Best $4 I ever spent on audio

I have a Heed Canamp headphone amplifier. It's gotten good word on the street and is touted to work well with AKG701's, which I also own. Yet I wasn't exactly thrilled. I thought there was a lot of god stuff I was hearing, but frankly, the AKG's sounded better through an old NAD receiver. So I investigated and there lots on the net about modifying the Canamp. I am fortunate that my Canamp is a current production unit which means its single op amp in the input stage (the output is a discrete class A stage) is mounted on a DIP socket. Out goes the TI 5532, which costs under 50 cents and in goes a National Semiconductor 4562 (TI owns National). With shipping the new op amp cost me a touch under $4. WOW- that's the technical term for the results. Firmer, fuller low end, more developed soundstage (701's have a pretty big soundstage- its no bigger now but it's more holistic), and no glare. I can only suggest that if anyone has any gear that uses op amps on a DIP socket, and the manufacturer used an op amp that costs 30 cents in bulk, it's certainly worth the few dollars. I found this little upgrade more satisfying that some costly cable upgrades.

Next- time to try the 4562 in my tuner, which uses two DIP mounted op amps. And it's not a cheap tuner- 3 big ones.

Wonder if anyone else had similar experiences. I suppose this is the solid state equivalent of tube rolling.
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You have to be careful since NE5532 is rated for 44V total supply voltage while LM4562 is rated only 34V. It would not work in my Benchmark DAC1 so I used LME49860 (11 of them). It sounds a little better than NE5532 but it depends. Some people praise sound of NE5532. I tried $7.43 OPA1612, that others swear by, and did not like it at all - too bassy and veiled.

LM4562 design won awards for National (including EDN and Electronic Products magazine product of the year awards) but it was for the fact that in spite of being audio amp it has very low offset voltage and drift. It is also more expensive than NE5532 because of that, but if your amp is not directly coupled or uses DC servo then it doesn't matter. I wouldn't also dismiss integrated output stages. Benchmark DAC1 uses integrated power amp BUF34 in headphone amp and sound is excellent. I have small $89 E07K Fiio DAC/amp with integrated output stage and sound with AKG k271 mkII is very good (WM8740+AD8692+TPA6130A). I've also heard good things about Canamp.
I seem to recall reading that the DAC1 HDR uses 4562's throughout its analog stage!

Whatever the case may be, what works is what works, and in the Canamp, the 4562 is very nice, nicer than the 5532. The use of the 5532 in the Canamp makes sense, thou. When you pop the hood you see that the components are not at all top spec components, and yet it still sounds quite good (excellent straight up with 2 pairs of Grados we have at home). This tells me two things- top spec components are snot the be all and end all- its how things are used, and 2- it's quite easy to make the Canamp someing that would costs at retail a few hundred more for what, under $50 in parts?
Yes, they use 4562 but very likely lowered rail voltage - nobody sane would risk overvoltage failure in mass production (rail voltage in DAC1 is +/-18V) especially when voltage regulators initial tolerance can make it additional 2x0.5V easily.

They often select very good inexpensive components to keep cost down but there is always room to improvement. It's great that it worked so well for you.