Playing with relatively basic opamp based amps... some questions
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dan1son

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I've been playing around with different setups for a headphone amp based on different designs I've seen online (cmoy, a47) and one my dad threw together (sort of a cmoy with a much better power source and different resistor values) and am just trying to figure a few things out. The first amp I laid down was an ne5532 based amp which sounded quite good on my MS-1's, but I thought I'd play around some more so I added the buf634 chip into the circuit and replaced the 5532 with an opa2132. The sound was different, yet it didn't seem to really add a significant amount of power or anything.

I've been searching around with google and through these forums trying to figure out some stuff and I've learned that I really don't understand the difference in buffering and the a47 layout. They seem to be relatively similar. Yet I've read that the a47 somehow runs the opamps in a parallel.

I suppose my question is what exactly the difference is and how the current increase works in both methods.

I'm trying to figure out what sounds the best with these MS-1's. I have come to the quick conclusion that an amp makes a huge increase in sound... I just want some more advice on what to play around with to see what I like the best.

Thanks everyone this is my first headphone amp.... I've been playing around with electronics a little, but I really don't understand a lot of stuff about how the feedback loops and gain structures work...
 
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Tomo

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Hi,

You have done good amount of studying on your own. You are almost there. ... Keep them in your mind for a minute when I give you an image.

Imagine when you are in your car. Lets say your car is in perfect condition but it is not new. You can put in premium or regular in your car. When you drive with premium, you should notice your engine sound better when you are accelerating; less crankles etc.

You are delivering power to your headphones whether you are using headphone amp or not. What is different is how well the power is delivered represending sounds in music.

Note, however, sound characteristics may depend strongly on your headphones. ... But this will be a story for another day. **

Tomo

**Nope, ye can't go though Conan the Barbarian and Conan the Destroyer in one sitting ...
 
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stereth

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You're right; the A47 is very similar to a simple buffered amp. If you look at the schematics, you can see that both opamps are connected to the output. You can remove the second opamp and have a cmoy. A buffered amp runs the signal in series through opamp and buffer. Also, with a buffered amp, you can have a multiloop configuration.
 
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tangent

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Change just one variable at a time. I.e. put the 5532 in the buffered amp instead of the OPA2132 and compare it against the plain 5532 amp.
 
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dan1son

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Well been playing around a little bit more... still wanting to play with a buffered cmoy type amp, maybe later tonight.

So a basic buffered setup would be the "high performance headphone driver" from the buf634 datasheet. And the simplest multiloop would be something like a pimeta, without the ground circuits, which is the same as a meta42? And a more complex one is the ppa which essentially just adds stacked buffers?

Unless I'm missing something else... Is there another simple multiloop design?

Thanks... These answers seem hard to find or I wouldn't be asking them
 
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tangent

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Quote:

So a basic buffered setup would be the "high performance headphone driver" from the buf634 datasheet.


Right, though I don't agree with shorting the bandwidth pin to V-. At minimum, put 100 ohms between them.

Quote:

And the simplest multiloop would be something like a pimeta, without the ground circuits,


The MINT schematic is nearly the simplest multiloop with virtual ground. Leave out D1 and D2 and you do have the simplest.

Quote:

And a more complex one is the ppa which essentially just adds stacked buffers?


The PPA adds a lot more than that. The input and output sections are isolated from each other, and the channels are fully separated. These features required other changes in turn.
 
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