Spade connection size for McIntosh MC2155 Amp

I think your amp has a barrier strip for speaker cable connectors. It probably will only accept a small spade, probably 1/4 inch. The 1/4 in are very nice, though. I prefer them myself. I would call McIntosh and find out, for sure, if it is the correct size.

As a longtime owner of a vintage Mac 2105 and a 2100, consider having a capable technician replace the old terminal strips with good quality modern posts that will accomodate spades or bananas. Yes, you will sacrifice the choice of 4,8 or 16 ohm taps, and will have to choose one of them, but it's worth it. Even if you can get the correct spades, connecting them with typically thicker, stiffer modern cables is a real pain. The small screws don't hold well, and sometimes just let go.
I made the change and love it. Sound quality was improved, and no more hassles. In my case, I always end up with 8 ohm speakers anyway.

I have a little wooden block made by Cardas with six inch leaders with small spades on one side and 4 multiple way binding posts on the block for exactly this use. I believe it ran about $100 or so a few years ago. I use it with an old MC2105 in the garage system.

Pepe

I think it all depends on the quality of the barrier strip. Some of my gear has them and I wouldn't trade them for anything. If, like Roxy54 says, you don't have good ones, it may be a good idea to replace them. I don't see why you would have to sacrifice the extra taps either. All of my tube amps have regular binding posts for all the taps.

Except Conrad Johnson. You can take it apart and change it, though.

Analysis Plus will terminate your cable selection with barrier spade.

The spade is 0.32" wide, 0.04" thick and 0.68" long.

Opening will fit up to 0.19" screw of binding post.

Zd542,
You are correct, and I should have made that more clear. If you choose, and assuming that there is enough space on the back panel, you can still have taps for all three impedances. For my amp, it would be tight, but I could have had 2.

I got adapters in eBay for my mc250 so I can use bananas. They work fine for $6

Signal cable makes speaker cables with smaller spade connectors for older amps. I use their cables on my Scott 299. Should be the same size for your Mac.

Joekapahulu,
I used those ebay adapters for years, and they made life much easier. They are not as secure as new binding posts though, and they don't sound as good.