[Redeamon]

Question 1: I noticed that my brand new tubes that were 100% clear are turning dark near the red glow. Why does this occur?

Question 2: Are tubes safe in terms of radiation. I understand that the plates inside the tubes contain high voltages of 300+ volts. Are these electrons harmful when the tube "leaks" them?

Question 3: On some tubes there is a ring and right above that ring it looks like the tube is coated in a black metallic coating. Why do they do this and/or does this happen naturally?

Question 4: Can sound be affected by temperature of the tube? For example, if I have a fan on my tubes will the sound change. This seems to be true in my tests, but I wanted a 2nd opinion or better a technical one.

Question 5: My tube is a CV 4015 with KB QDD under it. is this a Mullard?
Thanks!

 

[ldarcy]

1. I believe atoms of metal electrode are being emitted and they end up on the tube glass.

 

[tomb]

Quote:

Originally Posted by Redeamon /img/forum/go_quote.gif Question 1: I noticed that my brand new tubes that were 100% clear are turning dark near the red glow. Why does this occur?

Idarcy is correct, but it may be simpler to think in terms of the heater and small surface imperfections/oil/etc. eventually burns off in small bits of soot.
Quote:

Question 2: Are tubes safe in terms of radiation. I understand that the plates inside the tubes contain high voltages of 300+ volts. Are these electrons harmful when the tube "leaks" them?

If you believe that EMF radiation is harmful, then perhaps so, but I wouldn't worry about it. There's much more radiation from the typical television tube.
Quote:

Question 3: On some tubes there is a ring and right above that ring it looks like the tube is coated in a black metallic coating. Why do they do this and/or does this happen naturally?

The ring is a called a getter. In some tubes it can be a square or rectangular loop of wire, or even a cut piece of flat sheet metal. The coating is a catalyst chemical - actually with a chrome finish seen from the outside of the tube (black may be burned, white is all used up). The radiation from the ring combines with the chemical patch coated on the tube glass to oxidize any stray gas molecules that may have leaked into the tube. Of course, a vacuum is best for performance.

Old NOS tubes may need to be run with their heaters on for several days before the gas molecules infiltrated through the years are all "burned up." Then the original performance returns.

Quote:

Question 4: Can sound be affected by temperature of the tube? For example, if I have a fan on my tubes will the sound change. This seems to be true in my tests, but I wanted a 2nd opinion or better a technical one.

Yes - it the tube heater that heats the plates that causes the electrons to flow. Performance is usually enhanced if the heater voltage, and therefore the heat, is regulated to a constant value. Other parts in the circuit assume the tube is operating within certain parameters.
Quote:

Question 5: My tube is a CV 4015 with KB QDD under it. is this a Mullard? Thanks!

Don't have a clue on that one.

 

[Rob N]

Quote:

Originally Posted by Redeamon /img/forum/go_quote.gif Question 5: My tube is a CV 4015 with KB QDD under it. is this a Mullard? Thanks!

Look towards the base of the tube there should be some numbers/letters etched into the glass (if it's a phillips made tube (incl Mullard))

 

[ServinginEcuador]

Quote:

Originally Posted by Redeamon /img/forum/go_quote.gif Question 1: I noticed that my brand new tubes that were 100% clear are turning dark near the red glow. Why does this occur?

As the heater is powered up it deposits small amounts of material inside the glass. This is normal for a vacuum tube, and will slowly continue to build-up over time.

Quote:

Question 2: Are tubes safe in terms of radiation. I understand that the plates inside the tubes contain high voltages of 300+ volts. Are these electrons harmful when the tube "leaks" them?

Electrons don't simply float around or leak like you're thinking. If that were so you'd have billions of them leaking from every exposed electrical outlet in the house. Other subatomic particles may "leak", but from small signal tubes the amount is miniscule.

Quote:

Question 4: Can sound be affected by temperature of the tube? For example, if I have a fan on my tubes will the sound change. This seems to be true in my tests, but I wanted a 2nd opinion or better a technical one.

Yes, temperature effects the sound of the tube, but only so far as comparing how hot the heater gets the tube from when you first turn it on vs. having left it on to heat up.

No, by blowing a fan on the outside of the tube you can, in no way, affect the internal operating temperature of the tube. The vacuum inside the tube will effectively seperate and insulate the outside temperature from the extremely high temps created by the heater. In this case the sound would be affected more by the noise of the fan heard through your headphones.

 

[Ahriman4891]

Redeamon, I hope you don't mind me jumping in with my question, it's just your thread title will attract folks knowledgeable about tubes. I meant to ask this for a while, too. Some audiophiles constantly bring up "tube watts" vs. "solid-state watts". I understand that a watt is a watt is a joule/sec, but was there anything behind this? I.e. some characteristic of tubes vs. solid state that was greatly misinterpreted and served as a root for this whole "tube watts" thing?

 

[tomb]

Quote:

Originally Posted by ServinginEcuador /img/forum/go_quote.gif As the heater is powered up it deposits small amounts of material inside the glass. This is normal for a vacuum tube, and will slowly continue to build-up over time. Electrons don't simply float around or leak like you're thinking. If that were so you'd have billions of them leaking from every exposed electrical outlet in the house. Other subatomic particles may "leak", but from small signal tubes the amount is miniscule. Yes, temperature effects the sound of the tube, but only so far as comparing how hot the heater gets the tube from when you first turn it on vs. having left it on to heat up. No, by blowing a fan on the outside of the tube you can, in no way, affect the internal operating temperature of the tube. The vacuum inside the tube will effectively seperate and insulate the outside temperature from the extremely high temps created by the heater. In this case the sound would be affected more by the noise of the fan heard through your headphones.

It's sort of a bad road to go down to quibble about this stuff, but here goes:

* No, electrons don't leak, necessarily, but when AC current flows (not from an open outlet), EMF is created. These electromagnetic fields may have a definite, measureable form of radiation. To the extent that AC is in the tubes, such fields will exist. Although, as I originally stated - nothing to worry about compared to everything else in a typical house.

* The only heat transfer mode prevented by a vacuum is convection. There's quite a bit of radiation going on in side a vacuum tube. In fact most, if not all of the heat transfer is radiation. To the extent that this radiation and a certain amount of conduction (throught the tube base and socket) is transferred to the tube glass, then the convective action from a fan and moving air on the outside of the tube will have an effect.

This will tend to lower the temperature attained by the heater element, altering the amount of electron flow from the plates and therefore, the sound. My guess is that this effect is probably miniscule, but it may indeed be audible. If the bias were re-adjusted with the fan in constant operation, then any effects could be compensated so that there was no difference in sound.

 

[Roam]

Quote:

Originally Posted by Ahriman4891 /img/forum/go_quote.gif I meant to ask this for a while, too. Some audiophiles constantly bring up "tube watts" vs. "solid-state watts". I understand that a watt is a watt is a joule/sec, but was there anything behind this? I.e. some characteristic of tubes vs. solid state that was greatly misinterpreted and served as a root for this whole "tube watts" thing?

Assuming a well-designed tube amp, the saying which goes "tube watts are bigger than solidstate watts" holds a kernel of truth.

There are actually three aspects to this:

1) Tubes overload more gracefully. Solidstate chops off the signal peaks when pushed too hard, this is called hard clipping and leads to all sorts of nasty sound. Tubes tend to round off the peaks which is a far more benign form of distortion, and a fair bit less noticeable.

2) Tube amps have a greater peak power capability. A tube amp rated for 30W for instance can put out brief momentary peaks of 50W or more without distortion. Solidstate can have this capability, but not to the same extent.

3) Tubes recover more gracefully from overload. Solidstate tends to suffer from ringing and oscillations when they hard-clip, and they generally take more time to settle out and recover their normal operating points than tubes. Tubes don't suffer as much from ringing and the recovery from overload is faster & cleaner.

Why does all that matter? Music, unless it's horribly compressed crap with no dynamic range rarely demands large continuous power outputs from an amp. For example, if I were to play one of my symphony or jazz records, my speaker amps would be coasting along at around a watt or two for 98% of the time. Every once in a while there will be a peak to maybe 30W, and once in a blue moon I might see a 50W spike. Chances are I could use a 25W tube amp and never hear anything wrong. With solidstate, I'd have to make sure it can put out at least 50W so I never overload it; if it overloads I'm very likely to notice it since it does so in a fairly objectionable manner.

 

[Ahriman4891]

Thanks Roam. Yeah, that's pretty much what I was guessing. It's just the phrase itself bothers me and IMO adds unnecessary confusion. On the other hand, maybe for some it's a simplification

 

[Redeamon]

Thanks for the info guys. I appreciate it.