Tube amp question

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
I see lots of tube amps with the tubes mounted such that they point
down. This means all the heat rises up into the chassis. This seems
counter-intuitive to me. All those components baking all the time. Is
it just for convenience?
Eric

Re: Tube amp question
snipped-for-privacy@whidbey.com wrote:
Quoted text here. Click to load it

** 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  




Re: Tube amp question
:
Quoted text here. Click to load it

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.

Re: Tube amp question
On Thu, 11 Oct 2018 07:08:19 -0700 (PDT), "jfeng@my-deja.com"

Quoted text here. Click to load it

Quoted text here. Click to load it


Uh, I guess you are an audiophile?

I thought the latest craze was graphene wires...

Re: Tube amp question
On Thu, 11 Oct 2018 07:08:19 -0700 (PDT), "jfeng@my-deja.com"

Quoted text here. Click to load it

Quoted text here. Click to load it
I knew it! Instead of OFHC copper they will use OFHS silver.
Eric

Re: Tube amp question
On 10/10/2018 22:05, snipped-for-privacy@whidbey.com wrote:
Quoted text here. Click to load it

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

Re: Tube amp question
Abandoned Trolley wrote:

Quoted text here. Click to load it


** Some use white ceramic sockets - but most use plastic or phenolic bases.


Quoted text here. Click to load it

** Really has to be a faulty tube or a big problem in the biasing to make that happen.



...   Phil  


Re: Tube amp question
On 18/10/2018 01:33, Phil Allison wrote:
Quoted text here. Click to load it


  ++     I appear to be "blessed" with the ceramic variant
Quoted text here. Click to load it

++    Not completely certain about that - at the time the solution seemed  
to be to just double the power rating of the resistor - AT
Quoted text here. Click to load it


Re: Tube amp question
Abandoned Trolley wrote:


Quoted text here. Click to load it
ses.

  ** No fooling..........

Quoted text here. Click to load it

** 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  





Re: Tube amp question
On 18/10/2018 12:10, Phil Allison wrote:
Quoted text here. Click to load it


++ 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

Quoted text here. Click to load it


Re: Tube amp question
On 10/17/2018 2:19 PM, Abandoned Trolley wrote:
Quoted text here. Click to load it

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



Re: Tube amp question
Quoted text here. Click to load it

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.  

Re: Tube amp question
snipped-for-privacy@gmail.com says...
Quoted text here. Click to load it

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


Re: Tube amp question
On Wed, 17 Oct 2018 22:59:45 -0400, Ralph Mowery wrote:

Quoted text here. Click to load it

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.





--  
This message may be freely reproduced without limit or charge only via  
the Usenet protocol. Reproduction in whole or part through other  
We've slightly trimmed the long signature. Click to see the full one.
Re: Tube amp question
Quoted text here. Click to load it
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 >:-)

Site Timeline