Sequential Tube Monoblocks

Vintage McIntosh monoblock tube amps- MC 30 or MC 75.
Is it important to buy sequential units?


You bet it does..

Tubes, resistors and caps were made with sequential batches.

Channel balance will be off if not.


Totally depends on the manufacturer, but it’s ALWAYS better to have factory matched pairs or at least consecutive / close serial numbers. Hand wiring will have more chances for variance than PCB, obviously. Some manufacturers will also make minor parts swaps or circuit changes over time. Sometimes parts swaps are a necessity since they regularly go out of production (specific transistors, black gates caps, polystyrene caps etc). 

VAC’s owner auditions every component before it leaves the factory. If it doesn’t make the cut, it goes back for tuning. You can bet there’s an advantage to having this process done for a pair of mono amps, rather than cobbling together 2 units on the used market (many of VAC’s amps are switchable between stereo / mono modes).

I have had three ARC Reference 160 stereo amps and two of the same model monoblocks. The monos produced at least two years before the stereo versions and the stereo versions produced over about a year. They all sounded exactly the same… first when unbroken in, and then when broken in. I have been very impressed how exactly the same they all sounded. The monos had a lower noise floor and a wider deeper soundstage than the stereo, but the sonic character was exactly the same. 

So, I’m just guessing it is something unlikely to be of any importance. In theory it sounds good though.

Hopefully, the OP will realize access to a competent tech/shop for necessary replacement of ageing  components/adjustments are the only requirement.

Once done, it will outlast its owner.

I'd like to have the period appropriate Mac amps/pre to go with my 67 MR 71 tuner.

What @tablejockey said is right. With something that old it's more important that each has been  modded or repaired if you will, similarly. 

otoh if they're 100% original, then they definitely need to be from the same batch of parts 

I wouldn’t think so, I would just make sure they are from the same or similar time period/model/upgrade etc. 

As long as they haven’t changed any parts, then I’d think you’ll be okay.