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

[meanman1964]

Hi Owen,

Can you delete me from the list change of plans

Best Regards
Patrick

[DualTriode]

Is this kit thing happening any time soon?

[wendell c]

Interested in a pcb set.

[TheShaman]

Owen, what's the transformer you've been using? Looks nice and compact.

[qusp]

Originally Posted by DualTriode

Is this kit thing happening any time soon?

I would think so, but all these dropouts wont be helping matters, I mean sure plenty extras have joined, but after the D1 GB I wouldnt blame opc for wanting numbers to be solid before he makes the buy to cover the parts

[opc]

Hi Guys,

Quite a few people were asking about single ended performance, so I took some measurements the other day to show people what SE performance was like.

These measurements were taken with the - terminal tied to ground at the input of this amp. It was fed with a single ended source, and measured single ended on the output with a 32 ohms load. Drive level was 250mV.

As you can see in the graphs below, you don't give up too much performance going to SE input, so I would fully endorse using the amplifier in this manner. 2nd and 3rd harmonics are up about 10dB, but you still retain a very low noise floor and excellent drive capability. Overall distortion is still extremely low, and so is the noise floor.

[opc]

There were also some questions about FFT plots with a 10k tone, as well as capacitive loads on the output and a THD vs FREQ plot.

I performed several more measurements to capture most of this stuff, and they are all attached below.

The first three plots are all FFTs (balanced input):

1. 10k FFT at 1V into a 32 ohms load
2. 1k FFT at 2V with a 50 ohm load and a 220pF capacitor in parallel.
3. 10k FFT at 325mV with a 50 ohm load and a 220pF capacitor in parallel.

As you can see, there are no HF distortion issues, and even at 10kHz distortion is extremely low. The amplifier is also more or less unaffected by capacitive loads, and I even did a run with a purely capacitive load (only the 220pF) and there were no issues.

Next up we have distortion vs. frequency measurements. These are sweeps from 20Hz to 20kHz with no HF or LF filters in place. I performed these measurements with a variety of different loads and drive levels:

1. 32 ohm, 2VRMS
2. 50 ohm // 220pF, 2VRMS
3. 50 ohm // 220pF, 1VRMS

Hopefully this is enough to cover all the bases. I won't be doing anymore measurements on this, as the graphs presented should be more than enough to give you a good idea of performance, and there's far more information here than you would ever get with a commercial product.

Cheers,
Owen

[opc]

Hi Guys,

I've attached an updated list of those interested after the last few posts.

Looks like there are 31 boards spoken for, and 20 kits. At this point, it's looking like I'm going to drop the kit option all together and just sell the boards by themselves. For the kit to be worthwhile, I needed more or less everyone on board, and that's not the way it turned out.

Dropping the kit would also allow me to start accepting payments immediately, and I could start shipping boards next week. If I were to do the kit, it could be weeks before anything is ready to ship, and I don't want people to lose interest and drop out.

On that note, if you want boards and your name is on the list, feel free to make payment to owen dot columbus at my gmail account. The total is $20 which includes shipping to anywhere.

PLEASE MAKE SURE YOUR ADDRESS IS INCLUDED AND CORRECT IN THE PAYPAL PAYMENT! I will only be looking at the info in the payment when it comes time to ship, so please don't include the wrong address and then send emails with different addresses. I've had this problem in the past, and it was a serious headache. I will only ship to the address included with the payment, no exceptions.

Maybe once everyone has boards, there will be more interest in setting up a GB kit for parts.

Cheers,
Owen

[TheShaman]

Owen I hope you reconsider about offering kits. Could you at least offer the opamps?

[pidesd]

i agree. that would be cool if the opamps could be grouped bought somehow. one could save a lot of money on these and are required for every build (i guess most dont already have them?). and if it could ship with the boards it might be best of both worlds, except for owen who would have to organize something for us again .