Amplifier Input Impedance

But the real question is, what kind of source impedance should an amplifier designer reasonably expect to see from the driving source? And in a world where only the wimpiest of preamplifiers have an issue with a 10K-50K load, how much extra cost and design effort is one willing to spend in order to satisfy a few oddball cases?

^^ This.

02-13-14: Almarg
John (Jmcgrogan2) & Bombaywalla, see what I meant when I said that "I don't have a good feel for what the inevitable tradeoffs would be." :-)

You're still the man in my book Al! Who wants a silly SS amp anyway....I'll take your VAC amp any day Al.....seriously....I'll take it. LOL! ;)

Hi Atmasphere, what is your opinion for a impedence match for a 100Kohm solid state amp that I do have, no matter a pre-amp is tube or solid state?, what impedences will work to best effect for both tube and solid state pre-amps?, Thankyou.

Audiolabyrinth, if you have an amplifier, tube or solid state, with a 100KOhm input impedance, any preamp tube or solid state will work with it.

The general rule of thumb is that the source have an output impedance that is no more than 1/10th of the value of the load.

But there is a caveat- if there is a coupling capacitor at the output of the preamp, the value of the cap will interact with the output impedance of the preamp- meaning that it may be considerably higher at 20Hz than it is at 1000Hz. For this reason I feel that the output impedance at 20Hz is an important value, as it can effect apparent bass response (FWIW our preamps have the same output impedance at 2Hz, 1KHz, 10KHz and 100KHz).

If the output impedance is higher at 20Hz than 1KHz, you may experience a lack of bass with amplifiers that have a low input impedance.

Thankyou Ralph, You are the man in my book!, I do learn alot from you and Almarg, the both of you gentleman are a asset to us all!, I agree, my 100kohm amp does not lack in bass at all., help me out here, what is 1/10th of 100kohms?