C3G case removal - preamp tube

[Opti-cal]

Hi chaps,

how would one go about removing the protective casing of these C3G tubes?



My DAC only accepts the 'naked' tube without it's protective case.

Doesn't seem to twist much (don't want to force it) but there is a ridge with a slight lip where I assume the top separates from the bottom.

Gently heating it? A flat-head screw driver? Rubberised pliers?

They ain't that cheap so don't want to damage them!

Cheers

Chris

[Lawrence001]

What sort of base are they? Maybe there are base extenders or you could make one out of a socket with pins added to the bottom? Or buy an adaptor but change it to go pin to pin if that's possible.

[Lawrence001]

You'd have to look at compatibility (is it a standard octal base?) But will this help?


Look at this on eBay
https://www.ebay.co.uk/itm/1pc-Gold-...-/193443029180

[Barry]

Taken from https://www.jacmusic.com/techcorner/...-C3m-info.html



Cap Removal



It is really a matter of taste of you want to remove the cap or not. The optical advantage is beautiful. For myself, knowing what is inside, for me it is a tube as well also with the cap in place. Make good note, what the cap is intended for: It is an electrical shield for the tube, and the cap is electrically connected to the metal guide pin, in the center. So via the tube socket you can ground the cap. This is definitely a great advantage in case of very low signal applications. For a driver or headphone, removing the cap for optical reasons is sure nice. You can lift off the edges of the cap relatively easy, it is aluminum, and not aggressively attached or kitted. Also the tube glass will not break easily, because the location is the tube base, and this is pretty thick material. Yet, it is possible to break the glass still when you do not patiently peel the cap away.



After removing the cap, the part with the guide pin falls of, and I would recommend to glue this back on. Put two components glue on the sides. Important: Do not fill glue in the center adjustment hole. That will eventually break the glass pipe in the middle. Note that one pin hole is square, and is used for positioning. Also you can now still use the guide pin to ground this part, and one way or another that is simply good, because the ground plane comes now closest possible to the hum sensitive grid.

Note: Hum is greatly reduced by using a low driver impedance. Also, when working at very low signal level, beware that with all tubes, the grid noise, generated by the tube itself, is actually attenuated (better call it loaded), when using a very low impedance driver circuit. So the noise free signal from the driver and the noise from the tube, will not simply add up, but only one of the two will win. And that will be the driver signal, when it is low impedance. This has nothing to do with the C3g or C3m itself, but since C3g, C3m can be used in pre amplifiers, or even phono amplifiers, I think it is meaningful to mention this here still.

[Opti-cal]

You'd have to look at compatibility (is it a standard octal base?) But will this help?


Look at this on eBay
https://www.ebay.co.uk/itm/1pc-Gold-...-/193443029180

Hi Lawrence,

thanks for suggestion but it's not the issue. Issue is the surrounding case the tube is in as standard.

They are standard 9-pin configuration but to fit in a standard 9-pin socket the aluminum case needs to be removed.

I have a pair with them removed and they fit perfectly. Some sellers do offer them for sale without the case but not the one I bought these from unfortunately.

Cheers anyway.

[Opti-cal]

Taken from https://www.jacmusic.com/techcorner/...-C3m-info.html



Cap Removal



It is really a matter of taste of you want to remove the cap or not. The optical advantage is beautiful. For myself, knowing what is inside, for me it is a tube as well also with the cap in place. Make good note, what the cap is intended for: It is an electrical shield for the tube, and the cap is electrically connected to the metal guide pin, in the center. So via the tube socket you can ground the cap. This is definitely a great advantage in case of very low signal applications. For a driver or headphone, removing the cap for optical reasons is sure nice. You can lift off the edges of the cap relatively easy, it is aluminum, and not aggressively attached or kitted. Also the tube glass will not break easily, because the location is the tube base, and this is pretty thick material. Yet, it is possible to break the glass still when you do not patiently peel the cap away.



After removing the cap, the part with the guide pin falls of, and I would recommend to glue this back on. Put two components glue on the sides. Important: Do not fill glue in the center adjustment hole. That will eventually break the glass pipe in the middle. Note that one pin hole is square, and is used for positioning. Also you can now still use the guide pin to ground this part, and one way or another that is simply good, because the ground plane comes now closest possible to the hum sensitive grid.

Note: Hum is greatly reduced by using a low driver impedance. Also, when working at very low signal level, beware that with all tubes, the grid noise, generated by the tube itself, is actually attenuated (better call it loaded), when using a very low impedance driver circuit. So the noise free signal from the driver and the noise from the tube, will not simply add up, but only one of the two will win. And that will be the driver signal, when it is low impedance. This has nothing to do with the C3g or C3m itself, but since C3g, C3m can be used in pre amplifiers, or even phono amplifiers, I think it is meaningful to mention this here still.

Hi Barry - yes thanks that's where I got my information from too.

Not sure if the author had a much easier experience but I've exhausted a fair amount of pressure/elbow grease on getting a purchase on them and they are not loose in any way. The top 'cap' is too tightly mated to the base.

Looks like I will have to make a small incision and 'peel' away the aluminum housing. As the term 'peel' is actually cited in the instructions above it sounds like this is the process.

Will have another go soon anyway.

Cheers

[walpurgis]

If it was me, I'd use a Dremel type multi-tool with thin cutting disc to partly cut through the aluminium, maybe on two sides before prying free. You don't want it to touch the glass, as any scoring will induce a weakness. As mentioned, a two pack (heat resistant epoxy) adhesive is probably best for bonding the base in place.

[Lawrence001]

Hi Lawrence,

thanks for suggestion but it's not the issue. Issue is the surrounding case the tube is in as standard.

They are standard 9-pin configuration but to fit in a standard 9-pin socket the aluminum case needs to be removed.

I have a pair with them removed and they fit perfectly. Some sellers do offer them for sale without the case but not the one I bought these from unfortunately.

Cheers anyway.

I thought you meant the hole you push the valve into was too small therefore you can't push it down. What is the physical restriction in the DAC that causes the problem, a pic may help?

[Opti-cal]

I thought you meant the hole you push the valve into was too small therefore you can't push it down. What is the physical restriction in the DAC that causes the problem, a pic may help?

No restriction in the DAC as such, just normal 9 pin socket.

As you can see from the pics the bottom of the case has a much thicker center/guide pin than when the casing is removed.





It's the bit circled in red which is the problem as the standard 9-pin socket of the DAC won't accept this.

A dremel tool would seem to be the way to go.

(apologies just realised it's an 8-pin type but the issue is as described)

[Barry]

The valve base is a B8G, which has a centre hole with a keyway to take the splined centre locating spigot of the valve. The locating spigot is hollow and encloses the glass envelope pinch-off seal. If the centre hole in the valve base is the same as that for a B8G then it should accomodate the locating spigot containing the pinch-off seal quite easily.

For some reason the valve bases in your DAC would appear to have smaller central holes, just large enough to only accomodate the seal. If that is the case then you really have no option but to remove the aluminium case.

However before you attemp the above, I would mark the two pins flanking the spline of the valve loction spigot, so you know how to orientate the valves when fitting them inti their sockets.

I would use a jeweller's screwdriver to prise up the case where it joins the metal valve base, then with a pair of needle-nosed pliers enlarge the gap so that a pair of small side snip wire cutters could cut a slot so as to peel away the aluminium can.