Reviving a Zombie Thread since this is some of the most lucid thinking I've seen on the subjects. Great stuff guys.
I am reintegrating some DSP, specifically a DBX Venu360, into my rig. The above conversation has been en-pointe for the most part, but I want to address this above 55dB issue-
I regularly turn down my system 55dB or more, and have spent a lot of time with attenuation in various forms trying to maintain resolution and low noise. I've made transformer volume controls of multiple types, as well as buffers, traditional preamps and resistive attenuators. For the DSP, my input levels will be exceedingly low if I don't work around that issue. The problem is that high efficiency speakers, coupled with powerful and sensitive home amplifiers (without any input trimmers) will operate in home spaces at very low output relative to their maximum. I have some 200-500 "real" watts per driver available and most of my drivers are generally 97dB or more, in a modest space. I prefer the sound of big efficient systems (as we tend to around here), but it means that typical gain structures are way too much.
The solution is well known to many in the pro/venue space, where it's generally a mixer or the like feeding the DSP. Input trimmers on amplifier inputs allow you to structure your gain differently, so that you can avoid pushing against either the noise/resolution floor or potential clipping. The former is usually able to be fixed easily by adjusting the trimpots on amplifiers downward and the mixer master volume upward, leading to a higher voltage throughput on the DSP, and better noise and quantization performance. If you're clipping the mixer to get that voltage, you done gone too far, and you need to back off the mixer volume and up the trims on the amps.
So for me, I've spent the last day deciding around some of what I'll do to correct the issue- I've been waffling between two options:
- Simple DIY resistor networks, either as part of cables, or wired on the input XLRs of the amps
- Having someone else do it for me- https://naiant.com/custom_audio_repr...nline-devices/, either as an adaptor attenuator or built into some cable.
There are cheap XLR attenuators on market but they do not seem to be of sufficient quality for my taste, with many designed around 600 ohm operation (too low) or not properly balanced (an L-pad on just one leg of a balanced connection will lower the volume of a differential input, but isn't ideal). Naiant doesn't seem to suffer from any of those issues, and the adjustable units are very, very cool.
One can also change the gain structure as another way to get down that path, but the point is, where your gain takes place in a system with ADC is very important, and 55dB isn't an unheard of level of attenuation.