Red LED substitution questions

[sunrise]

-i am trully sorry - i did not know that this word is that hard.... i looked in the slang dictionary and found what is the correct meaning ....that is what you have when you learn english from the films that our children are looking too
oh well.... i admit i am ashamed and i am sorry.....so lets proceed quickly to the problem that is presented here

[Brian Donaldson]

I'm not bothered; I'm a crass ba$tard. I just think that some peoples wives check up on them to keep them in line...hence the languauge police to help prevent slaps and being forbiden to use the computer.

[sunrise]

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[EC8010]

Given that your circuit is preceded by a volume control, I assume that the signal level is fairly healthy. Changing things in the reference chain of the CCS will only affect noise/hum, but you have enough signal not to need to worry.

If you had a smaller signal you might be worried. The LED is quiet but even if you manage to find the old low brightness LEDs, the internal resistance isn't all that low (5R or so) so you don't get particularly good attenuation of power supply hum from the potential divider formed by the LED's internal resistance and R2. Replacing R2 with a crude CCS (DN2540N5 plus two resistors) can help considerably.

[sunrise]

EC8010 - thanks .... the problem is to use those exotic parts like DN2540N5 and LND150.... i am living at the end of the galaxy (hm, well it is maybe the begginning actually ) so i can't obtain those parts... but i can use normal ccs with BC550/560 - this would also help i think ........

LED diodes that i have are from some not known type and i have tried to pair them so i have 2 pairs (4 pieces) - one that is brighter and the other that is not that bright.... i would like to avoid that problem by putting something better - not to have those LED's - that was the reason for the original question.... oh well - i might try to find something that is bright and red.....in fact i like their look in the preamplifier - everything is glowing all around....tubes LED's yes, yes - that is what i like - but want to boost the quality if possible (using right now 12B4 tube in that configuration).....
i might also use some capacitor to put in paralel with the LEDS - lets say >10uF......??!!


opinions?

[EC8010]

OK, if you have trouble getting parts, then use an MJE340 as a crude CCS in place of R2. There's no need to fuss matching LEDs - and you don't want good ones! You want the cheapest nastiest oldest dimmest red LEDs you can find. The nice bright new ones have a much higher internal resistance...

There's no need to put a capacitor in parallel with the LED. Assume 5R internal resistance and that you want the capacitor's reactance at 100Hz to be equal to the LED's internal resistance. That's 330uF. It's hardly worth the trouble.

[sunrise]

oh yes - thank you......will do that .... thanks again