Wonderful video! I learned to bias from you and it has made a great difference in my amps. I too use the eurotubes meters at your recommendation; they are excellent. It is good to see you putting out new material. Thanks again for an entertaining informative lesson.
I have a Blackstar 40w club amp and Blackstar don't say how to bias the EL34 valves but from another channel here on YT I found their little secret, next to the tubes through the chassis there are 2 trim pots one for each valve and there are 2 LED's per valve one green and one red, adjusting the pot for no glow from either green or red LED the bias is set for one tube and just repeat the same for the other tube.
Yes, a 2205. I own one of these from 1985. Michael Schenker’s amp of choice. I love mine, has a much better rock tone than the 2203,04 800’s. They are a bit brash and brittle for me. These have more gain and are just a joy to play without paint peeling volume to get a good tone.
Great demonstration of how to bias this Marshall model. It's a pity that Marshall don't go one step further and fit an external adjustment that only requires a bog standard digital multimeter and small screwdriver like some on the Fender's have got. Hope you've managed to take advantage of the flying conditions of late 😅🛩
Yes had a nice day out on Isle of Wight yesterday! I think the reason they don't do this is because they really don't want people twiddling. Not one guitarist in 100 knows anything about biasing but will certainly respond to a forum post which goes: "Hey, Anyone else know this awesome Fender hack? There's a screwdriver slot on the top of the chassis, just turn it up to MAX and you'll get this AWESOME tone! Enjoy my dudes!".
this is a great tutorial. quick question though. When you buy a set of tubes and they write a number for the bias point. in my case i have a set of kt88's with 33 written on them. do they mean for me to treat that as the max dissipation instead of the blanket 35w given to kt88's?
My guess is that this is the bias current 33mA which these tubes drew under certain test conditions. Not really useful apart from matching. E.g. you want 2 x 33 or 4 x 33 tubes to be matched pair or quad.
I have an 18 watt marshall clone head. I've seen people add a potentiometer to the board to make a self biasing amp.....biasable. It's done by people who want to use variac voltage regulator. They run the amp on 90 volts and use the installed potentiometer to bias the tubes hot. This creates a sag in the or certain EVH sound. What do think about this mad science?
i have a marshal jcm800 2203 that sounds fine while playing 10-30 minutes then eventually i get about 25-50% volume reduction and the tone gets fuzzier. does this sound like a power tube issue or Output Transformer issue? thank you for this video.
Good to see a new episode, Stuart. I imagine that the Lead Series are extremely noisy due to the proximity of the power transformer , to the output transformer. What is your experience with them?
Tampoco son tan ruidosos..ten en cuenta que los transformadores están colocados de una forma estratégica para anular el ruido. Uno mira al sur, y el otro mira al oeste.
Lo causa el gasto normal de las valvulas con su uso. Es cierto que no se sabe de que medida partíamos.. por eso hay que bajar el pote y luego reajustar con un juego nuevo de valvulas.
It's very hard to say as I do not know the history here. It could be a lot of things. I doubt that the bias has drifted that low though. Maybe someone put in different tubes and didn't bias?
@@stuartukguitarampguy5830 I was playing the amp loud one day and it just went silent. Bought a set of new tubes, made no difference. All of them light up. Someone said it may be the output speaker transformer.
@@stuartukguitarampguy5830 I have some test equipment. Audio Generator, Variac, Oscilloscope, Fluke. I'm going to send a signal through the output transformer see if I get anything.
