Calculating Tube Parameters +SPICE - diyAudio
 Calculating Tube Parameters +SPICE
 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 November 2005, 05:07 PM #1 jackinnj   diyAudio Member     Join Date: Apr 2002 Location: Llanddewi Brefi, NJ Calculating Tube Parameters +SPICE When you go into the Radiotron or other handbook, you are given values of gm, rp etc. which are based upon the linear portion of the curve. For transconductance, dI(p)/dV(g), would it not be more appropriate to average all the slopes, including the non-linear portions. I have in my mind something like the "contrast index" for film in which the CI is calculated with a toe and head region -- of course RCA, Sylvania, Tugnsram and Mullard were doing this well before computers which integrate large numbers of values very quickly. Thoughts anyone??? ps -- maybe an exponential would be even more helpful -- and you could use the data to fill in the blanks when using the Koren Spice equations. The reason I ask is that I am finished Visual Basic programming of the form and mechanics for the Tube Tracer and have begun to wonder what data people would consider helpful for their analysis.
 18th November 2005, 05:36 PM #2 rdf   diyAudio Member     Join Date: Jun 2004 Location: big smoke Can't remember where I read it but apparently at one point designers modelled a tube's plate curves as a three-dimensional surface in clay. I'm guessing it was a simple matter of placing a straight edge across the model to find a linear operating region. Would something like this, and perhaps an additonal three-dimensional representation of the slope of this surface (don't know with respect to which variables though) be a valuable tool as well?
jackinnj
diyAudio Member

Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Well, here's what I am thinking of (see attached) -- calculating perhaps 32 slopes and averaging them.
Attached Images
 slopes.gif (22.2 KB, 110 views)

 19th November 2005, 12:23 PM #4 Robert McLean   diyAudio Member   Join Date: May 2005 Location: Stittsville, Ontario, Canada Maybe I do not understand exactly what you are trying to do, but I see no point in deriving an average value for gm or mu or rp. The fact that these parameters vary with the operating point is an important part of the reality of a tube. Using some sort of average value would just be false. The tube manuals are giving a value at a specific point, and state what that point is. They also will give the values at more than one point, and give graphs o gm, mu and rp versus plate current. Variations in gm and mu with bias point is used in radio AVC circuits, and are what set the amplitude of the output of an oscillator. Tubes with just one average value of mu, gm or rp would not work in these types of circuit. There are probably other examples. As for what data would be useful from a Tube Tracer, basically what I would want is the raw data in spread sheet form. In other words the very same data you would collect if doing the job manually : plate current, screen current, and grid current (if applicable) versus plate, screen and grid voltage. I can then import the data into Excel, or Mathcad or whatever, and do whatever math I want with the data, extract SPICE model parameters, graph it, plot load lines, or whatever. Or have you Tube Tracer do the same math on the data itself and output a Spice model with out the user ever seeing the raw data. I personally would want the raw data. __________________ Robert McLean

 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 nhuwar Tubes / Valves 45 25th November 2011 08:47 AM valveitude Tubes / Valves 5 5th July 2005 01:56 AM morfeas Tubes / Valves 4 16th October 2004 05:35 PM mars1 Everything Else 0 10th February 2004 04:28 PM tiroth Tubes / Valves 7 18th August 2002 11:22 PM

 New To Site? Need Help?

All times are GMT. The time now is 06:54 AM.