Burning in a 12ay7 tube for use in a C12 clone

[dmnieto]

Hi all,

I am still in the process of building my C12 clones, One of the thing I want to do is to burn in my 12ay7 tubes.

I was wondering if I could use my G9 preamp to burn in those tubes. The G9 pre uses the ECC82 tube (12au7), I was thinking about placing the 12ay7 tubes on the SRPP stage.

Would that be a dumb idea?

 

[dmnieto]

Any comments? I know this is not a help chat, but I was wondering if any of the most experienced forum members could tell me if what I was planing would be safe for the tubes...

 

[bockaudio]

why would it not be safe to use a tube before you intended to use a tube?

 

[dmnieto]

I mean,

If it would be safe to burn-in my 12ay7 tube (which I intend to use in a C12 clone) by placing it in the SRPP stage of a G9 preamp without any other modifications to the G9

 

[MagnetoSound]

why would it not be safe to use a tube before you intended to use a tube?

This is some weird syntax, what does it even mean?

 

[bockaudio]

why would it not be safe to use a tube before you intended to use a tube?

This is some weird syntax, what does it even mean?

No it's a simplification of his question. Essentially, a "burn in" is using the tube. Once it goes into the mic, he will be using the tube as well.
Burn in of tubes is essential for microphones, especially since it's not 1955 anymore and we don't have a wonderful flow of well made tubes coming from multiple sources.

 

[MagnetoSound]

Ah, thanks for clarifying what you meant there.

 

[dmnieto]

I got my answer from Gyraf in another thread.

The G9 can be used to burn in the 12ay7 tube if placed in the SRPP stage.

 

[Gus]

IIRC Steve Bench had a write up about burning in tubes I have not been able to find it with searching.  Does anyone remember this?

 

[dmnieto]

IIRC Steve Bench had a write up about burning in tubes I have not been able to find it with searching.  Does anyone remember this?

No Gus I didn't, I even found out your 2004 post about how you burned the tubes... you said you have built a fixture to provided a fixed bias.

 

[Matador]

IIRC Steve Bench had a write up about burning in tubes I have not been able to find it with searching.  Does anyone remember this?

No Gus I didn't, I even found out your 2004 post about how you burned the tubes... you said you have built a fixture to provided a fixed bias.

What is the issue with burning the tube in in-circuit?

Using a C12 is (almost always) the best way, as you can hard ground the grid via a jumper wire, and crank the preamp gain to hear the noise of just the tube.  The C12 circuit isn't fixed bias so I'm not sure where the "runaway" fear is coming from.

 

[Gus]

What is the issue with burning the tube in in-circuit?

Using a C12 is (almost always) the best way, as you can hard ground the grid via a jumper wire, and crank the preamp gain to hear the noise of just the tube.  The C12 circuit isn't fixed bias so I'm not sure where the "runaway" fear is coming from.
[/quote]

You mean I wasted my time doing experiments with burning in tubes?  Now why would I post something if I did not test it. 

 

[Matador]

You mean I wasted my time doing experiments with burning in tubes?  Now why would I post something if I did not test it.

I wasn't addressing you:  and I wasn't even think of you (or anything you may or may not have wrote 10 years ago) when I was typing.

I was address the OP's question of whether or not it would "harm" a tube or be dangerous to the tube to burn it in in-circuit:  specifically about the possibility of current "runaway" which isn't even possible in a C12-like circuit.  The OP seems to have an idea that only fixed-bias circuits can be used to test tubes which simply isn't true.

 

[dmnieto]

I wasn't addressing you:  and I wasn't even think of you (or anything you may or may not have wrote 10 years ago) when I was typing.

I was address the OP's question of whether or not it would "harm" a tube or be dangerous to the tube to burn it in in-circuit:  specifically about the possibility of current "runaway" which isn't even possible in a C12-like circuit.  The OP seems to have an idea that only fixed-bias circuits can be used to test tubes which simply isn't true.

It is not exactly that way, my concerns were addressing the following statement by chunger in the official C12 thread:

[quote author=Chunger]
Note:  It is imperative if you are following this "unscientific" initial verification process to make sure the tube and capsule that are being used for calibration and function verification are 100% stable, broken in, and functional.  Otherwise, all manner of problems that are difficult to trace can surface.  The 12AX7 tube that originally shipped with my HT-11A was a hissy, intermittent, crackling mess and totally unsuitable for even function testing.  The Electro Harmonix 6072A tube used for function testing was fired up in a guitar amp for about a week and tested in studio to be completely stable in another microphone.  If purchasing a nice NOS tube from Christian Whitmore for this project and you do not have a known, stable tester tube on hand, please consider sourcing a stable but cheap tube from him for testing purposes.  . . perhaps a tube that is more microphonic than acceptable for microphone use, but is stable and good enough for setting up voltages and function checking.
[/quote]

So my question was not about the unsuitability of burning in in the C-12 , but actually the opposite: If the biasing of the SRPP output stage was appropriate to burn-in and test the tube, so I could have one to fulfill the "imperative" requirements in the C12 build thread.

I agree that it is possible to hard-wire the grid to test the noise, but that precludes that my C12 is already built, which it isn't. I am trying to get the path of less pain.

Thanks anyways!