Hi all, Would appreciate all the experts help here to verify if my understanding is correct before I start building. Many thanks in advance.
As per mentioned (don't know if this had been discussed before, if so pardon me) - would like to DIY a pair of XLR inter-connect between the pre-amp to power amp with in-built attenuation (~12dB) at the power amp plug side. I reference the article/formula at this site: http://wiki.slimdevices.com/index.php/DIY_passive_attenuation. The connection circuit I think should be something like this (in which I think both R1 & R2 values used have to be halve w.r.t. if it was unbalance), right ? 17147 The formulas from the site are:- Attenuation [dB] = 20 * Log( R1 / ( 1 / ( 1/R2 + 1/IMPload ))) New Source Impedance = 1 / ( 1 / (IMPsource + R1) + 1/R2 ) New Load Impedance = R1 + 1 / ( 1/R2 + 1/IMPload) The values I gathered from my pre and power amp are:- Power amp input impedance = IMPload = 104K-Ohms Pre-amp output impedance = IMPsource = 500 Ohms Using the following values:- R1 = 82.4 K-Ohms - Or for Balance Line = 0.5*R1 = 41.2K-Ohms R2 = 27.4 K-Ohms - Or for Balance Line = 0.5*R2 = 13.7 K-Ohms The resulted values are:- Overall attenuation ~ 11.6 dB New Source Impedance ~ 20.6 K-Ohms New Load Impedance ~ 104.1 K-Ohms Are all my above assumptions + calculation/result correct ? Regards, EH. +-------------------------------------------------------------------+ |Filename: XLR Plug Attenuator Circuit.jpg | |Download: http://forums.slimdevices.com/attachment.php?attachmentid=17147| +-------------------------------------------------------------------+ ------------------------------------------------------------------------ tane0019's Profile: http://forums.slimdevices.com/member.php?userid=56241 View this thread: http://forums.slimdevices.com/showthread.php?t=102904 _______________________________________________ diy mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/diy
