as of now with the 4v on the cathode, i like the sound allot better, just that i wanted to see if i have room to tweak it, ive read that these 6n6p like to be run hotter.
I only use led's in my amplifer gain stages, cathode follower stages, phase inverter stages, and biasing for power tubes.... Been doing it I believe before it really started to catch on...I have saved many threads written by others who used to flame me for doing it.....
I agree completely, ANY semiconductor in a tube circuit/PSU will kill the sound. I tried semiconductors in the PSU, cathode, anode etc. Don't do it. I know there are some "gurus" out there telling us "no, no, you will not hear any semiconductor nastiness with my CCS" oh please...
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Cool it guys, note that the next person who attempts to circumvent the auto-censor will get points. Keep the posts respectful in tone or this thread has breathed its last.
I've been using LED bias with good results, but was wondering if NFB could be added there as it is with resistors. Apparently it can be, reading posts 62 & 63.
So if one wanted to add NFB at the cathode as shown in Fig. 1 (classic), it can be done as shown in Fig. 2, right? Just use a low value resistor below the LED.
(Yes, I left out a few parts)
So if one wanted to add NFB at the cathode as shown in Fig. 1 (classic), it can be done as shown in Fig. 2, right? Just use a low value resistor below the LED.
(Yes, I left out a few parts)
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Is one of the parts you left out a capacitor ? just wondering if without a bypass capacitor you are now going to have a.c. across the diode. And we know what that means...
That means almost nothing, look at curves for LED on working cathode currents. If still worries, provide some additional current through resistor from B+.
No cap needed on the LED. I did leave out the bias cap on the Pentode.
In my app I'm pulling about 6mA thru a red LED (1.75V)
In my app I'm pulling about 6mA thru a red LED (1.75V)
Yes, you do get AC thru a forward biased diode..
No bypass cap required...
-very respectfully;
-gary
I thought (for 3 seconds) "Do I want a bypass cap on the resistor below the LED?"
Duh, no! Who knows why? 🙂
Duh, no! Who knows why? 🙂
Has anyone ever set up a concertina / split load phase inverter with LED bias?
With a 300v B+ I'm planning to use a 6CG7 with 22k at anode. Grid has 470k coming off it that joins the bottom of a string of 3 red LED's under the cathode, followed by the second 22k to ground. The 2 signal feeds to the output tubes comes from anode and from below the 3 LED's respectively.
Any of the LED users see a reason as to why this won't work?
With a 300v B+ I'm planning to use a 6CG7 with 22k at anode. Grid has 470k coming off it that joins the bottom of a string of 3 red LED's under the cathode, followed by the second 22k to ground. The 2 signal feeds to the output tubes comes from anode and from below the 3 LED's respectively.
Any of the LED users see a reason as to why this won't work?
One of these days I need to quit building speakers and finish my RLD. It is a modified Meng P61, which is no longer a P61 anyway. I keep meaning to build some really efficient speakers but my brief adventures with full range drivers sent me back to traditional inefficient multi-way speakers totally unsuitable for a 7 W amp.
Hi Guys,
I have what is very likely a dumb/newb question, can you parallel a resistor + LED(s) instead of a resistor + cap in the cathode (since AC can pass through the LED)?
Doug
I have what is very likely a dumb/newb question, can you parallel a resistor + LED(s) instead of a resistor + cap in the cathode (since AC can pass through the LED)?
Doug
Well, as I said, it's a naive question, but I have just been wondering if one could reasonably use LEDs when the cathode sits at a pretty high voltage, i.e. 70v for a 300b.
Doug
Doug
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