News: Not receiving your account activation email? Contact [email protected]
November 30, 2020, 12:12:59 PM

Author Topic: How hot should this preamp get? Also purple dot in center of tube  (Read 1250 times)

0 Members and 1 Guest are viewing this topic.

Offline Sonido

  • Jr. Member
  • **
  • Posts: 31
I finished building one last night and it sounds fine (as in it sounds like it's working properly). I noticed the transformer itself doesn't get as hot as the Crack transformer, but the center tube gets pretty hot. The center tube is suppose to be a cold cathode right? Well it's not very "cold". It's just as hot as the other two tubes. Perhaps it's heat radiated from the other tubes, but I just want to make sure this is working as intended.

One other thing I noticed is there's a bright purple dot that's in the middle of the center tube on the central metal rod when powered on.

Online Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 13893
Re: How hot should this preamp get? Also purple dot in center of tube
« Reply #1 on: July 04, 2014, 10:41:17 AM »
Yes, the Smash doesn't draw nearly as much high voltage or heater current as the Crack, so the transformer will run cooler.

The 0D3 uses a cold cathode, but cold in this case refers simply to not being heated.  The tube still draws current, and dissipates a few watts in the process.

The bright purple dot inside the 0D3 is quite normal.

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Sonido

  • Jr. Member
  • **
  • Posts: 31
Re: How hot should this preamp get? Also purple dot in center of tube
« Reply #2 on: July 04, 2014, 12:12:14 PM »
Also I have noticed some distortions when the volume knob is turned past 12 o'clock (with 6 o'clock being the starting point and 4 o'clock being max volume). It seems noticeable for only some lower frequencies. Is this normal?

Online Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 13893
Re: How hot should this preamp get? Also purple dot in center of tube
« Reply #3 on: July 04, 2014, 01:03:08 PM »
Yes, you can overdrive the input of the Smash, which will be most immediately apparent with low frequency content.

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline porcupunctis

  • Sr. Member
  • ****
  • Posts: 386
  • 0D3
Re: How hot should this preamp get? Also purple dot in center of tube
« Reply #4 on: July 04, 2014, 02:28:02 PM »
I'm a big fan of the purple glow.  It's a mini electron accelerator.   Awesome.  See my profile pic.
Randall Massey
Teacher of Mathematics
Lifetime audio-electronics junkie