Al, (Almarg) has answered this question numerous times. Maybe he can find the response(s) and copy and paste them here. Actually I found one of Al's posts: http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1323999458&openusid&zzAlmarg&4&5#Almarg |
The general rule of the thumb is, the input impedance of the amp should be ~15 times or more than the output impedance of the pre (or the source unit, generally speaking). That's generalising, of course. As Aporter mentions, amps with 10k inputs are a tad difficult to match, while others with 150k are very easy to drive. |
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. |
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! |
