Power DAC as HPA?

iWoofer · 发表于 2018-9-27 17:11

本帖最后由 iWoofer 于 2018-9-27 17:16 编辑

One of my first thread on this forum was the idea to use Power DAC i.e. digitally generated PWM + LVC logic as an output stage for headphones. At those time I had just an idea, no any implementation, however, forum's administration did delete my topic as "commercial". Today I want to show you guys practical result of that idea and the schematic diagram as well. So I hope that time administration will not delete my thread ;)

1) Schematic 2) PowerDAC TOY in the 3D printed case 3) max output THD+N 0bdfs 3.5VRMS at he400i load, no any feedback 100% open loop DAC! 4) output THD+N -3bdfs 2.5VRMS 5) frequency response

我在这个论坛上的第一个主题是使用Power DAC，即数字生成的PWM + LVC逻辑作为耳机输出级的想法。那时我只是一个想法，没有任何实施，但是，论坛的管理部门确实将我的主题删除为“商业”。今天我想向大家展示一下这个想法的实际结果和原理图。所以我希望时间管理不会删除我的线程;）

[img=[img]https://photosp.ru/images/2018/09/27/0dbfs_3.5VRMS_at_43ohme873273777f9c0d1.png[img]https://photosp.ru/images/2018/09/27/2018-09-08_10-54-51.pnghttps://photosp.ru/images/2018/09/27/2018-09-08_11-05-55.png[/img][/img]2557,1300]https://photosp.ru/images/2018/09/27/0dbfs_3.5VRMS_at_43ohme873273777f9c0d1.png

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zying · 发表于 2018-9-27 17:31

效果怎么样？

iWoofer · 发表于 2018-9-27 18:22

I'm an engineer who designed that, hence, my opinion about the sound should be biased. I only can say it is a razor-like detailed sound toy. I sent few samples to head-fi and diyaudio enthusiasts, let's wait for their opinion. Actually, it should be interesting to hear "amp" completely without a feedback, because all what you listened before has feedback and in the most cases tonnes of feedback. Even if the feedback was "local" current one as in the emitter follower, it is the feedback. In fact, does exist only one way to get THD+N = .01% at the clipping level without feedback, it is digitally generated PWM and ultrafast power stage with dead time in pico-seconds. For a high current speaker's amps, Ti offered just last year GaAs MOSFETs, and it is very expensive. In case of headphones, we don't need high currents and can successfully use cheap logic IC with an excellent final linearity. It is unreachable in the linear amps world.

我是一名设计的工程师，因此，我对声音的看法应该有偏见。我只能说它是一个类似剃刀的详细声音玩具。我向head-fi和diyaudio爱好者发送了一些样品，让我们等他们的意见。实际上，在没有反馈的情况下完全听到“放大器”应该会很有趣，因为你之前听过的所有内容都有反馈，大多数情况下都有反馈。即使反馈是射频跟随器中的“本地”当前反馈，也是反馈。事实上，确实只存在一种在没有反馈的情况下在削波电平获得THD + N = .01％的方法，它是数字生成的PWM和超快功率级，其死区时间以皮秒为单位。对于高电流扬声器的放大器，Ti仅提供去年的GaAs MOSFET，而且非常昂贵。对于耳机，我们不需要高电流，可以成功使用廉价的逻辑IC，具有出色的最终线性度。它在线性放大器世界中无法实现。

iWoofer · 发表于 2018-9-29 21:45

Today I've got short review from England:
"Here's some more thoughts on the True Digital One.
It's very detailed and also at the same time very clean so there is no fatigue.
The HE-560 is a headphone that clearly separates sounds at different points in the soundstage (I think this is a characteristic of planars) and with your amp this separation and placement was superb.
I sometimes described the sound of my Lyngdorf direct digital as crystalline because it seems pure and clear. You could choose which part of the music to listen to without having to make an effort, and the True Digital One is like this too.
Maybe direct digital amps do have a 'sound'?"

iWoofer · 发表于 2018-10-10 21:02

I've got one more positive feedback from the USA but this is pretty much general words. The much more interesting feedback I've got today in IAG SHZ office rather is the negative one, from Englishman which responsible for Quad sound quality. He said me - your PowerDAC sounds like all those $10000 digital amps, and I don't like it )) So he believes that it has "HiFi" sound which is annoyingly detailed and not smooth, unlike tube-amps. He agrees that probably this is clear and undistorted sound but he prefers to hear music when details aren't disturbing to do that. I think the fully digital approach with no feedback is true as is, and sweet sounding tube-amps are pleasantly distorted. I had experimented a few years ago with such DSP sweet-processing, and actually, a few persons which listened processed sound liked it better than the original sound. I have ideas how to hide away that processing to be under AudioPrecision radars ;)

iWoofer · 发表于 2018-11-26 00:15

iWoofer · 发表于 2019-3-17 09:27

iWoofer · 发表于 2019-3-17 09:28

iWoofer · 发表于 2019-3-17 09:40

莫乃柏 · 发表于 2019-3-19 11:02

本帖最后由莫乃柏于 2019-3-19 11:18 编辑

I think it may not have something like yamaha motorbike "touching you heart " 。 He said not smooth .sorry,my english is poor.

莫乃柏 · 发表于 2019-3-19 11:03

本帖最后由莫乃柏于 2019-3-19 11:20 编辑

about the yamaha piano “感动”

iWoofer · 发表于 2019-3-19 21:26

well, who said that Yamaha is the best? What about Steinway or Baldwin? The same thing about an audio gears. Those guy showed me his headphone amp which he likes, it was Soundkey https://www.cyrusaudio.com/products/soundkey/ Extremely cheap design, BOM about 20RMB(PIC MCU 24/96 + pcm5102 + cheap Ti amp, no capacitors, power not specified because it the same as your smartphone, there nothing about precise audio gear!), yes, it sounds muddy and low detailed but do you believe all want to have that junk for 100 GB pounds? On the my desk now two more projects based on AK4490 and SE9038Q2M, both has THD <.0005% at half of max power, and .0003% at -10db(half of Windows Volume slider), first one has S/N <-120dbA second <-125dbA. What do you think they sound like, closer to my PowerDAC or to the PIC MCU 24/96 + pcm5102 + cheap Ti amp?

Remember, any kind of distortions never sound like more details but rather hazy and smooth.

莫乃柏 · 发表于 2019-3-20 19:30

sorry,I am amateur.I often use smartphone to hear music many years . a PCM58 DAC mod by pioneer PD737 and a panasonic vcd with mash..now,I usually use an Audio Frequency Transformer between the machine and a headphone akg514. I can hear a long time. Without transformer I feel irritable

iWoofer · 发表于 2019-3-21 11:14

I noticed that most people prefer to listen headphones with Harman frequency response i.e. perceptually most linear. If harman curve is implemented, people don't feel sibilants are annoying and not tired. For harman curve you need planar/electrostatic headphone and 5-7 parametric EQs(I have it for he400i, LCD2, if anyone wish to try, let me know). Dynamic headphones have worse initial linearity and compensation will not be easy. Here you can read about harman's curve https://www.innerfidelity.com/co ... 3Kf2SHs6zb2mmP96.97

iWoofer · 发表于 2019-5-4 23:45

PowerDAC V2 loaded to Hifiman HE400i power sweep vs THD+N

iWoofer · 发表于 2019-5-4 23:46

PowerDAC V2 loaded to 32ohm resistors power sweep vs THD+N

iWoofer · 发表于 2019-5-4 23:47

PowerDAC V2 loaded to 16ohm resistors power sweep vs THD+N

iWoofer · 发表于 2019-5-4 23:53

All measurements were performed with PowerDAC V2 powered from standard PC USB port.
S/N -108dbA, Crosstalk -90db. THD+N@1kHz and 6.6kHz the same but low freauency THD+N getting higher:

online image hosting

iWoofer · 发表于 2019-5-4 23:56

the frequency response 3-40000Hz +/-3db, 10-20000Hz +/-.2db

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iWoofer · 发表于 2019-5-5 00:01

PowerDAC V2 powered with 5V 2A charger by "Y" USB power splitter provides 688mW@16ohm 1kHz@THD=1% per each chennel, or 374mW@32ohm.

[DAC] Power DAC as HPA?