5881 Replacement for 6L6? - CORRECTION 6L6GB

[kd4e]

Just looked at the specs for my Multi-Elmac AF-68 (chose
the AF-68 instead of the AF-67, swapped the AF-67 for a
PMR-8) and observed that the modulator tubes are 6L6GB's
rather that the metal 6L6.

Why would they have chosen glass vs metal?

Modifying my original question a little:

If the AF-68 is designed for the 6L6GB which of the
following are likely to be acceptable & which better
than than the 6L6GB in the AF-68 (it will be both base
and portable so resilience to vibration is valuable)?

6L6
6L6G
6L6GA
6L6GAY
6L6GC
5881
Other?


 > Bry Carling wrote:
>> Is it correct that the 5881 is shorter, more physically rugged,
>> and more electrically rugged than the 6L6?
> 
> Not really no. There are MANY varieties and many brands of both 
> that are all different.
> 
> So many other variants too, like 8417 etc.
>  
>> Is it OK to sub the 5881 for the 6L6 in the modulator circuit
>> of a Multi-Elmac AF-67?
> 
> Probably, although I can tell you from experience from 
> exchanging 5881s and 6L6es in guitar aos some years ago, 
> it is possible to get a very different sound.
> 
> The characteristics and the bias needed are NOT necessarily 
> the same. It depends a lot on which circuit is in use.
>  
>> Since it is a mobile-portable rig a more rugged tube makes
>> sense.  Is there a "gotcha" here that I am missing?
> 
> A more rugged tube would be the 6L6 WGB or other variants 
> with a W in the designator. 6L6GC by RCA is a great tube
> IF you can find them still...
>  
>> I found this descriptive Tungsol text from 1950:
>>
>> "The 5881 carries ratings similar to the 6L6, except that the allowable 
>> screen dissipation is 3.0 watts instead of 2.5 watts while the maximum 
>> plate dissipation is 23 watts instead of 19 watts for the 6L6. The tube 
>> has a low loss micanol base."
> 
> There CAN be more to it than that.
> 
> http://firebottle.com/ampage/td/vtd5881.html
> http://www.r-type.org/exhib/aaa0451.htm
> http://www.wps.com/archives/tube-datasheets/Datasheets/CBS-PA-
> 5/4.JPG
> http://www.mif.pg.gda.pl/homepages/frank/sheets/127/5/5881.pdf
> http://oldradio.qrz.ru/tubes/foreign/01/5881.gif
> http://firebottle.com/ampage/td/
> 
> I hope that hepls, but you may find some more anecdotes
> around the web. Chances are that your 6L6es would do fine 
> mobile anyway!
> 
> When will you be on 75m or 40m mobile ? We can try for a QSO!


-- 

Thanks! & 73, doc, KD4E
Personal: http://bibleseven.com/kd4e.html

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