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In Reply to: 'Loading' a preamp with a poweramp, input impedance, and the load resistor posted by jeffreybehr on February 29, 2012 at 10:33:05:
Hi Jeff,
On their website to their volume pot. Included is a chart for the desired db reduction based on specified R values.
Typically this is done in the preamp. Some mfg's put series resistors in line with one or more inputs before the selector.
Voltsecond whitepapers on series/shunt:
http://www.siteswithstyle.com/VoltSecond/12_posistion_shunt/12_Position_Pure_Shunt.html
Bear in mind, the preamp's output impedance isn't the same as mating the corner frequency (RC coupling) with the amp. Providing it's a tube preamp and cap coupled on the outputs.
Before change the input impedance resistor of a amp, best to check with the mfg.
I've just done so to a DNA-125 amp.
Input imp. > 220K and pulled the input blocking cap > good quality wire in place of the cap.
Fed from a tube pre, once the amp's blocking cap was removed, the veil was lifted, very open and detailed. If this is implemented, the SS amp should only be driven by a tube - cap coupled preamp.
Enjoy the new SMc amps Jeff.
Regards,
Wheeze
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- Goldpoint shows how to accomplish this... - wheezer 12:12:10 03/02/12 (0)
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