Issues with Texas Instruments OPA637-AP Op Amp

Hello all…

My name is Ben Herrmann and I’ve got an issue with the Op Amp that I ordered in Web Sales Order 68340907

Received the Texas Instruments OPA637-AP Op Amp today for use in a highly customizable Douk Audio U3 Mini Headphone Amplifier. I’ve used a variety of different Op Amps in the past with this particular head phone amp, but this Texas Instruments model does not function at all.

I ordered this particular Op Amp for a Headphone Amplifier made by Douk Audio - the U3 Mini which features removable and customizable Op Amp capabilities.

This particular Douk Audio Head Phone Amp has the following specs:

1. Comes with the NE5532 as the stock Op Amp. I’ve used a variety of Op Amps with this unit - all functioned just fine, however, the one I just ordered from you does not. Note: The Douk Head Amp I’m using is advertised as being able to use a variety of 8 prong Op Amps.

2. The Douk Audio U3 Head Amp has a working volage of DC 5V - 20V (I am using a 12 volt power adapter).

Everything was handled with care and was inserted properly in the right direction. I inserted this particular OPA637 into several other headphone amps that I have (all customizable) - yet it did not function either. In each case the voltage requirements were met with ease.

What you do hear is very slight and the audio barely comes through. You literally have to turn up the volume control all the way to maximum to just hear a whimper of sound.

What do I do? What am I missing here? I was really looking forward to this. Anyone…?

Thanks for getting back to me on this…

Ben Herrmann



The NE5532 is a dual-channel op amp, whereas the OPA637AP is a single-channel device. The pin functions on the two are entirely different, so there is no way that a circuit designed for one will work with the other in drop-in fashion. The availability of both types in similar packaging is something that the literature for your product should probably mention (if it doesn’t) as products that have been mis-applied in this way are non-returnable.

When browsing the op amp family for potentially compatible devices, you’ll want to select a value of 2 under the “Number of Circuits” filter.

If you what the drawings from the datasheets to compare, Here is the pinout for the NE5532

And here is the pinout for the OPA637

Thanks for the clarification. I guess I’m “SOL” now, ehhhh? It was recommended to me to get this particular OpAmp. Does this mean I cannot return it for a refund?


Your original email to me read:

Thanks for the clarification on this. I guess I’m “SOL”, ehhhhh? Does this mean I cannot return it for a refund due to it being the wrong type?


Your original email to me read:

That is correct; much like a toothbrush, electronic components loose their sale value once used or opened.

It may or may not still be functional however, so you could hang on to it for some occasion where you might care for a single op amp.