plumsolly
Well-known member
I am in the final stages of refurbishing a PR&E ABX-18, which is a pretty neat beast - more to follow.
I would like to use it's CRM in place of my current outboard one - It will save me some money and the console's solo functionality only works in the context of monitor path - It is not destructive solo, but has a separate solo bus.
I have attached the specs and the schematic. The specs are nothing to sneeze at: 0.5db down at 20khz, and .004% THD.
However, I would like to make this path even cleaner. I realize that the improvements will most likely be inaudible, especially in the context of my amp/speaker/room system. Consider it an academic exercise.
I plan to replace the volume pot with a rotary switch to maintain L&R matching.
I am going to experiment with replacing the CMOS switches with DIP plugin relay cards made from these: http://capi-gear.com/catalog/product_info.php?cPath=102&products_id=195
I ordered some fancier chips to replace the 5532/4s -LM4562 and LME49710.
I think the bandwidth is set by the feedback caps - (C6, 9 14 & 20 for the left channel) - I calculate 0.5db down at 20khz for the current values, which is in line with the specs. I'd like to shoot for something like -0.1db at 100khz which would mean replacing the 100pf with 5pf.
Will I be able to get away with this? Is this the sort of thing that depends on layout? RF present? Specific opamp?
I see here: http://www.soundskulptor.com/docs/mc624-schematic-02.pdf, no feedback c.
Lastly, I am wondering whether it would be worthwhile to try to change the instrumentation input amps with THAT chips - I'm thinking/hoping that with the fancier opamps, the distortion of this stage as is will be vanishingly low.
Thanks for your input,
Ben
I would like to use it's CRM in place of my current outboard one - It will save me some money and the console's solo functionality only works in the context of monitor path - It is not destructive solo, but has a separate solo bus.
I have attached the specs and the schematic. The specs are nothing to sneeze at: 0.5db down at 20khz, and .004% THD.
However, I would like to make this path even cleaner. I realize that the improvements will most likely be inaudible, especially in the context of my amp/speaker/room system. Consider it an academic exercise.
I plan to replace the volume pot with a rotary switch to maintain L&R matching.
I am going to experiment with replacing the CMOS switches with DIP plugin relay cards made from these: http://capi-gear.com/catalog/product_info.php?cPath=102&products_id=195
I ordered some fancier chips to replace the 5532/4s -LM4562 and LME49710.
I think the bandwidth is set by the feedback caps - (C6, 9 14 & 20 for the left channel) - I calculate 0.5db down at 20khz for the current values, which is in line with the specs. I'd like to shoot for something like -0.1db at 100khz which would mean replacing the 100pf with 5pf.
Will I be able to get away with this? Is this the sort of thing that depends on layout? RF present? Specific opamp?
I see here: http://www.soundskulptor.com/docs/mc624-schematic-02.pdf, no feedback c.
Lastly, I am wondering whether it would be worthwhile to try to change the instrumentation input amps with THAT chips - I'm thinking/hoping that with the fancier opamps, the distortion of this stage as is will be vanishingly low.
Thanks for your input,
Ben