The Objective2 (O2) Headphone Amp DIY Project

[RocketScientist]

Originally Posted by Yangoran

Nice heatsinking job with the zalmans - is it really worth the trouble though to heatsink the opamps?

For operation on AC power into challenging headphones (HiFiMan planars, etc.) the heatsinks might help the op amps perform a bit better. As long as you're using real headphones, real music (not sinewaves), and the ambient temps are reasonable, I don't think the op amps are in danger of failing without heatsinks. But the performance does degrade slightly as they approach their thermal limits.

For operation on battery, or with more typical headphones, I don't think heatsinks are necessary unless perhaps you plan to use your O2 out in the sun in hot weather.

As a rule of thumb, if you can stand to keep your finger on them for several seconds they're not too hot.

[2000impreza]

I did a bit of testing prior to sticking the heatsinks on. The test involved running 60 Hz sine waves for a couple minutes through the amp. The highest temperature I managed to get the output opamps is 47C without the heatsinks. With the heatsinks, the temperature reached 42C. The datasheet lists 85C max operating temprature so the 47C is still well within the operating range. In severe conditions, the heatsinks may help keep the opamp temperatures down.

The story behind the heatsinks is I originally got the idea from O2 threads on diyaudio and stumbled on the heatsinks at a local computer parts store. I got a pack of 8 for a few bucks on sale and thought I would try to fit them out with my latest O2 build.

RocketScientist - Thanks for your contributions. Love reading your blog articles.

[lorriman]

Originally Posted by 2000impreza

[COLOR=black][FONT=Verdana]I did a bit of testing prior to sticking the heatsinks on. The test involved running 60 Hz sine waves for a couple minutes through the amp. The highest temperature I managed to get the output opamps is 47C without the heatsinks. With the heatsinks, the temperature reached 42C. The datasheet lists 85C max operating temprature.....

What headphone is that? For planars it may be more of an issue.

[2000impreza]

Originally Posted by lorriman

What headphone is that? For planars it may be more of an issue.

It was done using 47ohm dummy load resistors. I didn’t want to run test sine waves through a headphone at full volume. Under lower impedance, higher current demanding load and less favorable environmental conditions it is possible to surpass the temperatures I reached in my test. Ie. Hifiman HE-5 at loud volumes on high gain with amp in a hot room or directly in the sunlight.

[Yangoran]

Originally Posted by 2000impreza

I did a bit of testing prior to sticking the heatsinks on. The test involved running 60 Hz sine waves for a couple minutes through the amp. The highest temperature I managed to get the output opamps is 47C without the heatsinks. With the heatsinks, the temperature reached 42C. The datasheet lists 85C max operating temprature so the 47C is still well within the operating range. In severe conditions, the heatsinks may help keep the opamp temperatures down.

Did you do testing with the amp outside of the enclosure though? I imagine that things would get quite a bit hotter when it is inside.

[2000impreza]

Originally Posted by Yangoran

Did you do testing with the amp outside of the enclosure though? I imagine that things would get quite a bit hotter when it is inside.

Good point. Testing was completed with amp board outside of the case. If I remember, I'll re-test the output op amp temperatures in the case for my next build and post the results. Honestly, even in worst case scenario I would expect the temperatures still well within the safe operating range (-40~+85C) based on NJM 4556A datasheet.

Anyone else tested output op-amp temperatures with or without heat sinks?

[greenalien]

If anyone is interested, I have a few O2 PCBs available for immediate shipping - see O2 Headphone Amp - PCBs from stock, worldwide
for details.

[BlueRob]

Originally Posted by 2000impreza

Good point. Testing was completed with amp board outside of the case. If I remember, I'll re-test the output op amp temperatures in the case for my next build and post the results. Honestly, even in worst case scenario I would expect the temperatures still well within the safe operating range (-40~+85C) based on NJM 4556A datasheet.

Anyone else tested output op-amp temperatures with or without heat sinks?

No offense mate but I think you worry to much....IC temps are not one of the things in life to worry about IMO. Plug the O2 and enjoy music

[2000impreza]

Originally Posted by BlueRob

No offense mate but I think you worry to much....IC temps are not one of the things in life to worry about IMO. Plug the O2 and enjoy music

No offence taken. You are probably right. I have way too much fun putting together DIY headphone amps.

[Yangoran]

Originally Posted by BlueRob

No offense mate but I think you worry to much....IC temps are not one of the things in life to worry about IMO. Plug the O2 and enjoy music

Yea I imagine the O2 will sound good regardless of whether or not you spend time heatsinking your opamp ICs but I am rather curious as to whether or not there is a measurable difference when driving challenging loads.