06-09-2021, 02:31 PM
Hi.
I've now started to compare the difference with the higher voltage Rod Pentodes. Today I substituted the output valve firstly with a 1J18B then I replaced it with a 1J24B. I had to separate the G2s obviously as the voltages would be wrong for both valves. Using either of the two the optimum value was 47k with a 100n decoupler. There was virtually no detectable difference between the 1J18B & 1J24B. In all honesty the increase of audio level was not that much but the plus is less distortion, no doubt the good output volume from using the 1J42A was due to positive feedback by strapping the G2s.
I'm at present running the 1J24B with 54v HT, dropping by 9v the output loss is marginal. Output valve current is exactly 1ma driving headphones.
I've now started to compare the difference with the higher voltage Rod Pentodes. Today I substituted the output valve firstly with a 1J18B then I replaced it with a 1J24B. I had to separate the G2s obviously as the voltages would be wrong for both valves. Using either of the two the optimum value was 47k with a 100n decoupler. There was virtually no detectable difference between the 1J18B & 1J24B. In all honesty the increase of audio level was not that much but the plus is less distortion, no doubt the good output volume from using the 1J42A was due to positive feedback by strapping the G2s.
I'm at present running the 1J24B with 54v HT, dropping by 9v the output loss is marginal. Output valve current is exactly 1ma driving headphones.
