• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Diode cathode bias?

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#24
disco said:
lookin' at Magz' graph that situation will probably hold for most semi's within a small current interval..
Click to expand...

Yes I think there only seems to be Mags that has tested the diodes and done research...I notice that I had to test the diodes with a 1K and 9 volt battery to be sure I had the correct forward VD.

😀😀..did you like the film..😀

I think its interesting when you have a tube symbol and a diode symbol and one has cathode emission and the other the symbol that seems to prove it wrong..😀

Regards
M. Gregg
 
#26
M Gregg said:
I think its interesting when you have a tube symbol and a diode symbol and one has cathode emission and the other the symbol that seems to prove it wrong..😀
Click to expand...
Conventonal current is not "the wrong way round". Anyone who thinks that clearly hasn't thought very hard about the physics and more importantly about the mathematics of electricity. I notice the article you linked to is written by a computer scientist. Since diode symbols are established as nice little arrows, let's not confuse matters.
 
#28
Hi MG, no problemos -I'm in for a joke but not a fan of Utube (getting sea sick easily 😀 )

Back to the bone.

Because of degenerative feedback the cathode impedance raises the plate impedance by Xc(mu+1). Compared to a cathode resistor a string of semis reduces the dynamic plate resistance with the difference in Rdc times (u+1). So, what we're actually experiencing is the reduction of the plate resistance.
 
#31
M Gregg said:
It was only a joke..(I'm sure Disco knew that and took it as such) Three minutes is a long time.. 😀

Conventional Current vs. Electron Flow#

Regards
M. Gregg
Click to expand...
I have articles from the 1950's saying current flow neg to pos not pos to neg . The reason they said it was not changed was so many textbook had it backwards . So they changed the definition of current flow to be the opposite of electron flow. This bit of work around causes the definitional problem for many. 🙄
 
#32
okcrum said:
I've used a couple of 1N4148s to bias 12AX7s with good results. At low current they are more linear than LEDs - you can see that in the even harmonics.
Click to expand...

AJT said:
i confirm this, tried it too....😉
Click to expand...
.

Now you only need to know what is about battery biasing Ni Cd or Ni Mh or Li po, I am in the first step with the led 🙂

I use the blue led with good sound, better than resistor and silmic II cap. After read your post I am going to change the led by 4 diodes, to have 2.4v more or less that need the 6e5p, I drive a 211 with very good sound, next weekend I will try the battery also
 
#34
Battery Ni Mh winner

Hego my friend looking the copon audio sound . ha ha ha

​
well after the check the diodes I my amp 6e5p - 211 the sound go down to terrible. I dont know wich diodes I used. 75v rectifiers four in line to have 2,9v.

Now the battery Ni Mh are the winner, better than resistor and better than all colors of led since red - green and blue, with the battery all is better,
3 batteries in line to have 3,8V too is true that the 6e5p fell better far of the bias at -2v.

Now only need check the fixed bias in the 6e5p to check all 🙂
 
#35
Reviving this thread to see if anyone else has been trying SIC diodes in series with a resistor. I'm finding the sound is smoother with a resistor to add some feedback. Plus I'm only using a single SIC diode, not a string. No cathode bypass.

2a3 + E180CC.png
 
#38
You ask about series one resistor + diode, but would be interesting with two diodes in series and parallel one resistor, diodes lock the voltage and resistor help to flow the feedback, I think that diode in series cut the feedback loop with the grid. But I never do
 
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