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Old 6th April 2012, 10:28 AM   #2331
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I do a fair amount of sine wave testing for headphone equalisation purposes.

Following RS's warning on heat (at the end of the 'cautions'), I would like to put some heatsinks on the opamps. I don't know how to go about this. Glue? Any suggestions, model numbers etc? I use Farnell.
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Old 6th April 2012, 11:57 AM   #2332
Turbon is offline Turbon  Sweden
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Be my guest...

"SINE WAVE TESTING: While I’ve abused the O2 in a variety of ways playing real music into assorted worst case loads, and it has survived nicely, it will eventually overheat the output op amps with sustained high power sine wave (or square wave) testing into low impedance loads. This is true of many high power headphone (and loudspeaker) amps that are designed for music not test signals. It’s important to limit full power sine wave testing to a few seconds below about 150 ohms and let the output ICs cool down between tests. You should also run sine wave tests with at 15 VAC or greater wall transformer. This is discussed more in the Circuit Description section."

Take your BMW and press the throttle - don't let it go and count the hours it will survive.

Now please discuss everyday normal use.

Brgds
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Old 6th April 2012, 12:06 PM   #2333
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Quote:
Originally Posted by Turbon View Post
Be my guest...

"SINE WAVE TESTING: While Iíve abused the O2 in a variety of ways playing real music into assorted worst case loads, and it has survived nicely, it will eventually overheat the output op amps with sustained high power sine wave (or square wave) testing into low impedance loads. This is true of many high power headphone (and loudspeaker) amps that are designed for music not test signals. Itís important to limit full power sine wave testing to a few seconds below about 150 ohms and let the output ICs cool down between tests. You should also run sine wave tests with at 15 VAC or greater wall transformer. This is discussed more in the Circuit Description section."

Take your BMW and press the throttle - don't let it go and count the hours it will survive.

Now please discuss everyday normal use.

Brgds
...sure...in the meantime how about some help with heatsinks?
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Old 6th April 2012, 04:08 PM   #2334
QRikard is offline QRikard  Sweden
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Quote:
Originally Posted by lorriman View Post
I do a fair amount of sine wave testing for headphone equalisation purposes.

Following RS's warning on heat (at the end of the 'cautions'), I would like to put some heatsinks on the opamps. I don't know how to go about this. Glue? Any suggestions, model numbers etc? I use Farnell.
I haven' used any of these but i guess that something like this might work since it's not much power to dissipate and not much force on the heat sink in normal use...
Insulators | Farnell Sverige | Results

Otherwise even a thin layer of epoxy or similar could work well as long as it's thin.
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Old 6th April 2012, 04:17 PM   #2335
Turbon is offline Turbon  Sweden
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I haven't experienced any heat from the 3 O2's in use today. They are totally lukewarm at the most... No difference between battery or AC use. I have one that charged unused for 3 weeks. Worked perfectly until I found out that this one needed to be tweaked regarding a few resistors...

This one is good. I use it as a preamp from some of my dacs - just perfect. Yes an old lazy amp in the background - keeps me happy thogh.

Brgds
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Old 6th April 2012, 04:36 PM   #2336
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Quote:
Originally Posted by lorriman View Post
I do a fair amount of sine wave testing for headphone equalisation purposes.

Following RS's warning on heat (at the end of the 'cautions'), I would like to put some heatsinks on the opamps. I don't know how to go about this. Glue? Any suggestions, model numbers etc? I use Farnell.
There is an old recipe to make a thermal adhesive by mixing epoxy with silver thermal paste, I'm not sure of the exact recipe but it shouldn't be hard to find. There are also self-adhesive pads which are commonly sold for xbox and pc RAM heatsinks, although it has been debated that they are worse than nothing.
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Old 6th April 2012, 06:58 PM   #2337
dook13 is offline dook13  United States
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Quote:
Originally Posted by lorriman View Post
I do a fair amount of sine wave testing for headphone equalisation purposes.

Following RS's warning on heat (at the end of the 'cautions'), I would like to put some heatsinks on the opamps. I don't know how to go about this. Glue? Any suggestions, model numbers etc? I use Farnell.
Here's one solution.
Used the silver compound on with success.
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Old 7th April 2012, 12:04 AM   #2338
regal is offline regal  United States
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Wow the O2 really shines with these planar heaphones like the Fostex T50RP, amazing power with low distortion, drives these things with authority.

I still have less distortion in the 1-5mW range for low volume listening with headphones like Grados using an tube SET-OPT, but with planars where you need more power the O2 just is amazing. I prefer the lower bandwidth design philosophy (vs the wire's) as the sound is cleaner and less likely to pick up rfi and junk from the mains and computer. The O2 also has a very innovative protection scheme (no relays). I no longer check dc offset ever time I use it.

JMHO:

High effeciency single milliwatt type headphones (grados) I still pick an good SET (the 2H is below -80dB but the cost to build one right is very high and fustrating.)

For med to high current low-mid impedance phones the O2 is king (this is the brunt of the market), and it does do a fine job with Grados.

For antique high impedance phones that need more than 7Vrms, there is still a hole for amplification choices (still fiddling with an SE-SE x2 balance wire, attenuation and extreme band width is an issue for my setup)
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Old 7th April 2012, 04:38 PM   #2339
nezbleu is offline nezbleu  Canada
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Quote:
Originally Posted by lorriman View Post
I would like to put some heatsinks on the opamps.
You can get clip-on heatsinks for DIP packages, like these: https://www.aavidthermalloy.com/prod.../580100b00000g

I think you might need to bend the fins to be more vertical for clearance. I have never used them, but I assume a tiny dab of thermal compound would also be in order.
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Old 8th April 2012, 07:17 AM   #2340
BlueRob is offline BlueRob  Mexico
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Quote:
Originally Posted by QRikard View Post
I haven' used any of these but i guess that something like this might work since it's not much power to dissipate and not much force on the heat sink in normal use...
Insulators | Farnell Sverige | Results

Otherwise even a thin layer of epoxy or similar could work well as long as it's thin.
Quote:
Originally Posted by dook13 View Post
Here's one solution.
Used the silver compound on with success.
Nop epoxy is not the way to go IMO....it is NOT a conductor.
Artic silver is the way to go
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