Foreplay I/II Alternate Tubes

[Caucasian Blackplate]

       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	0.001253	581	81,403	0.002777	17,938	6.82
5687	0.004283	350	23,816	0.009493	5,451	19.60
5965	0.001149	472	88,774	0.002547	19,380	7.88
7044	0.004182	290	24,388	0.009270	5,505	19.41
12AT7	0.000511	833	199,803	0.001132	43,359	4.76
12AU7	0.000839	1788	121,561	0.001860	27,825	5.39
12AV7	0.001302	478	78,336	0.002886	17,170	8.18
12AX7	0.000107	2376	950,329	0.000238	204,443	3.98
12AY7	0.000308	2069	331,075	0.000683	72,624	4.37
12BH7	0.001404	1101	72,648	0.003112	16,665	10.26
E80CC	0.000750	1259	136,000	0.001662	30,294	9.00
6DJ8	0.003497	221	29,169	0.007751	6,442	11.34
6N1P	0.000860	899	118,631	0.001906	26,200	9.21
6N30P	0.012082	141	8,442	0.026780	1,951	33.71
6SL7	0.000131	2776	777,152	0.000291	168,127	4.03
6SN7	0.000906	1407	112,544	0.002009	25,481	9.31
1626	0.0041	1241	24,800	0.009	6,672	14.3
5751	0.000132	2770	775,000	0.000292	167,700	4.66

[Doc B.]

This would look really cool if someone put the data into a table format. Looks like there are table buttons in the posting form.

[cvandyke]

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

[Air]

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