Preamp tube 'covers'- WHAT? - Jemsite
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post #1 of 9 (permalink) Old 08-01-2008, 04:01 PM Thread Starter
 
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Preamp tube 'covers'- WHAT?

Hi all, I've been looking at different amps and I've noticed that some amps (Peavey Valveking / one preamp tube on the Hughes and Kettner Trilogy has a 'cover' on it.)

The 'covers' I'm talking about are silver in colour and spring loaded type thing- why are they present on some amps and not on others? Please help me this is really confusing me lol!
Thanks
Regards
Jonny
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post #2 of 9 (permalink) Old 08-01-2008, 11:33 PM
 
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Re: Preamp tube 'covers'- WHAT?

Probably there to shield the tube from stray RF or EMI interference.
albee1952 is offline  
post #3 of 9 (permalink) Old 08-02-2008, 06:43 AM Thread Starter
 
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Re: Preamp tube 'covers'- WHAT?

Right- cool stuff! Thanks dude !
Regards
Jonny
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post #4 of 9 (permalink) Old 08-02-2008, 09:23 AM
 
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Re: Preamp tube 'covers'- WHAT?

i think it has more something to do with keeping the tube in its socket than shielding it. The spring in the cover pushes the tube down and holds them in place.
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post #5 of 9 (permalink) Old 08-02-2008, 09:36 AM Thread Starter
 
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Re: Preamp tube 'covers'- WHAT?

Yea, must be that makes perfect sense, but why do some amps have them and others not? Is it the way the tube is connected type thing or just more of an assurance?
Thanks
Regards
Jonny
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post #6 of 9 (permalink) Old 08-03-2008, 07:09 PM
 
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Re: Preamp tube 'covers'- WHAT?

Aren't they used to aid the preamp tubes? I think they are suposed to make the preamp tubes get warmer.
korvus is offline  
post #7 of 9 (permalink) Old 08-03-2008, 07:41 PM
 
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Re: Preamp tube 'covers'- WHAT?

They help prevent tube microphonics.
Lefty Robb is offline  
post #8 of 9 (permalink) Old 08-04-2008, 02:20 AM
 
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Re: Preamp tube 'covers'- WHAT?

some don't have it because some companies either because they are too lazy, or they are cutting costs.
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post #9 of 9 (permalink) Old 08-04-2008, 10:09 AM Thread Starter
 
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Re: Preamp tube 'covers'- WHAT?

Microphonics... I have had a very quiet 'tick' in the my amp (Peavey Valveking) for ages now, it sounds like its doing it every second- what could that be? I'm thinking EMF as another guy suggested that but it seems to be sounding all the time, wouldnt EMF be an intermittant thing? I'm unsure of whether the sound is present when I take the amp to the studio I go to 'coz the ticking is normally fairly quiet but we have the amp quite loud(nearly half way sometimes)
Thanks
Regards
Jonny
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