Question’s re: Output Taps
 

A few years ago when I had the MC302 power amplifier, I had the Martin Logan Spires connected to the 8 ohm taps, for whatever reason it sounded better than the 4 ohm taps but the amplifier would run for hours with the heat sinks just getting slightly warm. Do not even matter if I had it at max volume ( 300 watt peaks )

I then sold the Martin Logan’s and purchased Magnepan MG 1.7i speakers.
At first I hooked up the Magnepan’s to the 8 ohm tap , like the Martin Logan’s but after about a half hour the amplifier at just past 30 watts output, shut off and go into protection. Heat sinks would be hot enough to burn your hands. I was forced to use the 4 ohm taps and no more issues with heat sinks getting hot.
But the sound quality was not the same as when at 8 ohms. This goes back to 2016.

Later in 2018 replaced MC302 with MC312 ( part of insurance replacement due to break-in. At that time changed to Magnepan MG 0.7s as moved to apartment with smaller living room . I used the 4 ohm tap, afraid to try 8 ohm tap with past experience.

This January replaced the MC312 with MC462 power amplifier. Noticed that the 8 ohm, 4 ohm and 2 ohm taps had individual + and - post compared to 1 negative post and 3 posts + for 8, 4 and 2 ohms.

Ran the amplifier at 4 ohm taps for about a week and a half. The Magnepan’s did sound better than it did with the MC312.

Last night decided to try the 8 ohm taps again on the MC462.
This time, the heat sinks are just as cool to touch as it was on the 4 ohms tap. Does not matter how loud I am playing music. And yes it does sound better on 8 ohm taps than 4 ohm taps on the Magnepan’s.

What confuses me is why do both the Martin Logan and Magnepan’s sound better with the 8 ohm tap when the recommended impedance for both is 4 ohms.

Why does the MC462 stay cool on the 8 ohm tap with Magnepan’s but the older MC302 when go into protection + heat sinks getting super hot after half a hour?

Any scientific reason for this ?

Dan

Dan… everything you mentioned above tells me the Martin Logan, and Magnepan’s are power hungry. They like having the extra headroom that the MC462 provides. In addition the MC462 has the extra power to not only deliver it, but remain cool while doing so.

As far as the impedance taps go; manufacturer recommendations are just that. I have frequently strayed from the manuals Reco’s, and let my ears be my bible.

Glad to hear you are finally enjoying your speaker’s full potential, and not adding an additional space heater in your home. ;)

I think it's important to understand that most solid state amps are built around an optimum "tap". I have experience with the old Krells. I had an engineer at Krell explain this to me years ago. He explained that Krells were built around a 2 ohm tap. This means that a 400 watt Krell will deliver 1600 watts at 2 ohms. Modern Mac amps have much larger power supplies and better heat sinking but it doesn't change the fact that running a low impedance speaker with a minimum impedance of say 2 ohms, will over a period of years significantly reduce the life of the amp.

For example, a Wilson Sasha DAW goes for 39K. An appropriate amp for this price speaker would be around 20K, which would be a MC 611. Or a SS amp built around a 2 ohm tap. I totally understand that many will disagree but I am a proponent of running the SS amp so that under most conditions it is under stressed operating under optimum conditions, i.e. no impedance mismatch.

However, if you 462 is always running cool, well, who can argue with that??

Best

Charles