Myles
New member
Maybe some folks here will like this sort of thing. These are some test results that I posted in other places.
JJ803S test results October production run
Below is the latest run from 10/17 of the JJ 803S tube. This is a direct 12AX7 replacement.
This last run was in line with the previous run with perhaps a little more spread (read a little less consistency) in some areas.
The average plate current output was 1.0mA (expected design spec is 1.2mA)
The average transcunductance was 1496 (expected design spec is 1600)
The average actual gain in circuit is 93.5 (expected design spec is 100). This is higher than any current production tube at the moment. Most tubes today are in the 80-85 range.
The test voltages were book spec: 250 plate volts, 2 volt bias. Expected plate resistance was 62.5k and these tubes had an average plate resistance of 62.6K which is as good as it gets. This is a big part of the reason that these tubes have proper gain. Most production tubes today have low plate resistance and this results in lower gain.
The spread on gain ranged from 86.9 to 99.5 which is a 12.6% spread. This is very good for today's production tubes.
The transconductance ranged from 1010 to 1920 which is a 56.9% spread. This is not very good but is typical of today's production tubes. Low TC coupled with low plate resistance will produce low gain and this is why most other production tubes today have lower average gain.
Plate current output ranged from 0.6mA to 1.6mA which is a 83.3% spread. The average was 1.0mA which is acceptable and should work well for driver applications such as reverb drivers, effects loop use and phase inverters. I hope JJ addresses the spread of this plate current to tighten things up a bit in the future.
Overall, this is a great run of tubes and may be some of the best work at the moment in the 12AX7 business. In the end your own ears are the final judge as these tubes do have their own unique tone and response.
Below are some of the individual results. Two lines equal the results of one tube as there are two triodes in each tube. The first number is the plate current output. The second number is the transcondductance. The third number can be ignored as it is one of the pieces of data used for plate resistance. Plate resistance is not to be thought of in the same way as resistance of a resistor. It is a label that involves many factors and is more like impedance of say a speaker than resistance. Plate resistance will change depending on the voltages applied to a tube so it is not a fixed number. The last number is the true gain of the tube in circuit at 250 plate volts and 2 vold bias. Some people use the term mu and this is NOT the same as gain. Mu or mutual conductance or transconductance is a form of voltage gain but there are other factors when it comes to actual gain in a circuit. You can have very low mu/TC but if the plate resistance is high you can have high gain as an example. It is always best if a given tube comes close to design spec in all parameters.
1.1 1630 0.018 90.6
1.3 1920 0.0205 93.7
1.3 1820 0.02 91.0
1.1 1650 0.0175 94.3
1.4 1850 0.02 92.5
1.4 1870 0.0195 95.9
0.9 1420 0.015 94.7
0.7 1310 0.014 93.6
0.9 1440 0.016 90.0
1.1 1700 0.018 94.4
1.0 1370 0.015 91.3
1.3 1840 0.019 96.8
0.6 1120 0.012 93.3
1.1 1640 0.017 96.5
1.0 1500 0.016 93.8
1.2 1730 0.018 96.1
0.7 1130 0.013 86.9
0.8 1310 0.014 93.6
1.6 1890 0.019 99.5
1.3 1650 0.018 91.7
0.8 1270 0.014 90.7
0.6 1010 0.0115 87.8
1.1 1520 0.016 95.0
0.9 1370 0.0145 94.5
1.5 1750 0.0185 94.6
1.0 1430 0.015 95.3
1.6 1860 0.02 93.0
1.2 1730 0.0175 98.9
1.0 1400 0.015 93.3
1.2 1660 0.017 97.6
0.7 1130 0.012 94.2
0.8 1320 0.014 94.3
1.0 1360 0.015 90.7
0.7 1140 0.0125 91.2
1.3 1760 0.0185 95.1
0.9 1410 0.015 94.0
0.9 1480 0.015 98.7
0.6 1090 0.012 90.8
0.6 1070 0.012 89.2
0.8 1300 0.014 92.9
-end-
JJ803S test results October production run
Below is the latest run from 10/17 of the JJ 803S tube. This is a direct 12AX7 replacement.
This last run was in line with the previous run with perhaps a little more spread (read a little less consistency) in some areas.
The average plate current output was 1.0mA (expected design spec is 1.2mA)
The average transcunductance was 1496 (expected design spec is 1600)
The average actual gain in circuit is 93.5 (expected design spec is 100). This is higher than any current production tube at the moment. Most tubes today are in the 80-85 range.
The test voltages were book spec: 250 plate volts, 2 volt bias. Expected plate resistance was 62.5k and these tubes had an average plate resistance of 62.6K which is as good as it gets. This is a big part of the reason that these tubes have proper gain. Most production tubes today have low plate resistance and this results in lower gain.
The spread on gain ranged from 86.9 to 99.5 which is a 12.6% spread. This is very good for today's production tubes.
The transconductance ranged from 1010 to 1920 which is a 56.9% spread. This is not very good but is typical of today's production tubes. Low TC coupled with low plate resistance will produce low gain and this is why most other production tubes today have lower average gain.
Plate current output ranged from 0.6mA to 1.6mA which is a 83.3% spread. The average was 1.0mA which is acceptable and should work well for driver applications such as reverb drivers, effects loop use and phase inverters. I hope JJ addresses the spread of this plate current to tighten things up a bit in the future.
Overall, this is a great run of tubes and may be some of the best work at the moment in the 12AX7 business. In the end your own ears are the final judge as these tubes do have their own unique tone and response.
Below are some of the individual results. Two lines equal the results of one tube as there are two triodes in each tube. The first number is the plate current output. The second number is the transcondductance. The third number can be ignored as it is one of the pieces of data used for plate resistance. Plate resistance is not to be thought of in the same way as resistance of a resistor. It is a label that involves many factors and is more like impedance of say a speaker than resistance. Plate resistance will change depending on the voltages applied to a tube so it is not a fixed number. The last number is the true gain of the tube in circuit at 250 plate volts and 2 vold bias. Some people use the term mu and this is NOT the same as gain. Mu or mutual conductance or transconductance is a form of voltage gain but there are other factors when it comes to actual gain in a circuit. You can have very low mu/TC but if the plate resistance is high you can have high gain as an example. It is always best if a given tube comes close to design spec in all parameters.
1.1 1630 0.018 90.6
1.3 1920 0.0205 93.7
1.3 1820 0.02 91.0
1.1 1650 0.0175 94.3
1.4 1850 0.02 92.5
1.4 1870 0.0195 95.9
0.9 1420 0.015 94.7
0.7 1310 0.014 93.6
0.9 1440 0.016 90.0
1.1 1700 0.018 94.4
1.0 1370 0.015 91.3
1.3 1840 0.019 96.8
0.6 1120 0.012 93.3
1.1 1640 0.017 96.5
1.0 1500 0.016 93.8
1.2 1730 0.018 96.1
0.7 1130 0.013 86.9
0.8 1310 0.014 93.6
1.6 1890 0.019 99.5
1.3 1650 0.018 91.7
0.8 1270 0.014 90.7
0.6 1010 0.0115 87.8
1.1 1520 0.016 95.0
0.9 1370 0.0145 94.5
1.5 1750 0.0185 94.6
1.0 1430 0.015 95.3
1.6 1860 0.02 93.0
1.2 1730 0.0175 98.9
1.0 1400 0.015 93.3
1.2 1660 0.017 97.6
0.7 1130 0.012 94.2
0.8 1320 0.014 94.3
1.0 1360 0.015 90.7
0.7 1140 0.0125 91.2
1.3 1760 0.0185 95.1
0.9 1410 0.015 94.0
0.9 1480 0.015 98.7
0.6 1090 0.012 90.8
0.6 1070 0.012 89.2
0.8 1300 0.014 92.9
-end-
