[David[_16_]]

Hi everyone,

Great to see such a great group available like this one.
I was recently suprised to learn that the 6386 Ge and RCA tubes /
valves were so saught after.
I currently have a few for sale;

http://www.oztion.com.au/buy/auction...itemid=4193316

http://www.oztion.com.au/buy/auction...itemid=4193318
And I plan to list a few more soon.

I hope this information helps some people out that need these tubes /
valves.

I have a few other tubes listed as well.

Cheers,

David

[Scott Dorsey]

David wrote:

Great to see such a great group available like this one.
I was recently suprised to learn that the 6386 Ge and RCA tubes /
valves were so saught after.
I currently have a few for sale;

Here are some of the problems. The 6386 is a variable-mu triode, with
a very nonlinear curve. If you have a small signal voltage and a large
bias voltage, by changing the bias you can alter the point on the curve
that you are working, thereby changing the gain.

Because of the way they operate, they don't have as long a life as
a conventional dual triode like a 12AX7, and on top of that folks tended
to swap them out pre-emptively long before the emission dropped, because
they were cheap and plentiful.

Now they are no longer cheap and plentiful, and they have become somewhat
rare. Therefore, a lot of people are selling their old pulls as NOS tubes.
Some of those pulls are fine, some of them are not, but they are not NOS.

On top of this, at least one company has been taking Shuguang tubes
which are NOT variable-mu devices, and badging them with GE 6386 logos.
There are a LOT of forged tubes selling on the market out there, and
it is a big deal right now.

I hope this information helps some people out that need these tubes /
valves.

It does... but make sure you know the origin of what you're selling and
you're prepared to certify it. Also if you can, get full curves run on
a curve tracer. One of the problems with these is that you cannot just
measure transconductance at one point in the curve and say they are good
or bad... you need to be able to look at the whole curve. And it helps
to be able to match pairs of them too.

You can draw out the whole curve by hand with a transconductance tester,
just adjusting the bias voltage and plotting on a piece of graph paper.
It takes forever though, so if you have a lot of tubes, sending them to
a lab with a curve tracer will save time and money.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."