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Tom Christiansen Audio HPA-1 Headphone Amp Review

tomchr

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Yeah. Your amp shipped in the large batch I shipped Friday January 31st. Normally, Small Packet US takes 1-2 weeks to arrive. Sometimes 2-3 weeks. It all depends on how busy the customs guys are. Your package will be delivered by the USPS. The fact that some received their amp within a week is pretty amazing. That's faster than normal.

I generally need to do a better job at communicating which shipping options feature tracking, etc., and edit the email templates accordingly. I'll get to it...

Tom
 
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@tomchr Running the Topping D90 into the XLRs inputs and Chord Qutest into RCA Have work to get these two volume matched. Default Topping D90 is running not as hot signal wise as the Cord at 2 Volts. Both are good DACs
 

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Do you have the new one, I am seeing the new model just finally hitting the market now.
It's the RME ADI-2 DAC FS that I have. I bought it in the fall.

Tom
 

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Finally had some time to take more measurements on the HPA-1. Expect a "Performance Graphs" tab to show on the product page within the next few days.

Here's a preview. THD+N vs output voltage, load impedance. The HPA-1 drives a 12 Ω load just fine. The THD does start to creep out of the noise floor at that kind of load, but is still well below audible.
HPA-1 R1.0_ THD+N vs Output Voltage, Load Impedance (1 kHz, 20 kHz BW).png


Tom
 

tomchr

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Yeah. It's basically showing the THD+N floor of the APx525 analyzer from 32 Ω and up.

Tom
 
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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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@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 review communities

SPL Phonitor x headphone amplifier new is a $2500 USD

Single-Ended aka standard headphone jack - note the performance SE as highlighted
  • 6.35 mm TRS connector
  • Pin wiring: Tip = Left, ring = right, sleeve = GND
  • Impedance: 0.18 ohm
  • Attenuation factor: 180 @ 40 ohms
  • Frequency range: 10 Hz to 300 kHz ( -3 dB)
  • Crosstalk at 1 kHz: -90 dB
  • THD & N: 0.00091% (at 0 dBu, 1 kHz, 100 kohms load)
  • Noise (A-weighted): -103 dB
  • Dynamic range: 135.5 dB
Balanced XLR headphone output note performance differnce with XLR
  • Neutrik 4-pin XLR connector
  • Pin wiring: 1 = L (+), 2 = L (-), 3 = R (+), 4 = R (-)
  • Impedance: 0.36 ohms
  • Damping factor: 180 @ 40 ohms
  • Frequency range: 10 Hz to 300 kHz ( -3 dB)
  • Crosstalk at 1 kHz: -90 dB
  • THD & N: 0.00091 % (at 0 dBu, 1 kHz, 100 kohms load)
  • Noise (A-weighted): -98 dBu
  • Dynamic range: 130.5 dB
Max. Output power (at +30 dBu @ 1 kHz)
  • 2 x 1 W at 600 Ohm impedance
  • 2 x 2 W at 300 Ohm impedance
  • 2x 3.7 W at 120 Ohm impedance
  • 2x 2.9 W at 47 Ohm impedance
  • 2x 2.7 W at 32 Ohm impedance
 

tomchr

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This is regarded as the benchmark solid-state amp for number of the headphone review communities

SPL Phonitor x headphone amplifier new is a $2500 USD
So since this is the HPA-1 thread, I'm guessing your point is that $899 is quite a deal for the HPA-1. That would be backed up by the comment by one of the visitors at the Florida Audio Expo last weekend, who stated that even $1299 would be reasonable for the HPA-1.

It also gives me a target for the large-and-in-charge amp with 4-pin XLR output that I've been mumbling about. Thanks. :)

You're welcome to toss me the market comps in PM.

Tom
 

tomchr

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You can extrapolate that from the plot above.

At 16 Ω (between 12 Ω and 20 Ω), I'd expect about 4 V RMS swing. 4^2/16 = 1.0 W.
For 120 Ω you'll be very close to the 9 V swing provided into 300 Ω, so 9^2/120 = 675 mW.

Tom
 
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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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Yeah. Somewhere north of 50 Ω (and certainly above 300 Ω), the amp becomes voltage limited. That's why the curves bunch up near the 9 V RMS limit. So I would expect 250 mW into 300 Ω, 125 mW into 600 Ω, 62.5 mW into 1200 Ω, etc.

Exactly where the transition between voltage limited and current limited is, is honestly mostly of academic interest. I'm sure I can develop a mathematical model for it and plot it for you, but I would rather focus on selling more HPA-1s at the moment. The bottom line is that you'll get 250 mW into 300 Ω at vanishingly low distortion and "around 1-1.5 W" into 12-50 Ω.

Another point I'm making with the graph above is that the amplifier is rock solid even with 12 Ω load.

Tom
 
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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 limited for these headphones and gets plenty loud ; ).

It bit interesting to see how SPL how optimized its power at 120 Ohms for its amp.

Looking at the spec on THX amp seam 16-ohm number more beat on my chest since I have hyper-power Yawn...


It will be between either two charts I think more like the first one.
Screen Shot 2020-02-16 at 4.09.35 PM.png


Screen Shot 2020-02-16 at 3.57.29 PM.png
 
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