Hi guys. I start with a new project- summing box, and I need a little help.
I read a lot of information, and special thanks to NYDave and all of you, about great information for this devices.
The overal idea is 16ch summing based overt passive summing design -> balanced to unbalanced part -> output high current buffer /gainstage/ and finaly , of course
, output transformer for balanced line output
First I think about passive-active switch. It's easy to do, but what about output levels and impedances and crosstalk of course.
Also, what's the best choice of resistor values for balanced signals? NYD use 10k for each pair. For output 600 ohm the overall insertion loss is circa 31dB. If I use 4k7 pair resistors @ 600 ohm output, insertion loss is 24dB - better, but what about crosstalk, and what's the best compromise
At this time I'm not about passive resistors value.
Next part is balanced to unbalanced schematics. I think about traditional opamp based schematics with small multiturn trimmer for better cmrr control, but I'd like to hear these THAT IC's model that1200 - with 0dB gain.
Next one is level pot and high current transformer driver. Again I have few ideas:
-opamp + transistor output with CCS with 50-60mA current capability. (see the attach)
-copy-paste from neve's output driver with 2n3055 - again similar current output
- National opamp application's idea. As I think it's Walt Jung's idea. The schematics is here:
http://www.analog.com/library/analogDialogue/archives/39-05/Web_Ch6_final_I.pdf
page 6.75. Actually all the part of this book for transformer driving is a good to read.
which one is a good choise? or something different?
Finally output transformer. I choose carnhill VTB1148 , because I can get it from Europe and the price is good.
Niki
I read a lot of information, and special thanks to NYDave and all of you, about great information for this devices.
The overal idea is 16ch summing based overt passive summing design -> balanced to unbalanced part -> output high current buffer /gainstage/ and finaly , of course
, output transformer for balanced line outputFirst I think about passive-active switch. It's easy to do, but what about output levels and impedances and crosstalk of course.
Also, what's the best choice of resistor values for balanced signals? NYD use 10k for each pair. For output 600 ohm the overall insertion loss is circa 31dB. If I use 4k7 pair resistors @ 600 ohm output, insertion loss is 24dB - better, but what about crosstalk, and what's the best compromise
At this time I'm not about passive resistors value.
Next part is balanced to unbalanced schematics. I think about traditional opamp based schematics with small multiturn trimmer for better cmrr control, but I'd like to hear these THAT IC's model that1200 - with 0dB gain.
Next one is level pot and high current transformer driver. Again I have few ideas:
-opamp + transistor output with CCS with 50-60mA current capability. (see the attach)
-copy-paste from neve's output driver with 2n3055 - again similar current output
- National opamp application's idea. As I think it's Walt Jung's idea. The schematics is here:
http://www.analog.com/library/analogDialogue/archives/39-05/Web_Ch6_final_I.pdf
page 6.75. Actually all the part of this book for transformer driving is a good to read.
which one is a good choise? or something different?
Finally output transformer. I choose carnhill VTB1148 , because I can get it from Europe and the price is good.
Niki
