D'Agostino Momentum amp melts down


The latest issue of Stereophile tests the Momentum amplifier and amp number 1 melts down during the precondition test. Atkinson is afraid to subject amp number 2 to the same test and only runs it for 1/2 as long as the standard test.

Parasound, Bryston, and others pass this test but the Momentum can't? Then they act like it's no big deal like it melted down. So, if that's the case, why perform the test?

The manufacturer response doesn't remark on the melt down. I would think Dan would be duly embarrassed but what the heck, those copper heat sinks sure look great.

Would a prospective buyer (not me) be hesitant to power an inefficient speaker to loud levels with this amp?

rhljazz
This amp will be unreliable. This should NEVER happen! The heatsink design is
BS!

The preconditioning is just a warmup to get the amp to a stable temperature for
testing.

BUYER BEWARE!
Taken form Sterophile review of Dartzeel amp

"I ran it at 1/3 its rated power into 8 ohms for 60 minutes, which thermally is the worst case for an amplifier with a class-A/B output stage. At the end of that period, while the shrouded heatsink on the amplifier's rear was too hot to keep my hand on, at 63.5°C/146°F, the top of the enclosure was ":

That is an extreme situation. This is probably an isolated incident with no real world application. No other reports that I a aware. It was tested by Martin Colloms.
Atkinson *should* have run the 2nd exactly as he ran the 1st. If it blew up, he should report it. What is it with these guys giving a pass on this gear. If it can't cut it, WE NEED TO KNOW ABOUT IT!!

-RW-
i thought that was there policy.
Well the stress test is hard on an amp.
It is true they let folks know.. So what is the problem. You can't figure it out for yourself?
Do they have to TELL you it sucks in black and white????
A quick internet search shows that the following amps did not, or could not pass the Stereophile administered 1/3 power test: Bryston 14BB-SST, Arcam Alpha 10P, McIntosh Mc1201 and Pass X1000. I can only imagine that a thorough search would turn up many more examples.

Not passing this test doesn't mean an amplifier is bad. It could mean underspecified heat sinking, very high bias settings or very conservatively set protection circuitry. In the case of the D'Agostino I suspect the copper heat things are an attempt to keep the amps weight manageable. Remember, the 1/3 power test does not reflect real world operating conditions. It's designed to stress a solid state amplifier in order to then measure distortion components.

Rhljazz, what exactly is your agenda in starting this thread? Nowhere in the Stereophile article does it say anything about a melt down. The amp stopped working. It didn't melt, catch fire or explode, yet you keep using language suggesting some Chernobyl style event. You actually seem to take pleasure in the amp's malfunction. The German language has a multisyllabic word for what you're exhibiting.
Most amps fail the test. Bryston amps are not musical to my ears. I'd bet the farm that the Momentum sounds wonderful, but a used FPB 600 would most likely embarass it! Dan's best work has already been done:)
^"Schadenfreude"
It is what it is. You don't have to ignore the fact that it exploded under test conditions. It did not in the other two reviews I read. It was not even hot when I listened to it. I'm sure at $40k it has a hefty warranty.
When you audition at the store push it hard and see what happens.
Sorry it did not explode. Perhaps the phrase is"thermal protection mode."
#1. What exactly does "Melts Down" mean? Something melted in the amp? Exactly what?
#2. Does this amp have thermal protection? If yes, why didn't it work?
#3. I'm gong to guess Dan D. is going to want to address this issue, before this design is branded a very attractive failure.
Onhwy61,

My apologies! You already answered my questions, I just didn't read all the responses before I jumped in..
If anyone wants to send me their "defective" D'Ag Momentum amps, I be happy to take them off your hands.

:)
I thought that was hilarious...understandable thermal issue, but people love this amp SO MUCH they stand up for it! I've read several reviews if the thing (and its stereo "el cheapo" 20 something grand version) and was surprised Stereophile got to it so late...but still...I absolutely take wholehearted pleasure in this amp shutdown issue, and further pleasure in the fact that anybody justifies or defends the embarassing shut down...really...55 grand! These amps should not only never ever do anything but look and sound fabulous, they should venturi their heat into little clouds of golden wonderfulness that water your house plants and make children happy all over the world.
"it is not enough to succeed. Others must fail."
-- Gore Vidal
Any thermal problem on a $55000. amp would make it unacceptable to me . Or $5500 for that matter .
That's a feature for superior sound.
If so many amps fail this test, and failing it is irrelevant, curious why they do the test.
At a proposed price of $55K(!) and knowing full well what it was potentially going to be subjected to, I think it's test results are disappointing.
Rhljazz, what exactly is your agenda in starting this thread? Nowhere in the Stereophile article does it say anything about a melt down. The amp stopped working. It didn't melt, catch fire or explode, yet you keep using language suggesting some Chernobyl style event. You actually seem to take pleasure in the amp's malfunction. The German language has a multisyllabic word for what you're exhibiting.

My agenda is three fold. First of all there are more amps that pass the test than ones that don't. The Momentum is a 55000.00 amp that I would expect to pass the test based on price and the designers reputation.

If the amp has proper protection, it should shut down and return to normal operation after it cools down. So a defect exists whether it is a design flaw or a single product failure we don't know since the second amp was not subjected to the same test.

I have a problem with Stereophile not making a bigger issue of it and basically sweeping the result under the rug. Then there is no defense from the manufacturer which I find unusual.

The third related problem with Stereophile is the test itself. If they deem the test as not being relative to the products performance, either change or eliminate the test.

Mr. onhwy61, what words would you use to describe a product that managed to get really hot on the test bench, shut down because of it, and then failed to operate after the fact? My first thought was melt down. Maybe you can make up a politically correct term for it. LOL!
More (post) Krell bashing is what this is; the emperor has no clothes. Also, the fact that Atkinson then continued on a modified test basis completely invalidates the test, Atkinson and the publication. This is pure entertainment with absolutely no value. Frankly, I stopped reading this magazine and the other one years ago; I have better things to do with my time, like read and respond to Audiogon threads such as this one. And no one so far seems to care what the amp sounds like...hmmm.
So you admit you have a agenda! I thought so.

Since when, especially on an audiophile internet forum where sound quality is praised and measurements denigrated, did the Stereophile 1/3 power test become the keystone of amplifier quality? A failure or malfunction during this test is cause for further investigation and a manufacturer's comment. To raise it to the level of an internet forum thread bespeaks an agenda.

BTW, if you Google the word "meltdown" the first few entries all refer to nuclear power plant disasters. Your language is intentional inflammatory which I take as further evidence of your multi-pronged agenda. Have you no shame?
Gregadd, I don't think that "thermal protection mode" is an accurate description of failure which is what happened to judge from Mr. Atkinson's comments.

The preconditioning test, as others have stated, is not very applicable to actual use. Nor are steady-state measurements of distortion, for that matter. But the amp failed the test and sustained damage. Stereophile reported on it and it is completely worthy of a thread here. Let each prospective buyer make of it what they will. Personally, it wouldn't bother me at all, but then again, I don't buy $55,000.00 amps.
Definition of AGENDA
1: a list or outline of things to be considered or done
From Webster's dictionary

It seems appropriate for a forum. I have clearly stated the concerns I have with the amplifier and Stereophile.

I will continue to subscribe to the magazine and I'm sure the amp sounds as good as Fremer describes it, but it does exhibit a problem.

FWIW, I think this thread is appropriate, but also think some of the words chosen are hyperbolic.
Really? "MOST amps fail the test?" Hmmm... also I disagree with the statement "This is pure entertainment with absolutely no value"...since when does "pure entertainment" lack value? Do happiness, mirth, delight, joy, glee, intense snarky and self righteous AH HA moments, or fun at the expense of the uber-sensitive lack value? I say NO NO NO...I love this aspect of the hobby: "when realities collide." The audio reviewmanati have their collective heads so far up the wazoos of some makers of VERY EXPENSIVE TOYS they get faint from lack of air (and sad from their inability to personally afford $175,000 speakers, $55,000 amps, or $15,000 phono cartridges). Of COURSE a 50K amp pair should be flawless...otherwise why pay 50k for this stuff? And why not delight when a spanner hits the works. It's fun! Still...I think Momentum stuff is great, looks amazing and sounds fabulous...when it works!
I think, but only Wolf will know this for sure. That people that pay 55,000 for an amp or an ape or a meal or what ever, they want attention. So in that respect Dan A' is a genius. His product breaks and the owner gets some more attention. So does Dan A' like in this thread. Brilliant I say Brilliant!! I wish I would of thought of that. I guess that is what it takes to be an audio designer you gotta think outside the amp.
I am sorry that you interpret this as a meltdown. The momentum amplifiers normal operating temperature is 42 -44 degrees c(107-111f) the temperature rise to 48c (118f) is inconsequential. The amplifier in question failed from a non-related component failure in the power on circuit. The Momentum amplifier is designed to shut down at 70 c (158f) The unit under test was not close to that temperature. Many amplifiers operate temperatures at 70c(158f) and above. If John had continued his test the second amplifier would have passed without any problems. The Momentum amplifier has more than enough thermal head room for any load or any speaker. I was unable to give a comment
Until the unit was returned to me from testing.
Thank you for your concern.

Dan D’Agostino
I am sorry that you interpret this as a melt down. The Momentum amplifiers normal operating temperature is 42-44c(107-111f)the temperature rise to 48c (118f) is inconsequential. The amplifier in question failed from a non related component failure in the power on circuit.The Momentum amplifier is designed to shut down at 70c (158f). The unit under test was not close to that temperature.Many amplifiers at higher temperatures than that.If John had continued his test the second amplifier would have passed witout any problems. The Momentum amplifier has more than enough thermal head room for any load or speaker. I was unable to give comment until the unit was returned to me from testing. Thank you for your concern.
Dan D'Agostino
I'm an old fud and the last thing I want is attention but after reading the sonic description in that review I wouldn't mind comparing them to my Constellations (which are currently powering the Magico Q7's residing one of my dream systems).

Lets face it QSC makes amplifiers that can run all day at that load if you don't mind the sound of a high capacity switch mode power supply. Not to discount the test but according to the review the power meter barely got off the peg in listening tests. If the manufacture stands behind the design who cares.

I trust any ultra high end audio manufacture to funnel profits back into the system more than some 1%'er, screw them. Besides, they're an important function of the used market. We need to stop wising up these chumps.