Attenuation help

[epistaxsis]

I am using these crossovers in conjunction with my new extended foreplay pre-amp:

http://greygum.net/sbench/sbench101/Crossover/xover.gif

The component vales are:

        LF Side   LF Side   HF Side   HF Side   HF Side   LF Side   LF Side   LF Side   HF Side
Freq   R4          R5,6       R9           R10        R11,12      C2         C3           C4         C6,7,8

2200   73.2k     80.6k     154k      32.4k      2.2M        1000pF   4700pF   120pF   100pF


Sorry that is a bit of a mess but I just copied it straight out of the text file!

The first question is I need to attenuate the HF by 3.5Db - any ideas?

Of course I could just stick a dirty great big resistor inline with the tweeter - but again what value?

The second question is how and where do I add C4s's?

I though I would ask here as you lot know much more about this sort of thing than I do.

Cheers,

[Paul Joppa]

To attenuate the tweeter, replace R1 with a potentiometer - I'd use 20K. Connect the tap to the HF circuit, leaving the LF channel as shown.

You can replace the cathode load resistors (R7 and R13) with C4S current sinks - make sure they are sinks not sources, with NPN transistors not PNP. Just like the second stage of the Foreplay Extended setup. It appears that this circuit uses very nearly the same current as the Foreplay and Seduction, so the same current set resistor (237 ohms) will work well.

[epistaxsis]

Paul,

Thankyou for that.

I will order the necessary C4S.

By the way I am using another Extended Foreplay Power Supply to power the crossovers.

I ahve noticed that someone else who changed the valves also changed the valve in the shunt regulator.

Do I need to do the sam,e or can I just stick with a 12AU7?

[Paul Joppa]

Looks like the currents and voltages from the power supply are basically identical to those of the Foreplay III, so the same regulator will work very well - the 12AU7 is fine.