Almost forgot, as concerns input impedance; R total should be selected as to maintain yours. For instance if it's 50k and you plug a 50k attenuator into the inputs, your CD player will see a 37k load.( when set for 1/3 attenuation) and will vary over the range of the attenuator. And yes, if your source impedance is high enough, the upper frequences will be rolled off. Finding Rtotal is way too easy, it equals 150% of input impedance.(are you seeing that 1/3 relationship again?). Input impedance at audio frequences is almost purely resistive, so this can be measured with an ohm-meter. Alternatively, you could simply add a series resistor,to the CD input, of a value of 50% of input resistance and achieve the same voltage reduction. This of course would raise the input resistance by a third. All the above advice assumes a standard circuit design pratice used in almost all high end products. Mock it up first, with a set of male and female RCAs and resistors from Rat Shack, plug it in and listen, before taking the hammer and tongs to your preamp. O.K., now I'm done.
CD output voltage too high for preamp: what to do?
I have an Audible Illusions preamp which is designed for a 1.5v input signal. I am told that this is standard. My Ayre CX-7e puts out 2.25v. They play beautifully together but I have too little control over volume: I cannot use the preamp vol controls beyond 9 o'clock because it is way too loud. Likewise it is hard to get just the right volume in the limited range available. This is worse with some CDs for reasons I do not know.
Audible Illusions will change the preamp attenuation board for $275, but before I do so I wonder how others have dealt with the problem of newer CD players with higher outputs than their preamps were designed for.
Audible Illusions will change the preamp attenuation board for $275, but before I do so I wonder how others have dealt with the problem of newer CD players with higher outputs than their preamps were designed for.
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- 29 posts total
- 29 posts total