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BEST OFFER FOR: Vintage (1950 - 60's) spring loaded metal tube heat (cooler) shields

Item #649341024
Info: Vintage (1950 - 60's) spring loaded metal tube heat (cooler) shields

Asking Price:
CAD $1.00
Payment method: Cash, Money Order, Money Wire, Interac/EMT
Condition: 8 - Very good (?)
Date Posted: Sep 12, 17 8:39am (PST)
Edited: Sep 12, 17 10:00am
About Seller: David Dov
David Dov is a premium user
North York,Toronto, ON
Canada
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Up for sale are very good condition used vintage spring loaded metal tube heat (cooler) shields
They are the cylinder type for smaller power 7 and 9 pin tubes used in vintage tube amps,pre amps & tuners
Good for: 6AU6/ 6BE6 / 6BA6 / 12AX7/12AU7/12AT7 6299/6DJ8 + most other smaller sized working tubes
Cooler shields are: $1.00 each/or best offer for all!

Tube shields are those little metal cylinders you find over the small tubes in your amplifier.
They're used to reduce the chance of picking up hum and noise.
Sometimes they're also used to hold the tubes securely into the tube sockets.

With smaller 7 - 9 pin tubes, you usually see a combination of tube socket and shield or retainer.
Probably the most common in guitar amps is the spring loaded metal shield that twist-locks to the base.
This acts as a retainer to keep the tube seated and a protective shield for the glass bulb.

It’s supposed to provide both mechanical protection and radio frequency (RF) shielding.
These tube shields will provide mechanical protection and hold the tubes in place.
The problem is that some tubes made today come very close to jamming in the raised base attached to the socket. It can be really difficult to get the tubes out and the force required to insert them is almost more than you want to apply.
As for RF shielding, you may be able to really shield a tube from RF if you used a modified shield built like a faraday cage.
However, shielding the tube may not be enough to kill hum or RF if you have nothing more than a single wire between the amp inputs and the grid of the first pre-amp.
The other 9 pin retainer used in many amps is a simple wire clip. There are 2 loops on the socket base, and a spring steel clip attaches there. When the tube is installed the wire clip is raised and slips over the top of the tube, holding it in place.

The tube has an element called a "cathode" which gives off electrons.
Electrons are attracted to a positive charge and repelled by a negative charge.
The cathode is in the center of the tube element called the "plate".
The plate has a positive charge which it uses to attract electrons.
OK, so now we have a cathode flowing electrons to the positive plate and all is well.
Then we install a tube shield that connects to the chassis which is negative in relationship to the plate.
So are the electrons that see this negative charge past the positive plate.
Also the plate and the shield form a small value capacitor.
To test this for yourself, start with the tube shields off.
That way you won't be dealing with hot tube shields later in this test.
Warm up the amp and play, listening to the tone with a critical ear.
Next put the tube shields back on.
Be careful, the tube shields will be cool but the tubes will be hot.
Do not change any settings on the audio tube amp or guitar amp and listen to the tone again.
I rest my case......
If your amp makes too much noise or does any nasty tricks with the tube shields off, do put them back on.

I think most people think they are there to protect the preamp tubes from falling out, which they also do.....
Its like when you have a long pedal chain - and that little bit of noise in the first effect is amplified and reamplified by the drives coming after it until it sounds huge.....having the sheilding covers on early in the chain reduces more noise than later in the chain...
Thats one reason they arent on the power tubes that are near the end of the gain chain in an amp....
They also hold in heat which can wear your tubes out faster I believe......
But as was stated you may not want it any brighter....
and they can keep microphonic tubes from ratttling as bad......

http://musictoyz.infopop.cc/groupee_common/emoticons/icon_smile.gif


Additional Information:

Sep 12, 17 10:00am
Tube shields are those little metal cylinders you find over the small tubes in your amplifier.
They're used to reduce the chance of picking up hum and noise.
Sometimes they're also used to hold the tubes securely into the tube sockets.

With smaller 7 - 9 pin tubes, you usually see a combination of tube socket and shield or retainer.
Probably the most common in guitar amps is the spring loaded metal shield that twist-locks to the base.
This acts as a retainer to keep the tube seated and a protective shield for the glass bulb.

It’s supposed to provide both mechanical protection and radio frequency (RF) shielding.
These tube shields will provide mechanical protection and hold the tubes in place.
The problem is that some tubes made today come very close to jamming in the raised base attached to the socket. It can be really difficult to get the tubes out and the force required to insert them is almost more than you want to apply.
As for RF shielding, you may be able to really shield a tube from RF if you used a modified shield built like a faraday cage.
However, shielding the tube may not be enough to kill hum or RF if you have nothing more than a single wire between the amp inputs and the grid of the first pre-amp.
The other 9 pin retainer used in many amps is a simple wire clip. There are 2 loops on the socket base, and a spring steel clip attaches there. When the tube is installed the wire clip is raised and slips over the top of the tube, holding it in place.

The tube has an element called a "cathode" which gives off electrons.
Electrons are attracted to a positive charge and repelled by a negative charge.
The cathode is in the center of the tube element called the "plate".
The plate has a positive charge which it uses to attract electrons.
OK, so now we have a cathode flowing electrons to the positive plate and all is well.
Then we install a tube shield that connects to the chassis which is negative in relationship to the plate.
So are the electrons that see this negative charge past the positive plate.
Also the plate and the shield form a small value capacitor.
To test this for yourself, start with the tube shields off.
That way you won't be dealing with hot tube shields later in this test.
Warm up the amp and play, listening to the tone with a critical ear.
Next put the tube shields back on.
Be careful, the tube shields will be cool but the tubes will be hot.
Do not change any settings on the audio tube amp or guitar amp and listen to the tone again.
I rest my case......
If your amp makes too much noise or does any nasty tricks with the tube shields off, do put them back on.

I think most people think they are there to protect the preamp tubes from falling out, which they also do.....
Its like when you have a long pedal chain - and that little bit of noise in the first effect is amplified and reamplified by the drives coming after it until it sounds huge.....having the sheilding covers on early in the chain reduces more noise than later in the chain...
Thats one reason they arent on the power tubes that are near the end of the gain chain in an amp....
They also hold in heat which can wear your tubes out faster I believe......
But as was stated you may not want it any brighter....
and they can keep microphonic tubes from ratttling as bad......

http://musictoyz.infopop.cc/groupee_common/emoticons/icon_smile.gif



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