Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: GLFSHNT on March 03, 2018, 07:26:44 am

Title: shrink wrapped tube?
Post by: GLFSHNT on March 03, 2018, 07:26:44 am

The 12AX7 preamp tubes on my 65 Lil Elvis amp have a heavy shrink wrap covering them. One of them also has several large O-rings over the shrink wrap. It looks like the intent is to allow the tube to get as hot as possible.  I have not seen this before. Is this a "known thing" to do with preamp tubes?
I replaced the tubes without all the wrap....  Amp sounds good.

Title: Re: shrink wrapped tube?
Post by: sluckey on March 03, 2018, 07:45:02 am

I have never seen shrink wrap (I assume you are talking about heat shrink tubing?) placed on a tube, but I have seen O-rings used to reduce microphonics due to tube vibration. That's probably the intended use in your amp.

Title: Re: shrink wrapped tube?
Post by: GLFSHNT on March 03, 2018, 08:28:54 am

That's possible  one of the 12Ax7s was "bad" microphonic.

I think it was, from the factory with the heat shrink covering.   
I send a note to 65amps but have not received a reply.

Title: Re: shrink wrapped tube?
Post by: SILVERGUN on March 03, 2018, 12:45:16 pm

Mesa Boogie sells these

Title: Re: shrink wrapped tube?
Post by: sluckey on March 03, 2018, 01:22:34 pm

Aw, that's cute. Think I could get some with my name on them?  :icon_biggrin:

Title: Re: shrink wrapped tube?
Post by: shooter on March 03, 2018, 02:28:40 pm

Quote

Aw, that's cute.

:laugh:

is that for modesty or safe tubing :icon_biggrin:

Title: Re: shrink wrapped tube?
Post by: sluckey on March 03, 2018, 02:57:34 pm

yes

Title: Re: shrink wrapped tube?
Post by: PRR on March 03, 2018, 03:05:06 pm

> Think I could get some with my name on them?

https://www.heatshrink.com/content/custom-printing.asp

About $0.80/inch for 12AX7-size tube, min order 25 (inches? reels?)

Title: Re: shrink wrapped tube?
Post by: shooter on March 03, 2018, 05:50:25 pm

Thanks PRR, I now know 1pt = 1/72" !  Not too sure I'll retain that :think1: