[tangent]

Quote:

How would the sound improve just by raising the rail voltage if I am already within the chip's parameters?

If the chip is clipping or near to it, raising the supply voltage will remove this source of distortion. Also, some chips just sound a bit better as you raise the supply voltage, no doubt due to internal design issues. It's not my impression that the OPA132 family is one of those, though. The 134 datasheet says "most behavior remains unchanged throughout the full operating voltage range".

It's not hard to try it and decide for yourself, though. Don't modify your current amp, just lash two 9V batteries in series to your existing battery clip.

One thing you might try: next time you've run down a battery, measure its voltage. If it's near 5V, you're getting the most out of it. (If it's an alkaline, that is.) If it's well above this, 2x9V in series will let you get more out of your batteries because each one will be drawn down more completely. If you are getting the most out of your batteries, instead consider 2x9V in parallel for lower impedance and more mAh.

Quote:

would the opa2604 just drop in to the socket, with no other changes?

Maybe. It depends on the layout of your circuit. It may work fine, or it may oscillate.

Quote:

what would be a good selection of dual opamps to get for trying different sounds?

http://tangentsoft.net/audio/opamps.html

Don't ignore the possibility of taking two single-channel chips and putting them on an adapter.

 

[fureshi]

Thanks for all of the suggestion guys! I went ahead an ordered the 2227 and the AD823. I'll be trying both of them in my CMoy.

Donovan, what do you mean by buffering? Sorry, I'm a newbie so any extra info you can give me would be great.

 

[Ghostie]

The AD823 is okay buffered, but it sounds a little thin and shrill with the Cmoy.

 

[tangent]

Quote:

what do you mean by buffering?

If an op-amp is a voltage amplifier, a buffer is a current amplifier. The AD823 will only put out about 16mA, but your average buffer will put out 100mA or more. This helps your headphones sound better, partly because it relieves the op-amp of having to drive the load directly, and also because buffers are made more for the purpose of driving difficult loads.

A buffer can either be a single chip, or it can be a circuit made of discrete components.

Common single-chip buffers used for audio are the Elantec EL200x series (discontinued), the Burr-Brown BUF634, and the Intersil HA-5002. You can also use some high-current op-amps as buffers, but that's often sonically compromised relative to using a dedicated buffer.

The Szekeres headphone amplifier described in the Headwize library is basically a buffer made of discrete components. You may also hear talk about Jung diamond buffers, simple emitter followers, and other things. There are many, many ways to make discrete buffers.

 

[averydonovan]

Quote:

Originally posted by fureshi Donovan, what do you mean by buffering? Sorry, I'm a newbie so any extra info you can give me would be great.

Tangent gave an excellent explanation on this. You would put the buffer on the output on the opamp, so it would go opamp-->buffer-->headphones instead of just opamp-->headphones. Buffering also makes opamps behave a little better since buffers act as a high-impedence load to the opamp, which opamps seem to like. So you get both more current to drive your headphones and an overall better sound.

This might be a bit much for your first project, though. I would just stick the OPA2227 in your CMOY, and sit back and enjoy your new creation

 

[fureshi]

Well, I'll see how it goes with both op-amps. Since it's my first amp, I'll keep it simple and run a single battery. Then I'll consider two batteries in either series or parallel, depending on the condition of the battery. As for the buffer, it's something that i'll consider for my next project. Thanks for all of the great information!

Btw, I've also been reading the Op-Amps for Everyone...pretty dry stuff...

 

[alley-kat]

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