CYBERSHEB Posted November 15, 2001 Share Posted November 15, 2001 My friend wants to get a Mcintosh Amp to drive his Jamo's which are 150watt @8 ohms, with 92db sensistivty..he's decided ona MC162 or MC202 both stereo amps. The MC162 gives 100watts @ 8ohms & 160watts @ 4ohms where as the MC202 gives 200watts @ 8 ohms and the same at 4 ohms also. Why is that? What is the theory behind that and would there be any difference between the two othere than their power. thanks Quote Link to comment Share on other sites More sharing options...
Ray Garrison Posted November 15, 2001 Share Posted November 15, 2001 The MC202 uses the Mcintosh transformer coupled output configuration called an "autoformer", and the MC162 does not. Here's a brief overview from the Mcintosh site on just what this widget is and what it does: "About the McIntosh Output Autoformer Transistor power output circuits can match 8-ohm loads directly. This eliminates the need for the output transformer for most manufacturers. However, output stages that are designed to operate into an optimum load of 8 ohms can double or quadruple heat dissipation when operating into 4 or 2 ohm loads. At some frequencies, speakers rated at 8 ohms can dip as low as 4 ohms. Some 4-ohm systems can dip even lower. This mismatch can cause the amplifier to exceed its thermal dissipation limits. On the other hand, if an amplifier is designed for an optimum load of one or two ohms, a low impedance load would be no problem. However, less power would be available for a speaker having 4 or 8 ohms impedance. The unique McIntosh output autoformer is the answer. Since McIntosh output stages are connected in a single ended push-pull circuit, one side of the output is always connected to ground. They are typically designed to work into an optimum load of 2.1 ohms. The matching autoformer is connected directly to the output. In the MC2505 amplifier, the matching output is for 4, 8 and 16 ohms. Other impedances become available in later amplifiers. Full continuous amplifier power can be delivered to each of these loads. There is no danger of exceeding safe limits or overheating. The autoformer also protects the speakers from damage in the event of amplifier failure. Should a direct current component appear at the amplifier output, it is shunted by the low DC resistance of the autoformer, instead of passing through the speaker voice coil, which could damage the speaker or even cause a fire. McIntosh autoformers continue to be used in the "top-of-the-line" amplifiers. They are all designed and manufactured by McIntosh. Although the autoformers add extra cost, weight and take up extra space, they assure a safe, optimum match to a variety of speakers and speaker hook-ups. They are constructed and perform in the McIntosh tradition of excellence. " *** END OF CUT AND PASTE FROM MCINTOSH SITE *** This autoformer means that the MC202 is delivering it's specified output, which is 200 watts/channel, into whatever impedence the speakers might present. The MC162, lacking this configuration, is providing more output into lower impedences because the lower impedence speaker is drawing more current at the same output voltage level than a higher impedence speaker. While it might seem like it would be a good thing to allow the amp to deliver more current into the lower impedence load, the point Mcintosh is making is that the autoformer provides a more consistant and thus, theoretically, more optimal output across any load. How this impacts the sound of the MC162 vs the MC202 is something I'm not qualified to comment on, having heard neither amp. Ray ------------------ Music is art Audio is engineering Ray's Music System Quote Link to comment Share on other sites More sharing options...
Colin Posted November 15, 2001 Share Posted November 15, 2001 yeah, but the theory is that the autotransformer will be able to handle tha wild impedances curves better,so it would be better with difficult loads, and the bass, for example, might sound slightly tighter, I do not know what the Jamo curves look like and I have not heard them either ... ------------------ Cornwalls & Klipsch subs; leather couch & feet up; lights out & tubes glowing! Quote Link to comment Share on other sites More sharing options...
Kevin S Posted November 15, 2001 Share Posted November 15, 2001 Although I cannot speak for McIntosh, it would be my guess that they would tell you that if each amp was connected to a speaker that matched the amps operating limits properly, that they would sound the same as each other ie: neither adding or subtracting from the signal put into them. So unless the Jamo's have unusually low impedances (below 4 ohms) over most of their operating range, which wouldn't seem to be the case with an overall 8 ohm rating, the 162, which I believe is the least expensive of the two, should sound identical to the 202. Now I am going to duck before everyone who thinks all amps sound different start throwing things at me! ------------------ L/C/R: Klipsch Heresy II Surround: Klipsch RS-3 Subwoofers: 2 HSU-VTF-2 Pre/Pro/Tuner: McIntosh MX-132 AMP: McIntosh MC-7205 DVD: McIntosh MVP-831 CD Transport: Pioneer PD-F908 100 Disc Changer Turntable: Denon DP-72L Cassette: Nakamichi BX-1 T.V. : Mitsubishi 55905 SAT/HDTV: RCA DTC-100 Surge Protector: Monster Power HTS-5000 Quote Link to comment Share on other sites More sharing options...
Ray Garrison Posted November 15, 2001 Share Posted November 15, 2001 There are a few non-sound-related advantages to the MC202. The autoformer will protect the speaker from receiving a DC component in the event of upstream or amplifier component failure, for example, and the amps have different clipping characteristics (the 202 is less obnoxious when overdriven). Mcintosh engineers tend to be, er, somewhat undisposed towards unverifiable subjectively evaluated differences in the sonic characteristics of things like amplifiers, cables, and what not, but THEY certainly seem to think the 202 has some advantages over the 162. Of course, they would like to sell the 202, so make of that what you will... ------------------ Music is art Audio is engineering Ray's Music System Quote Link to comment Share on other sites More sharing options...
Kevin S Posted November 15, 2001 Share Posted November 15, 2001 Ray, I think the Power Guard, as well as the other McIntosh "safety" features such as Sentry Monitor, and Thermal Protection, function the same for both amps, so neither amp will be allowed to clip in the conventional sense. From what I've read you are correct about the DC protection provided by the autoformers. However I believe non-autoformer amps, such as mine, have "Direct Current Protection" that senses DC and shuts the amp down before it can be damaged. Luckily, I've never actually tested any of these features! ------------------ L/C/R: Klipsch Heresy II Surround: Klipsch RS-3 Subwoofers: 2 HSU-VTF-2 Pre/Pro/Tuner: McIntosh MX-132 AMP: McIntosh MC-7205 DVD: McIntosh MVP-831 CD Transport: Pioneer PD-F908 100 Disc Changer Turntable: Denon DP-72L Cassette: Nakamichi BX-1 T.V. : Mitsubishi 55905 SAT/HDTV: RCA DTC-100 Surge Protector: Monster Power HTS-5000 Quote Link to comment Share on other sites More sharing options...
Kevin S Posted November 15, 2001 Share Posted November 15, 2001 Oop's, a quick check of the McIntosh web site shows that the MC162 does not have the DC protection. What would cause DC to be presented to an amp anyway? ------------------ L/C/R: Klipsch Heresy II Surround: Klipsch RS-3 Subwoofers: 2 HSU-VTF-2 Pre/Pro/Tuner: McIntosh MX-132 AMP: McIntosh MC-7205 DVD: McIntosh MVP-831 CD Transport: Pioneer PD-F908 100 Disc Changer Turntable: Denon DP-72L Cassette: Nakamichi BX-1 T.V. : Mitsubishi 55905 SAT/HDTV: RCA DTC-100 Surge Protector: Monster Power HTS-5000 Quote Link to comment Share on other sites More sharing options...
Ray Garrison Posted November 15, 2001 Share Posted November 15, 2001 Can't list the causes of this, 'cause I really don't know, but it is possible for a malfunctioning or (my opinion) poorly designed preamp to have a very small, but not zero, amount of DC in the output. If your preamp had, say, 1 millivolt of DC across the output, and your amp has 30dB of gain, then the amp would be putting a constant 1 volt into the speakers, whether signal was present or not. Now, I don't think 1 volt (.25 watts into 4 ohms) is going to hurt anything... but anyway, you get the idea. If you have a tube preamp, and one of the tubes starts to fail, you can get significant DC content presented to the amp. ------------------ Music is art Audio is engineering Ray's Music System Quote Link to comment Share on other sites More sharing options...
ckt Posted November 16, 2001 Share Posted November 16, 2001 Its good for protection, if an output transistor fails - which in most cases short - which puts the speakers strait on the power supply rails. Quote Link to comment Share on other sites More sharing options...
dubai2000 Posted November 16, 2001 Share Posted November 16, 2001 CYBERSHEB, does your friend insist on a new Mcintosh amp? I once tried the 162 at home and though I found it quite detailed and clean-sounding, I nevertheless opted for a vintage 2105 which I find simply less sterile. So why not give it a try and save some $$$? Wolfram Quote Link to comment Share on other sites More sharing options...
CYBERSHEB Posted November 17, 2001 Author Share Posted November 17, 2001 Yeah.. i will check out the MC2015.. What do you guys think about bi-amping with 2 pairs of mc162's.. cos they cost almost the same one MC202 Quote Link to comment Share on other sites More sharing options...
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