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Input capacity (100 pF, 250 pF and 430 pF) phono preamp help please! - Gearspace.com
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Input capacity (100 pF, 250 pF and 430 pF) phono preamp help please!
Old 26th January 2009
  #1
Gear Head
 
🎧 10 years
Input capacity (100 pF, 250 pF and 430 pF) phono preamp help please!

My USB preamp has 3 settings and ive lost the manual! Can't find any info on the web!!

Input capacity adjustable in three stages (100 pF, 250 pF and 430 pF)

If im sampling vinyl direct from a turntable into the pre-amp which setting is best

thanks!
Old 26th January 2009
  #2
Les
Lives for gear
 
Les's Avatar
 
🎧 10 years
Hi,

Long ago I used to design phono cartridges for a living.

What cartridge are you using? For my designs I generally suggested a load of 47K ohms and 250 pF. Some of the 250 pf comes from the capacitance of the cable. If you have 5 feet of 50pf/ft cable connecting the cart to the pre you don't need to switch in any extra capacitance to get 250.

This affects the high frequency response in moving magnet designs.

Les Watts
L M Watts Technology
Old 26th January 2009 | Show parent
  #3
Gear Head
 
🎧 10 years
Thx Mr Watts!

Im using either a standard 500 Stanton or a 680L Stanton
Old 26th January 2009 | Show parent
  #4
Les
Lives for gear
 
Les's Avatar
 
🎧 10 years
Quote:
Thx Mr Watts!

Im using either a standard 500 Stanton or a 680L Stanton]
YW!
Well, I didn't design that one. I worked at Shure.

But I did hunt it up for you. The 680 is about 1 henry inductance with
275 pf reccomended, so if you are using a typical 5 foot or so cable at 30pf/ft (=150pf total) then switching in 100pf ( total 250) will be closest for you.

Les Watts
L M Watts Technology
Old 26th January 2009 | Show parent
  #5
Gear Head
 
🎧 10 years
Les you are a diamond!!

Appreciate your help mate thank you
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