Amp preamp impedance matching...can anyone explain?


Hi, I currently have vintage tube gear, but want to try a SS amp with my tube preamp, and may try a SS preamp with my tube amps. I have noted there is an impedance matching issue, but do not understand it. Can anybody provide a quick summary?
Thanks
Jim
river251
I have a tube DAC that uses a single 6SN7 tube with 1 microfarad coupling caps. I was told it has 8 kohm output impedance. I wanted to get this integrated SS amp but the input impedance is 10 kohm. So this is a horrible match, so I stayed away. My tube amp with passive stepped attenuator at the input of the amp has 100 kohm impedance. This DAC/amp combo sounds dynamic as hell with deep bass extension. But I really wanted that SS integrated.
Reading this as well and I wanted to add my specs from my Marantz PM-KI-Pearl Integrated that I would like to entertain using as a preamp and then adding an amp...tube or ss still not determined.

The testing of this Pearl unit shows "The output impedance from the Preamp Out jacks was 217 ohms at high and middle frequencies, rising to 495 ohms at 20Hz."

Based on this information, does one still look for the above in the input impedance of 47k or higher?
Vineman, since the worst case (20 Hz) output impedance is known, just multiply that by 10 to calculate the minimum desirable amp input impedance.

495 ohms x 10 = 4.95K (minimum)

Nearly all power amps will meet that criterion.

Regards,
-- Al
07-19-12: Dracule1
I have a tube DAC that uses a single 6SN7 tube with 1 microfarad coupling caps. I was told it has 8 kohm output impedance.
that is correct. impedance at 20Hz = 1/2*pi*20Hz*1e-6 = 7957.7Ohms, which could be rounded up to 8KOhms. The manuf wasn't lying! ;-)


I wanted to get this integrated SS amp but the input impedance is 10 kohm. So this is a horrible match, so I stayed away.
right again! a horrible match down the in bass region. Your system would have sounded tinny. So, good thing you stayed away.

But I really wanted that SS integrated.
better put a lid on that desire while you have this particular tube DAC! ;-)