Sure 2x100w distorting (overheating?)... |
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alphabetikal
Registered User Joined: 20 May 2010 Location: UK Status: Offline Points: 217 |
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Posted: 03 October 2011 at 3:48pm |
Hi
We have had a hot week across Europe. Here in London I took my system out. It was used for voice and also playing some bass booming reggae. The system is the one ive posted the DIY step on before - a 24V SLA, Sure 2x100 w amp, with crossover, single eminence tweeter and 12" driver (mono). It runs a mini mixer (9V) and a mp3 player. After about 1 hour of playing in 30C temperature I started to notice some distortion in the sound. The bottom end (bass) was breaking up as well as the high freqs. (like in saxaphone etc). The fan was spinning quite fast on the old Sure 2x100W amp. I checked my battery (24v SLA) and that was full and also my mixer and mp3 player - full also. Could it be the amp over heating? Really only at 30C?! Is distortion in the frequency range a characteristic of an overheating class D amp? anyone know? I might consider adding some cooling. A 12v fan or heatsink or something. At the moment the amp is in a top box with the mixer and crossover, not the main cabinet. It can be modified. I did notice that after riding the system down the road back home (on a bike trailer) it seemed to sound okay again! maybe it cooled off... :( Any help? A |
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Saturnus
Old Croc Joined: 13 July 2010 Location: Copenhagen Status: Offline Points: 2025 |
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I would try if I could measure the DC offset on the outputs. Distortion like you describe is typical for that. It may very well be that the sustained high temperature notched the DC offset tuning out of whack, and it needs to be recalibrated.
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Hemisphere
Old Croc Joined: 21 April 2008 Status: Offline Points: 2272 |
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If the heatsink and fan don't have cool air to disperse into or to fan onto the chip then they'll definitely be less effective - also you're driving one channel really hard which I guess is less than optimum for that board.
What's the case you're using made of? The lepai amps use an aluminium case that doubles as a heatsink extension, you could possibly do something similar with the Sure amp. |
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alphabetikal
Registered User Joined: 20 May 2010 Location: UK Status: Offline Points: 217 |
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holy shit that sounds serious.
How can you measure it? How would you re-calibrate it??? I have no idea what DC offset is!! Help!! ahahahahah no seriously.,,, help? ;D a |
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Hemisphere
Old Croc Joined: 21 April 2008 Status: Offline Points: 2272 |
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Saturnus: He said it got better on the bikeride home. If DC was knocked out of wack wouldn't it stay that way?
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Saturnus
Old Croc Joined: 13 July 2010 Location: Copenhagen Status: Offline Points: 2025 |
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No, you can just readjust it. It's just not as easy as it may sound, but not that complicated either. To measure it you just run the amp at high power level for 10-15 minutes in order for components to reach working temperature. Then short inputs to ground and simply measure the voltage across the outputs. Should be less than 50mV, + or - doesn't matter. To adjust it there's some really small pots on the Sure board. Unfortunately they're under the heat sink so you have to take the heat sink off. Adjust the pot, reattach heatsink, measure again. Rinse and repeat until you get lucky. Remember to let it run for a little while measuring as it will jump up and down a bit after you adjust it until it settles. The pots and resistor network used for DC adjust on the Sure amp is horrible. You get huge changes almost without touching the pot so it's very likely that this happens to a lot of people. |
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alphabetikal
Registered User Joined: 20 May 2010 Location: UK Status: Offline Points: 217 |
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me thats shit
i hope it was the heat. if it happens again im going to have to throw this shit in the bin. haha. but seriously, thats rubbish! thanks for explaining tho, very nice of y'all. ill let you know what happens next time its hot.
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alphabetikal
Registered User Joined: 20 May 2010 Location: UK Status: Offline Points: 217 |
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Hemisphere - good idea about the heat sink bro - im going to look into that. ive heard about mods using CPU fans and bigger heat sinks, which ill try too as i have some spare at home
a
Edited by alphabetikal - 03 October 2011 at 4:39pm |
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infrasound
Old Croc Joined: 13 May 2011 Location: Brizzle Status: Offline Points: 2276 |
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I successfully modded several Sure TK2050 with the Zallman ZM-NB47J heatsink.
It stops overheating. Period. Also costs a fiver. Operating temperatures dropped from warm / very hot to cold / slightly warm. You don't need a fan! Just this passive heatsink and access to open air. |
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infrasound
Old Croc Joined: 13 May 2011 Location: Brizzle Status: Offline Points: 2276 |
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Let me know if you do want to remove the heatsink, I'll find some old instructions on how to do it - it's all too easy to fry the chip or twist it off the board.
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alphabetikal
Registered User Joined: 20 May 2010 Location: UK Status: Offline Points: 217 |
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Bro if you could post those instructions to remove the naughty old heat sink that would be great and i can buy a Zalman on amazon for £8 or so
Cheers! a |
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infrasound
Old Croc Joined: 13 May 2011 Location: Brizzle Status: Offline Points: 2276 |
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enjoy! |
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