From 6N2P spec sheet:
Input Capacitance = 2.35pF
Output Capacitance = 2.5pF
Transfer Capacitance = 0.55pF
How do i calculate the miller capacitance in grounded cathode config with a gain of 60? Basically, i'm trying to figure out which of the above are Cgk, Cga and Cak.
If i have to guess, Cak would be the smallest value since a-k distance is the furthest so 0.55pF. That being said, Cgk should be the input capacitance 2.35pF and Cga is the output capacitance 2.5pF.
Soo.. Cdyn = Cgk + (Cga * A)
Cdyn = 2.35 + (2.5*60) =152.35pF.. let's round up to 160pF
If i want a cutoff freq somewhere close to 20kHz, the grid stopper should be 47k for an actual cutoff of 21.2kHz.
Did i make any mistake?
Input Capacitance = 2.35pF
Output Capacitance = 2.5pF
Transfer Capacitance = 0.55pF
How do i calculate the miller capacitance in grounded cathode config with a gain of 60? Basically, i'm trying to figure out which of the above are Cgk, Cga and Cak.
If i have to guess, Cak would be the smallest value since a-k distance is the furthest so 0.55pF. That being said, Cgk should be the input capacitance 2.35pF and Cga is the output capacitance 2.5pF.
Soo.. Cdyn = Cgk + (Cga * A)
Cdyn = 2.35 + (2.5*60) =152.35pF.. let's round up to 160pF
If i want a cutoff freq somewhere close to 20kHz, the grid stopper should be 47k for an actual cutoff of 21.2kHz.
Did i make any mistake?
Maybe i made a mistake.
Googled for the same terms for MOSFET, i found this:
Ciss (input) = Cgs + Cgd
Coss (output) = Cds + Cgd
Crss (reverse transfer) = Cgd
If we assume g = grid, d = plate and s = cathode, then:
Crss = 0.55pF
Ciss = 2.35pF = Cgk + 0.55 --> Cgk = 1.8pF
Coss = 2.5pF = Cak + 0.55 --> Cak = 1.95pF
Crss = Cga = 0.55pF
That means correct Cdyn would be = 1.8 + (60*0.55) = 34.8pF. Let's round up to 40pF (strangely small value. 12AX7 which is said to be the equivalent of 6N2P has Cdyn of around 100pF).
Grid Stopper Resistor or Rg would then be around 180k for a cutoff at 22.1kHz
So, which one is correct? First post or this second post?
Googled for the same terms for MOSFET, i found this:
Ciss (input) = Cgs + Cgd
Coss (output) = Cds + Cgd
Crss (reverse transfer) = Cgd
If we assume g = grid, d = plate and s = cathode, then:
Crss = 0.55pF
Ciss = 2.35pF = Cgk + 0.55 --> Cgk = 1.8pF
Coss = 2.5pF = Cak + 0.55 --> Cak = 1.95pF
Crss = Cga = 0.55pF
That means correct Cdyn would be = 1.8 + (60*0.55) = 34.8pF. Let's round up to 40pF (strangely small value. 12AX7 which is said to be the equivalent of 6N2P has Cdyn of around 100pF).
Grid Stopper Resistor or Rg would then be around 180k for a cutoff at 22.1kHz
So, which one is correct? First post or this second post?
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Here is 6N2P specs: http://www.mif.pg.gda.pl/homepages/frank/sheets/113/6/6N2P.pdf
Cga = 0.7 p
Cgk = 2.25 p
Cak = 2.3 p
Cga = 0.7 p
Cgk = 2.25 p
Cak = 2.3 p
Thank you. Just realized that 6N2P and 6N2P-EV are internally different as well. My numbers are from 6N2P-EV specs.
I guess then it goes like this:
Input Capacitance = Cgk
Transfer Capacitance = Cga
Output Capacitance = Cak
Thank you.
I guess then it goes like this:
Input Capacitance = Cgk
Transfer Capacitance = Cga
Output Capacitance = Cak
Thank you.
Wow, that's impressive! I almost don't believe it... I suddenly wish I had some to test :S
I once made comparative measurements of the input capacitance of 6N2P-EV, 12AX7LPS and ECC83.
It is difficult to get absolute values, but it was obvious that 6N2P-EV has at least 1 pF smaller Cag than the two other types.
It is difficult to get absolute values, but it was obvious that 6N2P-EV has at least 1 pF smaller Cag than the two other types.
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Artosalo, how do you suppose that might have been achieved? Have you ever tried it as RIAA input valve?
Below is my test circuit.
The idea was to measure the gain difference when 100 k resistor is placed between signal source and the grid of the tube under test forming a low pass filter with 100 k resistor and total input capacitance of the tube.
The gain of the stage was measured and so the Miller effect was determined and finally Cag calculated. The used test frequency was 10 kHz. I did the measurements with 6N2P-EV, 12AX7 LPS and Philips ECC83.
The input capacitance of 6N2P-EV was clearly smallest.
I have used 6N2P-EV for RIAA.
The idea was to measure the gain difference when 100 k resistor is placed between signal source and the grid of the tube under test forming a low pass filter with 100 k resistor and total input capacitance of the tube.
The gain of the stage was measured and so the Miller effect was determined and finally Cag calculated. The used test frequency was 10 kHz. I did the measurements with 6N2P-EV, 12AX7 LPS and Philips ECC83.
The input capacitance of 6N2P-EV was clearly smallest.
I have used 6N2P-EV for RIAA.
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So the 2nd and 3rd (cathode follower?) stages are 6n2p-ev? 6n2p-ev has much shorter anodes than any of the ecc83/12ax7 that I have; appearance is very different.
I must say I am surprised and impressed; very neat RIAA stage. If you hadn't done the measurements, I would not have believed it. What do you think the trade-off is? Perhaps lower gm for 6n2p-ev compared to ecc83?
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