Question in regards to Bias and Fuses

[Dallas Marlow]

I have two pretty easy to answer questions:

First, I read on here to upgrade the fuses from the standard 250 to 400-500, I put the 500's in the tube fuses, are these too high because I now notice that most of the posts are saying 400s, the 500s are fast blow and it's all I could locate.

Second, according to the Randall Manual the highest you should bias standard EL34's was either 38 or 39, however; from all my previous knowledge I thought that 45 was the appropriate way to go with el34's, I notice it says up to 45 with EL34L's but not EL34's, which I REALLY don't get because don't the EL34L's draw a lot more plate voltage than normal EL34's? I've noticed when swapping between the two you have to turn your bias up a significant amount to get it into the same range as the EL34L's. I heard 45 was on the hotter side, but not out of a safe range, and that is just with standard EL34's, I believe that was according to Marshall for their DSL series.

Is running my Shugwang EL34-B's safe up to 45? This is what they are currently running at, amp doesn't seem to get to hot, sounds beautiful and runs great, and I do 3 hours of pretty high volume band a few nights a week along with gigs etc. no issues as of yet.

Thanks for your help!

Dallas

 

[Dallas Marlow]

No one knows the answer

 

[JKD]

I don't have a definitive answer but I do know EL34s run hot anyway and if you look at the power rating and plate voltage you are running them on the high end at 45...EL34 is a 25W tube right, which makes 50mA with 500V plates = 100%?, 45/50 = 90%

Your tube lifespan will be lower and since tube quality is generally agreed to be very variable today you could be risking blowing something..hopefully the fuses kick in first.

 

[Dallas Marlow]

Thanks for the reply man, but does anyone else have any input or know about the fuses?

 

[Soulinsane]

I would think that the 500 fast blow would be fairly safe but at the price of putting more stress on the other components before it blows if there is ever a fault. The 250 fuses were obviously to small in some cases but the ideal is you want a fuse big enough to handle random peak surges but small enough to blow before something else does.