Matching Pre-Amp to Amp

Hello Nab2,

I had seen your initial post, but I didn't respond as I have no particular knowledge of how various preamps tend to synergize with McIntosh amps.

I would just suggest, though, that your questions would be seen by a vastly larger audience if you posted them in the regular part of the Forum, rather than in the Insider section.

Also, when you consider alternative preamps I would keep in mind that the 22K input impedance of your amps is too low to be optimal for some tube-based models.

Good luck. Regards,
-- Al

Thanks for the response. I've been doing some reading based on your comments. I did find this at Stereophile regarding my CJ17LS2: "The output impedance was below a lowish 800 ohms in the midband and above, but rose to 1.6k ohms at 20Hz, due to the presence of a finite-sized output coupling capacitor. The C-J should therefore be used with a power amplifier having an input impedance of at least 22k ohms if the bass is not to sound a little lean." My CJ 18 has an output impedance of 200 ohms. So both should be OK with regard to matching the output of the pre-amps to the input of the amps. I'll move the post for a wider audience. Heck, I almost don't want to given the reaction I've seen here regarding McIntosh.

Thanks again Al.

Have you considered a McIntosh? I have a C-2600 and like it.

joe

Here's some generalities that hopefully might help:

• Most Transistor amplifiers (not all) have a relatively low input impedance and higher gain (than tube amps).
• Most transistor preamps have an accordingly low impedance and lower gain (than tube preamps).
• Tube amps almost always have a quite high input impedance but relatively low gain.
• Tube preamps accordingly usually have higher output impedances (higher than many transistor amps are comfortable with).  They also tend to have higher gain (which matches the lower gain of tube amps).

So if your amp is a all-tube MAC amp, it probably has a sufficient input impedance for any preamp.

If your amp is a transistor amp then the impedance may be marginally too low for a match with some tube preamps.

Ideally you want the input impedance of your amplifier to be 10X the output of your preamp at any (or at least most) frequencies.  Anything 5X or below should be avoided.  Thus if you model amp really does have a 22K input impedance at 1K, then you need a preamp with an output impedance no higher than 2k at that same frequency.  So check the CJ's output impedance, or any other preamp you may think of pairing.