Well ok, it seems to be using both, so…

Thank you all for very interesting responses, I really enjoy reading all of this, so many good stories.
Keep it coming.

Here is a sub-question, to this topic:
The smokers, do they smell differently than a regular jet?

I imagine in my head the difference between a good diesel engine exhaust and one that leaks oil into the cylinder and has bad combustion too. The first one smells sweet-ish, as if something eatable is cooking, while the second one is a bit heavier and suffocating.
Is the same different present in clean vs. dirty jets? How do smokers smell?

Well I did a little more research on this subject, and I find it quite interesting…

The sound in the clip is indeed probably a diesel unit, the whine seems to be characteristic of such devices as screw or vane pumps. It kind of reminds of root blower sound.
But there is very little info on such devices.

I wish there was more interest on aviation history on WWW.

Now that I’ve watched it with what you said in my mind, I see it makes sense. At 1.18 the whine “struggles” a bit, which would indicated that this is the point when the air cart is first loaded by the resistance of the actual engine of the DC8

About that whine from the ASU, then….what kind of engine would make that kind of whine? Doesn’t sound like a regular jet engine at high rpm. Is that some kind of alternative kind of compressor or what?

Is there a specific popular brand (any names to remember?) of ASU’s back in the days of 707 and DC8 that most airports used or were those custom solutions by every airport?