[Boatanchors] Tube reciever design banter

[Carl]

----- Original Message ----- 
From: <match at ece.utah.edu>
To: "Carl" <km1h at jeremy.mv.com>
Cc: <boatanchors at mailman.qth.net>
Sent: Tuesday, December 22, 2009 4:39 PM
Subject: Re: [Boatanchors] Tube reciever design banter


> On 21 Dec 2009 at 18:26, Carl wrote:
>
>> > Yeah, we've discussed this before, however I found another that looks
>> > interesting. Have a look at the 6MU8 triode/pentode. Semi-remote 
>> > cutoff,
>> > 9000 uM, 3.75 W plate diss., and an extra free triode section as a 
>> > bonus.
>> > Designed around 1970 and I think it's a frame-grid. I like 
>> > multi-section
>> > tubes
>> > when it makes sense to use them. $2.43 right now at AES.
>>
>>
>> There are many nice tube possibilities at the end of the era altho many 
>> are
>> the same tube with different pin outs or slightly fudged specs simply to
>> generate captive audience sales.
>
> Yes, from about the mid 60's there was not much new, just mostly the same
> tubes repackaged to woo the TV manufacturers.
>
>>  However the 6MU8 pentode is a sharp cutoff
>> and the 6LM8 isnt very exciting for a high performance receiver.
>
> Now this is very interesting! My RC-30 databook lists it to be a 
> semi-remote
> cutoff pentode. But everywhere I can find it's specs listed online has it 
> as a
> sharp cutoff.


The full RCA spec sheet has it as Sharp along with the curves. Its dead in 
the water at -9V which doesnt give a good AGC window without getting fancy.

BTW, The Halli SX-140 uses the 6AZ8 pentode as the RF amp.


Carl

>
> Oh well. One or the other must be a misprint. Wouldn't be the first time. 
> I
> guess the only way to find out would be to test one or break one open.
>
> Gee, I was all set to build something like "The Simple X Super" with an
> added RF stage and AVC out of them... I guess I still could.
>
> Marvin
> KA7TPH