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Unequal Filament Glow Between Tube Pair
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Author:  Dr G [ 15 Aug 2020, 15:56 ]
Post subject:  Unequal Filament Glow Between Tube Pair

Hello,

I just installed some (new to me) tubes in my Marblewood amp. These are NIB RCA 6W6GT's. I bought 4 of them. The first pair I picked to try out have a very noticeable difference in the glow from the filaments. See here:

Image

This is the first time I have noticed this out of the many, many tubes I've rolled through.

Seems one of the filaments has a lower resistance and is letting more current flow through it? I am not too concerned as these tubes were very affordable. But does anyone know what causes this and what is the effect on audio performance? I could not really detect any in my short listening period.

Thanks - Gustave

Image

Author:  Suncalc [ 15 Aug 2020, 16:25 ]
Post subject:  Re: Unequal Filament Glow Between Tube Pair

This is usually due to manufacturing variations or inconsistencies in the filament insulation. It usually has no impact on tube performance or audio reproduction.

Author:  Dr G [ 15 Aug 2020, 17:13 ]
Post subject:  Re: Unequal Filament Glow Between Tube Pair

Suncalc wrote:
This is usually due to manufacturing variations or inconsistencies in the filament insulation. It usually has no impact on tube performance or audio reproduction.


Excellent. Thanks. The third tube I tried also had a high filament glow. So I've paired it with it's brother.

Have not yet tried the fourth. Hopefully it is "low-glow".

Gustave

Author:  gofar99 [ 16 Aug 2020, 15:32 ]
Post subject:  Re: Unequal Filament Glow Between Tube Pair

Hi, The amount of glow is as noted a variation of assembly of the tubes and I have never seen it cause any audible effect.
Good listening
Bruce

Author:  Dr G [ 17 Aug 2020, 08:12 ]
Post subject:  Re: Unequal Filament Glow Between Tube Pair

gofar99 wrote:
Hi, The amount of glow is as noted a variation of assembly of the tubes and I have never seen it cause any audible effect.
Good listening
Bruce

Thanks Bruce.
Gustave

Author:  ILoveHiFi [ 21 Aug 2020, 20:38 ]
Post subject:  Re: Unequal Filament Glow Between Tube Pair

Hi you can measure the current of the tube, I have seen tube glow in very expensive 12ax7-T shuguang, one side has slightly more heater poking out and glows brighter.

Thoguh never had a prolbem with current or sound, and some of the best tubes I've heard.

I see you also have some telefuken in the amp, nice.

Author:  Dr G [ 22 Aug 2020, 12:01 ]
Post subject:  Re: Unequal Filament Glow Between Tube Pair

ILoveHiFi wrote:
I see you also have some telefuken in the amp, nice.

Good observation!

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