Nobelium - tube bass preamp project

I would guess that it would be the Super Bright pink LED SKU: A-4732 from Tayda, whatever LED you use make sure it is Super Bright with very high MCD rating.
You can increase the brightness of the LED by using a lower value dropping resistors R4 and R6, you can lower the resistor as low as 510 ohms and still be within the LED's specs. I think I often use 820 ohms for my LED resistors on my builds.

The resistance will vary with the LED choice also, the pedal can take 12v and the pink LED has a voltage drop of 3.2v so you have 8.8v over the resistor, if you use a 820 ohm resistor you have a current of 10.7mA going through the LED
12v-3.2v= 8.8v, so - 8.8v / 820R = 10.7mA (0.0107 Amps)

If you want to run max current which is 20mA you use 8.2 Volts / 0.020 Amps = 440 ohms.
I would never use less then 510 ohm and I prefer to go to about 10mA to 15mA in my LED's

You can also put reflective tape inside the box to reflect the LED light better of the walls but I would not go that far myself, I got some spare copper tape I use in my guitars to limit interference so I might try it one day though.
 
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Hey All,

I have Good news & Bad News. The Good News is The pink LEDs look excellent! The Bad News is the lights are on but nobody's home...

The LEDs light up, and the tubes get a little warm so I guess the heaters are working? That seems to be the extent of it at this point. No sound whatsoever from the XLR & 1/4" outs. No magic smoke released so that's good too I guess! Everything went fine during assembly right up until I realized that I had a better switch to use for the HPF. I decided to pull the switch that I'd installed which was unwise. Pretty challenging with just de-soldering braid. I eventually got it out but I'm wondering if during that process I may have cut a trace or something... This will at least be a good learning experience on troubleshooting. :) I was careful not to leave any stray solder, trimmed all of my joints, and cleaned up with 99% isoprophyl. I'll get pics of the backside tomorrow. Maybe I need to make an audio probe? If anybody sees anything suspicious or has any tips that'd be really great.

I just checked the voltage in a few spots and the highest voltage I'm seeing is 177v. That's much lower than what Toasty was seeing when he made the Nobelium Kit video. Maybe not enough voltage to fully light up the tubes?

Thanks
Nobelium - Gut Shot 2.jpeg

Nobelium-Gut Shot.jpeg
 
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Thanks Rev! That got me past at least my first rookie mistake! I'm now getting beautiful warm tube goodness through my XLR out. A couple of things are still not right though. Following the troubleshooting steps outlined in:

I

Thread 'No sound from Nobelium'

Hi,
I just finished my Nobelium build (from Musikding in Germany) yesterday. Unfortunately I'm not getting any sound at all. Neither through the di or the amp out.
Both LEDs light up, I can measure ground all the way through, the connection is fine between input jack and in on the PCB. Both tubes heat up as well - no more than they're easy to touch.
The soldering looks quite fine, but does anyone have some indications as to what and where I could measure, as I'd rather try to narrow it down before aimlessly reflowing all the soldering.
Thanks for your help!
PS - i know there's a 12ax7 in...
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Thanks So Much
 
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