Microphonics in EF804's

[Dennis A.]

Hi All,
Has it been anybody's experience that EF804's are prone to microphonics?
I have several telefunkens that are. I was about to bid on a few on ebay
but the seller said that all of his tubes were also microphonic. Is this
just how it fares for this tube or is just bad luck?

Thanks,

Dennis

[Scott Dorsey]

Dennis A. > wrote:
>Has it been anybody's experience that EF804's are prone to microphonics?
>I have several telefunkens that are. I was about to bid on a few on ebay
>but the seller said that all of his tubes were also microphonic. Is this
>just how it fares for this tube or is just bad luck?

Well, in general it's a lot harder to make a pentode with tight pin spacing
and not have it be microphonic. There's a lot to move around inside there,
and there doesn't need to be much motion in order for it to be a serious
problem.

Since the EF86 is in current production, doesn't cost very much, and is
electrically identical and tends to be less microphonic, it might be
worth repinning EF804 gear to take EF86es.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."