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PostPosted: 15 Aug 2020, 15:56 
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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

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Last edited by Dr G on 15 Aug 2020, 17:13, edited 1 time in total.

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PostPosted: 15 Aug 2020, 16:25 
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This is usually due to manufacturing variations or inconsistencies in the filament insulation. It usually has no impact on tube performance or audio reproduction.

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PostPosted: 15 Aug 2020, 17:13 
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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


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PostPosted: 16 Aug 2020, 15:32 
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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

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PostPosted: 17 Aug 2020, 08:12 
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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


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PostPosted: 21 Aug 2020, 20:38 
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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.


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PostPosted: 22 Aug 2020, 12:01 
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ILoveHiFi wrote:
I see you also have some telefuken in the amp, nice.

Good observation!


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