Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: Jameson on January 04, 2020, 01:08:44 PM

Title: Question about jumpers vs. LED
Post by: Jameson on January 04, 2020, 01:08:44 PM

I just have a general question since I’ve seen this offered as a solution when people have had issues: why is it that it’s ok from time to time to replace the LEDs on the A socket with a jumper? Is there a degradation in sound by doing so?

Title: Re: Question about jumpers vs. LED
Post by: Paul Birkeland on January 04, 2020, 02:13:03 PM

If you have an LED on each cathode, you'll know that both halves of the tube are conducting because both of the LEDs illuminate.  With the jumper in place, you lose this ability.  With the cathodes tied together, there may be less channel separation, but I would expect it to be very slight. 

Title: Re: Question about jumpers vs. LED
Post by: Jameson on January 04, 2020, 02:15:42 PM

Ah ok, so in this specific scenario they’re largely there for a proactive troubleshooting measure? Are LEDs in other spots used to bias the tubes?

Title: Re: Question about jumpers vs. LED
Post by: Paul Birkeland on January 04, 2020, 02:18:18 PM

Quote from: oguinn on January 04, 2020, 02:15:42 PM

Ah ok, so in this specific scenario they’re largely there for a proactive troubleshooting measure?

Well, we want the LEDs in there because they are an excellent biasing device, but individual ones aren't explicitly necessary.

Quote from: oguinn on January 04, 2020, 02:15:42 PM

Are LEDs in other spots used to bias the tubes?

The Smash preamp, Foreplay III preamp, and the Paramount 1.0 built for 2A3s all used the HLMP6000 to provide biasing voltage.  The Seduction/Reduction also uses the HLMP6000 as a tube biasing device. 

Title: Re: Question about jumpers vs. LED
Post by: Jameson on January 04, 2020, 02:34:46 PM

Cool, thanks for the explanation!