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Tom Christiansen Audio HPA-1 Headphone Amp Review

amirm

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#1
This is a review and detailed measurements of the Tom Christiansen Audio (TCA) HPA-1 headphone amplifier. It was loaned to me by its designer and member @tomchr. The unit I received has production PC board and components but the case is not the final one. The HPA-1 has a final cost of US (?) $899 but there are discounts for preorders and first set of units. I let Tom give that detail. Production is slated for January.

The HPA-1 has a rather elegant, calming front face:

Tom Christansen Audio TCA HPA-1 Audio Review.jpg

While symbols are used there are only two switches for setting gain and input type so not hard to figure out.

The volume control has a very nice feel which I appreciated. The switches have long travel which makes it easy to know if you have or have not pressed them.

The back panel has what you expect:

Tom Christansen Audio TCA HPA-1 Back Panel Connectors Audio Review.jpg

XLR input is mandatory in any premium audio product and that is what I used for my testing.

Inclusion of AC power supply is always appreciated as it nicely declutters your desk/power strip. It also gives the unit additional heft so it doesn't move around on your desk.

In use, the case didn't seem to even rise above room temperature. So heat dissipation is not a concern.

Headphone Amplifier Audio Measurements
As usual, we start with our dashboard view with unity gain (what goes in, is what comes out as far as voltage):
Tom Christansen Audio TCA HPA-1 Audio Measurements.png


Distortion levels are beyond even remotest threshold of hearing at -130 dB. By itself it would set the SINAD to 130 but since there is noise both in my analyzer and HPA-1, it gets set at 119 dB. This puts the HPA-1 right at the top of the chart:
Best Headphone Amplifier Review and Measurement.png


What embarrassment of riches with so many high performance headphone amplifiers!

Dynamic range is excellent at 4 volt output and very good at 50 millivolts (simulating what you need with very sensitive IEMs/headphones):
Tom Christansen Audio TCA HPA-1 Signal to Noise Ratio Audio Measurements.png


Most quiet headphone amplifier tested.png


Frequency response is flat to 40+ kHz as we would expect:
Tom Christansen Audio TCA HPA-1 Frequency Response Audio Measurements.png


Most important measurement for any headphone amplifier is power versus distortion and noise. Here it is into 300 ohm load:
Tom Christansen Audio TCA HPA-1 Power into 300 ohm Audio Measurements.png


Low gain mode reduces noise and works to the threshold of measurement (the analyzer can do better but I don't want to change it and invalidate earlier measurements in this graph). High gain produces 200 milliwatts, doubling my requirement of 100 milliwatts into 300 ohms. It goes beyond Drop/Massdrop THX AAA-789 in unbalanced mode.

Power is still good but more limited into 33 ohm load:
Tom Christansen Audio TCA HPA-1 Power into 33 ohm Audio Measurements.png


Noise and distortion is exceptional just the same as 300 ohm.

Channel balance relative to volume control position was exceptionally good for an analog volume control:
Tom Christansen Audio TCA HPA-1 Cahnnel Balance Audio Measurements.png


Not sure if this is representative of larger production sample or not.

Output impedance was excellent at just 1.1 ohm:
Lowest Impedance Headphone Amplifier.png


Edit: additional tests as requested in the thread.

Multitone:

Tom Christansen Audio TCA HPA-1 Distortion vs frequency Audio Measurements.png


Tom Christansen Audio TCA HPA-1 IMD vs Power Audio Measurements.png



Thermal Stability
I warmed up the unit prior to testing for 10 minutes. Baseline performance did not change. However, I noticed some occasional spikes. I traced this to BNC connectors of my headphone lead to the analyzer! Just sitting there, it would change its impedance enough to cause a spike. We are talking such sensitive measurements that seemingly breathing on the instrumentation the output can change! Anyway, until I sort this out, I am not posting the graph.

Headphone Listening Test
I started my testing with Sennheiser HD-650 headphones. The sound here was wonderful. Plenty of dynamic range, detail, bass, etc. With well recorded content you just want to sit there and keep cranking the volume up. :)

Next I switched to 25 ohm and inefficient Drop Ether CX closed back headphones. There was plenty of power here as well, eliminating my doubt that there may not be. The difference between HPA-1 and something more powerful is that you get scared of pushing the volume to max. Here, I was able to go to max volume but just for a second or two.

Lastly I tested with my Hifiman HE-400i. As with HD-650, the sound was a delight with ample volume, dynamics and detail.

Conclusions
The Tom Christiansen Audio HPA-1 provides exceptional measured performance. It has no weakness subjectively or objectively. It is fully transparent and as such, joins an exclusive club of half a dozen headphone amplifiers that provide such superlative performance. Cost is up there though, second only to Benchmak HPA-4. So you need to judge whether the look & feel together with superb support from Tom is worth the premium or not.

On performance basis, the TCA HPA-1 gets my strong recommendation.

------------
As always, questions, comments, recommendations, etc. are welcome.

Been too busy with testing to get a haircut. Need to go and get it done today before I start to look like a hillbilly. So please donate money to help me maintain my good looks using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

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Veri

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#2
Conclusions
The Tom Christansen Audio HPA-1 provides exceptional measured performance. It has no weakness subjectively or objectively. It is fully transparent and as such, joins an exclusive club of half a dozen headphone amplifiers that provide such superlative performance. Cost is up there though, second only to Benchmak HPA-4. So you need to judge whether the look & feel together with superb support from Tom is worth the premium or not.

On performance basis, the TCA HPA-1 gets my strong recommendation.
Personally I really really dig the aesthetics. Good work @tomchr and thanks for the review/measurement @amirm :)
 

graz_lag

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#5
Thank you so much @amirm for this review!
I was really waiting for it, have been collecting all @tomchr' posts into what will be 'the collection of perfect forum posts' to read and share to my grandchildren in front of the fireplace sooner or later one day ... as his posts represent to me the best balance between technical knowledge, fair commercial marketing psychology, overall education & kindness.
Looking forward to his posts following this review, which happens with the good timing, wanted to complete my collection book of his posts before Xmas!
With the best wishes for your business venture, @tomchr! You definitively deserve it, and much more than it!
 

JJB70

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#6
Splendid performance, this may be expensive but at least it offers first class performance. Next to alternatives like the JDS Atom and latest Schiit Magni this is expensive, but if compared with premium low volume alternatives from Violectric/Lake People, Benchmark, SPL etc it looks very attractive. For those looking for something rather nice and don't mind paying more this looks like a terrific option even if you can get pretty much SOTA performance for a lot less.
 

Azeia

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#8
Better as SMSL SP200 ?
The SP200 has more power from what I can tell, although @tomchr I think initially had measured 250mW into 300 ohm, amir's measurements say 201mW into 300 ohm. The SP200 does 326mW into 300 ohm at high gain (and 200 in low gain).

However, the HPA-1 has better SINAD and lower distortion, so it seems like a tradeoff in terms of whether you want more power or lower THD. Price is also a factor of course. Another thing is I think there may be more variance in channel balance on the SP200, as different units seemed to have different channel balance, whereas HPA-1 is using a top of the line alps blue velvet pot, so should be more consistent.
 
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#10
The SP200 has more power from what I can tell, although @tomchr I think initially had measured 250mW into 300 ohm, amir's measurements say 201mW into 300 ohm. The SP200 does 326mW into 300 ohm at high gain (and 200 in low gain).

However, the HPA-1 has better SINAD and lower distortion, so it seems like a tradeoff in terms of whether you want more power or lower THD. Price is also a factor of course. Another thing is I think there may be more variance in channel balance on the SP200, as different units seemed to have different channel balance, whereas HPA-1 is using a top of the line alps blue velvet pot, so should be more consistent.
According to the price of SP200 it's more convenient deal and lower TND is not a problem, it's difficult to hear..
 

tomchr

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#15
@amirm: Thank you for your review and measurements. I appreciate it.

Just to clarify: The amp Amir reviewed contains the final production version of the electronics. The chassis is the final design of the chassis, but is a preproduction version. The production version of the chassis will differ cosmetically from what you see in Amir's pictures.
The differences are as follows: The production version of the chassis will be anodized after machining, thus, all exposed bits of aluminum will be black. The preproduction version was anodized black before machining, thus, the insides of the holes in the chassis and the counterbores around the RCA plugs are raw aluminum. It's purely a cosmetic difference.

A few notes/comments regarding the measurements:
  • Max output power: The most likely reason for the difference between Amir's measurements and mine is that I measure until the amp clips (i.e. the THD starts shooting up) using 90 points in the sweep. I'm guessing Amir uses the default 31-point sweep in the APx software. In a log sweep, the points near the end of the graph can be quite far apart in output power, which likely explains the difference there.
  • I'm puzzled by the 1.1 Ω output impedance measured here. That's way higher than the 35 mΩ I measured. Is part of the wiring harness used for testing included in that 1.1 Ω by any chance?
  • I'd welcome a 32-tone IMD test as well.
Price: Yeah... All my products are designed and assembled in Canada. The only bits not coming from Canada are the chassis and the electronic parts themselves. All the labour (chassis excluded) is performed in Canada, which is expensive. That said, I find the quality is well worth paying for - especially when it comes to the the circuit board manufacturing and assembly. I also find it quite reasonable to charge for a quality product.
Note that some of the features in the HPA-1 enhance durability and reliability. For example, I use an internal aluminum panel to provide support and strain relief on the headphone jack and volume pot, thereby, ensuring that the plugging/unplugging of headphones and the turning of the volume pot do not strain the solder joints. This enhances the durability and reliability of the amp.
But such a sub panel comes at a price. Custom metal work in low quantities is expensive. It increases the assembly cost too. So the manufacturers of cheaper goods cut corners there. On the $100 amps, you're lucky if the volume pot is even attached to the chassis. So, sure, you only spend $100, but the amp won't last as long.
In any case, I have no plans to join the race to the bottom. I'd rather wait for people to figure out that in many cases you don't get something for nothing.

I was really waiting for it, have been collecting all @tomchr' posts into what will be 'the collection of perfect forum posts' to read and share to my grandchildren in front of the fireplace sooner or later one day ... as his posts represent to me the best balance between technical knowledge, fair commercial marketing psychology, overall education & kindness.
Looking forward to his posts following this review, which happens with the good timing, wanted to complete my collection book of his posts before Xmas!
With the best wishes for your business venture, @tomchr! You definitively deserve it, and much more than it!
Thank you. I appreciate. Also thank you for your feedback on my forum posts. I'm glad to hear you find them to provide a good balance between technical knowledge, marketing, education, and kindness. That brings a smile to my face.

I still have a few HPA-1s on preorder special. You can buy yours here: https://www.tomchr.com/products/hpa-1

Tom
 

amirm

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#17
I'm puzzled by the 1.1 Ω output impedance measured here. That's way higher than the 35 mΩ I measured. Is part of the wiring harness used for testing included in that 1.1 Ω by any chance?
Yes, the best case scenario on my setup is around 0.9 ohm so 1.1 ohm is almost as good as it gets. I have not tried to optimize this for consistency and the fact that it shows what a typical headphone would see.
 

amirm

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#18

tomchr

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#20
No Canadian pricing?
I'll be happy to invoice in Canadian dollars at the current exchange rate if you pay by eTransfer. That saves you the exchange fee and saves me the PayPal fee. Win-win. Just email me if you'd like to order that way.

Tom
 
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