How much light in Power Tubes?

[AFguitar76]

Hello!

I'm new in this forum and it's a pleasure to be here.

I have just completely re-tubed and biased my Fender HotRod Deluxe amplifier bought in 1999, made in USA.

The technician installed a new set of Groove Tubes Golden Series (3 x 12AX7 and 2 x 6L6).

I compared my amp with another new hot rod bought by a friend of mine and I noticed that my power tubes have less brightness.

- Is the intensity of brightness related to the value of Bias?
Or is there any other factor that influences the overall brightness of power tubes?

- Is the brightness different for 6L6 "white" (normal distortion rating) and 6L6 "blue" (early distortion rating)?

I would like to know more about it because it is my first time I re-tube an amp!

Cheers from Italy

Angelo

[Enzo]

I have to say I am not yet sure what you mean. Audio brightness, as in treble? Or do you mean the glow seen visually in the tubes?

If visual glow, brands of tube differ.

If audio brightness, you replaced ALL your tubes, so how can you decide the power tubes are where the brightness is lacking? Again, no matter why, brands of tubes differ.

[AFguitar76]

I have to say I am not yet sure what you mean. Audio brightness, as in treble? Or do you mean the glow seen visually in the tubes?

If visual glow, brands of tube differ.

If audio brightness, you replaced ALL your tubes, so how can you decide the power tubes are where the brightness is lacking? Again, no matter why, brands of tubes differ.

I mean the glow, but not the orange glow at the cathode, the brightness of the light emitted by the power tubes.

I saw another hot rod deluxe with same brand (GT 6L6 "white") and they had more total light than mine.

What does it depend upon?

[Enzo]

They were white Groove tubes maybe, but were the tubes really the same? Held side by side, do the innards look identical? They could be SOvtek or JJ or EH or who knows what under that Groove tube label.

Unless there is some noticable performance problems, the glow inside the tubes is not usually a service criteria. If one tube was not glowing at all and the others were, for example, we might infer that the dull tube was not running. But that would assume same type tubes in the one amp.

[Steve Conner]

The amount of light just depends on how much heater wire is sticking out of the top of the cathode.

The heater wire glows bright orange, but some tubes have it all hidden inside the cathode, and others have loose ends sticking out.

It has no effect on the tube performance.

Of course if your tubes are glowing like this:

http://www.youtube.com/watch?v=iD40DvztY4E

you have a real problem

[Enzo]

Nah, he means the purple glow inside the glass envelope.

[AFguitar76]

Nah, he means the purple glow inside the glass envelope.

Hi Enzo,

no, I don't mean the purple glow, I mean the overall intensity of the light I see in the tube.

I think Steve is right ("heater wire sticking out of the top of the cathode").
And a friend of mine who is technician told me that tubes of same brands are not made exactly the same.

What do you think?

When I have time I will take pictures of power tubes on my amp and another one of same model, I hope you can see what I mean.

Thanks
Angelo

P.S. are you Italian? I see your name Enzo

[Steve Conner]

Here is another picture of some glowing tubes :-)
http://scopeboy.com/crown-sxa/IMGP1427.JPG

If you look at the four large tubes at the back of the chassis, there is a white light inside the top part of each one. Is this what you're talking about?

[Enzo]

Sorry then. You said not the orange glow, so I assumed....

The heater in the center has to heat the cathode inside. ANy part that sticks out the top or bottom is irrelevant.