I spoke with Alex at Hovland a couple years ago, and got the following information about amplifier compatability with a long cable run: Output impedance of preamp is 2500 ohms has a unit gain FET at the output to help drive long cables. Long cables and 30kohm amp is fine, but wouldnt go so low as 10 kohm. |
Taken from DECWARE Audio White Paper: All sources and preamps have what is called "output impedance". Think of it as the units ability to drive difficult loads, like might be experienced with super long interconnects, or obnoxious amplifiers. On the flip side, all amplifiers have what is called "input impedance". Think of it as the difficulty level the amplifier imposes on the preamp or CD player. As a general rule, the lower the output impedance is, the better it will drive difficult loads. And, the higher the input impedance is the less difficult it is to drive. A good example of a happy situation is a preamp with an output impedance below 1000 ohms driving an amplifier with an input impedance of 100,000 ohms. Taken from "Enjoy the Music": 1. The output impedance of the preamp should be not more than 1/10th of the input impedance of the power amp(s) it is connected to in order to avoid degradation of performance due to overloading the preamp's output stage. (Most amps range in impedance from 20kohms to 100kohms. A few are as low as 10kohms. Below that is irresponsible). 2. The output impedance of the preamp forms a low-pass filter with the capacitance of the interconnect cable (rolling off the high frequencies). The 3dB down point of this filter is inversely proportional to the product of the source resistance of the preamp and the capacitance of the cable. Accordingly, the lower the source resistance of the preamp, the wider range of types and lengths of cable the preamp will work well with. |
From the Stereophile review: Output impedance: approximately 2500 ohms http://www.hovlandcompany.com/pdf/reviews/HP-100Stereophile.pdf |
