Tube amp question

** It is certainly not ideal, plus the tubes can overheat when mounted this way too.

Octal types with plastic bases are prone to "bias creep" when the plastic base begins to become conductive.

.... Phil

Uh, I guess you are an audiophile?

I thought the latest craze was graphene wires...

On Wednesday, October 10, 2018 at 1:59:46 PM UTC-7, snipped-for-privacy@whidbey.com wrote :

You don?t appreciate the effort being made to improve the euphoniou s presence in these vacuum tube electronics. This orientation is applicabl e in the Northern Hemisphere. It is to optimize the curvature in the paths of the electrons due to the Lorentz forces induced by the earth?s magnetic field, and to match that curvature with the helicity of the windin gs of the grid wires. This was commonly done in other vacuum tubes: color monitors with cathode ray tubes had opposite magnetic field compensations for the two hemispheres for improved convergence and image quality.

The next technological improvement will be to replace the copper wiring wit h silver, just as they did on the Manhattan Project. Of course, the silve r will be carefully annealed to be oxygen-free and single-crystal.

I knew it! Instead of OFHC copper they will use OFHS silver. Eric

Not sure ... I know that a lot of Fender guitar amps have their tubes mounted "upside down" - but the output pentodes are all fitted on ceramic bases. I have one which I use on a daily basis and it seems to be OK to me in spite of being more than 40 years old. I have noticed on certain other makes that the screen grid resistors unsolder themselves and fall off when they get very hot, although I don't suppose that was one of the design criteria.

AT

** Some use white ceramic sockets - but most use plastic or phenolic bases. ** Really has to be a faulty tube or a big problem in the biasing to make that happen.

... Phil

They want the knobs at the top. It is most logical to mount them to the chassis as it IS convenient and that also provides shielding.

They could build 2 chassis' and put the "sub' chassis lower so as to facilitate this but the hot air would still go up. Same difference. With the sometimes very high impedances involved shielded triax could make for problems with capacitance.

To the tube itself it doesn't matter, what would matter is mounting it horizontally, which I would not recommend and most would agree.

It all depends on the tube. Some tubes specify that for horizontal certain pins have to be in a certain position.

++ I appear to be "blessed" with the ceramic variant ++ Not completely certain about that - at the time the solution seemed to be to just double the power rating of the resistor - AT

ses.

** No fooling..........

** Other makes may use EL34 tubes instead of 6L6GC, which draw much higher screen currents particularly when the output stage is overdriven. Typically , 1000 ohm resistors are used for each screen resulting in them running ver y hot with peak signal currents of about 80mA to 100mA. 5 watt wire wound types are normally used, but even they get hot enough to de-solder themselves if there is a loose socket connection to the plate pin of the EL34.

.... Phil

++ I assume "plate" = anode ?

Anyway, it all sounds uncannily similar to my fading memories of HiWatt

100 watt guitar amps from the 70's - happy days ...

... AT

The main problem with the upside down tubes is that when you clump the amp with a wellington boot to jar a bad connection back to life, eventually they fall out. Back in the 50s we used to keep a wellington boot beside each of the tube devices in the house just for this purpose. I'm giving my age away at bit here with this admission, but what the hey.

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certain pins have to be in a certain position. "

You are obviously trying to make me spend my last brain cell here...

Octals they want 3 & 6 to be on a vertical plane, novar 2 & 7, no clue about the 12 pin, or loktal. (like those old 7L7s n shit)

This is from memory so don't go designing shit without checking the book. I won't be responsible for your weird interelectrode shorts >:-)

I actually built an amp that way.

It was using 6L6 metal tubes; the 6L6s were on the bottom so I could dump them into a bucket of old style transformer oil ...

During a long set, the oil would start to bubble and then steam.

RwP