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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    @tomchr "As seen on the graph, it is only with 12 Ω load that the THD+N of the HPA-1 finally exceeds that of the Audio Precision APx525 audio analyzer." Are you really trying to say "As seen on the graph, it is only with 12 Ω load that the THD+N of the HPA-1 finally exceeds the analysis limit...
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    @kn0ppers it is ok... I am not offended. Sometimes it good to get away from this and work, I spent the afternoon with my son and best friend and his son at Circut fo the Americas for Lone Star Le Mans. Nothing makes me forget all this stuff more than watching him smile from ear to ear...
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    AKM4499 has a number of new changes over the 4497 to better compete with Cirrus logic DAC, but yes it is a 4 channel DAC. https://www.akm.com/content/dam/documents/products/audio/audio-dac/ak4499eq/ak4499eq-en-productbrief.pdf https://www.akm.com/kr/ko/products/audio/audio-dac/ak4499eq/ I...
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    "The main challenge there is that it needs to support USB in a graceful manner. It's unfortunately not as simple as "just use XMOS and be done". The XMOS chips are (pretty kick-ass) microcontrollers. It would be nice if I could use them in a way that would allow them to handle the UI as well as...
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    @kn0ppers it is an expression, It means he is a very good analog engineer. I am an engineer I get it, I build super-computers and high-performance GPU's for my day job. You need to talk to SPL why they want that much headroom in their Opamp. As I said it not just headphone amp I...
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    Topping D90 Balanced USB DAC Review

    APOS is where I picked up my, it is coming from Hong Kong
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    Is Topping D90 USB interface class 2?

    Yes the XMOS XU208 is USB 2.0 Phy and Chipset.( Datasheet on hyperlink) There have been vendors who put USB-C on XMOS design like xDuoo with XDO5 plus, but it is still USB 2.0, now that one needs Special OTG USB-C to USB-C cable to work, you can not use standard USB-C cable with it. It...
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    @kn0ppers it is really +/-60V rail to rail op-amp that yes they using creative marketing on, there are time and place to have more voltage swing for certain solutions. Remember the SPL Phontior x is not just for Headphones but also pre-amp for powered Speaker and amplifiers. This really...
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    I had to extrapolate 120 watts for the Monoprice and Drop THX amps. Need to measured since it could be If you could hit 1.5. -1.6 watts clean it would clean sweep from 32 Ohms to 600 ohms against THX based amps. Honestly, I have the evil 13 Ohm Headphone, your amp shows it is not current...
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    I was thinking it was more linear in behavior post 50 Ohms
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    600 would be close to 125 mW
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    What surprises me on the Monoprice and Drop THX amp is how fast they fall in power aka if you graphed it from 32 ohms to 300 ohms and 600 Ohms. Like a steep negative S-curve, your change is much shallower as Ohm increase
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    Tom have you measured at 16 Ohms and 120 Ohms loads what your power will be
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    Exactly, HPA-1 is a fantastic deal and fantastic sounding amplifier.
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    @tomchr I realized I dumped this the wrong forum, For the earlier Single-end vs XLR discussion, you had with the community, even inexpensive SPL amp has engineering trade-off for XLR support vs Single-ended. This is regarded as the benchmark solid-state amp for number of the headphone...
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    Tom Christiansen Audio HPA-1 Headphone Amp Review

    I have been A/B with SPL Poinitor x with both Topping D90 and Qutest DAC. It holds its own. I which they had little wider number of closer to make easier to read the cart above ; )
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    Topping D90 Balanced USB DAC Review

    The HPA-1 is very nice amp.
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    Topping D90 Balanced USB DAC Review

    I spent the day with it evaluating D90 on the SPL Phonitor x and Tom's TCA HPA-1 with the following headphones. Audeze LCD-4, Rosson Audio RAD-0, and Hifiman Ananda. D90 used XLR inputs on Phonitor x and HPA-1, but did try the RCA on Phonitor x as well. It is a very nice DAC, AKM step...
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