bungimeala
New member
I have acquired an Engl Savage (built in 2011) which I guess never sounded "right", just kinda average. I have retubbed it, re-biased, try all kinds of tubes in, but it never sounded as brutal as I would like it to be. I also own a Fireball 60 which is just great.
Now I have come to think that there might be something wrong with the actual distortion or something else is faulty. I have a general understanding of electronics and tube amps and I am able to repair faulty components, but it is a pain to remove the main PCB to check all the components one at a time. Therefore I am hoping someone might be able to chime in on this.
I have done some tests with the oscilloscope, applying a 1KHz, 150 mV input signal to see what kind of output do I get. I have tested channels 2 and 3 (Crunch I and Crunch II) on roughly everything set to noon and this is where I can see some interesting results.
On CrunchI I get a good distorted sound which has the fundamental frequency as well as 3rd harmonic quite high and so on. I assume this is good.
On CrunchII I get a distorted sound which has the 2nd harmonic very high and as far as my knowledge goes, it appears the preamp tube is cold biased somehow (not properly biased by the cathode resistor) as it is kinda clipping on the low level input.
Basically I have 2 questions. If anyone is able to test the "distortion" shape with an oscilloscope, would you please confirm that indeed, this is the way it is supposed to look on Crunch II vs Crunch I?
If this is not how it is supposed to look like, should I then look at replacing the cathode resistor and capacitor? Or could there be other issues to look for?
Thanks for any inputs.
Now I have come to think that there might be something wrong with the actual distortion or something else is faulty. I have a general understanding of electronics and tube amps and I am able to repair faulty components, but it is a pain to remove the main PCB to check all the components one at a time. Therefore I am hoping someone might be able to chime in on this.
I have done some tests with the oscilloscope, applying a 1KHz, 150 mV input signal to see what kind of output do I get. I have tested channels 2 and 3 (Crunch I and Crunch II) on roughly everything set to noon and this is where I can see some interesting results.
On CrunchI I get a good distorted sound which has the fundamental frequency as well as 3rd harmonic quite high and so on. I assume this is good.
On CrunchII I get a distorted sound which has the 2nd harmonic very high and as far as my knowledge goes, it appears the preamp tube is cold biased somehow (not properly biased by the cathode resistor) as it is kinda clipping on the low level input.
Basically I have 2 questions. If anyone is able to test the "distortion" shape with an oscilloscope, would you please confirm that indeed, this is the way it is supposed to look on Crunch II vs Crunch I?
If this is not how it is supposed to look like, should I then look at replacing the cathode resistor and capacitor? Or could there be other issues to look for?
Thanks for any inputs.