Passive summing w/ makeup gain vs line level amp saturation?

A lot of this is over my head. I just want some analogue tone, it doesn't have to be equal to an SSL 9000 or a Helios or API or Neve console, just wider, deeper, sweeter, more low level detail on my 2 bus when final mixing. I bought the Black Box Analog Design HG-2 plug-in after listening to some tracks online done with the hardware. It definitely got me 25-30% of the way there. I still think the Dangerous 2 Bus + might be what I need. I didn't like the SSL Fusion, it seemed not to add much, and what it did add, I didn't like. The Silver Bullet is really good too.

I can't afford new gear now anyway, so I have time to listen and learn.

AFAIK, yes, and the only thing really missing is the makeup gain from a real console. But, the SumBus has plenty of mojo as it is.

There's some different things going on here Otis. One is the tone of the circuitry on each input - the transformer and op amp. The other is the sum amplifier. A summing amplifier is basically just an inverting op amp, which by itself isn't necessarily going to give any tone. But, when you're summing lots of inputs you can actually be asking quite a lot from the amplifier. Let's say you're summing sixteen inputs at unity gain, that's a gain of around 24 dB - similar to what a mic pre might be doing. So, summing amps can generate tone because of how they'll handle the gain being asked from them. API style summing uses the op amp to sum and to drive a step-up transformer, so you get the added benefit of what you might call a 325 style line amp tone as well.

If you're only summing two channels, you have only the "thumbprint" of the input stage on two tracks, and the "sum" amplifier has become a simple inverting op amp driving a transformer - basically just a second line amp.

I have not used the SumBus - it looks incredible - so I can't speak to it specifically, but because of what I lined out above generally the more you sum the more you get out of summing because the sum or makeup gain amplifiers are working harder, and so imparting more tone.

I’d be really interested in your thoughts on the matter if you care to try it out with your SumBus Bat, if there is more desperation, width, detail with the additional xformers/opamps treating things separately I’d be a happy adopter but I’d just like to know before I make a rather expensive decision.

Well, if each stem is running through an input transformer or amplifier, each stem will sound a little different just from that.

Then when they're all combined, the amp is "working harder" to sum more inputs. Each input you add to the amp is more gain coming from the amp. Just like a mic pre sounds different when you're at 20 dB of gain vs 40, the more you "ask" from the summing amp the harder it has to work, the more distortion you get. So even if you were doing totally transparent inputs, more channels will have more "sound" from the summing.

Kinda. So, there's a difference between active and passive summing. Passive summing you tie all the bus resistors to a bus and that has a drop, and that drop is fixed by the number of resistors on the channel, and the amp is fixed gain to make up that loss. Active summing has an advantage that you can turn on and off resistors from the bus, and change the gain being asked of the amp (and the noise gain!).

I don't know how the SumBus architecture works, whether it is actually removing bus resistors from the bus (which lowers the amount of gain) or if it is grounding or muting unused resistors (which does not).

API consoles didn't sum at unity gain, they summed at like 0.6, then made up the sum loss with a 1:2 output transformer. This kept the noise gain of the summing stage down. But the consoles themselves ran at an internal -2 dBu nominal level, meaning everything that came in from the outside world was dropped 6 dB, and then before the console went back to the outside world there was a 1:2 step up back to nominal +4 dBu. In API consoles the summing amp took the -2 internal level and summed it back to -2, then used a second line amp to go from -2 dBu to +4 nominal.

If I had to guess you're going to get a lot more of a tone from the input stage using a transformer and op amp than just the line amp from the summing. And, I think you'll probably hear a difference as you add more channels. YMMV

You have Coils right? Planning to use them as the makeup gain preamps?

I do wonder what that difference sonically will be between operating this way, vs using the Coils on their line settings, and as hardware inserts. I know it would save some conversion trips, though I recall seeing a video Eric made where he said he couldn't hear the difference between 1 pass and 20 passes through his Lynx converters. 

Also, thinking the Coil Preamps will act as "compressors" without timing artifacts, which might be really nice on a "vocal bus", "music bus" and "drum bus", without the need for bus compressors. Thoughts on this? I would tend to compress the lead vocal, and the background vocals as a group, but not sure I would need to compress the lead and backing vocals together as a group; though running them through a pair of CA70s might add some nice glue.  

Steven, curious to hear your intended signal flow with hardware, compressors and eqs, etc with your Pyra-Sum. I am interested in it!

I ended up getting more elaborate than expected and am enjoying the Pyra-Sum and process of setup.

A+B are my music bus and sum to Pueblo JR preamps, Buzz Audio DBC-M, Coil 70s and a B32.

C is my vocal bus and sums to Pueblo JRs and Buzz Audio SOC-M

Bricasti M7 is sent direct to Mix Bus

Mix Bus is summed to Pueblo Audio JR and Bettermaker Mastering Limiter to Aurora(n)

Hadn’t been reading this thread: interesting.

i have noticed on Facebook that Josh has been launching hos new 16 channel summing box I believe with different transformers(api, neve?).

His new partner, associate, lives in Rome, so these are only made there. I think now working on second batch, first sold out quickly.