[Hammarlund] Hello list - HC-10 and 6AU6s.

[Richard Knoppow]

----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: <Hammarlund at mailman.qth.net>
Sent: Monday, April 02, 2012 12:38 PM
Subject: Re: [Hammarlund] Hello list - HC-10 and 6AU6s.


> On 2 Apr 2012 at 12:10, Richard Knoppow wrote:
>
>>      The 6AU6 and 6BA6 have virtually the same
>> transconductance with equal plate and screen voltages.
>
> Although I have not been able to get to my tube databooks,
> I distinctly
> remember the 6AU6 having higher transconductance than the
> 6BA6.
>
     The RCA handbook RC-24 shows both tubes to have about
4500 uMho with similar voltages. The 6AH6 has about 9000
uMho.  I am not sure why a sharp cut-off tube is better as
an oscillator or even if it is, but they seem to be
generally used. I think the 6AU6 was originally built as an
RF tube. They can be problematical as audio tubes due to
microphonics and heater to cathode hum but were widely used
nonetheless until better tubes such as the 5879 became
available.
     There is a lot of tube data on line including scans of
several RCA handbooks including most of HB-3, the big,
multi-volume one.  I've been collecting tube handbooks for
decades, mostly because I hate throwing stuff out. Sometimes
it pays off:-)
     BTW, I think the introductory section of the RCA tube
manual is about the best primer on vacuum tube technology to
be found.
     I suppose to be academically correct I should call uMho 
uSiemens but that just jars my sensibilities, something like 
walking barefoot on crushed lightbulbs.

--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com