[Jeb Listens]

don't shoot me down for this... just curious..
 
Thoroughly enjoying my journey into the world of tube amps - but I was recently with someone who suggested that vacuum tubes used in amps, can produce radiation and x-rays that could be absorbed by the user at close proximity.   He likened them to CRTs found in old televisions.
 
Judging by how many people are using tube amps safely and have done for years this sounded like complete  nonsense to me but I didn't have a grasp on the science to refute him,  other than to say that even powerful audio amplfiers do not carry the kind of voltage needed to produce any significant level of radiation,  though I don't fully understand the science of why.   Perhaps it has more to do with frequency.
 
would anyone be able to explain the reason simply and how they differ from cathode ray tubes ? is it just a matter of the voltage used?
 
 
Regards
 
Jeb.

 

[superjawes]

Scary, right? As with most "radiation" legends, there is an element of truth, from the X-ray tube Wikipedia page: "Any vacuum tube operating at several thousand volts or more can produce X-rays as an unwanted byproduct..."

Emphasis mine. Sure, we like tubes because they tend to handle higher voltages better, but we do not operate them at "several" kV for normal operation. Electrostatic amps might hit a few kV, but I doubt they hit the "several" threshold to make people worry. And even if you do emit X-rays from your audio tubes, these tubes aren't designed to emit x-rays, so there won't be any focus to where the radiation goes. This spreads out any potential exposure, further reducing the risk.

One last note. "Radiation" is a very general term that scares people by conjuring images of people with several deformed limbs (or superpowers...if you're weird like me). Cell phones expose you to a lot of radiation. However, you can split radiation into two types: ionizing and non-ionizing. Ionizing the the stuff that messes with your body chemitry, resulting in not-so-good issues. Non-ionizing radiation is basically just heat. Cell phones? They give off the non-ionizing type, as do many other electronics (microwaves are non-ionizing).

If there really was a risk with tube amps, someone would tell the government and get the recalled/banned. Just ask yourself: "Why hasn't that happened?"

 

[Jeb Listens]

One last note. "Radiation" is a very general term that scares people by conjuring images of people with several deformed limbs (or superpowers...if you're weird like me). 

 
Indeed I was hoping that activation of dormant super-powers might be pleasant by-product of late late listening sessions to a tube amp! Looks like that won't be the case.   
 
 
Getting back to the matter in hand -  thanks for your answer SuperJawes, very helpful.  
 
It sounds like in audiophile application there is nothing to worry about.
 
I wonder if there was any harmful exposure for the operators when lots of these NOS tubes were used in their original application (e.g. in large-scale military electronics and radio transmission) ?  For example the USAF SAGE computer facility at Virginia 1957 -  200,000 vacuum tubes @ 3,000,000 watts! 
 
 
 

 
 
Regards,  Jeb.

 

[billybob_jcv]

Well, let's not forget that the first sustained atomic pile was built under the stands of an old football field in the middle of Chicago!

 

[Jeb Listens]

I wonder if they put one under Arsenal's football pitch it would help them play any better. 

 

[Jeb Listens]

By the way, what kind of level of voltages are involved in a typical modern day tube-amp?

 

[billybob_jcv]

I'm not sure, but I seem to recall 300 (or was it 600?) volts in a typical stereo power amp? Something like that.

Here's a spec sheet for a 12AX7, and it shows a plate voltage of 300 volts:
https://d1sjrnpi226dnf.cloudfront.net/spree/attached_files/12ax7-tung-sol.pdf?1383243669

 

[superjawes]

Not a tube amp designer, but I wouldn't expect any kV's from normal tube amps. Electrostats mights get a couple kV, but 300-600 V from most amps wouldn't surprise me at all.