TubeNet

Even Mirafones can sometimes be lemons, I suppose, but by and large, they are as consistently in tune as any tuba available. The 186 is the standard for reliability and durability. Try some others. Where are you located? There are shops that specialize in tubas and they may be where you need to go.

I have played both BBb and CC versions of 186 and both had good intonation. The only significant issue was the 1st valve C (for the BBb) or D (for the CC) (in the staff), which needed a bit of a slide tweak -- a Miraphone "characteristic". With many of my tubas, I've found that the intonation isn't absolutely perfect -- but with my Conn 56J and my previous Miraphone 186, they were very close. I only had to pull a slide on the 1st valve C with the 186 CC. But I had a couple of intonation improvements using the lower octave fingerings for some of the notes in the upper octave.

If you have a Miraphone and consider the intonation "terrible", and if you're using a "typical" mpc, then I'd return it and try again with a different horn -- same model.

Cheers,