TubeRiaa - How to calculate the impendance?

Gudmund · 27th February 2010, 06:36 PM

On the attached circuit the +B is 250V -

C4 is 1,0uF and is calculated to -3dB at 20Hz when "looking" into 100K pot.

R11 is 470K.
R4 and R9 is 30K/2W - R 12 is 1K
C7 and C8 is 10uF/400V.
R3 and R10 is 500R parallel with 100uF/10V

Anyone who has the math formular to calculate the -3dB point (depending on C4) ?

The lineamp might be the Aikido. Have already one 100K ALPS log. stereo pot.

Gudmund

DF96 · 27th February 2010, 08:22 PM

-3dB LF point at output is given by 2 pi f = C4 x ( R9||Ra + 470K||100K), where Ra is the anode impedance of V2, and Rx||Ry means Rx and Ry in parallel.

Gudmund · 28th February 2010, 08:13 AM

Quote:

Originally Posted by DF96

-3dB LF point at output is given by 2 pi f = C4 x ( R9||Ra + 470K||100K), where Ra is the anode impedance of V2, and Rx||Ry means Rx and Ry in parallel.

DF96 - Thank you!

Gudmund

Gudmund · 28th February 2010, 02:55 PM

Quote:

Originally Posted by DF96

-3dB LF point at output is given by 2 pi f = C4 x ( R9||Ra + 470K||100K), where Ra is the anode impedance of V2, and Rx||Ry means Rx and Ry in parallel.

Referring to the attached circuit the C3 is 0,100uF/400v and R7 is 470k. There have be some sort of roll-of connected to the two components? Could DF96 show us how to calculate the CR math?

Could you please let us have your opinion ralated to the phono circuit? Is it worth working with? - The phono riaa is used only occational - the Aikido phonostage uses more tubes for the same funktion.- Would like to keep the phonostage simple.

Gudmund

Gudmund · 4th March 2010, 08:24 AM

Anyone - please let us have your opinion related to the phono circuit? Is it worth working with? - The phono riaa is used only occationally - the Aikido phonostage uses more tubes for the same funktion.- Would like to keep the phonostage simple.
Gudmund

Nb. Anyone who has the formular to calculate C3 and R7 on the attached circuit?

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27th February 2010, 08:22 PM	#2
DF96 diyAudio Member Join Date: May 2007	-3dB LF point at output is given by 2 pi f = C4 x ( R9\|\|Ra + 470K\|\|100K), where Ra is the anode impedance of V2, and Rx\|\|Ry means Rx and Ry in parallel.

4th March 2010, 08:24 AM	#5
Gudmund diyAudio Member Join Date: Feb 2010	Anyone - please let us have your opinion related to the phono circuit? Is it worth working with? - The phono riaa is used only occationally - the Aikido phonostage uses more tubes for the same funktion.- Would like to keep the phonostage simple. Gudmund Nb. Anyone who has the formular to calculate C3 and R7 on the attached circuit?

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