Such math is not my strong suit, all I can say is that after picking through my selection of resistors I had on the truck it solved the problem, your mileage and results may vary. It's a simple matter to increase the values of 2,2k resistors for more attenuation.
On Wed, 3 Jul 2002 14:10:08 -0700 "Paul H. Gusciora" <[EMAIL PROTECTED]> writes: > Relative Power = 20 Log10( Voltage_Ratio ) dB > > so the attenuation of a 220 ohms tap series with 2 2.2 K ohm > resistors is: > > 20 Log10( 220 / (220 + 2200 + 2200) ) = 20 Log10( 1/21) dB = > -26 dB > > this assumes that the page port output has fairly low impedance (is > > not loaded by the attenuator), and the microphone input has fairly > high impedance (does not load the attenuator), and the microphone > input to the amplifier is isolated. If one side of the microphone > input to the amplifier is essentially ground, one resistor does > essentially nothing and the attenuation will be > > 20 Log10( 220 / (220 + 2200) ) = 20 Log10( 1/11) dB = -21 > dB > > I estimated Log10 in my head. A calculator will give more accurate > numbers. > > BTW: I assume that the first poster already made certain that the > music-on-hold source is connected to something (radio) or grounded, > > and that the system is not set up to send the music-on-hold source > to > the amplifier when no paging is occuring. > > Paul Gusciora > San Rafael, CA > > (Chemical Engineer, Control Systems person, and amateur radio > wannabe) > > To: [EMAIL PROTECTED] > Cc: [EMAIL PROTECTED], [EMAIL PROTECTED] > Subject: Re: KX-T: Humming sound on KX-TA624 > From: chris Snyder <[EMAIL PROTECTED]> > Date: Wed, 3 Jul 2002 08:11:43 -0400 > > I would highly recomend not going into a mike input of an amp with > out an > input attenuator, microphones typicaly put out a -60 db signal and > page > ports put out 0 db or greater so you end up with a terrably > destorted > audio as well as possably picking up all sorts of electrical noise. > > An attenuator I have used sucessfully is made from three resistors, > one > 220-270 ohms acrost the mike input then a 2.2k ohms from each mike > terminal ( pins 2 and 3 on an XLR jack) to the page port. > > On Tue, 2 Jul 2002 22:26:16 EDT [EMAIL PROTECTED] writes: > > you may have a ground loop. try putting either .01 mfd > capacitors in > > series > > with the output and input, or a 600-600 ohm matching transformer > for > > > > isolation. Depending on how the circuit board is laid out > inside > > the TA624, > > you may be picking up hum from a power supply, or transformer. > Be > > sure to > > use good shielded wire, West Penn 292, or equivalent, or good > rca > > type phono > > coax cable. Be sure your impedence between the TA624 and the > input > > of the > > paging amp is the same, or the input on the amp is Hi Z 10K-50K. > If > > you are > > going into a mic input, which is typically 150 ohms, you are > loading > > down the > > TA624, and that can generate noise and hum. Always go from a > lower > > impedence > > to a higher one, never the reverse. > > > > So endeth the lesson. > > > > Steve L. Martin > > <A HREF="http://www.geocities.com/surfsidesound/";>Surf Side > Sound, > > Inc.</A> > > Chris Snyder > Advantage Telcom > Cosby, Tn. > Sevier County's oldest interconnect. > > Chris Snyder Advantage Telcom Cosby, Tn. Sevier County's oldest interconnect. _________________________________________________________________ KX-T Mailing list --- http://kxthelp.com/ Subscription changes: http://kxthelp.com/mailman/listinfo/kxt
