CAPI SumBus ACA Summing Mixer

Awesome! Glad it worked for ya! Here's a new one to try if you haven't yet per Jeffs suggestion: Instead of turning up the mic pre for your make up gain, try turning up the Channel Fader gain. It's a slightly different sound and well worth experimenting with. Also, I have been experimenting with hitting the SumBus just a tad harder (maybe 1.5dB) and then hitting the VP28s a tad harder and backing down the input to my Burl B2 A/D by 2dB so that everything is hitting those transformers a couple dB hotter and man I gotta say, I'm really digging it. Sometimes it's a bit over the top but sometimes it really glues things together incredibly well. I just ran an ITB mix into the Sumbus chain with that setting and it absolutely destroyed the ITB mix. It just sounds freaking ANALOG!! Imagine that! Haha! The main difference was how wide the vocal became and how clear the drums and bass were. Gotta love it!

Maybe I misunderstood you the first time, but that’s what I’ve been doing - output faders dimed and then bringing the input up to a decent level.

bartacusad the VP28 channel isn't quite the same as the master fader on the mix bus. On the VP28 in line mode you're padding the signal down 35dB, then raising it up through the input transformer, the first op amp, and the output transformer. That feeds the 'channel fader' which attenuates a fixed gain 325 style line amp (I'm guessing +6 dB on the op amp, and +6 dB on the output transformer). So with the fader wide open, you're doing no attenuation before the +12 dB of the second stage. The +12 dB is always there, though.

On Jeff's ACA Booster card, the summed signals come into the ACA at -2 dB, the ACA op amp combines them for a 4.5 dB loss, and then adds +6 dB across the output transformer to bring the whole thing to a nominal -0.5 dB. (I think this is where the SumBus box "ends".) In the ACA-BO card, this goes into the master fader which works the same as the stepped attenuator in the VP28, but in the console booster the op amp is set to nearly unity and the final +6 comes from the output transformer. Without transformer insertion loss you have a nominal +4.79 dB output for a +4 line input, which hits the program bus at -2 dB.

So - using the VP28 at unity from the SumBus is taking a nominal -0.5 dB signal, padding it by 35 dB, bringing it back up 35 dB through the mic pre (~17 and 6 from the input and output transformers and I suppose ~12 dB from the op amp) to come back to -0.5 dB. Then, bringing the fader to +12 does no attenuation before a second round of +6 and +6 from the op amp and second output transformer respectively. (If you pull the fader back you're actually dropping the signal again, only to boost it again at the line amp by 12 dB).

Long way to say, the closest way to approximate the booster on a console is to get a 325 (or a API 535-LA) and set it to +6 dB. Or, get a CAPI card and rig it without the input transformer as a unity line amp with +6 on the output transformer.

Not that y'all are doing anything wrong! If it sounds good it is good! Just that there's a lot going in the VP28, even at unity.

Well right, I'm speaking more on John's point about hitting the mixer harder from the DAW when I need that push. If I mix with my peaks hitting the suggested sweet spot of 0db, only my kick and snare are really living in that sweet spot. If, during my mix, I want to boost the DAW outputs to drive the mixer harder, I assume that I'd get my color at the cost of compression. The kick and snare might start getting shaved and the mix balance itself would determine which instruments start driving the mixer channels.

The difference I'm trying to suss out is how using the SB1 allows you to individually dial in those sweet spots on each channel and mix with the knobs like faders. You'd have the color you want from the start and could even drive selective channels harder without disturbing the mix balance by attenuating with the knob. 

My curiosity is how important this particular difference is (getting every instrument into the sweet spot) to achieving the coveted "console sound."

I appreciate the honesty! 

The SB1 does not have in hand gain, as in you can't boost the level coming into it right there on the "fader" of the SB1. You can only attenuate it, as in turn it down. Which means you could drive your DA output more if you wanted. 

You wouldn't setup your outputs of your computer and then mix on the SB1. I mean you could to a very limited point. if you want to turn things down with the rotary knobs live, you totally could However, don't think you could do a full 16ch mix all analog on this this with rotary knobs. Theres a reason why Tom Dowd said "screw this, I want to us all my fingers" and invented faders. You'll still want to do just about all your mixing(think automation) ITB and then you are flavoring it with the SB. This also helps with recall for later. Which in some ways is an advantage to the SB2 as you just have to push a few buttons likely to recall a mix instead of trying to reset your rotary knobs just right. 

This is true, but I had the idea of trying to clip my drum bus aggressively on parallel channels (in place of reaching for Decapitator or Devil-loc). I've found distortion to be a good tool for gluing a hip-hop kit, but it might not be as necessary when moving OTB to a colored mixer. Again, this is a new world for me to hit multiple op-amp stages like this and tbh I'm worried about the adjustment period 

Also, sorry for mixing up the Sumbus types guys! Probably very confusing to you! I assumed SB1 was the first released, but it might be about the mono cards? I've amended the original post in case anybody follows this thread top-down.