McIntosh Technology

[leftside]

I just gave mine a listen at max volume. 100 on the C2300 and full gain on both amps - with no music playing. Couldn't really detect any "noise" until I hit 78 on the C2300. Gradually got a little more hiss as I went higher than 78. Though, I've never actually had the C2300 any higher than 60. At this volume it was causing the drainpipes outside to rattle.

 

[damacman]

Well that's to be expected. This is a reflection of the Signal to Noise ratio of each component.

When you start lighting the PG lamps while playing music ... then you're having fun.

 

[4-2-7]

BTW this is a great thread Tony with lots of info and time taken to post.

We need it to be a sticky since a lot of mac owners double up.

 

[W9TR]

damacman,
Thanks for the great explanation. Much appreciated. I had two MC2102's which can be run bridged or parallel mono with a flip of a switch on the back and rewiring the speaker terminals.

The big thing I noticed was that when I ran the amps bridged they sounded much clearer and cleaner. This is because a lot of the distortion is cancelled out when the amps are run this way. In parallel mono I got a sound that had a little better bass, but was very much "more of the same". It was a lot of fun to play with both options. For this specific amp the results were very different. I was running Vienna Acoustics Beethoven Grand speakers.

 

[62caddy]

I just learned the MC2155 is also designed for both - mono parallel AND bridged operation allowing for 300W into 0.5, 1, 2, 4, 8 and 16 ohm.

 

[kevzep]

damacman,
Thanks for the great explanation. Much appreciated. I had two MC2102's which can be run bridged or parallel mono with a flip of a switch on the back and rewiring the speaker terminals.

The big thing I noticed was that when I ran the amps bridged they sounded much clearer and cleaner. This is because a lot of the distortion is cancelled out when the amps are run this way. In parallel mono I got a sound that had a little better bass, but was very much "more of the same". It was a lot of fun to play with both options. For this specific amp the results were very different. I was running Vienna Acoustics Beethoven Grand speakers.

This is what I would expect from bridging as opposed to parallel mono, the cancelling effect of the bridge will improve noise and distortion....

 

[damacman]

kev, many car audio amplifiers that can be bridged use the LEFT + / RIGHT - scheme where the right channel is inverted and its negative is the hot.

Interestingly enough, McIntosh amps are the only that I'm aware of that do not quadruple power when bridged - comparing say the 8 Ohm single channel rating to the 8 Ohm mono rating. whoareu99's math in post 2 is spot on and addresses that.

Finally, MC2105s cannot be operated in mono without being modified to do so ... which looks to be simple.

 

[62caddy]

BTW this is a great thread Tony with lots of info and time taken to post.

We need it to be a sticky since a lot of mac owners double up.

I agree. It should be "stickified".

 

[kevzep]

kev, many car audio amplifiers that can be bridged use the LEFT + / RIGHT - scheme where the right channel is inverted and its negative is the hot.

Interestingly enough, McIntosh amps are the only that I'm aware of that do not quadruple power when bridged - comparing say the 8 Ohm single channel rating to the 8 Ohm mono rating. whoareu99's math in post 2 is spot on and addresses that.

Finally, MC2105s cannot be operated in mono without being modified to do so ... which looks to be simple.

Thats very interesting about the car amplifiers. They must be fully floating (each channel in normal stereo configuration) if they can do that, and it then simplifies the inversion requirement which can then be done at the output....

Crown Macro-techs are 1300 watts per channel @ 8Ω, in bridged mono they are 4000watts @ 8Ω, so they don't quite quadruple either. Perhaps the McIntosh don't because of the autoformers? The Crown, not sure why they don't....

 

[teisco]

Is there anyway to tell if an amp can be bridged? I have a couple of Proficient M2's that I would like to bridge or strap but there is no info on how that I can find. Only thing that gives me a clue is a brochure that states they can be bridged but leaves it at that.

 

[damacman]

Is there anyway to tell if an amp can be bridged? I have a couple of Proficient M2's that I would like to bridge or strap but there is no info on how that I can find. Only thing that gives me a clue is a brochure that states they can be bridged but leaves it at that.

I'd call them in regards.

 

[teisco]

Old amps so not sure they are even in business anymore.

 

[chef free]

Great info in this thread, thanks to all! I run a pair of strapped MC2200s and I'm wondering about damping factor. Would it be cut in half?

 

[whoaru99]

Is there anyway to tell if an amp can be bridged? I have a couple of Proficient M2's that I would like to bridge or strap but there is no info on how that I can find. Only thing that gives me a clue is a brochure that states they can be bridged but leaves it at that.

Go back to your original thread about bridging the amp. I'll give you some ideas on way(s) you might be able to tell if it can somehow bridge itself.

 

[Mike Gibson]

OK, it's now a sticky. Just lets not let it degenerate into a mess.. Thanks.

 

[mech986]

Is there anyway to tell if an amp can be bridged? I have a couple of Proficient M2's that I would like to bridge or strap but there is no info on how that I can find. Only thing that gives me a clue is a brochure that states they can be bridged but leaves it at that.

I'd call them in regards.

Old amps so not sure they are even in business anymore.

They're still around, they even have a webpage about the M2, you should be able to get some guidance from them if they will talk technical with you over the phone or supply

http://www.proficientaudio.com/products/archived-products/m2-power-amplifier

Manual if you don't already have it.
http://www.proficientaudio.com/images/stories/pdf/manuals/M2Manual.pdf

 

[VintageMac]

To date (2017) McIntosh has produced 5 different versions of the MC275 amplifier based on electrical design, layout of the front panel and electrical specifications. Within some of those versions there are also variations - cosmetic differences.

With only a couple of exceptions, each of these versions have been known as MC275. McIntosh had a different stock number for each version and variation, but from a branded aspect, all are known as MC275.

Along the way there became a need to differentiate the various iterations of the amplifier. One way or another, these were given the unofficial “Mark” designation. However, the early use of this system was different than what has been settled on later. So, some of the older information about a particular “MK” unit may no longer be valid.

****************************************************

MC275: (1961 ~ 1970) Chromed steel chassis. Point-to-point wiring.

(450 v power supply). Tubes: 4-KT88/6550 output, 1-12AX7, 2-12AU7, 2-12AZ7, 2-12BH7. S/N: 10,001~10,147 & 100E1~572E9

Specifications: 16-40kHz (+0,-0.1dB). Distortion: 0.5%. Noise & Hum: -90 dB. Output impedance: 4, 8, 16 67 and 600 ohms.

MC275 “Spotting features”: 1. Octal output on front angled panel. 2. Terminal strips are vertical. 3. Gain controls. 4. Balance control. 5. Stereo/Twin Amp/Mono switch. 6. Power cord is on the vertical front panel and fuse is on the angled front. 7. 117/125V Line Voltage switch. 8. Stereo, Twin and Mono audio inputs. 9. Convenience outlet on vertical front panel.

****************************************************

MC275 CE: (Gordon Gow Commemorative Edition): (1993 ~ 1998) Chromed steel chassis. Gordon Gow badge. Hybrid point-to-point and PCB wiring. Balanced inputs in addition to unbalanced inputs.

(450 v power supply). Tubes: 4-KT88/6550 output, 3-12AX7A, 4-12AZ7. S/N: E1001~E????

Specifications: 20-20kHz (+0,-0.2dB). Distortion: 0.5%. Noise & Hum: -100 dB. Output impedance: 4, 8, 16 ohms. Damping factor greater than 10.

MC275 CE “Spotting features”: 1. Side Gordon Gow Commemorative Edition badge. 2. Gain controls. 3. Unbalanced inputs on far right-hand side of the vertical front. 4. Power cord and fuse are on the vertical front. 5. Convenience outlet on vertical front panel. 6. Terminal strips are horizontal.

****************************************************

MC275 SS [MK III]: (1997 ~ 1998) Stainless steel chassis. Same design as CE.

(450 v power supply). Tubes: 4-KT88/6550 output, 3-12AX7A, 4-12AZ7. S/N: ??1001~?????

Specifications: 20-20kHz (+0,-0.2dB). Distortion: 0.5%. Noise & Hum: -100 dB. Output impedance: 4, 8, 16 ohms. Damping factor greater than 10.

MC275 [MK III] “Spotting features”: 1. No Gordon Gow Commemorative Edition badge. 2. Gain controls. 3. Unbalanced inputs on far right-hand side of the vertical front. 4. Power cord and fuse are on the vertical front. 5. Convenience outlet on vertical front panel.

****************************************************

MC275 G: (1998~1999) Titanium gold stainless steel chassis. Same design as CE.

(450 v power supply). Tubes: 4-KT88/6550 output, 3-12AX7A, 4-12AZ7. S/N: MC275G-01~MC275G-71

Specifications: 20-20kHz (+0,-0.2dB). Distortion: 0.5%. Noise & Hum: -100 dB. Output impedance: 4, 8, 16 ohms. Damping factor greater than 10.

MC275 G “Spotting features”: 1. Gold finish. 2. Gain controls. 3. Unbalanced inputs on far right-hand side of the vertical front. 4. Power cord and fuse are on the vertical front. 5. Convenience outlet on vertical front panel. 6. Silver McIntosh 275 emblem.

****************************************************

MC275 [MK IV]: (2004 ~ 2006) Stainless steel chassis. Changes: Power on/off switch added. Power cord moved to a socket in the rear. Changes to the vertical and angled front panels. Printed Circuit Board wiring.

(450 v power supply). Tubes: 4-KT88/6550 output, 3-12AX7A, 4-12AT7. S/N: VN1001~VN????

Specifications: 20-20kHz (+0,-0.2dB). Distortion: 0.5%. Noise & Hum: -100 dB. Output impedance: 4, 8, 16 ohms. Damping factor greater than 14.

MC275 [MK IV] “Spotting features”: 1. Power on-off switch. 2. Gain controls. 3. Unbalanced inputs right-center on the vertical front. 4. Power cord socket and fuse are on the rear panel.

****************************************************

MC275 [MK IV] GOLD: (200? ~ 200?) Stainless steel chassis with gold finish. Same design as MC 275 [MK IV].

(450 v power supply). Tubes: 4-KT88/6550 output, 3-12AX7A, 4-12AT7. S/N: VR1001~VR????

Specifications: 20-20kHz (+0,-0.2dB). Distortion: 0.5%. Noise & Hum: -100 dB. Output impedance: 4, 8, 16 ohms. Damping factor greater than 14.

MC275 [MK IV] GOLD “Spotting features”: 1. Power on-off switch. 2. Gain controls. 3. Unbalanced inputs right-center on the vertical front. 4. Power cord receptacle and fuse are on the rear panel. 5. Gold finish. 6. Silver McIntosh 275 emblem.

****************************************************

MC275 [MK V]: (2009 ~ 2012) Stainless steel chassis. Changes: RoHS. Gain controls eliminated. Early small 5-way plastic binding posts changed to gold metal in later production. Changes to the vertical and angled front panels.

(450 v power supply). Tubes: 4-KT88/6550 output, 3-12AX7A, 4-12AT7. S/N: WM1001~WM????

Specifications: 20-20kHz (+0,-0.5dB). Distortion: 0.5%. Noise & Hum: -100 dB. Output impedance: 4, 8, 16 ohms. Damping factor greater than 14.

MC275 [MK V] “Spotting features”: 1. No gain controls. 3. Unbalanced inputs on far right-hand side of the slanted front panel. 4. 5-way speaker binding posts. 5. 5-way speaker binding posts. 6. Power cord socket and fuse are on the rear panel.

****************************************************

MC275 50th Anniversary: (2012 ~ 2016) Stainless steel chassis with gold finish. Changes: Large WBT gold metal speaker binding posts. New design – new output transformers. Sentry Monitor sequential testing/lighted bases for small tubes. Feedback taken from the speaker side of the output autoformer (all previous versions the feedback is from the amp side of the output transformer). Changes to the vertical and angled front panels. Power control added. Power indicator light added.

(490 v power supply). Tubes: 4-KT88/6550 output, 3-12AX7A, 4-12AT7. S/N: ABH1001~ABH????

Specifications: 20-20kHz (+0,-0.5dB). Distortion: 0.5%. Noise & Hum: -105 dB. Output impedance: 4, 8, 16 ohms. Damping factor greater than 22.

MC275 50th Anniversary “Spotting features”: 1. McIntosh 275 50th Anniversary badge. 2. Large 5-way speaker binding posts on angled front panel. 3. All other connectors and controls are on the vertical front panel. 3. Unbalanced inputs on the right of the vertical front. 4. Power cord socket and fuse are on the rear panel. 5. Stainless Steel chassis with gold finish. 6. Output tubes are recessed. 7. Small tube light-up feature. 8. Power Control In/Out. 9. Power-on indicator. 10. Gold McIntosh 275 emblem.

****************************************************

MC275 [MK VI]: (2012 ~ Current) Stainless steel chassis. Same design as MC275 50th Anniversary.

(490 v power supply). Tubes: 4-KT88/6550 output, 3-12AX7A, 4-12AT7. S/N: ABP1001~ABP????

Specifications: 20-20kHz (+0,-0.5dB). Distortion: 0.5%. Noise & Hum: -105 dB. Output impedance: 4, 8, 16 ohms. Damping factor greater than 22.

MC275 [MK VI] “Spotting features”: 1. Large 5-way speaker binding posts on angled front panel. 2. All other connectors and controls are on the vertical front panel. 3. Unbalanced inputs on the right of the vertical front. 4. Power cord receptacle and fuse are on the rear panel. 5. Output tubes are recessed. 6. Small tube light-up feature. 7. Stainless steel chassis. 8. Power Control In/Out. 9. Power-on indicator.

****************************************************

The McIntosh Compendium - More complete information on each of the various MC275 versions can be found: Here
...........(Information on the MC275G can be found: Here)

...........Excel Spreadsheet with differences: Here

If you have additions or corrections, please send them to: VintageMacPDX@gmail.com

Thanks!
Larry Hodson - VintageMac

.

 

[welcomdmat]

I believe this should be available to all folks. There is solid information in the post.

 

[whoaru99]

...

Crown Macro-techs are 1300 watts per channel @ 8Ω, in bridged mono they are 4000watts @ 8Ω, so they don't quite quadruple either. Perhaps the McIntosh don't because of the autoformers? The Crown, not sure why they don't....

Older sticky, but since it's a sticky the loop probably should be closed on this question/point.

Quadrupling power by bridging is generally theoretical, on the basis that an amplifier is operating as a true voltage source. That is to say, the amp will hold output voltage without sagging regardless of load impedance. Some amps claim to do that but the vast majority do not (even some of those that claim to don't, actually, but that is a different matter).

So the theory (re. true voltage source) would be if, for example, the 2-ch amp can swing 20V @ 8 ohms, 20V @ 4 ohms, and 20V @ 2 ohms, the power would double with each numerical halving of load impedance; 50W, 100W, 200W, respectively.

Continuing with that, since bridging is the sum of the voltage swing of the two channels, from the above example you'd get 40V @ 8 ohms, or 200W, which is 4x (quadruple) the 50W per channel @ 8 ohms in this example.

The fly in quadrupling where rubber meets the road is that very few amps actually operate as true voltage source, so they can't "double down" which of course then precludes quadrupling.

For the specific example of the Crown MA-5000, yes, the 8 ohm rating is 1300WPC but when you look at the 4 ohm rating it is "only" 2000WPC, not 2600WPC that would be indicative of true voltage source operation. So, where does 4000W @ 8 ohms bridged come from? Since each channel sees half the load you have to look at the 4 ohm rating. 2000W @ 4 ohms is 89.44 volts. Double that, 178.88V, figure that back against 8 ohms, and you get the 4000W @ 8 ohms bridged rating. Or, just refer back to the progression examples in post #2.

 

[PanheadXR290]

While not a white paper,and this info being common to most McIntosh nutts I find Roger Russell's writings on how he & Carl came about creating the McIntosh house sound ,and world class line arrays to be an interesting read ,for non Mc gurus or those without 1st hand experience with McIntosh line arrays this link may help people understand why most of us who experience a Mcintosh line array in our home will never go back to more traditional speaker systems ,I do know that reading about McIntosh's research into line arrays helped my brother understand why the XR-290s I gave him are so special in the speaker world .

http://www.roger-russell.com/columns/columns.htm