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Mc2155 vs mc2255

nolasally said:
The wood base is essential when shipping their amps. With the double walled inner and outer boxes and foam suspension pieces of foam between the two boxes I’m confident in items arriving intact no matter who ships it. FedEx, UPS etc.

I have shipped around 15 SS glass faced McIntosh amps over the years. Never had a broken faceplate. Never would remove glass either. If one feels like it you could remove knobs to prevent any glass damage. I would never recommend glass removal if proper packing is used.
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Perhaps you got lucky but there have been cases where the amplifier had broken free from the plate it had been bolted to. @damacman can tell you all about it - and I had personally supervised pre-shipment preparation.

For the the small amount of time & effort it takes glass (and knobs) to be removed, it's well worth it. This is especially true of units still retaining original glass as replacements are known to have illumination issues.
 
62caddy said:
Perhaps you got lucky but there have been cases where the amplifier had broken free from the plate it had been bolted to. @damacman can tell you all about it - and I had personally supervised pre-shipment preparation.

For the the small amount of time & effort it takes glass (and knobs) to be removed, it's well worth it. This is especially true of units still retaining original glass as replacements are known to have illumination issues.
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Newton's first law applies.
 
62caddy said:
Your thoughts on glass removal sir.
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I never did. Sure, I suppose the faceplate assy is easily enough removed and shipped separately. But then the chassis itself loses rigidity and could easily be tweaked or distorted in a good drop.

Problem is nowadays, the conveyor systems in the DCs - your 85lb amp falls 5ft off that and is stopped by the concrete floor. It stops, the transformers don't ... that 2500 was so bent up internally I had to use a 3ft long prybar to get the transformer mounting plate back into position. That's 3/16" thick steel bent on all four sides by a brake to give it rigidity. Then the way it's mounted into the chassis gives the whole amp rigidity. It was bent like it was a pop can.

Personally, I will no longer purchase any Mc amplifier which needs to be shipped by courier. Either I collect it in person or I don't need it.
 
damacman said:
I never did. Sure, I suppose the faceplate assy is easily enough removed and shipped separately. But then the chassis itself loses rigidity and could easily be tweaked or distorted in a good drop.
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Remember we're dealing with MC2155 here where the glass framework & side tabs are very light and thin. However, it may be a different story for the MC2300/2500/2600.
 
I had to disassemble my MC2500 (remove all the transformers) and use a press (usually used on autos) to bend the inner bracket somewhat back to shape after ground service used my new amp to calculate the value of g.

Still not perfect, but at least I was able to put the meters back in after buying very $$ bezels from Mc (and stole the meter housings from my spare 2255 as they were crushed by the transformers)
 
SaturationPt said:
As @Alguymcgee mentioned they learned/evolved in generations where the MC2505 and MC2105 were the first-generation of solid-state (well, there are significant differences between those so really the first generation and 1/2?) and the 2205 started the next generation with powerguard and a new topology. I believe the 2155 is considered similar to the 2205 in amplifier design with an improved Powerguard.

As to the main difference I would say Powerguard. It is also a new topology and has a more stable driver & thermal protection, they are completely different. Sound-wise I will say it’s a matter of preference between the 2105 and 2155, there are those who feel the 2105 sounds more vintage-smooth or other descriptions, so you’ll have to decide on that one yourself if you can audition good examples of both. Dynamic / reserve power is the other big difference, a little more power and just starting to step into the demands of the digital-music era with a little more headroom.
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Thanks for that great answer. It sounds right. Vintage-smooth, yup. There is a bit of a thermal surfing thing, with my set up. I listen at medium volume, i'd say. The output pot on the preamp is very useful in that regard. Powergard is the next thing I have to learn about. Is it, like, a breaker? Sorry. You've done enough already. ;-)
 
Alguymcgee said:
I mean, you can learn a fair amount from spec sheets; low THD, high damping factor is a decent start... but past a certain point you just gotta listen.

Also, stuff comes out in generations, with the basic idea being that each new generation is a little better than the previous one. Of course it doesn't always work out that way, but a little homework on that goes a long way. For example, as much as I LOVE my 2105 for pretty much anything recorded before 1990, it just can't seem to provide the right bass response I want for speed metal and other hard rock. Since that's half my collection, that's kind of a deal breaker for me.. but based on what I've heard it do, I probably wouldn't be trading up if I wasn't such a metalhead.

Beyond that, it's always good to have a grasp of the bells and whistles on your particular unit. There are just too many variables between rooms and speakers and so on. But the quickest check I know of is to crank the volume with nothing on... the quieter the background fuzz, the better.

Ooo! I almost forgot... I pulled the trigger and got the 2155. I'll let you know how it compares after my A/B
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I grasp at straws in margaritas. I don't do homework. Never did. That's why I vampirise you nerdy, techie lot. Keep us posted on the a/b!
 
Powerguard is fairly simple in operation: It compares the input signal to the output, any time there is a deviation >.05% (distortion) it reduces the output power until the distortion is reduced below that threshold. Typically this is clipping when the amplifier is pushed beyond its max. Available power. While it is reducing power, the Powerguard light is on.
 
62caddy said:
For years I've been saying McIntosh can no longer be shipped safely with the faceplate installed regardless of the packaging used! This is especially true with heavy power amplifiers with glass faceplates. Without exception, faceplate and knobs should ALWAYS be removed and shipped separately from the main unit!!!

I too would like to know whether the 2155 was bolted to the 1/2" plywood skid plate which is a requisite part of the factory packaging kit from Audio Classics or McIntosh itself. Packaging for lighter electronics such as preamps, tuners etc do not come with this; the feet cutouts in the cardboard are supposedly sufficient for these units but I don't think I would trust that system- not nowadays.
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Good advice
I did that when I sent out a C33 for restoration.
Easy to take off and shipping went without a hitch both ways. In my custom made box.
 
ddwiggins said:
I had to disassemble my MC2500 (remove all the transformers) and use a press (usually used on autos) to bend the inner bracket somewhat back to shape after ground service used my new amp to calculate the value of g.

Still not perfect, but at least I was able to put the meters back in after buying very $$ bezels from Mc (and stole the meter housings from my spare 2255 as they were crushed by the transformers)
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That is exactly what happened to mine ...
 
Sorry for the long time between updates, but the mc2155 is back and fully repaired and it sounds an order of magnitude better than the mc2105 and has more headroom. Nice richer low end, better separation of voices, just all around cleaner. I have an mc2255 in the shop getting cleaned up, I'll probably run that into my lower driver's and let the mc2155 do the mids and highs. Any thoughts?
 
I apologize if it’s covered above, but are you going to add an active crossover after the preamp to drive the different amplifiers’ ranges?

I can’t imagine a downside to properly bi-amping speakers with these two amps as they have similar topology, should be a nice setup.
 
You probably won't need an active (outboard) crossover as it's likely that your speakers will take care of the frequency allocations via the existing components.

In most actively crossed systems, the inboard crossovers will be in 'series' with the active crossover so the inboard crossovers are generally bypassed so they don't interfere with the outboard device.
 
CruzBay said:
You probably won't need an active (outboard) crossover as it's likely that your speakers will take care of the frequency allocations via the existing components.

In most actively crossed systems, the inboard crossovers will be in 'series' with the active crossover so the inboard crossovers are generally bypassed so they don't interfere with the outboard device.
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Yea that makes a lot of sense, and I can see why you wouldn't necessarily need a crossover to benefit from bi amping. However, it seems to me that running the signal through a crossover before the power amps would make a noticeable difference. I would think that only amplifying the signals you intend to reproduce would result in "unused wattage" that could be reinvested in the signal. Kind of a rough way of putting it, I know. Yea the speakers' crossover will clean it up but that seems inefficient?

But honestly I'm still learning, that's just my initial educated guess. At the end of the day I'm hear to learn so any thoughts are always appreciated
 
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