"The Wire" Ultra-High Performance Headphone Amplifier - PCB's

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Z

ziga90

Member
Joined 2015
Hey there. I'm also planning to build an headphone amp for my Sennheiser HD598 and this could be it. As checked these pcb's are no longer available.



Does anyone have the shematic and BOM for this AMP and PSU? I just got some info where can I order custom made pcb's here in Slovenia - EU.



Perhaps if the author OPC is still here and is willing to help me out a bit...? :D


Thank you.




Kind regards, Ziga










opc said:
A new run of these boards is now available! Please see the following thread for details:

"The Wire" Official Boards for All Projects Available Here! BAL-BAL, SE-SE, LPUHP - diyAudio

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
Click to expand...
 
nanchangbob

nanchangbob

Member
Joined 2009
Some parts not available!

I've been using this headphone amp daily with my HD600 and HD650's and it does everything I need. But even if you could get the PCB's made, the op amp used LME49990 and the regulators used in the power supply TPS7A3301 are no longer available.

Save yourself some trouble and pick-up the JDS Atom for $100 and you will have almost the same thing, or for a few dollars more buy the Topping L30 with even better spec's. They are so cheap it's almost not worth the trouble of buying all the parts and case and doing it yourself. My two cents!
 
BamboszeK

BamboszeK

Member
Joined 2012
Unfortunately looks like The Wire project went EOL. I built it way back and was very happy with it.
Currently there are some projects with similar performance, architecture and features.
You can take a look at Wynpalmer's amplifier or my composite amplifier.
Low cost, high performance headphone amp using OPA1656 and LMH6321
High performance OPA1602 + TPA6120A2 Composite Headphone Amplifier

JDS Labs Atom or Topping L30 are almost exact equivalents respectively of The Wire or my amplifier in ready made package, available at commercial market without need for DIY. Pretty much same thing without trouble of drilling enclosures (imho worst part of DIY :D). But of course, using self-made gear can be very rewarding.
 
BamboszeK

BamboszeK

Member
Joined 2012
My design already incorporate onboard power supply, but there are jumpers if you want to go with something more fancy.
All measurements were done using onboard PSU.
Composite amplifiers have very high PSRR so PSU shouldn't be big issue.
I decided to use halfwave LM317 / LM337 with some optimization and it is completely adequate as you can see in measurements. In this way we are omitting expensive and huge transformer with dual secondaries.
Now I'm thinking about redesign with SMPS as 16V AC adapters are getting harder and harder to get. SMPS should also have lower idle current if you are into being "green" and energy efficient ;)
If you have other questions I would suggest to move to my thread. I don't want to offtop in this one.
 
Kastor L

Kastor L

Member
Joined 2014
kiriel.se
hi everyone,

I still have some interest in the wire ultra-high performance headphone amplifier. Since it's difficult to buy a PCB these days, is there any other LME49990 equivalent - or similar - amplifier DIY project ? (using LME49990, I'm not going to entertain some EE's which think they know everything then select the cheapest chips & transistors as proof of their 'implementation expertise'). I've already used the LME49990 in other portable amplifiers & tried several products with OPA1611 / 1612 (i.e. LG smartphone (V20 / V30), a popular Xiaomi smartphone, & a Fiio DAP) so I'm confident about their sound & ultra-high performance specs (especially LME49990 although OPA1612 & LME49720 are in the same ballpark of sound - compared to the other average chips)
 
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P

patchoncas

Member
Joined 2013
Kastor L said:
hi everyone,

I still have some interest in the wire ultra-high performance headphone amplifier. Since it's difficult to buy a PCB these days, is there any other LME49990 equivalent - or similar - amplifier DIY project ? (using LME49990, I'm not going to entertain some EE's which think they know everything then select the cheapest chips & transistors as proof of their 'implementation expertise'). I've already used the LME49990 in other portable amplifiers & tried several products with OPA1611 / 1612 (i.e. LG smartphone (V20 / V30), a popular Xiaomi smartphone, & a Fiio DAP) so I'm confident about their sound & ultra-high performance specs (especially LME49990 although OPA1612 & LME49720 are in the same ballpark of sound - compared to the other average chips)
Click to expand...


I have my last unused SE-SE amp board if you want it. PM me for details.
 
M

mdr30

Member
Joined 2013
opc said:
L-Train:

It is not a schematic error... those are definitely the correct values for a unity gain amplifier. R15 and R19 were not originally the correct value and need to be 10k for unity gain.

This breaks down as follows:

R13 and R14 form an L-pad that gives a gain of 0.909

The gain of the amplifier section is 1+(R16/R15) which is 1+(1k/10k) or 1.1

The two together mean you have 0.909*1.1 = ~1

The amp was measured with a gain of 1 using exactly what is show in the schematic, but would be perfectly fine with a higher gain if needed. The noise floor might go up slightly, but what's show in the measurements is just the AP noise floor, so it might not even be a measurable difference if the gain is kept around 2x or 3x.

After using this amp and measuring it, I would actually agree that it's the only one of the amps you could really make a case for having more gain with. Many SE sources don't have much drive, and it might be reasonable to up the gain to 2x in some cases. For example, the AP measurements stop at 7.2VRMS since that's the highest voltage the generators can do in SE mode. This amp is good for roughly 9.2VRMS which might be more attainable with a gain of 4x if you really need all that voltage swing.

For a gain of 2x change R15 and R19 to 833 ohms
For a gain of 3x change R15 and R19 to 435 ohms
For a gain of 4x change R15 and R19 to 295 ohms

Cheers,
Owen
Click to expand...


I have the balanced version and want to increase gain. For gain 3x, does that mean I should change R22, R23 and R26, R27 to 435 ohms?
 
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