A new run of these boards is now available! Please see the following thread for details:
http://www.diyaudio.com/forums/soli...ble-here-bal-bal-se-se-lpuhp.html#post3516741
There is a Wiki here which contains all the project information, documentation and details for all "The Wire" projects:
The Wire - All Boards and Kits Explained Here!
Hi Guys,
I just finished building my latest headphone amplifier project, and this one is definitely worth sharing with the community. After a few prototypes, I went ahead and had some PCB's made, and there are plenty extra available if people are interested.
I basically wanted a headphone amplifier that was as close as could be to a wire with current gain. I didn't want it to impart anything at all to the source signal. That led me to the following design criteria:
- Perfectly flat FR from DC to over 100kHz
- No phase shift from 0-100kHz
- No capacitors (except for PSU)
- Extremely low harmonic distortion
- Extremely low IM distortion
- Extremely low noise floor
- Ability to drive down to 4 ohms with no load dependence
- Enough voltage swing to drive any reasonable headphone set.
- Excellent input CMRR
- Simple circuitry using the best parts available.
I needed a balanced input, and wanted to use a standard 1/4" jack for the output.
The resulting amplifier is basically an instrumentation amp using three LME49990 op-amps and an LME 49600 buffer nested into the last stage. These parts represent the absolute best you can get for this sort of application. I used all 0.1% Susumu thin film resistors, and all X7R ceramic bypass capacitors placed directly on the supply pins. Bulk caps are all solid polymer for the absolute lowest ESR and best HF performance. Layout was optimized for short signal length, low noise and low crosstalk.
The circuit provides differential input, or the option to ground one phase and drive the circuit with an SE input. Gain is set to 1, but can easily be changed to pretty much anything with just two resistors It runs on +/-5VDC up to +/- 15VDC and has enough drive to run anything you can throw at it.
As for sound, having a DC coupled amplifier makes for some of the most stunning bass I have ever heard. I'm driving a pair of Denon AH-D2000 headphones, and there's a world of difference between this amplifier and every other source I have ever tried when it comes to performance below 100Hz. It has incredible impact, depth and cleanliness. In the midrange and top end, it passes on the characteristics of the source like nothing I have ever heard. I've driven it with an Aikido linestage, a BZLS, straight from a DAC and a multitude of other devices, and all you hear is the device driving it. I now use this setup as my primary means of evaluating all preamps and sources since nothing else I have ever used even comes close to exposing the true nature of the sources like this circuit does. It's honestly like it's not even there... hence the name.
I've attached some pictures of the finished product below, and I'll follow up with some measurements done on an Audio Precision. Schematic to follow also.
Cheers,
Owen
http://www.diyaudio.com/forums/soli...ble-here-bal-bal-se-se-lpuhp.html#post3516741
There is a Wiki here which contains all the project information, documentation and details for all "The Wire" projects:
The Wire - All Boards and Kits Explained Here!
Hi Guys,
I just finished building my latest headphone amplifier project, and this one is definitely worth sharing with the community. After a few prototypes, I went ahead and had some PCB's made, and there are plenty extra available if people are interested.
I basically wanted a headphone amplifier that was as close as could be to a wire with current gain. I didn't want it to impart anything at all to the source signal. That led me to the following design criteria:
- Perfectly flat FR from DC to over 100kHz
- No phase shift from 0-100kHz
- No capacitors (except for PSU)
- Extremely low harmonic distortion
- Extremely low IM distortion
- Extremely low noise floor
- Ability to drive down to 4 ohms with no load dependence
- Enough voltage swing to drive any reasonable headphone set.
- Excellent input CMRR
- Simple circuitry using the best parts available.
I needed a balanced input, and wanted to use a standard 1/4" jack for the output.
The resulting amplifier is basically an instrumentation amp using three LME49990 op-amps and an LME 49600 buffer nested into the last stage. These parts represent the absolute best you can get for this sort of application. I used all 0.1% Susumu thin film resistors, and all X7R ceramic bypass capacitors placed directly on the supply pins. Bulk caps are all solid polymer for the absolute lowest ESR and best HF performance. Layout was optimized for short signal length, low noise and low crosstalk.
The circuit provides differential input, or the option to ground one phase and drive the circuit with an SE input. Gain is set to 1, but can easily be changed to pretty much anything with just two resistors It runs on +/-5VDC up to +/- 15VDC and has enough drive to run anything you can throw at it.
As for sound, having a DC coupled amplifier makes for some of the most stunning bass I have ever heard. I'm driving a pair of Denon AH-D2000 headphones, and there's a world of difference between this amplifier and every other source I have ever tried when it comes to performance below 100Hz. It has incredible impact, depth and cleanliness. In the midrange and top end, it passes on the characteristics of the source like nothing I have ever heard. I've driven it with an Aikido linestage, a BZLS, straight from a DAC and a multitude of other devices, and all you hear is the device driving it. I now use this setup as my primary means of evaluating all preamps and sources since nothing else I have ever used even comes close to exposing the true nature of the sources like this circuit does. It's honestly like it's not even there... hence the name.
I've attached some pictures of the finished product below, and I'll follow up with some measurements done on an Audio Precision. Schematic to follow also.
Cheers,
Owen
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