That's the process to find out why class-A amps have this fatigue free trait... Trying to lower the output impedance of the power supply, etc... Trying the Naim approach....
No, I don't like amplifier classes. I want an amp that covers all quality parameters/traits that I can perceive. From class-A, I like the fatigue-free trait. I don't like distortion so I don't like the idea to mask the high harmonics with increasing the lower ones.
Hi johnego,
What you have posted has no technical merit at all. Its all kind of hear-say type stuff.
I get what you are saying. Let's just say that "Class A" isn't the only type of amp that does that. Class "AB" doesn't create a spray of harmonics (to use a popular expression) when designed and executed properly.
Also, a power supply is a power supply. The larger capacitor size in value has more inductance (like in class A amps) and does not deliver energy as quickly if you want to look at it that way. But that is high capacitance, nothing to do with the class of the amplifier.
What you have posted has no technical merit at all. Its all kind of hear-say type stuff.
I get what you are saying. Let's just say that "Class A" isn't the only type of amp that does that. Class "AB" doesn't create a spray of harmonics (to use a popular expression) when designed and executed properly.
Also, a power supply is a power supply. The larger capacitor size in value has more inductance (like in class A amps) and does not deliver energy as quickly if you want to look at it that way. But that is high capacitance, nothing to do with the class of the amplifier.
Depends on where you are when AB class bias is adjusted. For, say, a Blameless topology:
- If the amp is already under biased, increasing the bias, within certain limits, improves the distortion performance.
- if the amp is already biased at the Oliver point (26mV across the emitter resistors, what that means in practice is not trivial) then any under or over biasing will only deteriorate the distortion performance.
- if the amp is already over biased, then biasing up or down will improve the distortion performance.
- If the amp is already under biased, increasing the bias, within certain limits, improves the distortion performance.
- if the amp is already biased at the Oliver point (26mV across the emitter resistors, what that means in practice is not trivial) then any under or over biasing will only deteriorate the distortion performance.
- if the amp is already over biased, then biasing up or down will improve the distortion performance.
Distortion can sound pleasing or awful (subjective).
In class AB usually I will set to over biased, which the distortion sound pleasing.
Class A amplifier not always sound better (subjectively) compare to class AB amplifier. My friend compare Nelson Pass's F5 with an amplifier class AB. He said although F5 in bass region more punch but the class AB is more airy and detail in high frequency. All amplifiers have no fatigue. He choose the class AB and sold the F5.
In class AB usually I will set to over biased, which the distortion sound pleasing.
Class A amplifier not always sound better (subjectively) compare to class AB amplifier. My friend compare Nelson Pass's F5 with an amplifier class AB. He said although F5 in bass region more punch but the class AB is more airy and detail in high frequency. All amplifiers have no fatigue. He choose the class AB and sold the F5.
Let's pick one example from class-A. A very old one. JLH1969. What is the comparable class "AB"?
Almost class B amplifier (under biased):
https://www.diyaudio.com/forums/solid-state/338815-anistardi-peletuk-4.html#post5835054
Thanks for bringing the Oliver stuff. Now we are in a position that I don't like to talk about: The small differences of resulting THD from this bias voltage variation, anybody can hear it? You know about engineering challenge (I don't remember the exact term): people build lower and lower distortion amps not because they can hear it.
Hi johnego,
You don't understand it, and we can't teach you a course on this. Don't worry about it. The technicians will worry about it. In practice, this is not a problem.
Also, I don't have time to chase down each example you want to bring out. That question is heading off topic for this discussion. However, you can do some technical research yourself and learn.
-Chris
You don't understand it, and we can't teach you a course on this. Don't worry about it. The technicians will worry about it. In practice, this is not a problem.
Also, I don't have time to chase down each example you want to bring out. That question is heading off topic for this discussion. However, you can do some technical research yourself and learn.
-Chris
For easily hear crossover distortion, please set volume as low as possible but you still hear the sound clearly. Pay attention to high frequency.
For people who trained, they should be can hear crossover distortion at normal listening test. When some of my friends tested symasym amplifier, one of my friend said, "It likely the bias current is under biased." Then we check the bias current. It is under biased.
Hi bimo,
Yes, you're right.
Interestingly, my SymAsym only needs 5 mA bias current. I used the new On-Semi MJW devices at the time, then they were discontinued.
-Chris
Yes, you're right.
Interestingly, my SymAsym only needs 5 mA bias current. I used the new On-Semi MJW devices at the time, then they were discontinued.
-Chris
Thanks, Bimo. But I'm not saying I cannot hear it. What I said was: If you cant hear X, why do you have to chase X. I chase Y because I can hear Y.
BTW, I have built most of your amps. My favorite is... I don't want to tell you 😀
Now that's weird. Related to fT or "speed" of output devices? Or hFe mismatch?
"speed of delivering current" I don't know what that is, unless that's related to output current slew rate? That's another thing that no-one measures...
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Not all amplifiers that I design, I like. I have my favorite too. But I do not share the design 😀 .
It fun for exploring many possibility in amplifier design. If you want high THD amplifier, just make it. If you want very low THD, just bulid it. You will understand what the sound different of those amplifiers.
If you believe that very low THD is better, you should compare to high THD amplifier. Who knows that you can tell the different? 😀
It is not compare with Pelatuk, but with over biased calss AB with very low THD in all audio frequency and have high slew rate.
Measurements vs Perception (Not Audio)
For most people in Jakarta, a room temperature about 24 degree Celcius is consider as cold. When I live in Japan, Japanese feel that a room temperature about 20 degree Celsius is hot.
The perception is different because of habit.
Why in audio not many people understand this? Why did they think audio is different?
For most people in Jakarta, a room temperature about 24 degree Celcius is consider as cold. When I live in Japan, Japanese feel that a room temperature about 20 degree Celsius is hot.
The perception is different because of habit.
Why in audio not many people understand this? Why did they think audio is different?
Yes, true story!
I was a bit surprise myself: that player didn't sound THAT bad, just annoyingly boring. But then again, ladies usually have better ears, and mine are trashed by years of live R&R. Anyway, I finished the review telling things as they were, and, another surprise, it got published, in a special issue on ReVox, no less!
And yes, that's the same lady you met. After 40+ years of mariage, we decided to part ways. We're still in good terms and we have diner together once in a while. She even manages to become a passable cook! 🙂
C'mon... You all fell into the implementation trap.... What set of measurement will ensure that all your design worries will be ok once fulfilled?
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