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Metal tube covers on MX-110 -necessary?

westeagle

westeagle

New Member
I have a newly acquired MX 110 which has replaced my C28. Hearing it for the first time literally made the hair stand up on my neck!
I love the look of the tubes at night as they glow, so was wondering whether the metal tube covers play an important role other than physically protecting the tube?

Do the tube covers provide shielding or additional heat dissipation?
 
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I have a metal cover on the 12AX-7 on my MC-275. It's my understanding that the 12AX-7's need to be covered. As for the other small signal tubes, none came shielded.
 
I got the answer when I removed the shields from some of the tubes (not all) and hum resulted when fingers were near or touching the tubes.

So apparently, the shields are used on the tubes which are prone to interference - which on an MX 110 is most of them.
 
@62caddy is correct - the MX110 is carefully shielded where necessary and these should not be removed.

The vast majority of the shields are in the FM tuner circuits, though not all. Keep them on! If you replace any shielded tubes, shield the replacements (ideally, make sure the replacements fit in the shields first).
 
Keep the shields where they were designed to go, some problems can happen that you do not notice at first, humm and RFI.
The tuner section alignment can be compromised due to the removal of the added capacitance from the shields, especially the 12AT7 mixer stage.
 
How about tube covers on MC30's, or MC240? If so, where to procure them? Many of the ones I have are "cosmetically challenged..."
 
thevinoman said:
How about tube covers on MC30's, or MC240? If so, where to procure them? Many of the ones I have are "cosmetically challenged..."
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On the MC240, only one 12AX7 tube is shielded; the MC30 does not have any shielded tubes.

They come up on eBay every so often, Audio Classics is your best bet otherwise.

The shield used in an MC240/275 is not used in an MX110.
 
Thanks for the info, but I guess my question is...Would it be best for all of the 12AX7's on the 30's and 240 to have shields?
 
thevinoman said:
Thanks for the info, but I guess my question is...Would it be best for all of the 12AX7's on the 30's and 240 to have shields?
Click to expand...

Special fastening rings/twisting devices are built into the tube sockets to secure the shields to the chassis where shielding is needed. It would be pointless to shield tubes without the proper grounding provisions which would need to be built into the chassis of the unit.

I would not second guess Sindney Corderman's engineering judgement by adding shields where their use is not indicated.
 
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