Home » Audio » Silicon Valley » Who knows about preamp input impedance?
Who knows about preamp input impedance? [message #7813] Thu, 05 May 2005 20:20 Go to next message
gumby1 is currently offline  gumby1
Messages: 63
Registered: May 2009
Viscount
I'm shopping for a solid state preamp and noticed what seems to be a substantial difference in input impedances between the models I am considering. The four brands and models I am looking at have input impedances at 10K Ohm (McCormack Audio), 22K Ohm (Zus Audio), 47K Ohm (Van Alstine), and 50K Ohm (Marsh). Can anyone explain to me how this is going to affect my system components that I might hook up to the preamp? I am considering building a Bottlehead Seduction phono preamp. The designer indicates that it is designed for preamps with input impedances of 50K or greater. What might happen if I hooked it up to a preamp with lower impedance? This particular phono preamp is not a high priority so I could choose a different one depending on which preamp I go with. I suppose the preamp designers choose input impedance based on certain criteria. I just don't know much about it.

Re: Who knows about preamp input impedance? [message #7814 is a reply to message #7813] Fri, 06 May 2005 07:52 Go to previous messageGo to next message
Bill Wassilak is currently offline  Bill Wassilak
Messages: 402
Registered: May 2009
Illuminati (1st Degree)
Usually the lower the input impedance on pre-amps less noise is likely to enter it (rf,emf,etc.). It's better to hook up a lower impedance output to the same or higher impedance input. If you do just the opposite higher impedance output to a lower impedance input distortion will result.

HTH
Bill W.

Re: Who knows about preamp input impedance? [message #7817 is a reply to message #7814] Fri, 06 May 2005 13:54 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18670
Registered: January 2001
Illuminati (33rd Degree)

Very true. I'd call Dan over at Bottlehead and see how he thinks the Seduction will do driving a 10Kohm or 22Kohm load. It may be too much of a load, and might modify the response or make it distort.


Re: Who knows about preamp input impedance? [message #7828 is a reply to message #7813] Tue, 21 June 2005 21:53 Go to previous message
sam9 is currently offline  sam9
Messages: 5
Registered: May 2009
Esquire
Depends on how the input impedance is obtained. While it is generally true that the the lower the figure the lower the noise due to resistor value, there are techniques to (namely "botstraping") where low value resistors can be made to appear to the signal source to have a high impedance.

At the same time a higher impedance at the input may improve the performance of the signal source to some degree. This depends on the capabilities of the source.

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