They also show if everything is working. If they don't turn on than you know something is wrong.
Someone correct me if I'm wrong but I believe the LEDs are used to bias the voltage the tubes receive. In older circuits biasing was done manually and often "wandered" in and out of the correct bias. Thankfully, the LEDs negate the need for manual adjustment as the resistor changes so does the voltage the tube sees.
I don't have much background in circuits just some light reading so this may be totally of base and is more or less my understanding of the matter.
Anyway hope it helps clear things up!
Well they also are diodes so current can only run in one direction. If that helps.
A few tube enthusiasts have opined to me that they found the Ken Rad 6C8G (RPs) to sound fairly similar to the (famed) Ken Rad 6SN7 (RPs). Now, I've haven't had a chance to actually hear the highly regarded 6SN7 version.. but if the sound of the 6F8G variant is any indication, the 6SN7 version must certainly be something special. The 6F8G's bass is definitely punchy and impactful.. w/ the focus being on the sub bass rather than the midbass. The treble has a smooth, balanced (in reference to the midrange) presence and good depth Treble is crisp & complimentary to the addictive bass and deep, engaging midrange. It's certainly in the top two or three favorite tubes I've rolled into the Crack.
May I ask what are the rest of your favorite tubes? I'm using the Raytheon 6SN7 thanks to your recommendation which you posted about a month ago and I love it!
Just be curious if the Raytheon is still in your favorite tube list
Congrats man and enjoy. Once the DIY bug bites it doesn't let go. Don't say I didn't warn you
LOL i still don't have my crack complete yet because of some parts i ordered went missing and are now on backorder. However, I now have a DIY Lightspeed Attenuator and First Watt F5 clone in the works. I'm in parts up to my elbows!
Thanks for your advice!
I believe the original lightspeed cost around $700.
There are several different approaches you can take. It can range from $50 in a cardboard box, to $2k for a fully decked out unit. I spent about $250 on my project and that includes a remote control!
DIY LDR3X board from Tortuga Audio. I got it on promo sale for $195, I can't tell if it's still on promo or not because the site is currently down. All i needed to buy was a suitable power supply, steel enclosure (with enough space for addon board in future), chassis jacks (RCA/PSU), status LED, and some wire.
If you want to go full-blown DIY without remote you can get matched LDRs here. Soon as you go into remote control territory, Tortuga Audio is the better deal because most the work is done for you. If you would like an assembled unit that has a very good price with remote, the EVA 2 is a great choice, but who knows when it will be back in stock.
No prob Adam
My LDR unit has shipped, but I'm waiting on a back order from pcX to be able to complete BOTH my Lightspeed and Crack lol. I'm hoping it ships this week!
EDIT: LDR3X diagram picture below
LDR3X diagram (Click to show)