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Author Topic: Foreplay I/II Alternate Tubes  (Read 4120 times)

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Offline Paul Birkeland

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Foreplay I/II Alternate Tubes
« on: October 16, 2009, 01:41:37 PM »
       Posted by Paul Joppa on March 20, 2001 at 18:16:12

    This subject comes up periodically, and I promised a week or two ago to post some numbers. (Took a while, I've had the flu.) Below are the circuit changes to duplicate the Foreplay normalized operating points with other tubes.

    Note the last column, which is an estimate of the power transformer volt-amps needed. The stock transformer is probably capable of no more than 7 volt-amps rms; you will notice that very few tubes require that little, so most will need a larger transformer. A good candidate would be the Hammond 369AX, which has universal primaries and 2A filament power.

    In the table, Ib is the plate current in amps, Rk is the cathode resistor in ohms, and RL is the plate load resistor in ohms.

     
       Voltage amplifier   Cathode follower
     
Tube Ib      Rk  RL     Ib        Rk      VA   
5670 0.001253581 81,403  0.002777  17,938  6.82
5687 0.004283350 23,816  0.009493   5,451 19.60
5965 0.001149472 88,774  0.002547  19,380  7.88
7044 0.004182290 24,388  0.009270   5,505 19.41
12AT70.000511833 199,803  0.001132  43,359  4.76
12AU70.0008391788121,561  0.001860  27,825  5.39
12AV70.001302478 78,336  0.002886  17,170  8.18
12AX70.0001072376950,329  0.000238 204,443  3.98
12AY70.0003082069331,075  0.000683  72,624  4.37
12BH70.0014041101 72,648  0.003112  16,665 10.26
E80CC0.0007501259136,000  0.001662  30,294  9.00
6DJ8 0.003497221 29,169  0.007751   6,442 11.34
6N1P 0.000860899 118,631  0.001906  26,200  9.21
6N30P0.012082141   8,442  0.026780   1,951 33.71
6SL7 0.0001312776777,152  0.000291 168,127  4.03
6SN7 0.0009061407112,544  0.002009  25,481  9.31
1626 0.0041  1241 24,800  0.009      6,672 14.3
5751 0.0001322770775,000  0.000292 167,700  4.66
« Last Edit: October 19, 2009, 05:45:56 AM by dbishopbliss »
Paul "PB" Birkeland

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Offline Doc B.

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Re: Foreplay I/II Alternate Tubes
« Reply #1 on: October 16, 2009, 02:42:43 PM »
This would look really cool if someone put the data into a table format. Looks like there are table buttons in the posting form.
Dan "Doc B." Schmalle
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Offline cvandyke

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Re: Foreplay I/II Alternate Tubes
« Reply #2 on: October 24, 2009, 07:11:36 AM »
Attached is a screenshot and an html file of the alternative foreplay tubes table. Alas, the forum software does not support any attributes in the supported HTML tags so those are mostly useless for making a readable table.

--Chris
Chris Van Dyke

Offline Air

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Re: Foreplay I/II Alternate Tubes (Excel)
« Reply #3 on: October 25, 2009, 08:19:59 AM »
Here is the same data in Excel. I saved it in 1997-2003 format so it would be available to more people. Also aligned the decimal points for clarity. Hope this is a useful addition.
Regards, Chuck
Chuck McCalment    Linn TT- Seduction (C4S), EFPIII, Parabees's w/ shunt reg and DC heaters. Nava interconnects, homebrew power and speaker cables,  Homemade three way & S8's w/ ribbons for Christmas.
a Technics RS1500 that needs a little love.