date: Sep 2009 Location: Catalonia - Europe Union Understanding load lines For example I want to understand the load line for 5687 tube, I have 209V as B+ and 10K as load anode resistor. To know the plate current is to divide 209V : 10.000 ohms = 0.0209 A = 20,9mA. Now I draw a line between these points to get the load line, If I choose the operating point at -3V as grid voltage the tube will draw 12mA, right? If I want each tube draws 10mA the grid voltage have to be -4.5V? The best OP is -7V as grid voltage? How to know the best plate current for each tube? Last edited by merlin el mago; 18th December 2016 at 03:05 PM.
merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe Union
Attached simulator pic
Attached Images
 load line 209V 25mA.png (183.9 KB, 487 views)

 18th December 2016, 03:13 PM #3 merlin el mago   diyAudio Member     Join Date: Sep 2009 Location: Catalonia - Europe Union Simulator says 14.2mA in place of 12mA?
merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe Union
Attached Images
 5687 load line 209V -B+ -3V grid 001.jpg (766.3 KB, 479 views)

Last edited by merlin el mago; 18th December 2016 at 03:19 PM.

 18th December 2016, 03:33 PM #5 audiofan   diyAudio Member   Join Date: May 2003 Location: quebec This graph give the operating point ( static point ) but you must keep in mind that when you will have some AC signal you must keep some margin on both side of the operation point ... otherwise with AC signal the tube will go to saturation ( reach maximum current ) or cutoff ( have zero current )
 18th December 2016, 03:56 PM #6 merlin el mago   diyAudio Member     Join Date: Sep 2009 Location: Catalonia - Europe Union Yes, two AC volts more or less at grid right?
Palustris
diyAudio Member

Join Date: Aug 2006
Location: Cape Cod
I am not certain I understand the question, but I can offer a little help with load lines. First you need to determine the voltage output that you expect which generally is a function of how much voltage you need to drive the next stage to saturation. Next you need to determine from the load lines the most linear region e.g., the load lines that are equally spaced. When the load lines start to bunch up is where you will get 2nd harmonic distortion.

You can see below that I have overlaid a 10k ohm load line in parallel with yours. Note the difference. You have a max output of 40V peak or 28.28 VRMS; my load line has a max output of 80V peak or 56.56 VRMS. The difference, then is that my load line can drive the next grid with twice the voltage.
Attached Images
 img140a.jpg (792.5 KB, 469 views)

 18th December 2016, 04:48 PM #8 merlin el mago   diyAudio Member     Join Date: Sep 2009 Location: Catalonia - Europe Union That's a very good advice: "most linear region e.g., the load lines that are equally spaced"
merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe Union
Quote:
 Originally Posted by Palustris I am not certain I understand the question, but I can offer a little help with load lines. First you need to determine the voltage output that you expect which generally is a function of how much voltage you need to drive the next stage to saturation. Next you need to determine from the load lines the most linear region e.g., the load lines that are equally spaced. When the load lines start to bunch up is where you will get 2nd harmonic distortion. You can see below that I have overlaid a 10k ohm load line in parallel with yours. Note the difference. You have a max output of 40V peak or 28.28 VRMS; my load line has a max output of 80V peak or 56.56 VRMS. The difference, then is that my load line can drive the next grid with twice the voltage.
145V x 0.015A = 2.175W so is OK because the max dissipation both plates operating is 7.5W : 2 = 3.75W each triode, are ok my calculations right?

mA is only related to to make sure that I'm not violating the maximum dissipation allowed in the tube?

merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe Union
The question is: I'm trying to know how many mA draws each tube (to make a CCS) with B+ 233V 10K anode load resistor so max plate current 23.3mA and -3V at grid, my calculations give me 14mA, I do it right?

Attached Images
 WP_20161218_003[1].jpg (568.7 KB, 414 views)

Last edited by merlin el mago; 18th December 2016 at 06:13 PM.

 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     Room Acoustics & Mods     Music     diyAudio.com Articles     Car Audio     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         Holton Precision Audio         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 lazzer408 Tubes / Valves 46 3rd November 2013 01:43 AM famousmockingbird Tubes / Valves 6 11th November 2011 05:55 PM tvrgeek Tubes / Valves 20 18th January 2010 06:16 PM astouffer Tubes / Valves 0 11th October 2006 02:19 PM

 New To Site? Need Help?

All times are GMT. The time now is 10:44 AM.