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Are amps that run hot a ticking time bomb?

104.162.146.91
Posted on January 31, 2016 at 14:26:09
digepix
 I was reading a post on another site about amps that run hotter than class AB amps being a lousy choice. I have one of those amps, it runs hot but you can keep your hand on the top without ever removing it. Tubes run hot but I've never heard anyone say they make a lousy choice. Is this someones opinion not entirely based on facts? My amp is old not as old as some tube amps being used. It's been serviced for the capacitors twice in it's life. It sounds great to me should I be concerned or should I listen and enjoy?

 

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listen and enjoy! , posted on January 31, 2016 at 15:07:02
chocolate_lover9999@yahoo.com
Audiophile

Posts: 1628
Location: South Central Coast, California
Joined: October 12, 2003
 amps that run hotter than AB are not a lousy choice, just another piece of misinformation among the millions on the web.

 

If you can keep your hand on it there should be no problem., posted on January 31, 2016 at 15:20:53
John Marks
Manufacturer

Posts: 7806
Location: Peoples' Democratic Republic of R.I.
Joined: April 23, 2000
 When I was writing for TAS I had three integrated amps in a row from the same manufacturer. They ran hot and each one failed and then went into runaway thermal overrun. Had I not been there they could have started a house fire.

Turns out that there were "weak" transistors in the batch and the "good" transistor in the complementary pair blew itself up trying to do the work of two.

Sad to say, the company owner was in a catastrophic auto accident and the company went into administration and the new owners/managers scrapped the product, and then the US importer died.

My general rule is that if a solid-state device gets past 90 days of regular use, it is past any teething pains.

Enjoy the music,

John

 

RE: Are amps that run hot a ticking time bomb?, posted on January 31, 2016 at 15:59:43
kenzo
Audiophile

Posts: 955
Location: San Francisco
Joined: September 27, 2003
 hot amps are certainly less energy efficient. it takes electricity to heat the thing up, and you can't hear hear so it ain't contributing to the sound.

 

Not when they are competently designed, posted on January 31, 2016 at 16:33:27
E-Stat
Audiophile

Posts: 37649
Joined: May 12, 2000
Contributor
  Since: April 5, 2002
 I ran a "hot running" Threshold Stasis 3 for over thirty years driving the reactive load of electrostatic speakers.

In that space of time, I replaced some fuses and proactively replaced the computer grade Mallory electrolytics in the power supply at about the twenty five year point.

I recently sold it to someone who will likely experience the same level of reliability.

 

No, posted on January 31, 2016 at 18:27:08
AbeCollins
Audiophile

Posts: 46294
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002
Unless it's very old on it's last leg, flakey, or poorly designed I'd say no.

Some of my best sounding amps have run warm to hot. With the hot ones, I just use common sense and caution by giving them plenty of room to breathe (dissipate heat) and I never leave them ON if I'm not home.



 

RE: Are amps that run hot a ticking time bomb?, posted on February 1, 2016 at 00:03:53
Frihed89
Audiophile

Posts: 15703
Location: Copenhagen
Joined: March 21, 2005
 Make sure the tubes have plenty of air, as in the top shelf (open on top), otherwise tube life will be reduced...or use a silent fan.

 

RE: Are amps that run hot a ticking time bomb? Only if improperly designed , posted on February 1, 2016 at 00:52:07
A.Wayne
Audiophile

Posts: 2527
Location: Front row center
Joined: November 30, 2011
 No heat, no sound ... :)

 

LEAVE the house NOW !, posted on February 1, 2016 at 05:52:14
airtime
Audiophile

Posts: 11287
Location: Arizona
Joined: February 4, 2003
 No only kidding. It would only be an issue if that was a new finding. If it never ran hot before and NOW it is.

Otherwise it's normal for most amps. Usually the high the power the hotter they get.

If it's getting too hot then I suggest a nice cool tall drink and enjoy the music.

 

RE: Are amps that run hot a ticking time bomb?, posted on February 1, 2016 at 09:16:58
6bq5
Audiophile

Posts: 4390
Location: SF Bay
Joined: August 16, 2001
 It sounds like there is some considerable misinformation in your source. Amps are classified by class-
Class A the device is conducting 100% of the time - the Bias is set so that the device amplifies the entire input signal- it is this biasing of the device that causes the temp to rise-
Class B is only conducting 50% of the time, and the bias is correspondingly lower - less energy put into the device is emitted as heat
Class AB, The device is biased higher than class B so as to minimize crossover distortion when the output signals are combined to provide the full signal amplified.

The Heat output is a function of the class, the bias current and the ability of the device to cool itself-
a hotter amp means higher bias
It is not inherently bad - but can be poorly executed.
If you want a class A amp - you will generate lots of heat

Happy Listening

 

RE: Are amps that run hot a ticking time bomb?, posted on February 1, 2016 at 09:32:41
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 A Totally old school approach would be a 10 watt 'a' amp and some HIGHLY sensitive speakers.

A pair of such amps (stereo) would kick out about as much heat as a 100 watt light bulb.

.
Too much is never enough

 

RE: listen and enjoy! , posted on February 1, 2016 at 10:10:33
dbphd
Audiophile

Posts: 1674
Location: Montecito, CA
Joined: September 6, 2006
 I'm running Parasound JC 1 mono blocks LCR that, IIRC, are Class A to 25 watts if set to low bias where they stay just barely warm to the touch. If set to high bias, they get too hot to touch, and must really spin the meter. Good if you live in a cold climate with no furnace.

 

RE: Are amps that run hot a ticking time bomb?, posted on February 1, 2016 at 13:37:23
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 Hmm, so class A biasing doesn't contribute to how an amplifier sounds?

 

RE: Are amps that run hot a ticking time bomb?, posted on February 1, 2016 at 13:42:02
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 You've left out what's actually getting hot. Generally speaking, if a heatsink or transformer is hot enough that a drop of water boils instantly off of it, it's running too hot.

Most transistors are fairly happy up to about 100C, while this kind of heat could make a heatsink and chassis uncomfortable to touch.

Power transformers are a different animal, as they can be designed to run a bit hotter.

There is no specific temperature at which class AB amps run. You could easily design a class AB amp that idles with a higher temperature than a class A amp, these are relatively unrelated.

Heat does decrease the lifetime of capacitors.

 

RE: Are amps that run hot a ticking time bomb?, posted on February 1, 2016 at 13:44:23
kenzo
Audiophile

Posts: 955
Location: San Francisco
Joined: September 27, 2003
 no of course not, but it is not the HEAT that contributes to the sound.

the HEAT is a waste byproduct.

hmmm

 

RE: Are amps that run hot a ticking time bomb?, posted on February 1, 2016 at 15:36:32
Palustris
Audiophile

Posts: 2408
Location: Cape Cod
Joined: September 12, 2008
 "it takes electricity to heat the thing up, and you can't hear hear so it ain't contributing to the sound. "

Nonsense, complete nonsense.

Compare a 2A3 single ended class A amp running 120 mA @ 250V consuming 30 Watts for two stages to a parallel push pull 6550 class AB amp running eight hundred mA @ 450v burning 360W. Now, tell me which one is "heating things up" and what exactly is not "contributing to the sound" with the single ended amp that can ONLY run in class A.

 

RE: Are amps that run hot a ticking time bomb?, posted on February 1, 2016 at 17:56:41
kenzo
Audiophile

Posts: 955
Location: San Francisco
Joined: September 27, 2003
 I guess some of us know the difference between electricity and heat, and some of us cannot comprehend the difference.

so be it.

 

RE: Are amps that run hot a ticking time bomb?, posted on February 2, 2016 at 08:51:59
Palustris
Audiophile

Posts: 2408
Location: Cape Cod
Joined: September 12, 2008
 Of all the injured vanities, that of the reproved buffoon is the most sorrowful.

 

RE: Are amps that run hot a ticking time bomb?, posted on February 2, 2016 at 10:33:59
kenzo
Audiophile

Posts: 955
Location: San Francisco
Joined: September 27, 2003
 [He] may look like an idiot and talk like an idiot but don't let that fool you. He really is an idiot.
— Groucho Marx as Rufus T. Firefly, Duck Soup

 

RE: Are amps that run hot a ticking time bomb?, posted on February 2, 2016 at 12:45:21
Bill Spohn
Audiophile

Posts: 33
Joined: March 4, 2000
 As the owner and operator of four Class A amps, the alleged relation of running hot to reliability is twaddle. Some of my amps are almost 30 years old now.

 

Its not twaddle, posted on February 2, 2016 at 13:14:48
3db
Audiophile

Posts: 1514
Joined: July 22, 2003
 Heat buildup is the 2nd worst thing to apply to semiconductors and that is a fact. The first thing being an EMP pulse.

That being said, your so called "hot amps" are probably running well within thermal specs thus creating the illusion that its twaddle. I have a Technics AVR running class H and it too runs hot and I've not had any issues with it. I give it some breathing room. Now if I were to block the airflow from the top of AVR or limit airflow around it in some fashion, then the life expectancy will drop considerably. Onkyo's HDMI cards kept failing prematurely because of poor thermal engineering ( poor draining away of heat ) which caused excessive heat build up in the chassis. The HDMI card were at the hottest point in the chassis and failed the most.

 

RE: Its not twaddle - 'tis, posted on February 2, 2016 at 16:17:33
Bill Spohn
Audiophile

Posts: 33
Joined: March 4, 2000
 If you assume competent amplifier design, including enough heat sink area to cope with whatever heat the amp will experience, there is no reason to believe that an amp that runs hot will have a shorter life.

If the amps are under-designed (i.e. incompetently) all bets are off and you have an expensive time bomb on your hands.

 

Thanks for agreeing with me, posted on February 3, 2016 at 04:45:50
3db
Audiophile

Posts: 1514
Joined: July 22, 2003
 Your basically reiterating what I've said.

 

RE: Are amps that run hot a ticking time bomb?, posted on February 9, 2016 at 23:16:36
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 Agreed about caps. If you think it's too hot and PS caps fail, try 105c rated.

Keep in mind that temp and heat are different but related.
The same amount of HEAT distributed thru more mass will have a lower temperature.
This is where the old rule of thumb about simply WEIGHING an amp to gauge its quality started.
Just to pick a number, I'd be wary of an 'A' amp weighing less than 1 lb per watt. Maybe more or less, but that's the general idea. A 30lb 'A' amp @30lb?
With a SHIPPING Weight of 75lb, the Pass Labs XA30.5 is a high bias A->a/b amp which might go just OVER 1lb per 'A' watt.
Too much is never enough

 

RE: Are amps that run hot a ticking time bomb?, posted on February 10, 2016 at 05:12:31
Kirk57
Audiophile

Posts: 607
Location: Chicago's North Shore
Joined: December 9, 2008
 What seems 'hot' to a human is not necessarily hot at all to electronics. Transistors and capacitors can be rated to run in ranges that you would not want to be touching for very long...

 

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