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otto88 25th September 2008 08:15 AM

GM70 sockets?

Does anyone have any (4?) for sale, or can you suggest a source?


Bas Horneman 25th September 2008 10:17 AM

Ebay or you can buy 6C33C tube sockets and drill out two holes for the filament.

Or you can buy them from deHavilland for 398US$ a pair ;)

otto88 25th September 2008 01:16 PM

Thanks Bas,

US$ 398 is . . er, a tad over budget ;)

I understood they were too rare for ebay, and the drilling out method may be a tad flaky for the volts.

But there they are - is Teflon a good material for sockets with such tubes, or is ceramic better in practise/ longevity?


nhuwar 25th September 2008 01:42 PM

Honestly it would be easier to drill out some 813 sockets then some 6c33 socket, atleast thats what I think.


danFrank 25th September 2008 03:40 PM

Drilling out 813 sockets isn't too hard of a job. Get a good quality masonry drill bit and put the socket in a pan of water so you are drilling the holes underwater. This keeps the bit cool and keeps the dust down when drilling. The small pins are 4mm and the large one 5mm.

kevinkr 25th September 2008 03:47 PM

Real GM70 sockets are relatively readily available on eBay:

The above are $20 each..

Russian made sockets at $40 a pair.

There are other choices as well, starting at as little as $10 each. (Basically modified 6C33 sockets)

Bas Horneman 25th September 2008 06:50 PM


is Teflon a good material for sockets with such tubes
Teflon is great apparently for that. But I have no experience though with teflon sockets. I've read though that the are more susceptible to wear and tear...i.e. holes becoming larger.

kevinkr 25th September 2008 07:01 PM


Originally posted by Bas Horneman

Teflon is great apparently for that. have no experience though with teflon sockets.

I have... Very expensive and while very pretty I think the teflon sockets are basically a waste of money. Six to seven years down the road the contact pins have loosened up enough to cause contact problems. Not funny when you think you were doing the right thing for your customers, and forked over 15X what a good ceramic socket would have cost. The ones I am talking about are a highly regarded boutique brand, not the much less expensive Chinese clones which actually represent relatively good value by comparison. (I've used both.)

Teflon flows long term and IMHO is probably not suitable for applications like the GM-70 where the heat is relatively extreme at the socket. (I could be wrong, but I am not encouraged by my experiences with 20 or so sockets in much more forgiving thermal environments.) Given the typical contact design I would also expect serious reliability issues with the filament currents present.

nhuwar 25th September 2008 07:30 PM

My problem with teflon is it's very soft and as Kevin mentioned it can exibit amorphous properties like glass, IE creep.

I'n my opinion a socket for this would need to be quite thick to take the force from the socket springs and not deform plastically.



Gluca 25th September 2008 07:50 PM

I drilled cheap 10euro ceramic sockets made for the 813's. OH! I must build again something with GM70s ... I loved that tube.

Hey Bas! is that you in the avatar? :D

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