6L6GB sub for 6L6GC?

  • Thread starter Rod Parsons
  • Start date
  • This site may earn a commission from merchant affiliate links like Ebay, Amazon, and others.

Rod Parsons

Friend of Leo's
Joined
Sep 26, 2009
Posts
3,161
Age
78
Location
Winchester, Va.
I have a reissue '63 brown Vibroverb that uses 6L6GC pwr tubes. I also have a pair of NOS Sylvania 5881s. When I bought the tubes from Angela's almost 20 years ago, he told me that they were the equivalent to a 6L6GB. Looking on-line at tubes, I often read that a 5881/6L6GB will substitute for all the 6L6s except the GC version. Will some one please explain why that is??.. Is there a simple mod to enable the usage of these 5881s? Maybe the amp could simply get biased to accomplish that..... Thanks!
 

muchxs

Doctor of Teleocity
Joined
Aug 14, 2004
Posts
13,175
Location
New England
Plate dissipation. 5881s dissipate around 19 watts, 6L6GCs around 25. In general fixed bias amps with high plate voltage exceed the ratings of 5881s.

You could bias 'em for around 70% of 19 watts each. Or you could use 6L6GCs.
 

Rod Parsons

Friend of Leo's
Joined
Sep 26, 2009
Posts
3,161
Age
78
Location
Winchester, Va.
Thanks. That answers my question.... I will get a bias control installed eventually. The GBs are cheaper to buy. I like the NOS ones, and since I have this matched pair..
 

schoolie

Tele-Afflicted
Joined
Apr 21, 2008
Posts
1,416
Age
58
Location
Portland, OR
I thought the 5881 max dissipation was 23W and the 6L6GC was 30W in PP. I've been biasing the 5881s to 16W in AB.
 

muchxs

Doctor of Teleocity
Joined
Aug 14, 2004
Posts
13,175
Location
New England
19 watts is the "by the book" max dissipation for 6L6WGB / 5881. Your "40 watt" amp won't be 40 watts with original 5881s. Maybe with Russian sorta 5881s that say 5881 on the glass...
 

muchxs

Doctor of Teleocity
Joined
Aug 14, 2004
Posts
13,175
Location
New England
You guys are right. I've been livin' out here in Little Amp World where the biggest tube we see is a 6V6...

6L6GB dissipates 19 watts plates, 3.5 watts screens (RCA data sheet)

6L6WGB / 5881 dissipates 23 watts plates, 3 watts screens (original Tung-Sol data sheet)

6L6GC dissipates 30 watts plates, 5 watts screens (GE data sheet)

I can tell I screwed up when the plates turn red... :oops:
 

SoK66

Tele-Afflicted
Joined
Oct 2, 2007
Posts
1,983
Location
Four Corners USA
I thought the 5881 max dissipation was 23W and the 6L6GC was 30W in PP. I've been biasing the 5881s to 16W in AB.

10-4. "True" 5881s (not the modern use of the designation) are 23w tubes, 6L6GBs are 19w tubes. The 5881 was originally developed for the military as a "rugged" 6L6GB. A 6L6WGB is a 26w tube. 6L6GCs are 30w.
 

vibrasonic

Tele-Afflicted
Joined
Dec 6, 2011
Posts
1,495
Location
sault ste marie canada
You learn something every day i guess, I did'nt know the WGBs were 26 watts I thought they were 23. I bought 4 matched sets or Nos Slyvania for some or my amps and they sound great
 
Top