5881 Replacement for 6L6? - CORRECTION 6L6GB

[Scott Johnson]

TRhe 5881's will easily handle 500V, and often did, even in military 
equipment.  The 5881 is a button base tube, which gives much better 
isolation than the older press seal tubes (even the KT-66 had a press 
seal).  I have also had good results using 5881's in Hi-Fi amps, I think 
yopur experience with the guitar amps may have been bias related, or you 
simply had bad tubes. I have a Soundcraftsmen mono amplifier that drives 
my shop radio speaker with 6L6WGB/5881's in it, it runs at 425 Va, and 
it has been playing on the same set of tubes for about ten years now.

Scott W7SVJ

Bry Carling wrote:
>> Their is a big difference between the 6L6GC and the 5881 in the maximum 
>> plate voltage. A 6L6GC has a max plate voltage rating of 500 volts and 
>> the 5881 has a max plate voltage rating of 360 volts. If your guitar amp
>> was designed for 6L6GC's, its no wonder it sounded terrible, not to 
>> mention the abuse those tubes saw.
>>     
>
> Abuse? I wouldn't call it that.... 
> They were only in there for a few minutes at 475 V. 
> Most tubes will easily withstand a little extra. Especally for 
> a short  time like that. 
> It is not totally uncommon, even for manufacturers to run 
> tubes at a higher B voltage than their official max rating.
>
> Some manufacturers wil rate their 5881s at 360 volts while 
> others rate them at 350, 400V etc.
>
> I will bet they usually do fine at 425V or 450V, but it would 
> be silly to push them like that day in and day out.
>
> I was referring to the sound quality rather than the reliability.
>
> Doc was referring to substituting in the other direction, using a 
> 6L6GB in place of the 5881, which should do fine IF it sounds 
> clean.
>
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