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Old 23rd February 2007, 08:33 AM   #1
Rodo is offline Rodo  Argentina
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Question STKs / TDAs /STAs - Heat - Help me!

Hi. Im new in DIY.
I apologize because my English.
I made a lot of amplifiers with STKs (Class AB). For instance I used STK401-120 with very good results. Problem I have with all ICs of this kind is the very large heatsinks they need especially over 50W RMS. So, anybody tested any chip or chipset that uses small heatsinks (or none) with similar specifications than STK?
Obviously Class D amplifiers could be a solution. But is there another one? In case not I will begin with class D technology but it seams to be not easy.
All I need is very lo THD+N, >=80 W RMS@8ohms x 2 (or 2 x mono) and full bandwidth. Also 4/6/8 ohms load options would be useful.
Thanks in advance, Rodolfo
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Old 23rd February 2007, 01:42 PM   #2
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Default Re: STKs / TDAs /STAs - Heat - Help me!

Quote:
Originally posted by Rodo
I made a lot of amplifiers with STKs (Class AB). For instance I used STK401-120 with very good results. Problem I have with all ICs of this kind is the very large heatsinks they need especially over 50W RMS.
What's wrong with large heatsinks? Is space a consideration? Consider using active cooling (eg. fans). Most chip-amp builders use much larger heatsinks than necessary anyway. STK's, as used in TV's (for both audio and video-convergence amps), are often run very hot indeed--enough to fry eggs on. Most models have build-in thermal protection, so if the chip doesn't shut down on its own then you can be pretty sure it isn't overheating.
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Old 23rd February 2007, 03:50 PM   #3
Rodo is offline Rodo  Argentina
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Hi male.
Thats right. STKs work very well with heatsinks. I designed heatsink to work up to 90C AT. I had no problem with about 70C.
Amplifiers are enclosed in cabinets that contain other pieces that add heat. Coolers are ok but requires maintain. Also have in mind that an amplifier with 50% efficiency to obtain 100W "burns" other 100W from supply.
Thanks, Rodolfo
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Old 23rd February 2007, 05:20 PM   #4
male is offline male  United States
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Quote:
Originally posted by Rodo
Hi male.
Thats right. STKs work very well with heatsinks. I designed heatsink to work up to 90C AT. I had no problem with about 70C.
Amplifiers are enclosed in cabinets that contain other pieces that add heat. Coolers are ok but requires maintain. Also have in mind that an amplifier with 50% efficiency to obtain 100W "burns" other 100W from supply.
Thanks, Rodolfo
My point is merely that STK's are routinely run at >100 degrees C continuously for years on end without problems--and how often does one run a Hi-Fi for more than few hours anyway? If ambient temperature is a problem then the STK heatsinks should definitely be external to the chassis--it only takes a few minutes to cut out an opening in a steel chassis with a nibber. I'd make sure that overheating is really a problem before I'd start worrying about it. Have you checked for oscillations?

As to an 80W amp with no heatsink: that technology doesn't exist. Even a class-D amp is going to require cooling, although often the some part of the chassis serves this purpose. Designing and building a class-D amp requires a significant investment in time--much easier to buy pre-built boards/modules.

Your point about class A/B efficiency is true across the board, and many chips have lower max temp. ratings than the STK series; that heat has to go somewhere. You could always go discrete--but then you'd lose those handy protection features.
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Old 23rd February 2007, 05:28 PM   #5
Rodo is offline Rodo  Argentina
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As you stated, STKs works with very hi temps. and for hi-fi users may be best option.
I found some Class-D solutions from ST, Sanyo, National, etc. but I cant evaluate all chips in market. If you have some time, please take a look to another post I made in Class-D forum. There youll find a resume that I found:
Class D, Z, KE, T - help me!!!!!
Thank, Rodolfo
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