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In Reply to: Re: damping factor posted by KLHman on June 29, 2005 at 22:16:52:
You got the idea, but measuring the source impedance is not as easy as that. You do it by applying a signal to the amp with no load, driving the amp to the rated output voltage (based on it's power rating), and then loading the amp with a resistor and measuring the output voltage again. From the change in voltage you can calculate the internal impedance of the amp, and from that you can calculate DF.I do it at three frequencies (50, 1000, and 10,000 Hz)as the impedance can change with frequency. Since most DMM's are not accurate at higher frequencies (my Fluke is good to 1 kHz, and my Wavetek to 2 kHz), I use a broad band AC voltmeter above 1 kHz, but it's an analog meter ands resolution suffers. Some of the True RMS DMM's do go to over 20 kHz, and that would be the best.
If it's a tube amp, you need to make the measurement for each tap as they are different. Also, on a tube amp, or a SS amp with an output transformer (like the Macs)you calculate DF by dividing the source impedance measurement by the tap impedance. For direct or capacitvely coupled SS amps you just use 8 as the divisor.
Jerry
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Topic - damping factor - KLHman 14:42:39 06/28/05 ( 15)
- Re: damping factor - Bold Eagle 17:51:07 06/29/05 ( 2)
- Re: damping factor - KLHman 22:16:52 06/29/05 ( 1)
- Re: damping factor - Bold Eagle 06/30/05 07:08:18 06/30/05 ( 0)
Re: damping factor - Kal Rubinson 16:11:25 06/28/05 ( 11)
- Re: damping factor - KLHman 16:40:26 06/28/05 ( 10)
- Re: damping factor - Kal Rubinson 16:59:40 06/28/05 ( 7)
- Re: damping factor - Bold Eagle 18:03:28 06/29/05 ( 1)
- Re: damping factor - Kal Rubinson 18:33:13 06/29/05 ( 0)
- Re: damping factor - airtime 17:23:09 06/28/05 ( 4)
- Re: damping factor - Kal Rubinson 18:04:44 06/28/05 ( 3)
- The 5% figure may go back to - E-Stat 04:51:11 06/29/05 ( 2)
- Re: The 5% figure may go back to - Bold Eagle 18:04:51 06/29/05 ( 1)
- Whatever the case - E-Stat 18:59:56 06/30/05 ( 0)
Re: damping factor - KLHman 16:42:30 06/28/05 ( 1)
- Re: damping factor - Bold Eagle 18:06:07 06/29/05 ( 0)