Balder, OPA2134+BUF634 Headphone Amplifier

[Neutrality]

Simple to build and great performance.

Using OPA2134 and BUF634, could have used OPA134 but OPA2134 made it simpler to layout and the extra cost is negligible.

Double sided board with solid groundplane on the bottom layer, tracks on top layer. The connectors, BUF634 and heatsinks are TH, everything else is SMD.

Smallest components are 0805 size.

Board size is 90mm x 50mm.

[mlloyd1]

just a tip - not always a good idea to leave unused inputs unterminated on parts that share power rails ...

mlloyd1

[Neutrality]

Originally Posted by mlloyd1

just a tip - not always a good idea to leave unused inputs unterminated on parts that share power rails ...

mlloyd1

You're right, I'll fix that asap.

[Neutrality]

Unused input terminated.

[Smiley 09]

Hello,

@ Neutrality,

My I propose to use full potential of this intend circuit and go also a Balanced (XLR) version, full use of OPA2134 & just add two more BUF634 chips, and You'll have a full balanced HeadhPh. Amp with great usability and top sound, directly from eg. a balanced I/V conv. stage which can be also mounted in an enclosure of the xx player or inside eg. a Sabre DAC encl.and use its dig. volume control.
This would be top sound from intend circuit - balanced all the way, & sound would be a whole range better than SE.
Maybe just for tough?

Cheers

[Neutrality]

Originally Posted by Smiley 09

Hello,

@ Neutrality,

My I propose to use full potential of this intend circuit and go also a Balanced (XLR) version, full use of OPA2134 & just add two more BUF634 chips, and You'll have a full balanced HeadhPh. Amp with great usability and top sound, directly from eg. a balanced I/V conv. stage which can be also mounted in an enclosure of the xx player or inside eg. a Sabre DAC encl.and use its dig. volume control.
This would be top sound from intend circuit - balanced all the way, & sound would be a whole range better than SE.
Maybe just for tough?

Cheers

Hi.

Well, I am not really into the whole balanced drive thing, I am more than happy with single ended. So basically it comes down to the fact that I could do a balanced version, but since I do not see a need for it, it will stay single ended.
Sorry.

[theAnonymous1]

You could also use the second op-amps for DC servos. Just take a look at the LME49600 datasheet for an example.

[Neutrality]

Originally Posted by theAnonymous1

You could also use the second op-amps for DC servos. Just take a look at the LME49600 datasheet for an example.

I know about DC servos and have used them before in my discrete Class A headphone amplifiers.

In this application a DC Servo is not really needed.

[theAnonymous1]

Originally Posted by Neutrality

In this application a DC Servo is not really needed.

I just remembered that it doesn't even get rid of all the output offset anyway. It only seems to null any input offset, there is still device offset present on the outputs.

[Neutrality]

Originally Posted by theAnonymous1

I just remembered that it doesn't even get rid of all the output offset anyway. It only seems to null any input offset, there is still device offset present on the outputs.

Well, the output offset in a OPA2134+BUF634 headphone amplifier is the offset of the OPA2134, which is only a few mV worst case.

But in cases where you have a source with a lot of offset, a DC servo could be a good idea, since that offset would otherwise be amplified by the gain of the OPA2134+BUF634 and appear at the output.

So I am looking into adding a DC servo.

Resistors and capacitors for the DC servo will be SMD and mounted on the bottom layer.