Post by myles on Sept 30, 2008 11:49:03 GMT -7
JJ803S Long plate - nice work JJ
This is the test results for the latest run of JJ 803S preamp tubes. These are a direct 12AX7 replacement.
The overall gain on these is high at 92.8 average gain. Other production tubes fall in the 80-85 range other than the JJ ECC83S which currently falls in the 85-90 range. The ECC83S used to be the tube most close to design spec gain but in the last two runs the ECC803S has been at the top of all production tubes; Chinese, Europe, Russia.
The reason for low gain on most tubes is that the plate resistance which should be 62.5K is typically less than 45k in an RCA test fixture. These JJs are right on target.
There are some "fliers" but overall results were very good. The gain tolerance spread was very tight compared to other tube makers at the moment.
In the end your ears will be the judge as these are a long plate tube design which sounds different than the short plate ECC83S, Tung Sol reissue or 12AX7EH as a few examples of a short plate tube.
The plate current output is very nice on these so their use for "current pushers" such as phase inverters could be a consideration.
JJ 803S tests 9/29/08
mA TC (gm) Gain
1.2 1600 100 are design spec
Plate current / TC / plate resistance / gain
1.8 2170 0.0225 96.4
1.1 1490 0.016 93.1
0.6 910 0.011 82.7
0.8 1230 0.014 87.9
1.2 1780 0.0185 96.2
1.2 1880 0.019 98.9
0.9 1320 0.0145 91.0
1.0 1440 0.016 90.0
0.7 1140 0.013 87.7
1.0 1570 0.017 92.4
0.9 1560 0.016 97.5
1.0 1660 0.017 97.6
1.1 1500 0.016 93.8
1.7 1960 0.02 98.0
0.8 1300 0.0145 89.7
0.9 1340 0.015 89.3
0.8 1270 0.0135 94.1
0.6 1160 0.012 96.7
0.6 1000 0.012 83.3
1.0 1550 0.016 96.9
0.6 970 0.011 88.2
0.9 1420 0.016 88.8
1.2 1780 0.0185 96.2
1.0 1540 0.016 96.3
0.6 1120 0.012 93.3
1.0 1570 0.017 92.4
0.8 1290 0.0145 89.0
1.0 1560 0.016 97.5
0.7 1110 0.013 85.4
0.9 1440 0.016 90.0
1.0 1540 0.016 96.3
0.9 1410 0.015 94.0
1.0 1530 0.016 95.6
0.9 1410 0.015 94.0
1.2 1680 0.018 93.3
1.2 1750 0.018 97.2
1.0 1480 0.016 92.5
1.1 1520 0.0165 92.1
0.9 1330 0.0145 91.7
1.4 1980 0.0205 96.6
Averages:
Plate current / TC / gain
1.0 1467 92.84
[81.3% 91.7% 92.8% % of design spec]
Range spread:
High TC 2170 135.6%
Low TC 910 56.9%
QA tolerance TC 78.8%
High mA % 1.8 150.0%
Low mA % 0.6 50.0%
QA tolerance mA 100.0%
High gain 98.9 98.9%
Low gain 82.7 82.7%
QA tolerance gain 16.2%
This is the test results for the latest run of JJ 803S preamp tubes. These are a direct 12AX7 replacement.
The overall gain on these is high at 92.8 average gain. Other production tubes fall in the 80-85 range other than the JJ ECC83S which currently falls in the 85-90 range. The ECC83S used to be the tube most close to design spec gain but in the last two runs the ECC803S has been at the top of all production tubes; Chinese, Europe, Russia.
The reason for low gain on most tubes is that the plate resistance which should be 62.5K is typically less than 45k in an RCA test fixture. These JJs are right on target.
There are some "fliers" but overall results were very good. The gain tolerance spread was very tight compared to other tube makers at the moment.
In the end your ears will be the judge as these are a long plate tube design which sounds different than the short plate ECC83S, Tung Sol reissue or 12AX7EH as a few examples of a short plate tube.
The plate current output is very nice on these so their use for "current pushers" such as phase inverters could be a consideration.
JJ 803S tests 9/29/08
mA TC (gm) Gain
1.2 1600 100 are design spec
Plate current / TC / plate resistance / gain
1.8 2170 0.0225 96.4
1.1 1490 0.016 93.1
0.6 910 0.011 82.7
0.8 1230 0.014 87.9
1.2 1780 0.0185 96.2
1.2 1880 0.019 98.9
0.9 1320 0.0145 91.0
1.0 1440 0.016 90.0
0.7 1140 0.013 87.7
1.0 1570 0.017 92.4
0.9 1560 0.016 97.5
1.0 1660 0.017 97.6
1.1 1500 0.016 93.8
1.7 1960 0.02 98.0
0.8 1300 0.0145 89.7
0.9 1340 0.015 89.3
0.8 1270 0.0135 94.1
0.6 1160 0.012 96.7
0.6 1000 0.012 83.3
1.0 1550 0.016 96.9
0.6 970 0.011 88.2
0.9 1420 0.016 88.8
1.2 1780 0.0185 96.2
1.0 1540 0.016 96.3
0.6 1120 0.012 93.3
1.0 1570 0.017 92.4
0.8 1290 0.0145 89.0
1.0 1560 0.016 97.5
0.7 1110 0.013 85.4
0.9 1440 0.016 90.0
1.0 1540 0.016 96.3
0.9 1410 0.015 94.0
1.0 1530 0.016 95.6
0.9 1410 0.015 94.0
1.2 1680 0.018 93.3
1.2 1750 0.018 97.2
1.0 1480 0.016 92.5
1.1 1520 0.0165 92.1
0.9 1330 0.0145 91.7
1.4 1980 0.0205 96.6
Averages:
Plate current / TC / gain
1.0 1467 92.84
[81.3% 91.7% 92.8% % of design spec]
Range spread:
High TC 2170 135.6%
Low TC 910 56.9%
QA tolerance TC 78.8%
High mA % 1.8 150.0%
Low mA % 0.6 50.0%
QA tolerance mA 100.0%
High gain 98.9 98.9%
Low gain 82.7 82.7%
QA tolerance gain 16.2%