Compatibility between preamp and amps

Output impedance of preamp to input impedance of amplifier is the biggest concern.  There is a minimum ratio that plays well together.  

I have an Aesthetix Calypso with 1000 ohm output impedance which was not enough to make the Edge M8m amp with 30K input impedance happy.  That is 1:30 ratio.  It liked the 300 ohm output impedance of an Acoustic Research LS17SE much better at 1:100 ratio.

The equipment you noted above has the same 1:100 ratio which, on paper, should be an adequate mix.  

Good answer.

thanks but isnt there more to it than impedance ratios? like gain and sensitivity?

You've latched onto something of critical importance. So critical in fact that it applies not only to amp/pre-amp but to every component feeding a signal into any other component. From phono cartridge to phono stage to pre-amp, from CD to pre, from streamer, DAC, on and on. Critically important you study this to death until you understand it chapter and verse. 

Until one day you wind up just like me, so expert you haven't the foggiest what any of yours are. Because: I lied. Its just not all that.  

Lol SMH

With digital sources that output at higher voltages than most analog ones the 11 dB gain in the pre may be beneficial. You have 41dB of gain total which should  be fine. One thing I question is the amps sensitivity. At 0.85 volts, it is very sensitive if that is all it takes to drive the amp to full power. The sensitivity of the speakers also come into play. 

@mesch I do believe that the 0.85v may be a potential issue. My speakers are about 92db efficient. I get noise (hiss) from my system and I think it is incompatibility between the 2 pieces. each on their own with other components they are fine.

Yea, a 0.85V sensitivity 30dB amplifier is a candidate for a passive pre. Not to say that I prefer that route. I am currently using a active tube line stage preamp that has variable gain output with a SS amplifier. My take is that many digital based systems have too much gain that is then attenuated. Therefore a low gain preamp with a low sensitivity (high V = low sensitivity) amplifier can be beneficial.

thanks but isnt there more to it than impedance ratios? like gain and sensitivity?

@jimbones Yes.

For starters, the output impedance at 20Hz is probably where you should look. With many preamps, the output impedance rises at lower frequencies.


The gain is another matter- much depends on the gain of your amps and the sensitivity of your speakers. As a general rule of thumb, more powerful amps tend to also have more gain as they are used with less sensitive speakers. This should make the gain of the preamp a non-issue, but since the advent of Redbook (which set a standard of 2 volts output for single-ended digital sources) the amount of gain in the preamp has been a bit trickier to sort out. In general though, a reasonable amount of line stage gain is about 15dB. If you are only running digital though, a reasonable amount is about 6-10dB.

Had a huge worry myself, while u sing a Sanders “the preamp” with a McCormack mono pair. Volume would not start until I hit almost 40 or 50 on my vol knob.
   Turns out, it’s made that way, same with my McCormack preamp.

I’m fine now.

Yes, the gain provided by a preamp is one thing, and often more than needed. How the gain is distributed via the volume control is another.