2. amps-preamps
  3. 1198939834

Mac 275 questions........

After some months of up's and down's with my ASL Hurricanes (just seemed to never stay operational for longer then 2-3 months) I have decided o retire them and get the McIntosh MC 275 (2 amps).

I have some questions for you all and appreciate any input you may have (especially form Mac owners) but opened to all.
My speakers are Infinity RS 1-B's and I will be using the amps to drive the top end of the system (EMIM's and EMIT's). I have a Perreaux 3150B for the bass columns. The Infinities are rated at 4 ohms.
I plan to listen to one amp on top ( I will get one amp in a week) and then when I get the 2nd amp ( a week later) run both in mono.
What will I hear with each application? First with one and then with both? Also can any of you let me know if any of you compared the Mac 275 (in mono) 150 watts with the Hurricanes 200 wpc? The Hurricanes were great but I just could not live with them being up and down so many times.

Thanks to all for your input.

RWD (Rick)
rwd
bosrt
77 posts
 
I got into it last nite and had some success.

I preferred Mullards in the V2 12Ax7. Nice bass and some cleanish warmth in the mids. Highs nice. A Brimar was too bright. The other 12Ax7 got RCA 5751s. All these were more open and detailed than the original tubes. Also brighter.

For the AT7s, Brimars were good and RCAs good. The AT7s were substituted with what I could find on hand. Didn't work on rolling here much.

I also found as I replaced more small tubes the instrument solidity and location stabilized with a guitar intro that I know well. Cibelle/cibelle 2nd track.

B
nsgarch's avatar
nsgarch
2,524 posts
 
12AX7A's are simply 12AX7's with a filament center tap that allows them to be run in series or parallel. Not an issue with the Mac amp.
gregpen
9 posts
 
If one is looking towards the rear of the 2275 from the front, Which pair of 12ax7a is used for the phono, the pair on the left or the right pair?
nsgarch's avatar
nsgarch
2,524 posts
 
Greg, the fastest way to answer that question would be to call McIntosh. While you're at it, order a service manual/schematic -- that's what I did.

You can also find out by 'naming' the phono input something else (on the menu screen) if you do that, the phono tubes won't light up when you turn the amp on -- at least that's the way their preamps work ;-) (It's a way of saving tubes and reducing heat if you don't have a turntable.)
ontjesr
157 posts
 
Hey Gregpen, I have a 2275 and the tube slots/function follows. The best swap is what you have already performed, the 12AT7's in slots V1R & V1L. These peform the function of "preout" tubes and are VERY IMPORTANT. Slots V4 & V5 are for phono and V6 & V7 are for tone controls (bass/treble). If you aren't using a TT, then any ole 12AX7 is fine. Additionally, I have switched my tone controls to off on the front display, so, I have plain ole 12AX7's in those slots (V6 & V7) as well.
More to discover