horvitz
Well-known member
Sintech, looks really cool!
I've found that fooling about with it in different ways has shown me a lot. I'm getting REALLY close to dead quiet on mine.
Since the last time, I've made an input/bus board. I proto'ed a version using 5532 op amps, but elected to go with THAT 1200. It works really well! It's SO much better since I don't float the Lo input anymore, and have a good way to round up and deal with the grounds. Also, I'm not running cables all around hell and back to assign LCR via switches, but rather doing it with relays on the board. I'm rather proud of this part, being the relative noob that I am
I actually found that some portion of my noise is coming from the Bo section. If I go direct out from the 2-ACA, it's much quieter.. actually near to the level of the whole unit just being unplugged. There's just a bit of hum left, which I'm thinking is in my power supply - not sure how to fix that. I may actually just leave it this way since without the booster I'm actually at unity, which is all I really need in my application. I had mine set up so that we get -6 from the 2-ACA to BO (I think - it's grounding the lo output from the 2-ACA as per Jeff's schemo) and then the BO was just making that 6db back up again. No fader involved.
Although, I'd really like to tear apart the BO and see why it's noisy, just because it's bugging me!
So, my ground scheme looks like this:
input sig gnd -> star ground
input/bus board to 4-ACA -> shields grounded to at output from input board only, not at ACA
4-ACA to 2-ACA -> shields grounded at output from 4-ACA only
2-ACA to Bo -> shield+lo to ground at input side of Bo
Bo to XLR -> shields grounded at output side of Bo
Actually, as I write that all down, I notice that at the Bo is the only place where I ground the shields at the input side, rather than the output side. I guess it helps to say it out loud! I'll give a shot the other way 'round.
So, so close
Let me know what you end up with, Sintech. I'd love to compare notes.
I've found that fooling about with it in different ways has shown me a lot. I'm getting REALLY close to dead quiet on mine.
Since the last time, I've made an input/bus board. I proto'ed a version using 5532 op amps, but elected to go with THAT 1200. It works really well! It's SO much better since I don't float the Lo input anymore, and have a good way to round up and deal with the grounds. Also, I'm not running cables all around hell and back to assign LCR via switches, but rather doing it with relays on the board. I'm rather proud of this part, being the relative noob that I am
I actually found that some portion of my noise is coming from the Bo section. If I go direct out from the 2-ACA, it's much quieter.. actually near to the level of the whole unit just being unplugged. There's just a bit of hum left, which I'm thinking is in my power supply - not sure how to fix that. I may actually just leave it this way since without the booster I'm actually at unity, which is all I really need in my application. I had mine set up so that we get -6 from the 2-ACA to BO (I think - it's grounding the lo output from the 2-ACA as per Jeff's schemo) and then the BO was just making that 6db back up again. No fader involved.
Although, I'd really like to tear apart the BO and see why it's noisy, just because it's bugging me!
So, my ground scheme looks like this:
input sig gnd -> star ground
input/bus board to 4-ACA -> shields grounded to at output from input board only, not at ACA
4-ACA to 2-ACA -> shields grounded at output from 4-ACA only
2-ACA to Bo -> shield+lo to ground at input side of Bo
Bo to XLR -> shields grounded at output side of Bo
Actually, as I write that all down, I notice that at the Bo is the only place where I ground the shields at the input side, rather than the output side. I guess it helps to say it out loud! I'll give a shot the other way 'round.
So, so close
Let me know what you end up with, Sintech. I'd love to compare notes.