OPA627's running warm?

[lespaulplayer]

I just got a pair of OPA627's in the mail today and popped them in my cmoy via a brown dog adapter. When I put my finger to them, they feel pretty warm (but not hot enough to burn by any means). They still sound okay despite this. My previous amp (an OPA2277) didn't get warm at all. Is this anything to worry about? At 18 bucks a piece I'd hate to damage 'em.

Thanks.

 

[Currawong]

As far as I know it's normal. Circuits have to get pretty hot to be damaged, over 100 degrees Celsius.

 

[patton713MW]

I have a CMoy using an OPA2227P, and I have enjoyed the sound. How do you like it with the OPA627s? Is it a noticeable improvement?

I tried once using an AD8066 with the brown dog adapter, and it would clip horribly. My CMoy has Vishay-Dale resistors, 470µF caps, and a TLE2426 rail-splitter.

 

[lespaulplayer]

The OPA627 is the best opamp I have ever heard, by far. It's got a very wide soundstage and is very mellow, the perfect combo imo. I'm sure it's highly variable with different setups however. My cmoy is pretty sub-par, .1uF output caps, and it was my first diy project. I have pair of DT770's, a closed pair of cans with pretty high impedance (250ohm). That being said, if you like the mellow burr-brown sound, you'll love the 627...if you can put up with the hefty price tag

. Digikey's got a whole bunch in stock right now, so I'd get them while you can. I hear they sell pretty fast.

 

[MASantos]

I remember running a pair of opa627 in a cmoy and they didn't have enough current to drive headphones....

These opamps are best in the imput stages!

 

[FallenAngel]

Quote:

Originally Posted by MASantos /img/forum/go_quote.gif I remember running a pair of opa627 in a cmoy and they didn't have enough current to drive headphones.... These opamps are best in the imput stages!

They swing 2.7V away from +/- rails and have 45mA current output, not great (especially in battery amps), but should drive headphones OK, but yeah, seriously MUCH better with a buffer.

 

[DaKi][er]

Lets get some numbers on what the temperature should be. Iq of 7.5mA, +/-9v rails = 135mW, a Dip8 has a typical junction to ambient thermal resistance of 100c/w, gives the temperature you'd expect to be 13.5c degrees above ambient at idle. Of course powering headphones, you have more power loss in the opamp

 

[lespaulplayer]

My power supply is +/- 12v. amb at headwize came up with a figure of 170mW of dissipation, so that's definitely why they're warm. The datasheet says it's rated for up to 125C, so I think I've still got a ways to go before they get damaged.

I'm building a pimeta soon with buffered outputs. That would reduce load on the opamps, right?

 

[patton713MW]

Thanks for all the input. I plan on building a Millett MAX anyways, so my little CMoy will most likely stay as-is. Sounds like the heat won't be a significant problem for you, good luck!

 

[SteveZ]

The best thing to do is throw on some heatsinks. I have a pimeta using 3 opa627s that runs perfectly fine at room temperature. Being a college student though, I was in a dorm room last semester with no air AC, and the ambient temperature went up 15 degrees F. I heard a cracking noise from my amplifier, and took some measurements to find out that the opa627s were running at 150 degrees F. I slapped on some heatsinks I had left over from a thermalright VGA cooler, and the temp went down to 100 degrees F and everything has been fine since. Hopefully I didn't damage the opamps at all...

The heatsinks I used were ram heatsinks, and fit perfectly. I'll post a picture of my installation later if anyone is interested.

 

[lespaulplayer]

I actually did throw a couple copper heatsinks on them which seemed to help. I also took a current measurement and found out they are running perfectly fine with no oscillation. Plus the datasheet says they're good up till 125C, so I'm not too worried anymore.