Extra AVO mk4 test settings
|tube||pin settings||Uh (V)||Ug (V)||Ua (V)||Ia (mA)||gm (mA/V)|
|6B4G Sovtek single-plate||026 040 300||6.3||-36||250||60||5200|
|300B Sovtek **||264 300 000||5.0||-70||350||67||3200|
|300B Sovtek **||264 300 000||5.0||-70||350||52||3700|
|AVVT300B-SL||264 300 000||5.0||-76||400||70||3000|
|M7||642 300 000||4.0||-2||400||3||1600|
|RS241||642 300 000||4.0||-10||400||30||3500|
|S6||642 300 000||4.0||-4||400||34||4400|
|6H30P||741 326 410||6.3||-10||200||20||- - - -|
|6H6P||741 326 410||6.3||-7||200||20||- - - -|
|6S45P||141 321 641||6.3||-2.2||200||25||- - - -|
|6S19P||646 326 461||6.3||-46.5||175||50||3700|
|6S41P||301 640 200||6.3||-74||250||90||4200|
|1626||036 040 210||12.6||-31||250||20||2300|
The values for bias current at a given bias voltage is not always the same. Each tube has
it's own characteristic and will vary slightly at the same bias voltage. To test the tubes
you should always bias the tube at the given bias current (!), not the bias voltage. When
the tube is nearing the end of it's life the current will decrease to levels well below
the nominal values for new types.
** I tested two "matched" tubes but got results that were spread too wide to give an accurate reading for this tube. The tubes were also very unstable in their setting, resulting in a currently jumpy current through the anode. This too affects reliability of the results. In short: not a fun tube to measure. Trying the Sovtek on the standard 400V setting also caused my AVO to go into protection at around 70-80mA. I've tested other tubes at 400V / 100mA so the tester is not the problem, alas... These tubes might sound good, but don't try to run them at the edge of their specs, things might go wrong.
If anyone has other AVO data which they wish to share, I will be glad to place it here....
The specified values are not always the actual working parameters. The AVO has only a limited amount of heater voltages and some tubes will be a little over or a little under the nominal given value for a tube. Example: the RS241 is tested at 4V while the heater should be 3.8V.
The voltage applied to the anode for testing purposes.
The voltage applied to the grid in order to produce a current through the anode of the tube. This is also know as the bias setting.
The current that flows through the anode caused by applying a bias to the grid.
The relation between input voltage and output current of a tube. The values given are nominal values. NOS tubes are mostly higher than this value, but I have seen many that are just below it as well. The gm is the fastest way to see how far a tube is used, or if it is really still new. The gm gradually decreases as it nears the end of it's life. Values below 70% of the nominal gm are taken to be "bad" tubes for audio use although they still may be functional for a long time to come.