McIntosh A-116 A116 Biasing and tube swap

Hello all:

Just had a quick question. I've recently obtained the McIntosh A-116 Monoblocks and one of the 12BH7 tubes was DOA. I've read that I could swap it out for the 12AU7. Is that true? Also Can anyone share with me how to set the bias on the amp and if anything needs to be done so that I can use the 0.5 input terminal? Thanks in advance!
The 12BH7 has split duty, one side at 50V and the other at 240V. The latter voltage is a bit high for a 12AU7 but it will work since the cathode current is only 7.5mA. But I see no reason to do that when you can get 12BH7s just as easily and for equal cost.

No biasing needed - and it will probably sound better on the high-gain inputs. Just be sure to dial back the gain controls before turning it on that way.

If you decide you don't want these amps, let me know. :)


Thanks for your advice on what do to.. Right now I'm in the process of searching for some 12BH7 replacements on eBay. Turns out that one of monoblocks came DOA, not just the tube. So now I need to find a guy to fix it up and see what's going on with it. Any recommendations? I've heard a lot about Terry DeWick but I'm just not in the mood to ship it again. I'm in the local NYC metro area. Although on one channel though, I was pleasantly surprised that the amp was able to push my Maggies even at higher levels at 30 Watts.

They do give you that warm and fuzzy feeling inside

And thanks on the offer for the amps. Hope you have time to wait a while ;)
Yes, Terry is the man. But in the NYC area, you have who would be able to do all the work, no problem. They are in Vestal, near Ithaca - hopefully that is a doable drive for you because they are McIntosh experts.

Believe it or not, the new production Electro-Harmonix 12BH7s are quite good. Not quite the level of the NOS Tung-Sol black plates I am using now, but 90% of the way there for little cost and basically no risk.


Thanks for the input, I was looking into getting replacement 12BH7s but didn't know where to start. Ithaca is still about a 3-4 hour drive for me unfortunately though. I went to the web site and there were "certified technicians" but nothing special nor were they ever mentioned to do quality work.

On a side note, Should I install some sort of ON/OFF switch on these puppies? Or just leave them on all the time? (which seems like a waste on the tubes.)