I came across this video. I'm a Newby, but when I decided to do this hobby, I always thought I'd be doing it the way this guy is, totally experimentally. I have a lot to learn to get to this point. He made a "tube tester" that let's you set up and dial-in any operating point, while simultaneously obtaining the harmonic profile you like, in real time, while simultaneously hearing it musically in real time! He is a man after my heart. I know Spice is all the rage, and my journey has taken me on many tangents. I ought to go back to what I intuitively thought I would be doing learning tubes, which is what I'm seeing in this elegantly simple video. I don't understand everything he's doing like with the triangle waves, but the ability to dial in an operation point, harmonic profile and hear the music simultaneously is amazing to me here. Worth the watch. Its in German I think, but has subtitles.
It sounds like Swedish to me, but as I don't speak Swedish, I may be mistaken. At some moment he switches to English, and then back to Swedish, if that's what it is.
The triangle wave is to see the distortion, I think. He changes the biasing while looking at the amplified triangle wave and trying to make it look triangular. He then switches to a sine wave and distortion analyser for fine tuning.
Nice video anyway!
The triangle wave is to see the distortion, I think. He changes the biasing while looking at the amplified triangle wave and trying to make it look triangular. He then switches to a sine wave and distortion analyser for fine tuning.
Nice video anyway!
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Those large letters on the screen at the beginning of the video are a ham radio call sign. The LA prefix puts him in Norway. Ham call signs are public record in most countries, so much can be learned just by Googling the call sign. He is in Larvik Norway. Google will take you to his web site where he reveals a rather large collection of vintage radio equipment from all over the world.
I like the audio thru the tube, nice touch, can check for microphonics easily too.
The FFT test is super, wonder what test instrument he's using there.
And the triangle distortion test is graphic. It can be taken a step further by putting an IC integrator before the scope readout, so you get a square wave whose amplitude is the gain. Flat horizontal is good, any wrinkles or curves are distortion. Easy to flip in with a switch. Can crank the scope gain up to see the tiniest distortions on a flat line.
The FFT test is super, wonder what test instrument he's using there.
And the triangle distortion test is graphic. It can be taken a step further by putting an IC integrator before the scope readout, so you get a square wave whose amplitude is the gain. Flat horizontal is good, any wrinkles or curves are distortion. Easy to flip in with a switch. Can crank the scope gain up to see the tiniest distortions on a flat line.
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A question. If I do go this route of making a tube lab board that makes it easy to vary anode voltage, screen voltage, grid voltage, cathode resistor, anode resistor, etc. on the fly. What can I use that will give me that very simple real-time bar graph of the harmonic profile he is getting with his $5,000 audio analyzer there? I don't want to buy an expensive used analyzer. Should I get into maybe a Focusrite and some software that will spit out a bar graph of 2nd, 3rd, 4th harmonics? What software will do this task as a simple bar graph of the harmonic distortion components?
Yes, Norwegian.
Also has a registered DIYaudio profile, although I think he only made two posts:
https://www.diyaudio.com/community/...with-a-very-clever-trick.378418/#post-6821977
Also has a registered DIYaudio profile, although I think he only made two posts:
https://www.diyaudio.com/community/...with-a-very-clever-trick.378418/#post-6821977
I thought integral of square was triangle, integral of triangle was sine. ?
Yes, the integral of a square wave is a triangle wave.
But the integral of a triangle wave is a parabola.
The integral of a cosine is a sine.
And the derivative of a sine is a cosine.
Since differentiation (or integration) of a sine or cosine is a linear operation, you can only get the same frequency out.
So all that can happen is linear distortion (amplitude and phase changes).
And all waveforms other than sine/cosine have infinite harmonics.
But the integral of a triangle wave is a parabola.
The integral of a cosine is a sine.
And the derivative of a sine is a cosine.
Since differentiation (or integration) of a sine or cosine is a linear operation, you can only get the same frequency out.
So all that can happen is linear distortion (amplitude and phase changes).
And all waveforms other than sine/cosine have infinite harmonics.