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 ?
Suggestion: do not play your system that loud.
Otherwise, toss the amps and buy Bryston.
I had a problem at high volume using tube ARC monos.

I think the amp is seeing something it doesn't like impedance wise.

Are the bass panels rattling at these volumes? Are you playing very dynamic music? Things with sudden big bass hits?
I suspect there is a problem with the speakers. My Cary 500 MB's have never shut down driving my 3.7's. Do both channels of the Cary shut down?
I had a problem with the Cary SP-05 driving my Pass Labs Amp X350.5. The result was Low bass and Highs.
With your long interconnects that can't help.
I moved to a Pass Labs Preamp XP-10 and all is fine.

Call or email Pass Labs about the problem.


There could be something wrong inside your Maggies.

The Pass is stable into 4 ohms and lower. It has thermo protection. You may be overdriving it causing it to run hotter than designed and therefore shutting down "as designed".

How much does needle on the Pass deflect from the idle point?
Are the amps in a well ventilated place? They very big and heavy with LOTS of heatsink.
If in restricted space, they could simply be not getting enough air.

I don't know that Magnepan has ever made a speaker that was a 'bad load'.
Low sensitivity? sure. Low impedance? yes again. But I've never seen any data showing bigtime dips or huge phase angles. Is the new 3.7 an exception? It does use a new design series crossover, so MAYBE, but don't bank on it.

If you haven't popped a speaker fuse, I'd look back at the amp......Onemug's bias meter suggestion is good.
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).
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.
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.
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
You're not going to like this but perhaps the Maggie's are just the wrong speaker for you.
Get a pair of Krell or Levinson amps. They can handle 2 ohms.
That would be nice if the Maggies dropped that low....

See AA for resolution to OPs problem.....
Your in a world of hurt.
Who's 'in a world of hurt'?
The guy with the problem.Thanks
Over at the Asylum, the OP posed the same question.

He has resolved his problem...which didn't get updated over here.

So, painful as it was, problem solved...........
Say what who really cares??
I'll be sure to be as unhelpful as possible if you ever have a problem, ebm.
Nice attitude.

So what turned out to be the problem?
Sorry just joking.Please have a nice day SORRY!!
The OPs answer on the planar asylum: I can't figure out what he did except hook it back up after litle success with Cary amps.....?

I finally went back and hooked up my Pass Labs 250.5 and I've had nothing but great music since. The fact that my pass amp overheated was apparently not related to the Cary amps shutdown.

The Cary amps are new because just purchased off of Agon. I wanted mono blocks to place behind the speakers, But after listening to both amps there's no way I could go back to the Cary's. The pass amp just sounds so much better in every way. This is not to discredit the Cary but to my ears there's no comparison. Not to mention that the Cary's don't appear to be a good match for the Magnepan load. I should have known

Now these go back on Audiogon and someone will get a great deal. I now would like to see if I could get a another 250.5 and use one 250.5 to drive each channel. Not sure that would work with these amps but I guess that's for another post.

Thanks for all the suggestions and help
I'm not sure what the problem was with the OP's set up. Again, my Cary's are having no issues with my 3.7R's. They handle Mahler(front row loud)without complaint. There is not an inherent incompatibility between the Cary's and the Maggies. Something else was not right.

As for the OP's preference for the sound of the Pass 250.5, well, there is a reason Pass amps have such a great reputation. I wouldn't mind having a chance to A/B the Pass and Cary's myself.
"The OPs answer on the planar asylum: I can't figure out what he did except hook it back up after litle success with Cary amps.....?"
bought my first system in about 1987.
magneplaner IIc with an onix integrated
amp ( 30 watts per channel). didn't know
any better. but listened to 'thus spake zarathrustra'
many times and never had to ask myself "where's the bass".
never shutdown either.
Pass Amps are great and I've heard that the xa100.5s will drive the Maggies no problem so the 250.5s shouldn't break a sweat. I use a VAC 150 wpc tube amp and they play loud without breaking down on the 3.7s.
He had not installed the tweeter jumpers. No wonder the amp shut down.
And the stock tweeter jumpers are lousy. I replaced my jumpers with the Duelund Cast .6 resistor on the tweeter and an Empirical Designs custom jumper for the midrange.
Yes, I´m using the Cardas tweeter and midrange jumpers on my 3.7´s.
I tried the Cardas jumpers (have a new set if anyone wants to buy them). It was like using resistors...Cardas smoothed/dampened the sound out a little too much for my likes. The Empirical Designs are the bomb.
I think the impedance of the Maggies is too low to be safely handled by your power amp - the protection circuits see them as a fault (short) circuit load.
If you want to get loud, Maggies may not be the best choice.
"I think the impedance of the Maggies is too low to be safely handled by your power amp - the protection circuits see them as a fault (short) circuit load."

Nothing wrong with his amp;
"The main issue was the speakers ship with the tweeters disconnected; you have to install the supplied jumpers. After the Pass thermal protection shut the amp down I read the speaker manual and discovered I had been listening with no tweeters"
"Cardas smoothed/dampened the sound out a little too much for my likes. The Empirical Designs are the bomb."
I think I read somewhere that the Empirical Design jumpers are made of silver plated copper? All silver plated cables I´ve been trying have had a "tweeter-in-your-face-sound", is this true for the ED jumpers?
I am very adverse to silver in your face etchy sound. The Emp Designs are transparent and fast but not forward.