Midrange tone control

[sam14]

Hi, I would like to build a design based around the Pultec MEQ5 EQ but am not very electronically minded. I want to add some mid-cut at 1,2,3,4 Khz. Could someone tell me what the combo L & C values need to be at these freqs? Is it straightforward to calculate them? I have seen the MEQ5 schematic but couldn't figure it out! Doh! Thanks in advance

 

[sreten]

Hi,

you need to use or scale to the ~ 500R series resistor, the 270R
Q control and the inductor and capacitor values set by SW2.

This assumes your input can handle 600R loads.

/sreten.

 

[sam14]

Thanks, Sreten. If I've worked it out correctly then, 1Khz is 108mH & 220nF; 2Khz is 34mH & 170nF; 3Khz is 34mH & 68nF and 4Khz is 34mH & 38nF? Also, is the transformer I/P essential or can I use 600R / 510R at the I/P of some unbalanced phono connectors? Thanks again.

 

[sreten]

Hi,

Download tina ti free circuit sim and check that it works.

(stick an op-amp in the corner unconnected to get it to work, then
use AC analysis to plot the frequency reponse, quick and easy)

600R is a fairly hefty load for an output - can the equipment
drive 600 ohm loads ?

/sreten.

 

[sam14]

tina ti?

 

[sreten]

http://focus.ti.com/docs/toolsw/folders/print/tina-ti.html

 

[sam14]

Thanks again, will give it a try