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Just how bad is it? Audio mixer with headphone amp.
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BrianHG:
Go for the OPA552, costs a bit less and has 12MHz bandwidth, use DIP package.

Your headphones will consume maximum peaks at 100 ma, according to the datasheet, SOA at 85 degrees, if you use a 32 ohm series resistor for the headphone jack, meaning at a 6.5v output at the op-amp pin, you hit 100ma.  (3.25v at the headphone pin, 2x as much as your normal consumer grade headphone output level)  Your power supply is 15v-6.5v= 8.5v, according to the graph on page 19, figure 35, at 25 degrees, at 100ma, just over 10v is allowed, so, 8.5v is safe.  So, we know the IC will be hotter than this.  At 85 degrees, the SOA at 100ma voltage from supply to output pin is 6v.  So, if you use a +/-12v supply instead of +/-15, you will be in the safe zone.  As well, your entire design will run cooler as well at +/-12v instead of 15.

If you want to keep +/-15v,  use the DDPAK-7, you will be in the SOA up to 125 degrees on the copper of your PCB according to figure 37.
Audioguru:
You can buy the OPA551 in ordinary 8 pins through holes low power opamp package, a tiny surface mount low power package or a small surface mount package that has a metal tab for welding (?) onto a heatsink.
BrianHG:

--- Quote from: Audioguru on March 01, 2018, 04:30:32 pm ---You can buy the OPA551 in ordinary 8 pins through holes low power opamp package, a tiny surface mount low power package or a small surface mount package that has a metal tab for welding (?) onto a heatsink.

--- End quote ---
Everything about Paulca's project is driven to the extreme if you haven't already realized this by now.  Using the DDPAK-7, basic SMD soldered to his PCB with some PCB copper GND plane and vias to the under plane at the heatsink will allow him to max everything out by over 300% in an un-ventilated 50 degree Celsius crammed pre-amp box without any worry of the device going into thermal/current limitation mode.  PCBs with printed copper do some remove heat and it is what is called for in the data sheet.  I've used DPAKs with nothing but the PCB and a rectangle of printed copper with vias to connect the top and bottom with just more copper and they've worked great in apps where I had to dissipate around 4 watts, more than twice of what Paulca needs if he over drives to 300%.

It's what he's going for.

Agreed, if you will only be driving your headphones to 40ma, the 8 pin dip will work fine, especially with a +/-12v supply.
Bassman59:

--- Quote from: paulca on March 01, 2018, 03:24:30 pm ---I do like the idea of the OPA551 for the output stage.  How does it thermally handle the higher current?  Not that I could drive it's full output into headphones without killing them, but even at lower currents will it not get hot?
--- End quote ---

I used the DIP flavor in a studio-monitor controller design. Under load at "reasonable" listening volumes with four different pairs of headphones (Sony 7506, Sennheiser HD-280, Grado SR125e, Pioneer something-or-other) they don't get hot. It uses ±15 V rails but the output voltage swing is barely a third of that.
Bassman59:

--- Quote from: BrianHG on March 01, 2018, 04:25:22 pm ---Go for the OPA552, costs a bit less and has 12MHz bandwidth, use DIP package.
--- End quote ---

Watch it, it requires a minimum closed-loop gain of 5, and I found it to be twitchy. 551 was rock-solid stable. And that open-loop bandwidth gets dropped down by the closed-loop gain requirement, so I think it's a wash. (Kinda like OP27 vs OP37, if you remember them.)
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