5881 Replacement for 6L6? - CORRECTION 6L6GB

[Bry Carling]

6L6, 6L6G and 5881 will usually have a lower maximum
voltage rating for the HT (B plus) than the advanced types 
like a modern 6L6GC or maybe even a 6L6GB.

I would go with the manufacturer's recommendation if you have 
a choice.

> 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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