Tube glass design questions.
Nov 5, 2008 at 5:04 PM Thread Starter Post #1 of 12

Happy Camper

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I tried to google and search here but little information was found. So....

To our resident tube experts,

What is in the glass pudding? What determines the shape of the tube glass, it's thickness and shading? What (if any) sonic effects does the glass have?

Some tubes are straight, some shoulder type, some smooth top, others pointed, why?

Most are clear, some coated (by design), why?

Do the makers use microphonics to voice a tube for audio?


Any links would be appreciated and thanks for your input.
 
Nov 5, 2008 at 5:16 PM Post #3 of 12

Golden Monkey

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Have you tried those tubes manaox? Curious about the new prod Brit valves...
 
Nov 5, 2008 at 8:13 PM Post #5 of 12

nikongod

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Quote:

Originally Posted by Happy Camper /img/forum/go_quote.gif
Some tubes are straight, some shoulder type, some smooth top, others pointed, why?


The nipple is where the tube is sealed after they suck the air out. If the tube has a smooth top, the bottom has the nipple (in the plastic cup on an octal/loctal/4-pin, etc)

you can see this if you take apart an octal tube.

Im not sure why newer tubes have shaped glass, although i suspect it has to do with increasing surface area to improve cooling. in the case of older tubes (baloon, and bubble shapes in specfic) thats simply the easiest shape to hand-blow.
Quote:

Most are clear, some coated (by design), why?


It was discovered that not all of the electrons stay within the confines of the plate. some would stick to the glass, and creep along until they came to the leads in an uncontrolled fashion (technically called secondary emission). This can cause some distortions with low signal levels.

"black glass" or "grey glass" tubes were introduced to combat this issue, and do very well at it. They use a coating INSIDE the tube to control this problem.

later on, new types of glass were developed that avoided this problem without coatings.
Quote:

Do the makers use microphonics to voice a tube for audio?


there are some tubes that are marketed as low-microphonic by design. Others were cherry-picked and sold as such. Its a pretty broad topic, and realllly depends on the tube. MOST "audiophile" tubes marketed as low noise, and low microphonic versions of something else were cherry-picked from standard stock. There are some exceptions, where the MFR made the tube to be a "high quality" version from the start.
 
Nov 5, 2008 at 8:56 PM Post #7 of 12

manaox2

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Quote:

Originally Posted by Golden Monkey /img/forum/go_quote.gif
Have you tried those tubes manaox? Curious about the new prod Brit valves...


No, I'm mostly messing around with hybrid designs in DIY right now so that I don't get caught working with my hand out of my pocket working on an amp. Its too bad, I got to spend $$ on trying to find eight matched 6MG8 tubes now somehow.

EDIT: 6GM8 / ECC86 tubes, sorry
 
Nov 6, 2008 at 1:40 AM Post #8 of 12

sacd lover

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Quote:

Originally Posted by manaox2 /img/forum/go_quote.gif
No, I'm mostly messing around with hybrid designs in DIY right now so that I don't get caught working with my hand out of my pocket working on an amp. Its too bad, I got to spend $$ on trying to find eight matched 6MG8 tubes now somehow.


6MG8? .... or 6GM8?
 
Nov 6, 2008 at 3:03 PM Post #9 of 12

nikongod

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Quote:

Originally Posted by sacd lover /img/forum/go_quote.gif
6MG8? .... or 6GM8?


QFT.

As another question, does your design REQUIRE matched sections, and then matched bottles?
 
Nov 6, 2008 at 5:11 PM Post #10 of 12

manaox2

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Quote:

Originally Posted by nikongod /img/forum/go_quote.gif
QFT.

As another question, does your design REQUIRE matched sections, and then matched bottles?



6GM8, sorry. It might not require much matching other then brands long as they degrade at a constant pace for the Aikido. I'm not even considering matching any bottles now, they are too rare nowadays, it would be hard enough matching sections. Right now, I'm on the lookout and have only spotted nine at most at a reasonable price.
frown.gif


I need to learn too, I'm just getting into studying tube design as well and only have one tube amp with very limited tube rolling options as I know it (millett max).
 
Nov 7, 2008 at 4:46 PM Post #12 of 12

manaox2

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Quote:

Originally Posted by nikongod /img/forum/go_quote.gif
Unless I am WAY off base, the Akido dosnt require brand or section matching.


Right, I had read something that hinted at that when I answered your question, I wasn't sure it I needed to have section matching brands because of using the circuit balanced and tube degradation, not for sound. Matching Gm for these tubes now seems like it would cost a ton!

Its off topic, but if anyone wants to go to PM, I would like to ask for a good strategy on adding a negative power rail into the circuit if I need for going balanced. I've managed to afford all the tubes I'd need now, though I'm not very advanced at modifying schematics.
 

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