[Tacoboy]

I've been looking at these tube headphone amps.
Why are the tube exposed to the outside?
Would it not be safer to have them more protected?

 

[ozz]

Heat and cosmetics (glowing tubes are art to some) but mainly to keep them cooler (longer lasting).

 

[Denys]

And I would add... easier to change....

Cosmetic is a big plus in my opinion. I like closing the lights at night when music play and just look at the tube amp.... I find it nice..

Denys

 

[john53]

My x can v8 has the tubes enclosed...

 

[Happy Camper]

Heat.

You can run mini tubes under cover but the bigger tubes put out a lot of heat.

 

[Uncle Erik]

It's mostly cosmetics - people want to see the tubes. If you look back at vacuum tube equipment, you'll find some gear with exposed tubes from the 1920s. My favorites arethe old Atwater-Kent "breadboard" radios which are gorgeous. But by the late 1920s, the novelty had worn off and tubes went inside the case. You will no find exposed tubes on almost any of the "golden age" equipment, save for some power amps that also came with tube cages.

This changed in the 1990s, when tubes came back into fashion. People wanted to see the tubes, so they got put up top.

It is interesting to note that when lightbulbs first came into use, the fixtures were designed to display their bulbs. Lightbulbs were such a novelty that people wanted to see the bulb itself. Only when that got old did light fixtures begin to enclose the bulbs.

 

[TheAudioDude]

Quote:

Originally Posted by Uncle Erik /img/forum/go_quote.gif It is interesting to note that when lightbulbs first came into use, the fixtures were designed to display their bulbs. Lightbulbs were such a novelty that people wanted to see the bulb itself. Only when that got old did light fixtures begin to enclose the bulbs.

Well, it's a good thing you won't temporarily go blind if you stare into a tube for a long time, as opposed to a light bulb!

 

[Donald North]

Quote:

Originally Posted by Uncle Erik /img/forum/go_quote.gif It's mostly cosmetics - people want to see the tubes. If you look back at vacuum tube equipment, you'll find some gear with exposed tubes from the 1920s. My favorites arethe old Atwater-Kent "breadboard" radios which are gorgeous.

Those breadboard radios are beautiful. I've seen them before but forgot who made them - thanks for mentioning Atwater-Kent.

I've been thinking about building a 845 amplifier for myself this way with all the tubes and components displayed. One challenge is covering and protecting from the B+ which can reach 1000V or more.

 

[Redcarmoose]

I would guess heat displacement and looks. I have always thought that extra dust on the tubes would hinder heat from leaving the tube. For that reason and the fact that hand oil can cause different degrees of heat and expanding of the glass. I use a cotton tube sock over my hand to clean.

 

[Spareribs]

In my opinion, it's better to have the tubes exposed for quality control check. My guitar amp has tubes that are hidden and one of my tubes cracked and died. I had not realised it quicky and let it run for an extend period of time.

Since my tubes are exposed on my headphone amp, if this were to happen, I can immediatly change the tube and avoid any possible damage to my amp. Personally, I think it's safer in the event that a defective tube is used during tube rolling.

 

[adrift]

Quote:

Originally Posted by Uncle Erik /img/forum/go_quote.gif It's mostly cosmetics - people want to see the tubes. If you look back at vacuum tube equipment, you'll find some gear with exposed tubes from the 1920s. My favorites arethe old Atwater-Kent "breadboard" radios which are gorgeous. But by the late 1920s, the novelty had worn off and tubes went inside the case. You will no find exposed tubes on almost any of the "golden age" equipment, save for some power amps that also came with tube cages. This changed in the 1990s, when tubes came back into fashion. People wanted to see the tubes, so they got put up top. It is interesting to note that when lightbulbs first came into use, the fixtures were designed to display their bulbs. Lightbulbs were such a novelty that people wanted to see the bulb itself. Only when that got old did light fixtures begin to enclose the bulbs.

Very interesting history.

 

[Seamaster]

Quote:

Originally Posted by Redcarmoose /img/forum/go_quote.gif I would guess heat displacement and looks. I have always thought that extra dust on the tubes would hinder heat from leaving the tube. For that reason and the fact that hand oil can cause different degrees of heat and expanding of the glass. I use a cotton tube sock over my hand to clean.

Yes, it is for good look and cooling. I put NEW regular cotton socks over my hand to clean them.

 

[audiowize]

This is all about heat. Every 10 degrees celcius of temperature increase will decrease the life of an electrolytic capacitor by half. A 10,000 hour cap at 85c is a 5000 hour cap at 95c, etc. etc.

Tubes are way, way better off if they are enclosed in the chassis (Musical Fidelity) in terms of noise pickup. The other option is to use a tube shield and ground that to the chassis (steel is good for this).

Unfortunately, most of the newer tube headphone amps use 6AS7 variants which are large and hot, and the amps tend to be as small as possible, so this tends to not be an option.