Do gainclones run hot like Class A's? - diyAudio
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Old 21st June 2003, 07:54 AM   #1
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Default Do gainclones run hot like Class A's?

Hi everyone, I was just wondering if Gainclones operate like a class A amp and use a lot of energy and get hot. Or are they more like Class B's and up, that moderate there power usage?


I tried searching, but wasn't sure how that could be worded. I like the simplicity of a Gainclone and that the fact that a amauter like me could easily build one, but didn't know of it would be a room heater like my Monarchy Audio amp.

Thanks,
David
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Old 21st June 2003, 08:01 AM   #2
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GainClones are some of the coolest running amps around.

Most GainCloners don't even use a real heat sink, they just bolt the chip to the chassis or to a piece of bar stock.
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Old 21st June 2003, 08:06 AM   #3
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So is the heat what limits it's output. Like thereotically if you could keep it really cooled you could get like 75watts per channel, like overclocking a CPU.

Also is the stepped attentuator used to bias the amp or is it used a passive preamp?

And one more question...is the DC offset like the noisefloor or something?

I have some basic knowledge (community college classes) of electronics, but I have never actually built something, and I didn't want to start a seperate thread for basic stuff.
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Old 21st June 2003, 09:52 AM   #4
Raka is offline Raka  Europe
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Gainclone heatsinking is very easy, I used a LM3886 to feed a 60H sine wave to my TT (3 or 4 W) and gets hot but nothin evil with a very small sink. You can get out the maximum power with a small sink. What do you have there?
Nothing like a bias meter or whatever, the atenuattor is used as passive pre. You can also use a pot.
DC offset is the DC voltage that appears at the output of the amp, and it's aimed to 0V. If not zeroed, the cone of the speaker will be moved slightly to one side. GC will give you a maximum of 30mV which is negligible. Noise floor is a completely different thing. Is the sound that is not expected (that is : noise ) and is actually where all the sounds are put on. If you live in a noisy enviroment (60dB) you will have to talk louder to be understood. Same thing in a Hifi.
If you follow the scheme you won't have any problem, believe me.
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Old 21st June 2003, 01:42 PM   #5
Nuuk is offline Nuuk  United Kingdom
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Hybrid Fourdoor - you will find most of the information that you seek at Decibel Dungeon including a dedicated page for Gainclone beginners.
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Old 23rd June 2003, 11:54 AM   #6
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Use a small heatsink of attach it to a thin case, and then take the volume to party levels (more than half) with 4 ohm speakers and you'll hear the thermal protection in action.

Guys, it's better to cool it properly.
Or the box is thick, or use some decent heatsinks.
It really gets hot when you abbuse.
No miracles here.
At normal listening levels, though, it won't get hot.
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Old 23rd June 2003, 12:02 PM   #7
fedde is offline fedde  Netherlands
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Exactly. When I play at normal (or soft?) levels sometimes the chips are not even warm at touch. But when I push the amp really hard it can overheat (I have a small heatsink with bad thermic contact). So if you really need the full 50 watts, I would use a somewhat larger heatsink. Class A amps generate much more heat for less output power. And also in rest !!!

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Old 23rd June 2003, 02:12 PM   #8
ronc is offline ronc  United States
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Only reason i use large heat sinks is i had several left over from another project and wanted to use them.Run at high volume for an extended period of time they barely go above ambient temp.
ron
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Old 23rd June 2003, 02:18 PM   #9
JCoffey is offline JCoffey  United States
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Anyone tried CPU cooling techniques to really chill the chips? Something like this would be really cool I think.....
Click the image to open in full size.

http://www.3dcool.com/?module=product&sku=CP101###
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Old 23rd June 2003, 03:04 PM   #10
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i can run mine at full power and the heatsinks are cool. they are about 10cm by 7cm by 1.5cm. i do have +/-15v rails, so i have less power, but at full volume, my ears hurt.
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