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
 7th January 2013, 01:18 AM #1 SandyG   diyAudio Member     Join Date: Jul 2011 Location: Los Angeles Tube Load Lines and B+ Quick question on what I should use for the B+ on load lines. Do you use the B+ voltage before all series dropping resistors for all stages for calculating load lines? I 'assume' B+ always to mean the main voltage before all the dropping resistors. For example if I have several tubes in a circuit - amp, invert, drive, and each is powered by a series dropping resistor off of the main B+ out of the power supply do I use the Main B+ to calculate the load line voltage or do I work from the voltage at each stages dropping resistor before the plate resistor as the voltage for the load line. Hope this makes sense, I can toss up a simple schematic if that helps. Thanks Sandy
 7th January 2013, 01:47 AM #2 Miles Prower   diyAudio Member     Join Date: May 2005 Location: USA When doing loadlines, use the DC voltage at the far end of the plate resistor for the point along the Ip= 0 axis for the DC loadline. The AC loadline would include the effects of loading by the driven stage, which would be Rp || Rg of the driven stage. The AC loadline intersects the DC loadline at the Q-Point. __________________ There are no foxes in atheistholes www.dolphin-hsl.com
SandyG
diyAudio Member

Join Date: Jul 2011
Location: Los Angeles
Quote:
 Originally Posted by Miles Prower When doing loadlines, use the DC voltage at the far end of the plate resistor for the point along the Ip= 0 axis for the DC loadline. The AC loadline would include the effects of loading by the driven stage, which would be Rp || Rg of the driven stage. The AC loadline intersects the DC loadline at the Q-Point.
Thanks Miles and just to make sure, I use the voltage incoming to the plate resistor of each tube.

Is the process of calculating the dropping resistors (Not plate resistor) work from driver towards input each with their respective current draw to calculate resistors and voltages. (Hope this makes sense).

What I'm really trying to do is understand the process where to start, ie, do I pick my bias points (and thus current draw) on the tubes first then work back from that for B+ voltages...

Thanks

Sandy

 7th January 2013, 10:12 AM #4 DF96   diyAudio Member   Join Date: May 2007 You need to work in both directions and iterate a solution, unless you intend to use a custom mains transformer with exactly the secondary voltage you need. Remember that valves come with something like a 20% tolerance on most parameters so don't worry if something is 5% off from 'perfect'. After getting the basic design right, you may need to remember that at very low frequencies, where the supply rail decoupling caps no longer operate, each stage sees all the resistors from the anode right through to the reservoir cap in the PSU. To avoid subsonic problems, voltage dropper resistors in the supply rails should not be too big when compared with anode load resistors.
 7th January 2013, 05:29 PM #5 SandyG   diyAudio Member     Join Date: Jul 2011 Location: Los Angeles Thanks for the tips, I feel better knowing I have a bit of leeway! I have a lot of baseline values from amps of similar designs but want to actually do the work to make sure that I have the operating points in a good place at the start given my power supply, which is Heyboer 800VAC CT with Dual 5U4's then CLCL. I have run Duncan's PSUII and come up with some starting values for that and will end up just building it and see if it all matches computed values. It has been very close in the 2 other cases that I built and simulated. Then I guess start with common plate resistors values for 6SN7's in amp, invert, drivers and work in circles around those values and try to target my values on the load lines. Sandy

 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 famousmockingbird Tubes / Valves 6 11th November 2011 06:55 PM dsavitsk Tubes / Valves 14 30th August 2010 03:30 PM ChipTube Tubes / Valves 9 23rd August 2010 07:37 AM tvrgeek Tubes / Valves 20 18th January 2010 07:16 PM astouffer Tubes / Valves 0 11th October 2006 03:19 PM

 New To Site? Need Help?

All times are GMT. The time now is 03:10 AM.