2. amps-preamps
  3. 1391850212

Amplifier Input Impedance

Why are so many high-power solid state amps designed with such low input impedances. Doesn't that really low input impedance limit the range of pre amps that can be used? Are there technical reasons why designers make these impedances so low? Why not design your muscle amp with a really high input impedance so it will potentially work well with all pre amps?
stickman451
jmcgrogan2's avatar
jmcgrogan2
6,346 posts
 
I think the obvious answer is that the SS amp designer would prefer that you also buy their SS preamp. Yes, SS amps usually have lower input impedances than their tube brethren, but SS preamps usually have much lower output impedances than their tube counterparts. The SS amp designer does not really want you to use a tube preamp with their amp.
cobra2's avatar
cobra2
8 posts
 
Low input impedance is an advantage regarding noise, and a disadvantage regarding flexiblilty...
stickman451 OP
553 posts
 
But, a good designer could in fact design a powerful SS amp with a high input impedance if pushed...
atmasphere's avatar
atmasphere
11,841 posts
 
Stickman451, you are correct as is Jmcgrogan2. Its easy enough to design a solid state amplifier with a high impedance input (100K); they could even make it switchable if they wanted.

Although our preamps are vacuum tube, they can drive even 5K with ease (they are designed to drive 600 ohms). But this is unusual with tube preamps so for the most part its likely that this will continue to be part of the equipment matching conversation for the foreseeable future.
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