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TUBELOVER
 
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Default NEED ADVICE on preamp output capacitor

I have a solid state phono preamp which has a 50 micro farad electrolytic
capacitor in series with the preamp signal at the very output of the preamp. i
wish to replace this cap with a film cap. what is the minimum value cap i can
use and still have a response that is not rolled off due to too low a value?
the phono preamp will feed a line amp with a minimum of 10000 ohms input
resistance.

email
rg
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Stig Erik Tangen
 
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Default NEED ADVICE on preamp output capacitor

TUBELOVER wrote:
I have a solid state phono preamp which has a 50 micro farad electrolytic
capacitor in series with the preamp signal at the very output of the preamp. i
wish to replace this cap with a film cap. what is the minimum value cap i can
use and still have a response that is not rolled off due to too low a value?
the phono preamp will feed a line amp with a minimum of 10000 ohms input
resistance.

email
rg


1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should work.

Stig Erik Tangen

  #3   Report Post  
Stig Erik Tangen
 
Posts: n/a
Default NEED ADVICE on preamp output capacitor

TUBELOVER wrote:
I have a solid state phono preamp which has a 50 micro farad electrolytic
capacitor in series with the preamp signal at the very output of the preamp. i
wish to replace this cap with a film cap. what is the minimum value cap i can
use and still have a response that is not rolled off due to too low a value?
the phono preamp will feed a line amp with a minimum of 10000 ohms input
resistance.

email
rg


1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should work.

Stig Erik Tangen

  #4   Report Post  
Stig Erik Tangen
 
Posts: n/a
Default NEED ADVICE on preamp output capacitor

TUBELOVER wrote:
I have a solid state phono preamp which has a 50 micro farad electrolytic
capacitor in series with the preamp signal at the very output of the preamp. i
wish to replace this cap with a film cap. what is the minimum value cap i can
use and still have a response that is not rolled off due to too low a value?
the phono preamp will feed a line amp with a minimum of 10000 ohms input
resistance.

email
rg


1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should work.

Stig Erik Tangen

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Rich Andrews
 
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Default NEED ADVICE on preamp output capacitor

Stig Erik Tangen wrote in
:

TUBELOVER wrote:
I have a solid state phono preamp which has a 50 micro farad
electrolytic capacitor in series with the preamp signal at the very
output of the preamp. i wish to replace this cap with a film cap. what
is the minimum value cap i can use and still have a response that is
not rolled off due to too low a value? the phono preamp will feed a
line amp with a minimum of 10000 ohms input resistance.

email
rg


1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should
work.

Stig Erik Tangen


What is the formula for this?

r


--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.




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Rich Andrews
 
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Default NEED ADVICE on preamp output capacitor

Stig Erik Tangen wrote in
:

TUBELOVER wrote:
I have a solid state phono preamp which has a 50 micro farad
electrolytic capacitor in series with the preamp signal at the very
output of the preamp. i wish to replace this cap with a film cap. what
is the minimum value cap i can use and still have a response that is
not rolled off due to too low a value? the phono preamp will feed a
line amp with a minimum of 10000 ohms input resistance.

email
rg


1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should
work.

Stig Erik Tangen


What is the formula for this?

r


--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.


  #7   Report Post  
Rich Andrews
 
Posts: n/a
Default NEED ADVICE on preamp output capacitor

Stig Erik Tangen wrote in
:

TUBELOVER wrote:
I have a solid state phono preamp which has a 50 micro farad
electrolytic capacitor in series with the preamp signal at the very
output of the preamp. i wish to replace this cap with a film cap. what
is the minimum value cap i can use and still have a response that is
not rolled off due to too low a value? the phono preamp will feed a
line amp with a minimum of 10000 ohms input resistance.

email
rg


1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should
work.

Stig Erik Tangen


What is the formula for this?

r


--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.


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Norbert Hahn
 
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Default NEED ADVICE on preamp output capacitor

On Fri, 26 Dec 2003 20:58:44 +0100, Stig Erik Tangen
wrote:

1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should work.


Unfortunately this gives about 2 kOhm load to an induced current of
60 Hz. So there is some chance for hum.

What about checking the voltage across the current capacitor and if it
is some tens of millivolt the capacitor is not needed at all - unless
the power amp is fully DC coupled?

Norbert

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Norbert Hahn
 
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Default NEED ADVICE on preamp output capacitor

On Fri, 26 Dec 2003 20:58:44 +0100, Stig Erik Tangen
wrote:

1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should work.


Unfortunately this gives about 2 kOhm load to an induced current of
60 Hz. So there is some chance for hum.

What about checking the voltage across the current capacitor and if it
is some tens of millivolt the capacitor is not needed at all - unless
the power amp is fully DC coupled?

Norbert

  #10   Report Post  
Norbert Hahn
 
Posts: n/a
Default NEED ADVICE on preamp output capacitor

On Fri, 26 Dec 2003 20:58:44 +0100, Stig Erik Tangen
wrote:

1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should work.


Unfortunately this gives about 2 kOhm load to an induced current of
60 Hz. So there is some chance for hum.

What about checking the voltage across the current capacitor and if it
is some tens of millivolt the capacitor is not needed at all - unless
the power amp is fully DC coupled?

Norbert



  #11   Report Post  
TUBELOVER
 
Posts: n/a
Default NEED ADVICE on preamp output capacitor

i received info that a 2 uf cap gives -3 db at 10 hz . i will use a 4.7 uF
cap.thanks to all.
rg
  #12   Report Post  
TUBELOVER
 
Posts: n/a
Default NEED ADVICE on preamp output capacitor

i received info that a 2 uf cap gives -3 db at 10 hz . i will use a 4.7 uF
cap.thanks to all.
rg
  #13   Report Post  
TUBELOVER
 
Posts: n/a
Default NEED ADVICE on preamp output capacitor

i received info that a 2 uf cap gives -3 db at 10 hz . i will use a 4.7 uF
cap.thanks to all.
rg
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Arny Krueger
 
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Default NEED ADVICE on preamp output capacitor

"Rich Andrews" wrote in message
.44
Stig Erik Tangen wrote in
:

TUBELOVER wrote:
I have a solid state phono preamp which has a 50 micro farad
electrolytic capacitor in series with the preamp signal at the very
output of the preamp. i wish to replace this cap with a film cap.
what is the minimum value cap i can use and still have a response
that is not rolled off due to too low a value? the phono preamp
will feed a line amp with a minimum of 10000 ohms input resistance.

email
rg


1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should
work.


F(-1 dB) of 20 Hz is a common standard. This requires a 1.6 uF cap for a
standard 10K line level load. I'd recommend more like 2 uF.

If this is for driving power amps, there are power amps with input impedance
that is more like 5K, so now a 3-5 uF cap seems to be in order. If you have
really good subwoofer, 10 uF might make sense.

What is the formula for this?


F(-3 dB) = 1/(2*pi*R*C)

R in ohms, C in Farads

For high pass:

F(-1 dB) = 2* F(-3)
F(-0.1 dB) = 6.666* F(-3)


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Arny Krueger
 
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Default NEED ADVICE on preamp output capacitor

"Rich Andrews" wrote in message
.44
Stig Erik Tangen wrote in
:

TUBELOVER wrote:
I have a solid state phono preamp which has a 50 micro farad
electrolytic capacitor in series with the preamp signal at the very
output of the preamp. i wish to replace this cap with a film cap.
what is the minimum value cap i can use and still have a response
that is not rolled off due to too low a value? the phono preamp
will feed a line amp with a minimum of 10000 ohms input resistance.

email
rg


1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should
work.


F(-1 dB) of 20 Hz is a common standard. This requires a 1.6 uF cap for a
standard 10K line level load. I'd recommend more like 2 uF.

If this is for driving power amps, there are power amps with input impedance
that is more like 5K, so now a 3-5 uF cap seems to be in order. If you have
really good subwoofer, 10 uF might make sense.

What is the formula for this?


F(-3 dB) = 1/(2*pi*R*C)

R in ohms, C in Farads

For high pass:

F(-1 dB) = 2* F(-3)
F(-0.1 dB) = 6.666* F(-3)




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Arny Krueger
 
Posts: n/a
Default NEED ADVICE on preamp output capacitor

"Rich Andrews" wrote in message
.44
Stig Erik Tangen wrote in
:

TUBELOVER wrote:
I have a solid state phono preamp which has a 50 micro farad
electrolytic capacitor in series with the preamp signal at the very
output of the preamp. i wish to replace this cap with a film cap.
what is the minimum value cap i can use and still have a response
that is not rolled off due to too low a value? the phono preamp
will feed a line amp with a minimum of 10000 ohms input resistance.

email
rg


1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should
work.


F(-1 dB) of 20 Hz is a common standard. This requires a 1.6 uF cap for a
standard 10K line level load. I'd recommend more like 2 uF.

If this is for driving power amps, there are power amps with input impedance
that is more like 5K, so now a 3-5 uF cap seems to be in order. If you have
really good subwoofer, 10 uF might make sense.

What is the formula for this?


F(-3 dB) = 1/(2*pi*R*C)

R in ohms, C in Farads

For high pass:

F(-1 dB) = 2* F(-3)
F(-0.1 dB) = 6.666* F(-3)


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