You can be sure of having a perfect match if you use the same brand of amp and preamp. Not only will you have an electrical match, but you will also have a sonic match. I have mixed amps and preamps on many occasions and came up with some interesting sounds. However, when using the same brands I always hear a rightness to the sound that can not be achieved by mixing brands.
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1:10 min. ratio output to input impedance. THis is the accepted ratio for minimal impact on freq. response. Eg: pre out= 100ohms matched well with amp input impedance at 1kohm (1,000 ohms). My CAT pre ouput impedance is listed at 75 ohms, so will match well with any amp input impedance of 1K ohms and above. |
I just researched this topic yesterday. The output impedance of the preamp should be within 10:1 ratio to the input impedance of the amplifier. Thus, the preamp is the lower number in the equation in this example. I have a solid state amplifier which provides 50k ohm input impedance. My tube preamp provides 592 ohms output impedance. Given the formula above, the two units are compatible. Hope this helps! |
Mofi, thanks for linking to my post. As I indicated there, and as you realize but others may not, it is not as simple as taking the two published numbers and seeing if they differ by a factor of 10 or more. The published impedance numbers are typically at a mid-range frequency (e.g., 1 kHz), and can be much different at other frequencies, especially in the case of most tube preamps. Here is a quote from another thread on this topic: 07-11-12: AlmargIf the component has been reviewed by Stereophile, the measurements John Atkinson usually provides will indicate its worst case impedance across the audible frequency range, to which the 10x factor can be applied. Regards, -- Al |
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