Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: computerman on April 10, 2023, 07:58:35 AM

Title: RF shielding for the Crack?
Post by: computerman on April 10, 2023, 07:58:35 AM: I have my crack on my desk. My last post was about a bad tube, which even after cleaning was returned and replaced. No more problem!

This time, I noticed some intermittent buzzing, which I tracked down (thanks to others here) to some random RF interference. Moving the Crack solved the issue, however the place I "want" it to be has frequent buzzes; no other location (of course!)

Anyone have an idea for a good-looking shielding? If I wave my hand over the the 12AU7, this dead-zone it appears to be about 1 inch above it. I'm thinking I could do a neato faraday cage. I went to calculate the mesh size I could use for common frequencies around my desk: (2.4/5G wifi, 4G LTE/5G cell phone, bluetooth mouse/keyboards, etc.).

The calculation seems to be .5m (since Î» = c / f). Hilarious number, so I figure classically like 1mm.

I'm worried about thermals of this tube if it gets insulated. Does anyone have recommendations for this? Right now it's perfectly operating 2ft from where I'd prefer it, so it's not the end of the world.
Title: Re: RF shielding for the Crack?
Post by: Paul Birkeland on April 10, 2023, 08:02:15 AM: https://www.tubesandmore.com/products/tube-shield-high-quality-fits-p-st9-700-spring (https://www.tubesandmore.com/products/tube-shield-high-quality-fits-p-st9-700-spring)
Title: Re: RF shielding for the Crack?
Post by: computerman on April 10, 2023, 12:57:30 PM: Wow. Absolutely stunning and quick :P

Hides the good glow, but definitely worth a shot; I'll use that in the meantime! I assume that this casing won't thermally insulate the tube? I'm not familiar with "good lifecycle practices" with tubes.
Title: Re: RF shielding for the Crack?
Post by: Doc B. on April 10, 2023, 01:38:25 PM: The best bet for a shield that keeps the tube cool is an IERC shield. But the shield PB mentioned is the type we supply in some kits and will do the job just fine, assuming that a tube shield will solve the issue. Which you won't know until you try the shield.
Title: Re: RF shielding for the Crack?
Post by: computerman on April 11, 2023, 07:54:59 AM: Quote from: Doc B. on April 10, 2023, 01:38:25 PM
The best bet for a shield that keeps the tube cool is an IERC shield. But the shield PB mentioned is the type we supply in some kits and will do the job just fine, assuming that a tube shield will solve the issue. Which you won't know until you try the shield.

Thanks Doc. Do you have a link to buy one here? Preferably if it can screw into the existing chassis holes on the Crack. The one Paul linked has what appears to be a twist-on that connects to a bracket that could replace the Crack's existing one (but I have yet to pull out the calipers to check).
Title: Re: RF shielding for the Crack?
Post by: Paul Birkeland on April 11, 2023, 08:22:01 AM: Yes, that shield will just replace the retaining ring.
Title: Re: RF shielding for the Crack?
Post by: Doc B. on April 11, 2023, 08:32:17 AM: I think you can find all sorts of them on ebay. Typically you just get the shield, the black bayonet bases are very rare. But luckily the IERC shields fit the standard silver bayonet bases just fine.