How do I combine several instruments into one Line In, in live performance?

Question

Reading the help pages at Sweetwater and a few other sites, I see a Line Mixer “Live, line mixers let you combine multiple sources such as in-the-booth playback devices into a single output, freeing up channels (and preamps) on you main board.” which sounds kind of like what I'm looking for.

But by definition those take line level, meaning each instrument already went through its own DI.

Is there a combining DI that allows multiple instruments to be plugged in and delivers a mixed line level output? Especially if the inputs are from identical pickups and each has its own little gain control already.

The final goal here is to have our own instrument mics and mixing, so we're not at the mercy of the venue if it's a stage, and will have portable amp and speakers for playing e.g. outside in the park.

The size of the amateur gathering varies. I don't want a huge mixing board with 18 or so inputs, for expense and bulk, and it doesn't need that fine of control.

For this specific question, I'm considering this performance were there were 5 urhus, and the venue used 3 mics for them and ended up not having enough channels or mics available. They got some contact "pickup" microphones, so everyone has his own. I'm thinking I want to have a combiner to bring out a single Urhu Line to the mixer. When I start doing mixing as part of the troupe, I'll have one Line for each group of identical instruments. One time there might be 5 urhus, another day maybe 2 urhus and 2 or 3 pipas. The mix setup stays the same and the cluster acts as one voice.

Answer 1

For what its worth you generally never combine inputs with out having level control even if the devices have their own level control. You generally want to have control over the level of each input and there really are no multi-input signal combining DI boxes I know of (that does not mean they don't exist though). The way I read what you are asking is that you are looking for something like this a nice low profile rack mount mixer with 8 in and a stereo out. I personally would want some more control than what that offers and would opt for maybe a small 8 channel desk but that's just me.

On a side note, engineers at venues may not like you giving them a stereo feed where they have no control over individual levels but this depends on the venue and what not.

--Edit--

To answer the question about moving rack mounts around. The short answer is yes I do it all the time. I generally use something like this. I always add an extra slot when I buy a case so i can put a nice rack mount PSU in it as well for what ever I intend on running. Granted it adds something to carry but most things are made to that size anyway so you are going to end up with something similar in size in the end of the day.

Answer 2

There is an inexpensive way to create input "clusters" as JD describes, though some sound engineers may look askance. You can make a balanced, buffered contact mic preamp circuit and wire several piezo contact mics into the circuit (being careful to keep them in-phase). Out of the circuit comes one mic cable with a blended signal. This can run straight to FOH or any mixing console that can supply phantom power. When you have fewer than three urhus at your gig, you just leave the unused pickups neatly rolled up -- just don't kick them during the show! (We publish plans and offer this kit). If this sounds useful, let me know and I can provide details.
(BTW, I would love to play in that ensemble!)