Mac stereo amps in mono mode?

[FreddieFerric]

Aside from the MC275 which current production Mac stereo amps can also be run in bridged mode?

[Tony007]

Originally Posted by Charles

I don't understand why Mac doesn't provide a mono option with the new amps like the 1502. Is it sonics or something else? I think most would enjoy having a mono option.

Charles

Perhaps we will see the vintage look 300wpc monoblock design in the future.

Just some wishful thinking

[minplus]

Never a problem with my 504 or 6800.
Why should there be a problem?

[70sMac]

Originally Posted by minplus

Never a problem with my 504 or 6800.
Why should there be a problem?

minplus..... That's a very good question. I've read and/or heard that running certain Mac stereo amps in mono mode, especially if the internals have been modified, can be hard on them. So I'm not only asking about Mac amps that can be operated in mono mode via a rear panel switch, but also about Mac stereo amps that have been modified for mono operation.

[sberger]

So I can run my single 2250 in mono bridged mode and the benefit is more headroom? If so, other then adjusting my speaker connections(AR3a's moved from 4ohm to 2ohm), any other connections/changes that I need to be aware of?

[damacman]

Originally Posted by sberger

So I can run my single 2250 in mono bridged mode and the benefit is more headroom? If so, other then adjusting my speaker connections(AR3a's moved from 4ohm to 2ohm), any other connections/changes that I need to be aware of?

Well, you could certainly do that if all you were after is mono playback. Add another MC2250 in bridged mono mode (one per channel / speaker) and you're back to stereo.

[damacman]

OP - follow the guidelines in the OM for the respective amplifier for mono operation. If mono operation is not referenced, then it's incompatible. Modifying an early McIntosh power amplifier for mono use (IE - an MC2105) was possible. Modifying a late model McIntosh amplifier for mono use (IE - an MC452) is not possible. If the amplifier was designed to be used in mono, then no harm will come to it when doing so - the amplifier itself cannot tell the difference between being used in mono or stereo when connected correctly.

Over the years, McIntosh has made about the same number of stereo amplifiers which can be operated in mono as stereo amplifiers which cannot. The reasons for this vary on the specific model.

[70sMac]

Originally Posted by damacman

OP - follow the guidelines in the OM for the respective amplifier for mono operation. If mono operation is not referenced, then it's incompatible. Modifying an early McIntosh power amplifier for mono use (IE - an MC2105) was possible. Modifying a late model McIntosh amplifier for mono use (IE - an MC452) is not possible. If the amplifier was designed to be used in mono, then no harm will come to it when doing so - the amplifier itself cannot tell the difference between being used in mono or stereo when connected correctly.

Over the years, McIntosh has made about the same number of stereo amplifiers which can be operated in mono as stereo amplifiers which cannot. The reasons for this vary on the specific model.

As I mentioned in the original post, Dan (JDandy) used to write about using Mac stereo amps in mono mode. I recall him writing that it worked well for him, but I also recall him saying that he had heard of Mac stereo amps that had been internally modified for use in mono mode. As I don't recall a whole lot more than that, I was asking folks on the Mac board about it. I've never actually used our "bridgeable" Mac stereo amp in mono mode, so I'm trying to learn as much as possible about the practice before trying it ourselves.

The consensus seems to be that operating those stereo amps that have a "mono switch" on their rear panel, like ours, is a safe practice...but I'd still love to hear from anyone who's gone a step further with this...like an MC2105 owner, perhaps?

Thank you for the post

[damacman]

The MC2105 is the most commonly modded for mono use. The MC2100 and MC2105 are nearly identical amplifiers with a different feature set - the MC2105 being the consumer version with a glass faceplate and meters, the MC2100 being the industrial version built on a chrome chassis which included an octal connector for speaker wiring. As the MC2100 also includes a Stereo / Mono switch for various professional and industrial applications, folks simply replicate the circuitry in the MC2105 from the MC2100 service manual. While this can also be done with the MC2505 (by copying the MC250), I've never heard of anyone actually doing it.

Mono operation for all early SS stereo amplifiers (MC2100, MC2300, MC2120/2125, MC2200/2205) was accomplished by strapping channels (mono-parallel), not bridging (mono-bridged). Beginning with the next generation (MC2150/2155, MC2250/2255, MC2500) provisions were included to permit strapping or bridging to allow for more flexibility from the same number or even fewer output taps. [MC2125 included 2, 4, 8, and 16 Ohm taps and could be strapped into 1, 2, 4, or 8 Ohm mono loads . . . whereas the MC2155 included 1, 2, 4, and 8 Ohm Taps and could be operated into .5, 1, 2, 4, 8, or 16 Ohm mono loads - either by strapping or bridging.]

Your MC300 is one such amplifier which includes provisions for both strapping (mono-parallel) or bridging (mono-bridged). If you look at the OM, you'll see the difference in how such loads are connected.

I am not aware of any perceived SQ differences between mono or stereo operation and I've tried all of the above over the last three decades - I've had a few hundred McIntosh power amps (thankfully, I'm down to 8). Some report preferring mono-parallel to mono-bridged or vice-versa and I suppose that could be load dependent.

I think it's worth mentioning that most quad-balanced amplifiers (excluding the MC352 and MC402) are not mono capable. The reason McIntosh cites is that each stereo channel is already comprised of a bridged pair of output sections and thusly cannot be bridged a second time. However, McIntosh got around that with the mono-parallel feature of the MC352 and MC402, of which Mc has no comment on . . . magic, I guess.

[Cohibaman]

MC402’s in mono parallel sound quite good. No problems.