McIntosh with Magnepan not a good match?

[Mikado463]

Originally Posted by damacman

See my explanation above about using the 8 Ohm taps and my reference of phase angle - loudspeakers are a combination of capacitive, inductive, and resistive loads and most assuredly do not load an amp like a purely resistive load. This is where power supply design is most critical - to maintain output voltage as the load varies among these factors.

I did and thus my question ............again, correct me if I'm wrong, but is not 'watts' a measure of power, not 'current'. Trying to remember ohms law here ......

[damacman]

OK, I understand now. P = I * E where:

P = Power in Watts
I = Amperes in current
E = Voltage in Volts

This math can be used for comparative purposes but it's really not quite that cut and dry when computing power where voltage and current are out of phase - as when driving a loudspeaker. One has to use Power Factor to do so.

Lets say that a given amp can output 20V into an 8 Ohm resistive load. Then, we use the formula P = E^2 / R. P = 400 / 8. P = 50 Watts. Now, if we halve the resistance and the amp can maintain (very important!) its Voltage, then P = 400 / 4 ... = 100 Watts ... or double the power. Since Voltage didn't change, current doubled:

I = P / E
I = 50W / 20V = 2.5A
I = 100W / 20V = 5A

The trick is maintaining output voltage as the impedance decreases. And since loudspeakers aren't resistive loads, output voltage should remain stable even when voltage and current are out of phase with each other. Even the very best designs can't achieve these attributes perfectly due to inherent losses. But really good designs can come close.

So ... really a "high current" amplifier is simply an amplifier that can maintain its output voltage with complex loads. My experience has been that McIntosh amps are up to that task.

[Charles]

Originally Posted by damacman

Gotcha. I own MC2300s as well, the MC2100s bigger brother. I can tell you with certainty those amps are a little more difficult to achieve good synergy with than more current offerings.



Although the Classe amp is obviously a stellar performer, I don't understand why the MC601s couldn't perform equally as well when using the 8 Ohm taps.



See my explanation above about using the 8 Ohm taps and my reference of phase angle - loudspeakers are a combination of capacitive, inductive, and resistive loads and most assuredly do not load an amp like a purely resistive load. This is where power supply design is most critical - to maintain output voltage as the load varies among these factors.

damacman, Like some of folks on this site, I sometimes voice opinions based on old or insufficient data. Your argument is convincing.

[damacman]

Originally Posted by Charles

damacman, Like some of folks on this site, I sometimes voice opinions based on old or insufficient data. Your argument is convincing.

As do we all. I've always preferred the McIntosh amps with autoformers because of the incredible flexibility they offer. I've also owned some outstanding OTL designs from Crown, Spectral, and others that I greatly enjoyed.

No one design is best and there are certainly cases where McIntosh amps may not be able to achieve that perfect synergy with a given pair of loudspeakers that another design can. I have a theory on why that is, but current delivery isn't part of the equation.

[Pampero]

The singular argument that truly holds water against autoformers is that building excellent ones is really, really costly. In my career I rarely sold transformer coupled amplifiers apart from those designed to drive constant voltage lines (so called) . This was for the reasons that transformers/autoformers (done right) add both weight and expense, frequently abundantly so. In the pro/touring world where both those factors, especially weight figure prominently, the movement to "Class D"/switching amps was inexorable for those reasons.

Consequently like Damacman, I have a lot of experience with OTL amps (we usually called them "direct coupled"). I was the Crown audio rep for 15 years (on and off) as well as having had the same type of commercial ties to Carver, Hafler/Transnova, ATI (through JBL), Crest, UREI and so help me I can't remember them all.

The better of those could double down with impedance, and the best of them were really something else in their ability to deliver high current with low weight. However, when it came time for me to buy this time, I selected the MC lineup as a target because I wanted long trouble free life, low (measured) distortion, high current guaranteed into any load and
good retained value. I also wanted to rid myself of any notion that the amplifier I was buying and intended to keep for a long time might not be able to drive difficult loads within its rated capabilities.

That lead me to the McIntosh line. I gave considerable thought to the fact that I was buying an "autoformer" coupled amplifier, knowing that the general rule of thumb was that transformers are in the way. Again, I point out that this is perfectly true in any case where the device is not built with the utmost integrity to the best possible standards. A lot of what we pay for in the macs is tied up in those parts because it has to be.

In return we get guaranteed stability into almost any speaker load on the market. Are these the best sounding amplifiers on the market? Darned if I know, but they are without question among the most reliable, the the smoothest, exceptionally low in all distortions we can measure, and they retain excellent resale value. A very safe bet with almost any kind of load you will attach. Safe bets work well in my aging world, and it sounds great in my house. When I to elect to improve my system, I might consider biamping to wring the last bit of bass control and mid/high frequency response resolution out of my speakers. Another McIntosh to accomplish that makes good sense since my approach would require amplifiers with matched gain structures.

There are other great options and opportunities available, but McIntosh is one of a small handful of manufacturers who have an earned legacy of performance and reliability, especially in the amp arena. One reason for that is their uncompromising autoformer
quality. I'd surmise Mcs are right up there with the best when it comes to driving difficult loads. Always have been.

Thanks, Damacman......excellent posts.

[damacman]

Great dialogue for sure - always nice to learn. Interesting story Pampero. It's really hard to disagree with anything you've said. I really like the MC452 - such a timeless design.

I worked for Rockford from 2002-2008. By then the hafler Class AB stuff was phased out in favor of Class G designs. Given that the pro industry was in serious decline, hafler was put out to pasture entirely. Really it was a shame.

Jim Strickland was an incredibly brilliant engineer and his 9505 remains one of the most heralded of its time. I knew Jim, but not very well.

[miatadan]

Originally Posted by damacman

One really has to delve into the details of why McIntosh originally elected to employ autoformers with its solid state offerings to fully understand why some naysayers have no earthly idea of what they speak. To date, the MC2505 remains an amplifier that can shame current offerings from competitors.

Your MC302 could, within reason, drive nearly any speaker you could connect to its 8 Ohm taps - and without strain. The McIntosh design makes it possible to drive loads that would cause other amps to go into protection via the inclusion of 4 and 2 Ohm taps.

I'm not at all surprised that your MC302 drives your "4 Ohm" Magnapans better from the 8 Ohm taps. In this configuration, the amplifier can deliver greater current than from the 4 Ohm taps and easily double the power to the speakers when doing so.

Traditional OTL power amps can also double output power as impedance is halved. So can every McIntosh autoformer equipped amplifier, when using the 8 Ohm taps. The same can be said for 2 Ohm loads connected to the 4 Ohm tap, 1 Ohm loads connected to the 2 Ohm taps, etc. Traditional OTL designs have a very difficult time running 2 Ohm loads without significant current limiting and 1 Ohm loads are all but impossible. OTL designs capable of both certainly do exist but come at a premium. The problem is practicality. What good is it to own an amp capable of 300W/ch at 2 Ohms if you intend to use it with 8 Ohm speakers? [Using the math above nets 75W/ch at 8 Ohms.] Conversely, a McIntosh amp rated at 300W/ch at 2 Ohms can also make 300W/ch at 4 Ohms and at 8 Ohms! This is one of the main reasons I buy McIntosh amps - no matter the speakers you buy, a McIntosh amp with autoformers is poised to deliver its rated power to them with no funny business required. Synergy can be achieved in nearly every case.

Lower impedance loads create additional heat which can in turn reduce life of the electronic components themselves - a stark reality in all OTL designs, no matter the cost. McIntosh amps equipped with autoformers avoid that altogether by offering multiple taps as the outputs work the same driving a 2 Ohm load from the 2 Ohm taps as when driving 8 Ohm speakers from the 8 Ohm taps.

The power supplies in McIntosh amps are seriously overbuilt, beginning with the power transformer. The power supply is the determining factor on how well a given amp is at delivering current - the real story in driving difficult loads. And then there's phase angle ... the reality that current and voltage are often out of phase with one another when driving a loudspeaker playing music. Again, the power supply design is the determining factor at just how well a given amp performs in regards.

Let's just say that I've driven very difficult loads with my Mc amps when the need arises. Not only did they sail through unscathed, but they live to play another day.

To the naysayers, I say nonsense. Enjoy your combo.

For a experiment , I brought home a Rotel RB-1092 amplifier 500 watts per side class D ( was traded in ) and connected in place of my McIntosh ....

Sounded flat with less dynamics so this proved to me that autoformer is not limiting the amplifier at all

thanks damacman for your info, explains to me which the 8 ohm tap worked well for me

Dan

[damacman]

Not surprising. That MC302 is undoubtedly a very under-rated performer. The MC452 seems to get all the press!

Here's a post I made a long time ago at another forum that you may also find interesting in re: the McIntosh autoformer. True story.

While I was the Proceed rep in North Texas, I made a trip to the Madrigal factory for product training (this would have been in 1999 - I still have the certificate of completion). At dinner on the first night, I sat next to a gentleman that had apparently been with Madrigal for a very long time, and even before that was employed by Mark Levinson himself from what sounded like to be almost the beginning. He and I got to talking and he asked me about how I got into the audio business and I explained my fetish with McIntosh gear, etc. Imagine my surprise when he tells me, "I have a McIntosh MC2300 and I still use it on occasion!" Wow . . . when I asked him how he came across it, the story he shared with me was pretty cool!

Obviously, in the 1970s, McIntosh had a huge foothold in dealers. According to this gentleman, Mark had intended to demonstrate to dealers why putting a transformer of any kind between the output of a solid state amplifier and the loudspeaker was a bad idea. They obtained a MC2300, I'm assuming because of the power capability of the autoformers, and removed the autoformers from the amplifier. They connected them to one of their early offerings (I forget which ML model, sorry) in the lab to hear the results for themselves.

At about this time I responded, "I've never heard anything about this before." His response was, "That's because we could not hear a difference."

Apparently, he later obtained the amp for personal use for his band and had been using it on occasion ever since.

[Pampero]

Originally Posted by damacman

Great dialogue for sure - always nice to learn. Interesting story Pampero. It's really hard to disagree with anything you've said. I really like the MC452 - such a timeless design.

I worked for Rockford from 2002-2008. By then the hafler Class AB stuff was phased out in favor of Class G designs. Given that the pro industry was in serious decline, hafler was put out to pasture entirely. Really it was a shame.

Jim Strickland was an incredibly brilliant engineer and his 9505 remains one of the most heralded of its time. I knew Jim, but not very well.

Thanks, damacman! Did you know Rick Gentry? He was the SM for Hafler Pro at the time I was hired. They gave me a Transnova to run with my KEFs during beta testing. Long story, not to bore more than necessary, but it was not looking good for awhile especially when it passed DC to my speakers, a serious buzz kill. I was the Acoustat Rep at the same time but I was ill suited to the job, entirely apart from my lack of knowledge regarding retail high end. I thought the hybrid Acoustats had a lot of promise but needed more work on integrating the woofers. I couldn't get them to sound right in my house. This too was a buzz kill when it came to selling them but I thought the panels themselves sounded great.

But wait...there's more! I visited the factory. They held a meeting there. It was late winter, 106 outside on the pavement and I, coming from the northwest, thought that was odd. I don't remember which hotel we stayed at but it was very nice, and the factory was great to us, we ate well, I liked the people so I enjoyed the trip. I met Strickland on that trip, again at AES conventions and we spoke on the phone a few times but I can't say I knew him well either. He seemed a content guy, easy to talk to, no jive. Liked MOSFETs, you remember of course! I would not be the guy qualified to argue that with him on that or anything else and his amps sounded very good.

Now, I did think Jim Strickland did a great job with the Transnova when it actually was released. Also as you say, the studio amps were always very good. Reliable, inexpensive and they sounded just fine. They are still around here in Nashville which surprised me when I moved here last year. The biggest problem for Hafler really was the products focus, The studio market is a tiny vertical of the pro business. The real business for amps in pro is touring sound, churches, shopping malls, arenas, venues, schools and the like, and that's where hundreds of amp channels are sold at a time. Too, the immediate and broad acceptance in the studio market of active monitors made separate amplifiers redundant in many rooms.

The Transnova 9505 lived at my house for probably four years before I replaced it. My 452 is a better amp as it should be yet the TN sounded just ducky to me at the time and had enough power. I think it was highly underrated in respect to performance but if you had one, you knew it was good.

[damacman]

Originally Posted by Pampero

Thanks, damacman! Did you know Rick Gentry? He was the SM for Hafler Pro at the time I was hired. They gave me a Transnova to run with my KEFs during beta testing. Long story, not to bore more than necessary, but it was not looking good for awhile especially when it passed DC to my speakers, a serious buzz kill. I was the Acoustat Rep at the same time but I was ill suited to the job, entirely apart from my lack of knowledge regarding retail high end. I thought the hybrid Acoustats had a lot of promise but needed more work on integrating the woofers. I couldn't get them to sound right in my house. This too was a buzz kill when it came to selling them but I thought the panels themselves sounded great.

But wait...there's more! I visited the factory. They held a meeting there. It was late winter, 106 outside on the pavement and I, coming from the northwest, thought that was odd. I don't remember which hotel we stayed at but it was very nice, and the factory was great to us, we ate well, I liked the people so I enjoyed the trip. I met Strickland on that trip, again at AES conventions and we spoke on the phone a few times but I can't say I knew him well either. He seemed a content guy, easy to talk to, no jive. Liked MOSFETs, you remember of course! I would not be the guy qualified to argue that with him on that or anything else and his amps sounded very good.

Now, I did think Jim Strickland did a great job with the Transnova when it actually was released. Also as you say, the studio amps were always very good. Reliable, inexpensive and they sounded just fine. They are still around here in Nashville which surprised me when I moved here last year. The biggest problem for Hafler really was the products focus, The studio market is a tiny vertical of the pro business. The real business for amps in pro is touring sound, churches, shopping malls, arenas, venues, schools and the like, and that's where hundreds of amp channels are sold at a time. Too, the immediate and broad acceptance in the studio market of active monitors made separate amplifiers redundant in many rooms.

The Transnova 9505 lived at my house for probably four years before I replaced it. My 452 is a better amp as it should be yet the TN sounded just ducky to me at the time and had enough power. I think it was highly underrated in respect to performance but if you had one, you knew it was good.

Well, that name sounds really familiar but honestly, I think Rick may have been gone when I started. It seems to me that Brian Carlsness was running the home audio division for Rockford then and Brad Tabor was a sales manager.

I remember trying a P4000 as a sales rep myself ('98 maybe?) when that product line was newly introduced. It wasn't really my cup of tea. I thought it was a bit dry compared to what I was used to - a bit analytical. It was dead quiet though.

I was also a sales manager. I typically avoided bringing customers out during the summer months. I'd bring them out in the spring and fall and put them up at the Tempe Mission Palms (downtown Tempe, right off of Mill Ave). Many customers were really taken by the weather and the area and often remarked they'd love to move to Phoenix - especially if they had to go home to snow - as it's really nice here that time of year. After a while, you kinda' get used to the brutal heat of summer but by the middle of October I can promise you're done with it.

When I joined, Rockford had a general lack of focus period. The mothership was always Rockford Fosgate and the brand had slipped so bad by then it needed a major turnaround. In the second quarter of '03, Rockford had a massive restructuring and hafler and what was left of Fosgate Audionics and Acoustat were left without direction. Most of the inventory was fire-saled. When I look back, the P7000, the 9303, and the 9505 were the shining stars of hafler. The Class G amps never won me over in spite of their big power. We still had a guy in service that was versed in all things hafler and Acoustat. David continued to service those products for customers for a few years later. It wasn't unusual to see a pair of Acoustats down in tech repair, which was right downstairs from my office. A few years later, that also stopped.

Jim retired in 2007 or so but still came to work each day to keep busy. That guy was a part of nearly everything Rockford did in amplification for a very long time, the TransNova circuitry being his calling card. But, he also earned patents on several other designs including a switching automotive amplifier that Rockford classified as bd (beyond digital) - the Rockford Fosgate bd1000a1. It was the very first switching amp to ever sell in volume in the car audio industry and today I'm sure one of the best selling of all times.