6F8G tubes?

Cryok95 · 5857

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Offline Cryok95

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on: April 28, 2013, 10:25:20 PM
Hi all, was wondering if it is possible to place a 6F8G tube with an appropriate adapter in place of the input 12au7 tube in the crack.

I know it is possible to roll a 6sn7 there but was wondering of the 6F8G since I read that they are identical.



Offline Paul Birkeland

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Reply #1 on: April 29, 2013, 03:32:03 AM
The 6F8 will operate in the circuit with an adapter (or a socket change + plate cap wire).
-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline nick-seattle

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Reply #2 on: May 03, 2013, 12:40:01 PM
You will be very pleasantly surprised by the sound of 6F8G from Ken-Rad and Sylvania VT-99. These are definitely worth spending money on adapters.



Offline Wizzie

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Reply #3 on: December 06, 2015, 11:07:56 PM
the e80cc and 12BH7 needed a R1 resisitor mod the have it run optimally.

Do you know if there is any mods needed to optimise the 6F8G for BHC +SB?



Offline Chris65

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Reply #4 on: December 06, 2015, 11:20:03 PM
 8)



Offline Wizzie

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Reply #5 on: December 07, 2015, 12:39:08 AM
Looks cool Chris65

can you comment on the sound quality and also did you make any changes for the 6f8g?



Offline Tom-s

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Reply #6 on: December 07, 2015, 03:03:57 AM
For me the 6f8G is a step-up from the average 12au7 and a side step (different flavor) compared to a good 12au7.
I'm using the Tung Sol round plate version and i like it a lot. 
Overall the mids aren't as forward as with most 12au7's, bass is different (deeper?), soundstage is bigger.
Big downside is that mine are microphonic :(.



Offline Lee Hankins

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Reply #7 on: December 07, 2015, 08:16:53 AM
I believe that the adapter is the problem, not the tube.

Lee Hankins
"End of the Road"
Homer, Alaska


Offline Tom-s

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Reply #8 on: December 07, 2015, 09:53:53 AM
It's hard for me to differentiate the tube from the adapter. In case of one tube, it's only microphonic when completely warm > 1 hour.
Do you think it could be the adapter heating up and starting the microphonics?

One some other tubes it makes no unwanted noise.



Offline Wizzie

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Reply #9 on: December 07, 2015, 02:41:48 PM
Does the 6f8g require any hardware changes



Offline Chris65

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Reply #10 on: December 08, 2015, 01:08:29 AM
Can you comment on the sound quality and also did you make any changes for the 6f8g?

I would just echo Tom-s comments. A different flavour compared to a good 12AU7/ECC82.
No changes - only the adapter (machined teflon) in a stock Crack with Speedball (well, there are film output caps & a Tocos Japan volume pot).



Offline mcandmar

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Reply #11 on: December 08, 2015, 03:16:21 AM
I'm my limited experience with 6F8G tubes they did tend to be more microphonic than the smaller glass octal tubes.  I would almost say as a general rule the bigger the glass, the more microphonic the tube will tend to be.

M.McCandless


Offline InnerTube

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Reply #12 on: May 16, 2018, 07:12:31 AM
8)
This photo is a bit confusing to me.  The 6f8g or 6c8g (with adapter)  is my very favorite tube in the Crack, however, I am using it as a power tube - a replacement for the 6080, etc.  It is a much cooler tube than the 6080 and sounds just great.  If you can afford the Tung Sol, you will not be sorry.

Great listening, JS

Innertube (John Spain)
[email protected]


Offline Paul Birkeland

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Reply #13 on: May 16, 2018, 08:58:34 AM
The 6f8g or 6c8g (with adapter)  is my very favorite tube in the Crack, however, I am using it as a power tube - a replacement for the 6080, etc.
That's a great way to destroy the tube, at minimum, and maybe the amp while you're at it.  This is not a suitable replacement for the 6080 for a very, very wide variety of reasons.  Doing this will leave the amp distorting terribly until the grids of the 6F8 burn up from being positively biased, or maybe it will burn up from exceeding the plate dissipation rating.  It's just hard to tell which will happen first!




Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Doc B.

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Reply #14 on: May 16, 2018, 09:14:23 AM
To further PBs comment - 6F8G is rated for 9mA maximum plate current. The 6080 is drawing about 3 times that in the Crack.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.