Halo A51

[mitch57]

How are most of you handling the heat issue with Halo amps? I went to a dealer the other day and he had two JC1 monoblocks sitting on the floor wide open with nothing obstructing the back top or sides. They were powered on but had no signal and nothing was playing. They were hotter then hell!I could not rest my hand on top of either one of these amps for more then a few seconds.

My understanding is that the A51 is also a class A/AB amplifer and I'm concerned that heat will eventually kill it. I haven't made the purchase yet but will be auditioning one the week after next.

The cabinet I will be putting it in has a hinged oak framed door with glass inserts. The dimensions are 12" H x 22 1/2" W. The cabinet is open in the back.

Here's a picture of cabinet with the door open on the left and what it looks like with the door closed on the right. The A51 will take the place of the Rotel RMB-1095.

I see several pictures of Parasound amps stuck in a rack with very little clearance between components. How are they handling all that heat? Are you guys using fans? Should I be worried?

Thanks in advance.

[nicholtl]

Unless you have adequate clearing (I think Parasound recommends atleast 6 inches) on top, and a few inches to each side, you should strongly consider the use of a fan. I use a Sharper Image spire fan that automatically turns on once my system powers up via a switched outlet from my line conditioner. I know others have had success using computer fans, or even fans specifically designed for home theater installation use.

Ideally, you'd place your amp/s on amp stands on the floor. However, that sort of space is a luxury most people can't afford. Only demo rooms.

[soundhound]

Club Rotel has had posts recently pertaining to heat. Rest assured when our pre/amps are engineered they do their homework. The heat generators are the internal junctions of the output transistors, voltage regulators, etc... Most manufacturers will supply ample heat sink to allow the heat to transfer from the junctions well before the point a component will go into thermal runaway. (Exception being Carver in his TFM amps, many resistors are to low of wattage, and some of the drivers should have had heat sinks) You could look up data sheets on specific components and see what their operating ranges are, and mfgrs leave room for error. If the manufacturer feels the need for extra dissipation they will provide a fan on their piece. The last thing they want to be doing is relacing components under warranty because they "oopsed". All though heat tends to make us all nervous , if we follow their space guidelines all should be fine. Thats not to say certain loads (speaks) will not put some amps to the test, but here again most higher end mfgr's will put a cushion in as to where the thermal protection kicks in b-4 something gets away. For the sake of argument there are exceptions to every rule, but, you can feel confident when your'e goodies run hot, all the pieces are doing their job.

[Peter Nielsen]

They were hotter then hell!I could not rest my hand on top of either one of these amps for more then a few seconds.

They were obviously running in HIGH bias mode (25W class A). In LOW bias they do not run that hot at all.

The A51 runs even "cooler". The A51 runs 2W/channel idle, so it should be the same as a JC1 in low bias. However, it seems cooler to the touch probably because the heat output is spred onto 5 heatsinks instead of 4. Unless you run it hard, 3" clearance on the top and sides should be just fine.

Of course the ambient (room) temperature makes a BIG difference. In a 65 degree room the amp will get adequate cooling with minimal clearance. In an 80 degree room, the situation will be quite different. Anyting less than 3" might be bad for the amp...

The other day my room was getting hot as hell (82 degrees with the AC running like crazy). I wondered what was up and realized that I accidentally forgot all my four JC1s in HIGH bias mode after doing some critical listening :B

Peter

[MichiganMike]

The A51 placement guidelines in the manual call for 3" space around both sides and 6" above the top. The manual also advises do not to block the front of the A51 behind closed doors during use and do not stack with other components inside a cabinet unless you use a fan.

I suspect the guidlines are conservative. Class A operation of the A51 is only the first couple watts and the heat sinks are massive. I have my A51 installed at the bottom of an open rack with about 8 inches clearance above and several inches of clearance on all sides. After driving my 88 dB efficient speakers for several hours at normal listening levels (75 dB calibration with 100 dB peaks) the A51 is only slightly warm to the touch. Certainly no warmer than my prior amp, a Rotel RB993.

The A51 is a couple inches shorter than the 1095 which will give you more clearance in the same space. Side clearance may be a concern. I suspect that provided you leave the cabinet door open during operation and ambient temperature of the room is comfortable, the A51 should be fine. You can always try it in your cabinet and monitor temperature levels to determine whether a fan is prudent.

[Peter Nielsen]

For the sake of argument there are exceptions to every rule, but, you can feel confident when your'e goodies run hot, all the pieces are doing their job.

Let me add the usual dose of Fear, Uncertainty and Doubt:

Some electric components don't like heat. While the output transistors certainly can handle their share of heat, other components don't like it a bit. For instance wet components like capacitors usually suffer from heat (they dry out).

The general consensus is to always let the amp run as cold as possible. Heat will shorten the life of electronic components...

If you're afraid of dealing with heat issues, then digital amps (class D) might be the perfect solution. Have a look at PS Audio, Tact Audio and Halcro Logic for examples of amps that run completely cool to the touch.

Peter

[NMyTree]

I remember reading a post by John Curl on Audio Asylum, where he stated, that he likes his designs to run warm or hot. I would imagine he would take great care in selecting parts that can deal with the heat, of his designs. Just sharing what I have read, I'm certainly no expert.

http://db.audioasylum.com/cgi/m.mpl?forum=amp&n=22204&highlight=John+Curl&r=&session=

" Posted by john curl ( M ) on July 16, 2003 at 12:00:37
Parasound amps run hot, if I have anything to say about it. "

http://db.audioasylum.com/cgi/m.mpl?forum=amp&n=19343&highlight=John+Curl&r=&session=

" It is difficult to say. However, I prefer amps that run warm, because that gives the greatest class A region. However, listening level, load, airflow to the heat sinks, make it difficult to be sure by just touching it. The optimum operating point of almost all Parasound power amps is measured as: 15mV-22mV across one emitter resistor. This sets the optimum transistion point between class A and class B operation. If it is less than 10mV, then some measured crossover distortion will develop. Adjustment it tricky without an isolated screwdriver in some units and tends to be extra sensitive. "

[Peter Nielsen]

I remember reading a post by John Curl on Audio Asylum, where he stated, that he likes his designs to run warm or hot.

I'm sure he intended that he likes to run a high bias current in his amp designs (which makes the heatsinks run warm/hot). All those ventilation slots in the thick top panel of the A51,A21,JC1 surely adds to the cost. The reason for justifying that expenditure is because the innards should be kept reasonably cool. This is also why the manual stipulates no less than 6" clearance on top. I'm not so sure those capacitors like it hot - they were selected because they sound good, according to Bob Crump who chose the parts and auditioned the amp.

Personally, I like my amps to last 20 years. I think the JC1s will do this if treated right...

Peter

[mitch57]

Do you think it will run hotter then my Rotel 1095? If it gets to hot I might just remove the front door.

[NMyTree]

I'm sure he intended that he likes to run a high bias current in his amp designs (which makes the heatsinks run warm/hot). All those ventilation slots in the thick top panel of the A51,A21,JC1 surely adds to the cost. The reason for justifying that expenditure is because the innards should be kept reasonably cool. This is also why the manual stipulates no less than 6" clearance on top. I'm not so sure those capacitors like it hot - they were selected because they sound good, according to Bob Crump who chose the parts and auditioned the amp.

Personally, I like my amps to last 20 years. I think the JC1s will do this if treated right...

Peter

I didn't mean mitch57 shouldn't concern himself with proper ventilation.

I'm sure you're right, I'm sure those capacitors wouldn't deal well with being constantly hot. I just meant that the design runs hot, thus all the heat fins and vent slots. So proper ventilation should be a priority.

[netarc]

fyi, some innovative cooling solutions can be found at http://www.activethermal.com/

[Chris D]

Mitch, take a look at our Parasound picture thread here in the Club for some ideas. I rackmount my Parasound equipment with Parasound-designed vents inbetween the components for cooling.

As far as stuff at your dealer, remember that your dealer is going to be playing things LOUD and with as much power as he can put into it to entice buyers. So like Peter alluded to, I wouldn't worry about JC1's being that hot in your system, much less the A51. I have the A51 and A21.

[mitch57]

Chris,

Is your A51 just slightly warm to the touch under normal volumes?

The JC1's that I saw in the dealer weren't even playing. They were turned on but hadn't been playing anything for over 10 minutes. They were still hotter then hell.

Anyway, I hope to find out this weekend when I audition one for a week.

[Peter Nielsen]

Chris,

Is your A51 just slightly warm to the touch under normal volumes?

The JC1's that I saw in the dealer weren't even playing. They were turned on but hadn't been playing anything for over 10 minutes. They were still hotter then hell.

Anyway, I hope to find out this weekend when I audition one for a week.

Mitch,

Maybe this will help to put things in proportion (the watts I'm referring to are of course "class A watts" not the actual idling power):

The JC1 idles with 6.25 watts/heatsink in high bias (2.5 watts in low bias).
The A51 idles with 2 watts/heatsink

So, yes, the A51 does NOT run hot. It is only warm to the touch.

Tell your dealer to switch the JC1s to LOW bias. Then go back in a few hours and feel the difference in temperature :W

Peter

[Chris D]

I agree with Peter, Mitch. I wouldn't use any qualifiers like "slightly" or "very". I'd just say that my A51 runs warm to the touch normally. Not hot. Not really noticeable in the temperature unless you touch it. Then warm.

[mitch57]

Thanks guys. I've been concerned that I might have an overheating problem with the amp in my rack. But from what you describe I should be fine. I'm starting to get excited about my audition this weekend.

Chris,

Where did you buy your Halo gear at? I see you live in Puyallup, WA. I'm north of you up here in Bow, WA and will be picking up my demo amp from Speaker Lab in Seattle.

[Chris D]

Hey, cool. Through different circumstances, I bought my equipment direct from Parasound. When Good Guys had Parasound in their lineup, you could do it there. I'm not familiar with Speaker Lab, but I've heard the name. Maybe I should go check it out sometime.

[nicholtl]

Good Guys is CRAP now. I stopped in there the other day, and they've basically turned into a CompUSA with a side helping of Best Buy. It's really, really horrible now. So sad. I can't believe CompUSA did what they did with what was once a reputable high-end store for the masses.

[Peter Nielsen]

CompUSA with a side helping of Best Buy.

I never knew Good Guys, but I know how horrible Best Buy is!

I once used to by my DVDs at the local Best Buy. Once, I happened to get a DVD with an odd-ball manufacturing error. The transparent plastic of the case had a defect (it was warped in a weird way), so when I removed the anti-theft stickers, it tore the artwork over a 2x1/2" area. The idiots at Best Buy did not let me exchange the DVD since they only allow exchanges if the DISC is bad :roll:

Since then, I have bought more than 500 DVDs via mail order. Never even once I have seen that manufacturing flaw again... Talk about lost business for Best Buy... :B

(Oh, after taking that crap, I mailed the damaged DVD to Best Buy's national center, which promptly sent me a gift card for $20, so obviously they did not approve of the local Best Buy's practices either...)

Peter