I've been experimenting recently... (Uh ohhhhh.....)
I have a 6N30P line amp, common cathode amplifier, 15k plate load resistor, Va = 85V, Ia = 18mA, Vg = 3.6V. Using two series-connected red LEDs in the cathodes to get the grid bias.
I could use less gain. So... What if I change the LEDs to an unbypassed 200 ohm cathode resistor?
- Gain should go down from +25dB to about +20dB.
- 6N30P ra will go up from under 2k ohms to maybe 6k ohms. But I have a 15k plate load (B+ is +400V), so that should be OK with no changes necessary.
I've been reading all sorts of internet posts and articles about unbypassed cathode resistor. The conventional wisdom seems to be that it will lower distortion, possibly change distortion spectra to less 2nd HD, relatively more 3rd HD. Some say it's a bad thing to do, others think it's a good thing to get rid of the bypass cap.
I'm going to try it and see what happens, but I was wondering if there are theoretical disadvantages to reducing gain this way. Or is it the kind of thing where it's a good idea in some situations, not so good in others?
I have a 6N30P line amp, common cathode amplifier, 15k plate load resistor, Va = 85V, Ia = 18mA, Vg = 3.6V. Using two series-connected red LEDs in the cathodes to get the grid bias.
I could use less gain. So... What if I change the LEDs to an unbypassed 200 ohm cathode resistor?
- Gain should go down from +25dB to about +20dB.
- 6N30P ra will go up from under 2k ohms to maybe 6k ohms. But I have a 15k plate load (B+ is +400V), so that should be OK with no changes necessary.
I've been reading all sorts of internet posts and articles about unbypassed cathode resistor. The conventional wisdom seems to be that it will lower distortion, possibly change distortion spectra to less 2nd HD, relatively more 3rd HD. Some say it's a bad thing to do, others think it's a good thing to get rid of the bypass cap.
I'm going to try it and see what happens, but I was wondering if there are theoretical disadvantages to reducing gain this way. Or is it the kind of thing where it's a good idea in some situations, not so good in others?