I'ts not a joke, pdf64, I'm delighted to have shared this method and the good people can use it along will all the tedious to read, sometimes copied and pasted ones usually seen in these forums. it's not a dreadful idea and I'm sure people have already tried and and most certainly learned from it. Pdf64, working on any open live chassis is technically dangerous, and seriously. See, they sound different at different dissipation rates, take advantage of that and tune it with your ears, don't worry about numbers, numbers are for maths class.īecause its pitch black in that room, you can kill yourself real easy, don't do that. If it hums, then you know you've got lovely mismatched tubes ( more harmonics) if the hum is bad, then try a different combination of output tubes. You can back it right off if thats how you like the sound.hotter equals sort of a really cool alive sound to the amp, cold means boring.īoring means the tubes will live a lot longer. Get the amp chassis upright so it wont fall over, plug a speaker in to the amp, turn it all on and turn the bias pot slowly until you see one of the output tubes plates juuuust start to glow red, then back off a wee bit, it will not glow red anymore. You dont need ' matched tubes' ( they sound better when they're not matched, up to about 8 ma in difference, any more and the hum is a problem)Īll you need is a pitch black room, a screwdriver and some care. You don't need the volumes of data that people present in these forums every time the word ' bias' is used in relation to output tubes. You don't need a multimeter, you dont need any words like dissipation, or any numbers, or any 1ohm resistors or bias probes or anything like that. Guitar guys make a big deal out of the bias thing, but it's not a big thing at all. This time I set it at 37 just to be on the safe side. How is that possible? Why does a higher plate voltage equal and lower or colder bias setting?īTW The amp was set exactly at 40, the last time I blew the HT fuse I retubed the amp and followed the bias procedure of PV divided by 25 x 70% and set the amp to 40. In the video he says his tubes are rated at 26 watts, I use a 25 watt starting point and get the 40, if I use 26 I get 42. In the video the guy has a 460 PV and does the calculation and comes up with a 39 bias point.
#Biasing a tube amp how to
I always forget how to do the math from the plate voltage to get the bias point. I watch a video on YouTube to refresh my memory because I don't bias my amps all that much. I wanted to check the bias to make sure it was set properly because this is the second time I blew the HT fuse and both times was because of a bad power tube. My 2004 Marshall 1959 SLP Reissue blew a HT fuse so I checked the power tubes and V6 was bad, I have about 20 E元4 tubes and change the bad one out.
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