The pultec stereo balancing thread was timely. I finally got my QE712's in a case with rotary switches for gain.
http://img.photobucket.com/albums/v357/plushmore/QE712/2b718f0d.jpg
The two sides are not matching up as well as I would like. The way I derived my resistor values was by soldering two 4k99 resistors together with the wiper lead connected in the middle to mimic the 10K adjustment pot. I did this for six of the seven bands. I then used a 10k 10 turn trimmer that I selected to be close to 10k (9k91). I measured and wrote down the values. I did this for a few of the frequencies and got similar values. I set the gain range trimmers on the board for 8dB of boost/cut. All went pretty well.
Now that I have all the switches done and can do more thorough tests the sides aren't matching up as well as I'd like. On some bands I can't get the "0" position to be at 0 with both the boost and cut set to 8dB. I have .5 db steps and they don't exactly match channel to channel.
I used 1% resistors for the 24pos switches. I haven't measured all the switches to see how close they are. Would this be the first place you would look. Do I have to get .1% resistors. I can't imangine selecting resistors so every switch was exactly the same. Should I look elsewhere?
http://img.photobucket.com/albums/v357/plushmore/QE712/2b718f0d.jpg
The two sides are not matching up as well as I would like. The way I derived my resistor values was by soldering two 4k99 resistors together with the wiper lead connected in the middle to mimic the 10K adjustment pot. I did this for six of the seven bands. I then used a 10k 10 turn trimmer that I selected to be close to 10k (9k91). I measured and wrote down the values. I did this for a few of the frequencies and got similar values. I set the gain range trimmers on the board for 8dB of boost/cut. All went pretty well.
Now that I have all the switches done and can do more thorough tests the sides aren't matching up as well as I'd like. On some bands I can't get the "0" position to be at 0 with both the boost and cut set to 8dB. I have .5 db steps and they don't exactly match channel to channel.
I used 1% resistors for the 24pos switches. I haven't measured all the switches to see how close they are. Would this be the first place you would look. Do I have to get .1% resistors. I can't imangine selecting resistors so every switch was exactly the same. Should I look elsewhere?