50Hz hum is highly correlated across an entire country - you could even cancel hum here by taking a sample of hum over there! Random noise is not. Therefore the two situations are entirely different. Techniques which work well for hum (such as push-pull) are completely useless for random noise. Please go back to your textbooks.Kenneth Zhu said:
Fine. It seems that we have let theory play.
Well, we have to set a precondition in this particular case, as we're talking about Ge transistors, and the biggest challenge it faces, is the noise caused by leakage and usually this kind of noise will cause "hiss" sound in the higher frequency range.
In fact, this leakage noise is random, since it is discrete, seemingly only somewhat related to temperature of the junction.
But when we're talking about discrete or random, we mean we can't find any linear or unlinear function relation or law between its amplitude and time, if we're about to explain it in tme domain. Or in other words, the noise is irregular over a period of time.
But this technique (you call it technique, I prefer to use mechanism) will work at any given time point. It will work instantly, immediately from perspective of time scale. So when elapsed time is appoaching infinitely small, the randomness will also approach infinitely small. I think you can perfectly understand this theoretical analogy. And when the randomness is infinitely small, this mechanism will work. That's my explanation to why I can't hear any "hiss" from my earphones.
Anyway, despite all the theoretical discussions, the purpose of DIYing is stilll to listen to music. Have you downloaded the Bach violin concerto replay I recorded with this preamp and 12E1 ultralinear PP as power stage? I am now still trialling power transformers of my PCM1704 DAC, trying to make the sound gentler. To transistor gears, power transformer will play a key role in deciding their final sounding. A fact interesting and also annoying.
Well, we have to set a precondition in this particular case, as we're talking about Ge transistors, and the biggest challenge it faces, is the noise caused by leakage and usually this kind of noise will cause "hiss" sound in the higher frequency range.
In fact, this leakage noise is random, since it is discrete, seemingly only somewhat related to temperature of the junction.
But when we're talking about discrete or random, we mean we can't find any linear or unlinear function relation or law between its amplitude and time, if we're about to explain it in tme domain. Or in other words, the noise is irregular over a period of time.
But this technique (you call it technique, I prefer to use mechanism) will work at any given time point. It will work instantly, immediately from perspective of time scale. So when elapsed time is appoaching infinitely small, the randomness will also approach infinitely small. I think you can perfectly understand this theoretical analogy. And when the randomness is infinitely small, this mechanism will work. That's my explanation to why I can't hear any "hiss" from my earphones.
Anyway, despite all the theoretical discussions, the purpose of DIYing is stilll to listen to music. Have you downloaded the Bach violin concerto replay I recorded with this preamp and 12E1 ultralinear PP as power stage? I am now still trialling power transformers of my PCM1704 DAC, trying to make the sound gentler. To transistor gears, power transformer will play a key role in deciding their final sounding. A fact interesting and also annoying.
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He may have a great future in writing marketing blurb for audio systems. Already the 'evaluate systems via Facebook' meme is present!
As Tom Stoppard said in 'Jumpers' "St Thomas Aquinus died of fright"
(Zeno's Paradox for those who missed the reference)
(Zeno's Paradox for those who missed the reference)
Erm... graph labels? The first I would guess is Ic(Vce) in mA over V with Ib as a parameter, the second might be Ib(Vce) @ Ic = 0, but no idea whether that's pA, nA, µA or mA over V. 😕
Or as we were always told in physics labs, "Unlabelled graphs are useless!!!!11 😡"
Actually the horizontal axis is in Volts, standing for VCE. And the vertical axis is in mA, standing for Ic. This is a Ge transistor with Hfe a little more than 100, with each curve driven by 10uA Ib and its multiples. The lowest curve is measured with Ib=0, or the leakage. It is more clearly illustrated in the second picture.
As I mentioned at the beginning of the post, regularly such Ge transitors would have 50uA or even smaller leakage when VCE=10V.
As I mentioned at the beginning of the post, regularly such Ge transitors would have 50uA or even smaller leakage when VCE=10V.
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Well, please allow me to explain this in the language of your world.
"I think that it is a right given by God to seek pure audiophiling pleasure without pursuing economic return."
Eh, I just think that all rights enjoyed by earthly beings on Christian lands are blessings of God. Hope that I am not wrong.
This topic is drifting far away from the possibiliy of applying Ge transistors in today's (or nostagic?) audio applications.
This topic is drifting far away from the possibiliy of applying Ge transistors in today's (or nostagic?) audio applications.
Look, if we merely take the noise from the collector and the noise from the emitter, correct for amplitude and sum, voila! Zero noise! 😀
xiaoping, 這是一個英語論壇 Translation:Brother, I am from Guangxi. I am very interested in your germanium transistors, how can I contact you? My QQ1210536522
According to childhood memories, low-noise germanium transistors were rare 🙂
White and pink noise was less of a problem than shot-like noise.
I had to select from the party (by ear). Sometimes RF transistors were used, in which the noise spectrum was shifted above the audio range.
Basically, the problem was with the amplifiers for the microphone, tape recorder and electrogramophone (first stage). Used currents of 0.5-1mA at low voltage 1-5V. The gain was small. Subsequent stages had greater gain. Overall the signal-to-noise ratio was better.
I heard (didn't do it myself) that cooling the transistors was used to reduce noise.
White and pink noise was less of a problem than shot-like noise.
I had to select from the party (by ear). Sometimes RF transistors were used, in which the noise spectrum was shifted above the audio range.
Basically, the problem was with the amplifiers for the microphone, tape recorder and electrogramophone (first stage). Used currents of 0.5-1mA at low voltage 1-5V. The gain was small. Subsequent stages had greater gain. Overall the signal-to-noise ratio was better.
I heard (didn't do it myself) that cooling the transistors was used to reduce noise.
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