Pre-amp Tube Covers / Shields

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odgeuk
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Re: Pre-amp Tube Covers / Shields

Postby odgeuk » Mon Feb 14, 2011 9:23 am

From Tommer and Scootercaster's posts, it seems that the previous owner would have actually desoldered the original tube sockets to achieve this effects, as the sockets themselves have to have fitment to receive the tube guard bayonet fitting.

So, either this is a manufacturing 'variation' of the JSX where Peavey switched from sockets with tube sheilds to board mounted sockets (odd, given as it's the same year as two other JSX's I've seen with the guards).

OR.... the previous owner swapped out the actual tube sockets :!:

OR.......there is a Tube Guard from Peavey which simply screws into those two holes in the chassis and is grounded via the screwholes?

I've emailed Peavey-EU for more info.

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Re: Pre-amp Tube Covers / Shields

Postby Doug H » Mon Feb 14, 2011 10:55 am

I wouldn't worry about it, in all honesty. Those shields are generally intended for use with tubes operated at RF, not audio. I don't even know why they put them on guitar amps. I have never heard any difference in noise with/without tube shields in a guitar amp.

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Re: Pre-amp Tube Covers / Shields

Postby Nibbles » Tue Feb 15, 2011 2:34 pm

It's a little know secret that if you remove the tube shields the amp will sound better as it allows the tubes to "breathe". :lol: :lol:

Just like when you take the mufflers and catalytic converters off a car. It increases performance. Cars and guitar amps are the same thing. :lol: :lol:

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tommer
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Re: Pre-amp Tube Covers / Shields

Postby tommer » Tue Feb 15, 2011 6:23 pm

Nibbles wrote:It's a little know secret that if you remove the tube shields the amp will sound better as it allows the tubes to "breathe". :lol: :lol:

Just like when you take the mufflers and catalytic converters off a car. It increases performance. Cars and guitar amps are the same thing. :lol: :lol:


I declare.... misinformation :lol:
Epiphone LUCILLE stereo guitar, with TWO PEAVEY BANDIT 112 SHEFFIELD TransTube silver stripe amps. :mrgreen:
160 WATTS of BB King, homebrewed !

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Re: Pre-amp Tube Covers / Shields

Postby scootercaster » Tue Feb 15, 2011 9:40 pm

In most cases, tube shields are not there to "shield" in any electrical sense.

They are intended to hold the tube still and keep microphonics in check.
They don't always work, but more often than not they do.

They are also a good idea for protection if the area around the tubes is too easily accessed by foreign objects.

As to whether they make any real difference in sound, I personally don't feel they do. BUT - if YOU can hear the difference, then that is all that matters. It won't hurt anything either way.

Play on and use your ears! 8)
Therefore, all progress depends on the unreasonable man.
-George Bernard Shaw

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tommer
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Re: Pre-amp Tube Covers / Shields

Postby tommer » Wed Feb 16, 2011 8:42 am

scootercaster wrote:In most cases, tube shields are not there to "shield" in any electrical sense.

They are intended to hold the tube still and keep microphonics in check.
They don't always work, but more often than not they do.

They are also a good idea for protection if the area around the tubes is too easily accessed by foreign objects.

As to whether they make any real difference in sound, I personally don't feel they do. BUT - if YOU can hear the difference, then that is all that matters. It won't hurt anything either way.

Play on and use your ears! 8)


False, not so in old tube radios. They DO shield stray
electrical emissions in/at the RF frequencies.
8)
Epiphone LUCILLE stereo guitar, with TWO PEAVEY BANDIT 112 SHEFFIELD TransTube silver stripe amps. :mrgreen:
160 WATTS of BB King, homebrewed !

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Re: Pre-amp Tube Covers / Shields

Postby Fourtythree » Wed Feb 16, 2011 1:41 pm

Thats the same set up that the VK has. The tube guards mounted to the chassis using the two empty holes to the left and right of the socket. They are not physically attached to the sockets in any way. Peavey parts dept to the rescue.
VK212-head conversion, Heyboer OT, Weber choke, bias pot, bias test jacks, JCM/Mesa mods, pcb mods

odgeuk
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Re: Pre-amp Tube Covers / Shields

Postby odgeuk » Thu Feb 17, 2011 2:08 am

Called Peavey parts who struggled to find the Tube Shields on the inventory and promised me a call back (2 days ago). They didn't have any idea about whether there had been any sort of manufacturing variation only that, from my picture, "it looks like it should have them".

Getting some major squealing when guitar is close to the head on the Ultra channel, (and I swapped all the pre-amp tubes to eliminate dodgy tubes) so I wonder if this might be reduced by sheilds, either that or the JJ EL34's have had it.

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Re: Pre-amp Tube Covers / Shields

Postby odgeuk » Thu Feb 17, 2011 4:46 am

tommer wrote:obviously i am wasting my time here...

here we go with tube sockets again....

once didn't work, what makes you thing twice will ?
:lol:


I missed TedZomplin's post and I think he's got it spot on. I don't believe I need special sockets at all, look at this pic from a XXX:

Image

Looks to me like it's a two part piece even though the socket is board mounted. I guess the screw holes ground the shield when installed somehow.

So, it's not twice, it's three times now Tommer :lol: third time lucky?

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tommer
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Re: Pre-amp Tube Covers / Shields

Postby tommer » Thu Feb 17, 2011 9:53 am

Image

I believe on the right two tubes, the large ones...
the metal RING around the outside of the tube
socket that is mounted by two screws on the chassis
is in fact a older style of tube shield clip.

I was wrong! These are tube clips... to securely hold
larger tube bases to the chassis. See below entry from
Mr. Tedzomplin.
My memory recalls those big based tubes now too.
I believe the old 1930s 'Rogers Majestic' made in Canada radio
console I had... had those clips on the chassis.
:shock:

The left large tube has a white tube or something
coming out the side of an adapter socket... a socket
that is plugged into a socket... don't know what
that nonsense is about... probably just a money-maker,
to sell to a tube nut.
Sorta like the spark enhancers they used to sell
at the county fair in the fall, so you could get
better gas mileage on your car or tractor...
you plugged it in series with the vehicle's
spark coil... hahah.... it didn't work, but it
sure looked scientific as hek !
Maybe the white tube is a gas-vent for the
leaky tube? Hahaha.. only $49.95 S/H !

When you find a nut job, you make emotional-accessories to sell him!
:lol:
Last edited by tommer on Thu Feb 17, 2011 2:02 pm, edited 3 times in total.
Epiphone LUCILLE stereo guitar, with TWO PEAVEY BANDIT 112 SHEFFIELD TransTube silver stripe amps. :mrgreen:
160 WATTS of BB King, homebrewed !

Fourtythree
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Re: Pre-amp Tube Covers / Shields

Postby Fourtythree » Thu Feb 17, 2011 10:11 am

The power tube on the right is plugged into a bias probe.

The 12AX7 shield is grounded because it screws into the chassis. Once again, the shields have nothing to do with the sockets. The shield isn't going to stop your amp from squealing when you hold the guitar in front of it though.
VK212-head conversion, Heyboer OT, Weber choke, bias pot, bias test jacks, JCM/Mesa mods, pcb mods

odgeuk
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Re: Pre-amp Tube Covers / Shields

Postby odgeuk » Thu Feb 17, 2011 11:33 am

Mystery solved. Thanks all.

Just waiting for Peavey parts to get back to me. Not that I really think I need them, but hey.

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tommer
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Re: Pre-amp Tube Covers / Shields

Postby tommer » Thu Feb 17, 2011 12:41 pm

But hey !
Glad you're happy
:mrgreen:
Epiphone LUCILLE stereo guitar, with TWO PEAVEY BANDIT 112 SHEFFIELD TransTube silver stripe amps. :mrgreen:
160 WATTS of BB King, homebrewed !

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Re: Pre-amp Tube Covers / Shields

Postby Tedzomplin » Thu Feb 17, 2011 1:44 pm

In the pic what we see at the bottom of the power tubes is called a bear claw power tube retainer.It merely clamps or bites the base of the larger power tubes just to hold them down.Its got nothing to do with sheilding.On the other hand, for the pre-amp tubes,the previous owner probably discarded those tube sheild bases because they make it hard to grasp the small portion of the 12ax7 preamp tubes when changing them.Two little screws and they come off....but I would have put them back on.Nothing serious without them but,if it were my amp I'd want them back in there.These are modern tube guitar amps not old radios.Slightly different things going on.No insults intended.

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tommer
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Re: Pre-amp Tube Covers / Shields

Postby tommer » Thu Feb 17, 2011 2:53 pm

Well TZ, i corrected my 2nd entry above since
you jogged my memory a bit...
:lol: 8)
Epiphone LUCILLE stereo guitar, with TWO PEAVEY BANDIT 112 SHEFFIELD TransTube silver stripe amps. :mrgreen:
160 WATTS of BB King, homebrewed !


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