2. amps-preamps
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Calling all MC275 MK IV owners..............

I just set up my new MC275 and although the tubes have about 90 minutes on them, I'm blown away by the sound - I wish I discovered tubes 10 years ago.

Anyway, a few questions:

1. What gain level do I set the amp to. I cranked it all the way up but is there an "optimum setting?" I'm running these in stereo mode with unbalanced connections.

2. In a couple of days another MC275 gets delivered and I plan to run them in mono mode also using unbalanced connections. What gain setting is optimal for that configuration?

3. I have the amps on a trigger switch and noticed that on power up the tubes sort of glows a bit brighter for a second then settles back into the normal orange filament glow. is this normal?

4. What is tube rolling?

Thanks for all your help. I really appreciate it. Sorry if these questions are a bit stupid.
128x128pookie10
7 responses Add your response
pookie10's avatar
pookie10 OP
41 posts
 
More tube questions............just received my "back up" set of output tubes. 8 Winged C KT88 tubes. 6 of them have a bias of 45 and 2 have a bias of 44. According to the McIntosh literature, the MC275 is self-biasing. Since I have NO IDEA what ANY of this means, is it a problem that 2 of the tubes are "off" by one unit?

Also, the small output tubes say 12AX7A but all I could find are 12AX7 (no A). What is the difference?

I'm also looking for input tube recommendations. I'm running both in mono using the RCA inputs.

Thank you again for your help.
vincentkkho
53 posts
 
I don't think there is any optimum setting for the gain. It all depends on your speakers placement and the preamp that is coupled with it. The other factor to consider is the size of your room and the distance between the speaker and your listening position. Once all these are set, I would advise you to firstly set the volume control knob on your preamp to a predetermined setting. You will than go on to fine tune the gain setting in both MC-275. Try to play with the gain till you get the best result ( of course all depends on your ears). That is fun!
I would advise 12AX7 and 12AT7 to be used for all the small tubes. I did not have good result for 12AZ7, which was recommended by McIntosh before.
Hope it will help. Happy listening!
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superhonestben
199 posts
 
I use a C2200 into the MC275 1V and it is a killer, another way you may want to try is getting a VTL 2.5 tube preamp, if you don't need phono they are pretty inexpensive new and less here on the Gon. the 2.5 into the Mac is also a great combo.
bigjoe's avatar
bigjoe
693 posts
 
i own the c2200 preamp & i love it,i ran a mc2102 on the c2200 & the 2 tube units paired up nicely,you shouldnt have a mismatch with the c2200 mc275 combo.

mike.
tomryan
796 posts
 
Don't worry about tube on tube getting fuzzy or hazy. I've been running like that for years and years and with the right equipment, get magnificent music making. Just last night I was listening to a Gene Ammons CD which sounded open, clear, and as if the band was right in the room. And this with a tube pre-amp, SET tube amp, and I am sure the original recording was done with all tube studio equipment.

Both tube and SS stuff nowadays (and going back a few years) can make beautiful music. There are tube designs which can sound a but fuzzy and hazy (older C-J stuff) and designs that can sound crystal clear and almost over-lit (Some OTLs). You have to check out each piece on its own merit.
pookie10's avatar
pookie10 OP
41 posts
 
Thanks for your answers. I think I will just relax now. The rest of my system is:

B&W Nautilus 804 (MC275 will drive these), HTM2 center and a pair of SCM1s.
I'm using the MIT Magnum 3 for the fronts and cheapo wire for the rears.
All hooked into a McIntosh MHT20 via Synergistic Reaseach Designer Reference interconnects.

I'm at a crossroads where I have to decide if I'm staying with 5.1 or going back to dedicated 2-channel. If I went back to 2-channel I would get the C2200 pre-amp but I'm concerned that tube on tube might get to sonically hazy or muddy.

To be honest, I'm pleasantly surprised at the MHT200's performance as a stand alone pre-amp. Granted my expectations were low to nil but it would stand up against many dedicated pre-amps.
bigjoe's avatar
bigjoe
693 posts
 
hi pookie.

tube rolling is just trying out different brands & types of tubes.

the glow you spoke of is normal & after the tubes break in they will settle down.

there isnt a optimum setting for your gain controls but you can use them to your benifit,i set my gain to where my max listening volume is at 100% of the volume adjustment on the preamp.

you cant hurt your amps by running the gain any old way you like so just have fun & enjoy your new gear,the new class of mac amps are amazing & i get a ton of enjoyment out of mine too.

just out of curiosity what preamp are you going to run with the 2 mc 275's & whats the rest of your rig.

mike.
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