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Pass 250.5 shuts down driving Magnepan 3.7

This is my first post so please bear with me.

My Pass labs 250.5 protection circuit shuts the amp down when I drive my new Magnepan 3.7s at high volume. I'm talking about a volme higher than I might consistently listen, but not an unbearable level.

I'm using a Cary Slp 05 preamp with long balanced ICs (25 ft,) The amp is close to the speakers with less than 6 feet of speaker wire. The system works fine at normal volumes. I've tried the same thing with a pair of Cary MB500 (750 W @ 4 ohm) and they too shut down at high volume.

I believe the maggies drop below 4 ohms and I wonder if either amp can handle the impedance drop below 4 ohms.

Has anyone experienced this issue ?

Any suggestions ?
gcoxsom
charles1dad's avatar
charles1dad
10,250 posts
 
I suspect if could be a defective speaker. I`ve heard good tube amps drive maggies to loud levels with no sweat.
It`s hard to believe these large and powerful SS amps run out of gas with these speakers, they can`t be 'that' power hungry(given the sucess of the tube amps).
bvdiman
491 posts
 
Given two amps same problem, I'd first check your power source--wall AC. Make sure it is giving out ample supply, and preferably dedicated--for higher powered units.
magfan
1,583 posts
 
I LIKE that idea. If the wall voltage sags...badly, that'd do it.

Try a SINGLE channel at the offending level.

Borrow / buy a DVM and check line voltage during use. A 'Kill-a-Watt' meter would work, also. As long as you're on the same leg of the circuit as the amps, you'll be OK.

The Pass site also formerly listed output voltage of the amps, which would be another possible check.
jallen
502 posts
 
At high volume, my 4BSST would flash red driving the 3.6. They suck power and need to be fed. Try a 14bsst, a bit more power will help, or get a bigger Pass. Jallen
ngjockey
1,042 posts
 
You're not going to like this but perhaps the Maggie's are just the wrong speaker for you.
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