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"SQ tube" ?

2/20/2001 3:31 AM
"SQ tube" ?  
The link above will take you to the website for a new "all tube" recording console. That alone could probably be the subject for a few hundred posts on this newsgroup, but right now I'm only curious about the "SQ tube" that the manufacturer uses in this design. This tube type is used for every application within the console, all 26 tubes in every input channel! (that comes to well over 1,000 tubes for most console sizes to be offered.)  
What is an "SQ" tube?  
2/20/2001 3:54 AM
Dave R
Re: "SQ tube" ?
Holy crap! What does something like that cost?!?
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2/20/2001 5:35 AM
Todd Hepler

1200 tubes ?  
This would make a great space heater..  
It looks like the 'sq' tubes are just JAN 5751,  
which are, I believe, industrial-duty 12AX7's. At least that's as close as I could come from the photos.They are GE and say 'made in usa' on 'em.  
if that's true, where'd these guys score several thousand NOS 5751's ?  
2/20/2001 8:05 PM

i wouldnt buy it, pcb doesnt look easy to mod :D  
seriously that thing looks super cool!
2/20/2001 8:32 PM

Well, I'm befuddled! Is the tube description so seriously muddled from German that it's nonsense or is the description the excrement of an advertising moron? And I quote:  
"A stronger "underheating" makes the tube susceptible to toxications, while "overheating" causes an evaporation of the active layer. This might cause gridemission and produces intermediate-layers on the surface of the Cathode SQ-Tubes are equipped with special "High Durability Cathodes".  
Of course, not only the Cathode of a tube, but all other electrodes must be protected against inadmissible temperatures (transgression of  
the Anode load, insufficient heat discharge), to avoid grid emission , Gas eruption etc. In this respect, the maximum admissible Body temperature, as specified for special tubes by the manufacturer, is to be taken into account.  
Top of page  
3. Interlayer-free Special Cathode When tubes are operated, in heated condition, without Cathode current (Pulse-Mode), an Interlayerresistor arises within the Cathode, due to depletion of active layer.  
This Interlayer-Resistor, acts like an unshorted Cathode-Resistor and generates, particularly at low frequencies, an undesirable negative feedback, which is interfering especially in tubes with a high mutual conductance.  
Huh? I've never "toxicated" a cathode in my life - in face, I'm not sure creating a verb out of "toxic" in this manner is grammatical. Then there are those "transgressing" anode loads - perhaps they need "shock" boot camp. "Gas erruptions" - frijoles, of course!! Then there is this "interlayerresistor" - are we still talking about tubes, or even electronics? My best guess is poorly translated marketing fluff which has resulted in bullshit to the third power :) - got a term for this?  
2/20/2001 8:47 PM

My best guess is poorly translated marketing fluff which has resulted in bullshit to the third power got a term for this?  
i usually call that "crate" :D
2/20/2001 9:21 PM
Ray Ivers

I think what they're trying to say is:  
1) Operating the cathode at reduced heat (i.e. low filament voltage) makes the cathode vulnerable to 'cathode poisoning' (the attraction to the cathode surface of unwanted contaminants released by the other tube electrodes and/or floating about in the imperfect vacuum of the tube). I'd have to go along with this.  
2) Too-high cathode temps can prematurely age and weaken the cathode coating, although initially tube output and measured specs may be greatly enhanced. I don't think the cathode coating would ever actually evaporate unless the temp was super-high and/or plate current draw was really excessive, though. If it did, the coating particles would migrate from the cathode to the plate, "toxicating" everything in their path - and the newly-coated control and screen grids might well start to emit electrons themselves (grid emission).  
3) The "interlayer resistor" refers to space charge build-up around the cathode during periods of zero plate current flow. Electrons are emitted, they travel a short distance and find no positively-charged electrode to be attracted to, they lose their negative charge, and then are attracted back to the cathode again. I don't know if I would call it 'negative feedback' per se, but maybe in a way it is...  
I Just finished (mostly) reading the R.D.H., and this is all from my memory and therefore really suspect. I think it's pretty close, though. I can imagine what I would come up with in German!  
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