My LM5532 Headphone Amplifier project

[Kravchenko_Audio]

Any updates?

Looks like an interesting project.

 

[CharlieLaub]

I haven't done anything new with this project. I kind of put it away while I moved and I am still trying to get set up in my new place for hobby type stuff...

The board works well for a headphone amplifier in its current form. If I had to change anything I would like to make it easier to heatsink the regulators. There are a couple of ways to do it now, but none of them are super convenient. And it would be nice if I could find an inexpensive but nice looking case for the whole thing...

I was musing about adapting the circuit for a power amp. If I did that I would probably move the 2-sided 5532 area, which is nice and compact, onto a "card" and have the PS and connections for several cards on another board. The cards could then be built and added as needed, and they could be stacked up and air blown through for additional cooling if that was desired.

 

[Fast Eddie D]

I was musing about adapting the circuit for a power amp. If I did that I would probably move the 2-sided 5532 area, which is nice and compact, onto a "card" and have the PS and connections for several cards on another board. The cards could then be built and added as needed, and they could be stacked up and air blown through for additional cooling if that was desired.

You know that's been done, and it looked just like you described; stacked up.

I don't know how practical this is, but it can work. You won't get a lot of power, but it'll probably sound clean.

I think the original circuit employed a 5534 front end, swamping resistors on the outputs, and nested feedback topology.

 

[Kravchenko_Audio]

Thanks Charlie. I last moved ten years ago, and I'm still trying to find some stuff!

 

[Bugsi]

Necro thread, but would you have a schematic of what you ended up building? (Updated from the earlier schematic posted near the beginning of the thread?)

 

[xrk971]

I like what Charlie Laub did here - several years before I attempted my parallel opamp headphone amp. I did a parallel 8x OPA1622 which can drive a lot more current. It can actually power 8ohm speakers. More info here:
Cheap as Chips OPA1688 Low-THD Muscle Amp

 

[Kuzmenko]

I think, huge amount of low-current generic opamp (5532, 082, etc) in parallel has NO sense. Instead of these, pay attention to high- current opamp, used as line- driver in ADSL modems.

 

[Fast Eddie D]

Noise is a critical consideration for audio circuits, especially a headphone amp. I haven't looked at noise specs on high current op amps, but noise is the number one issue addressed by audio op amps like the 5532.

I've seen on the web where people built headphone amps using small DIP-8 audio amplifiers designed to drive like 400 mW into 8 ohms (I forget the part number) or even LM1875. I don't think these amplifiers provided high fidelity amplification, and I'm pretty sure they also provided pretty poor noise performance too. But they were easy to cobble together I guess.

I would think a parallel 5532 headphone amplifier would provide far superior performance. FWIW my headphone amplifier is a 5532 driving a BUF634 with nested feedback. Absolutely stellar performance and it will even drive 8 ohm speakers. The circuit is quiet enough to use at line level.

 

[xrk971]

Yes, good opamps are very quiet as headphone amps. That’s not to say a well designed discrete circuit can’t be as quiet. But the opamps make it easier. OPA1656 is another wonderful chip to parallel. Jhofland built one with 4x parallel and that was good for 400mA. It sounded super and measured absolutely quiet. Noise floor similar to the one I measured above for OPA1622.

Jhofland’s amp was called the “Muscle Lite”: