Why not take the record output of the DJ mixer and adjust the level on your record device?

The only way I know of to keep the DJs from slamming the levels on the mixer is to work with better DJs.

Like any good audio or broadcast engineer, you should probably run this signal into the protective arms of at least some kind of peak limiter/compressor. The idea here is high ratio, high threshold. This way, you would just be lopping off high end excursions before they have an opportunity to overblow your recorders input/computer audio input device. Some computer audio devices already have such peak limiters at their input sections. But most don't. So for the little bit of dynamic range you may lose in your first few seconds, you'll have a chance to tweak back to reasonable dynamic limits without overblowing your inputs. Of course, if they are purely clipping their own outputs, you are SOL. The latter scenario I just mentioned actually happened to me on a large and exhaustive all day jazz festival. When I heard that the next band up included a good chunk of the group Earth, Wind & Fire, I knew I was in for something good. And then they started (for this festival, there were no microphone checks for me). Well, to my horror, everything coming off of any directs were 100% pure clipped awful crunch unusable distortion. No resistive input pads on my console could rectify the 100% pure distortion coming from the keyboards, bass guitar & guitar effects processors, etc.. I sent my A 2 out to the stage & the PA guys to see what was going on? They too were experiencing the same 100% horror filled distortion problem as I. So I just walk out of the control room from the truck and go over to the stage. I get on to the stage while the band is playing (remember there are also camera guys walking around as well) and found every keyboard guy, guitar guy with little mixers on stage, with all of their mixers having all of their red LEDs fully lit 100% of the time. I was dumbfounded. And they worked with George Massenburg? This just proves you can't fix stupid even with some of the best. At that point, I declined to mix the rest of that set. I mean were they really that stupid? Nothing the PA guys or I could do about it. And those are probably the only master multitrack copies I didn't retain. It was unlistenable. It wasn't rock 'n roll, it was jazz. And that makes it even more unbelievable.

So who's going to the AES NYC?
Mx. Remy Ann David

the only way i can get it to not be peaking is to put a pad on the input. and as long as he doesn't adjust the master and uses his booth as his main's i should be ok. idk i feel un easy about the record out for some reason even tho it makes perfect sense hahaha. i just can't adjust the record level unless i pad it.

Pad it, record 24 bit files with lots of headroom, then sort out the volume later using automation if needed.

If the record out is on RCA and the main out is on TRS or XLR then the record out may have a significantly lower signal level.

Yes, just like bouldersound Indicated, most RCA "record outputs" are generally at levels of -10 DB as opposed to the line level outputs on TRS/XLR which are generally at a nominal level of +4 DB. Your record inputs are then not getting completely blasted out and you don't need a pad. And if you're recording 44.1 kHz at 24-bit, your record levels can be slightly lower than normal. After the fact he would then normalized to -.6 DB and you should be good to go. But if he is over crunching his summing bus and/or output bus, ain't nothing you can do about that except call stupid, stupid. Because you can't fix stupid.

Obviously you ain't stupid.
Mx. Remy Ann David