Is the red glow normal for 845 tubes?

What did he say about using a low dissipation (70w) 845s in the SETi40? That is the real question you should ask. If the SETi845 is auto biased for a standard 845, then the amp is over driving the Sino.

Good point Brf! He did not said anything regarding the low dissipation. I will ask him if the SETi 40 is biased for a standard 845 tube (100 W dissipation).

I got another answer from Bel canto stating that the dull red glow from the graphite plate is normal and that the amp can drive just fine the 845 low dissipation tubes. Bel canto did not said anything regarding the amp bieas for a hight dissipation tube or for a low one. Thanks again Brf.

Hi Tiofelon, Bel Canto's response has me puzzled. The SET40i is auto biased, therefore, it is either optimized for a 70w dissipation or 100w dissipation, it can't be both. If you are still curious, check with Bel Canto to be sure of the dissipation/op point. Ask what's the auto bias setting (in ma) and ask what the plate current is in volts. Once you know these two figures, you can calculate the tube dissipation. (plate voltage x plate current in ma = plate dissipation in watts. e.g. 1000v x 100ma = 100w ).

Yes, a "dull" red glow in an 845 is normal, but a prominent red glow indicates an over driven 845. As mentioned before, you are not hurting your amp.

Got an another answer from Matr Cramer at Bel canto. He says that "a dull red glow is normal for a 845 tube, but he recommends using a 845 tube with a 100W dissipation or they can fix the amp so that it can lower the dissipation rate as it prolongs the life of the tubes." So according to Bel canto and Brf the amp runs fine. It this the life of the tubes that is in danger of premature failure. Thanks Brf.