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Old 8th September 2014, 04:34 PM   #1
diyAudio Member
Join Date: Dec 2010
Default 6k5GT - Good Tube Curves?

Hi All,

Does anyone have any experience with this tube. Does anyone have information on it's max ratings? I can't seem to find any Max levels for current.
I have been told at another forum (different site) that it was a horrible tube for a pre-amp... However, it seems linear to me...am I reading the curves correctly?

Using the curves to calculate - I'm currently running it:
240V on the plate, 1.5mA cathode current.
Plate resistor is 20K with a 2K cathode resistor...B+ =293V

I'm having some good results with it in my current 2 stage 6L6GC home brew...but via my ears. I'm just wondering if I'm listening to distortion.

The 6K5GT sounds a brighter than a 6J5GT...but still with plenty of bass...the speakers just disappear.

Any info would be great...
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Old 8th September 2014, 04:48 PM   #2
diyAudio Member
Join Date: Jul 2012
The tube is good as long as you dont go over 250V and lower than 0.5mA.

You wont find max current rating because you would only be reducing the tubes life at currrents well off the Vp-Ip graph.

With that being said you are using a way to low plate resistor which will generate a lot of 2nd harmonic distortion. Try using a 120k plate resistor and running it at 170V 1mA (~2V on cathode) and see how you like it. Bear in mind you will have a lot more gain.
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Old 8th September 2014, 06:47 PM   #3
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Join Date: Dec 2010
Thanks Marcelop,

I'll look into that...I was afraid 1.5mA was too much. I'll plot out the 1mA, 170V on the curves.
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Old 10th September 2014, 04:33 PM   #4
diyAudio Member
Join Date: Dec 2010

I haven't obtained the 120K resistors yet...
I have been using 137K with 4k cathode... which gives 200V at .9mA
It sounds good.
The distortion calculates less...but I'm going for even less.

I'm using this article for calculations...

Of Loadlines, Power Output and Distortion.
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Old 11th September 2014, 07:35 AM   #5
gsmok is offline gsmok  Poland
diyAudio Member
Join Date: Jul 2004
Location: Warsaw, Poland
I suggest to use the online simulator in which 6K5-GT tube is implemented.
It is the direct link:
Triode Loadline Simulator v.1.0 (20140911 www.trioda.com)
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Old 11th September 2014, 06:03 PM   #6
diyAudio Member
Join Date: Dec 2010
Thank you Gsmok!

As I look at the 6sn7, it seems to have better distortion figures...I have 2 6j5gt's to play with...along with 2 6c5gt's.

Again...Thank you!
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