Tom Christiansen Audio (TCA) - HPA-1 Headphone Amplifier - Official Thread

I was wondering if the community was looking at the new Tom Christian Audio amp. Tom is a boutique builder in Canada.

Audio Precision APx525 Test Report for the TCA HPA-1 Prototype


Parameter Value Conditions
Output Power 1.5 W 20 Ω
Output Power 1.2 W 32 Ω
Output Power 250 mW 300 Ω
Total Harmonic Distortion (THD) < -130 dB 300 Ω, 100 mW, 1 kHz
Total Harmonic Distortion + Noise (THD+N) 0.0003 % (-110 dB) 300 Ω, 100 mW, 1 kHz
Intermodulation Distortion (IMD) - SMPTE < -108 dB 60 Hz + 7 kHz @ 4:1, 300 Ω, 100 mW
Intermodulation Distortion (IMD) - DFD < -112 dB 18+19 kHz @ 1:1, 300 Ω, 100 mW
Intermodulation Distortion (IMD) - MOD < -112 dB 917 Hz + 5.5 kHz @ 1:1, 300 Ω, 1 mW
Multi-Tone Intermodulation Residual <- 140 dBr AP 32-tone, 300 Ω, 100 mW
Gain 0 dB (1x) +12 dB (4x) Selectable by switch
Input Sensitivity 2.8/0.7 V RMS Low/High Gain, 32 Ω, 200 mW
Output Impedance 35 mΩ 1 kHz
Channel Separation 98 dB 1 kHz
Common-Mode Rejection Ratio (CMRR) > 70 dB 1 kHz, typ.
Common-Mode Rejection Ratio (CMRR) > 60 dB 1 kHz, typ.
Dynamic Range (AES17) 130 dB
Signal-to-Noise Ratio 132 dB
Residual Mains Hum & Noise 1.25 µV RMS A-weighted
Mains Voltage Requirements 80–264 V AC 47–440 Hz
Size 140 x 55 x 210 mm (W x H x D)
Weight 850 g
Designed and Manufactured in Canada


I hope to have one soon after it finally comes available.


I have one coming in as well. Tom has been great to interact with.

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Excited they are shipping soon.

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I just walked in the door from the office, and the TCA HPA-1 Amp was waiting for me.

First, the AMP has a solid build; the volume knob is silky smooth as you expect from an Alps RK271 volume pot. It does not use a wall wart, but an onboard power supply that uses a standard IEC power cable.

I had little time this afternoon to listen to it. At low gain, the TCA Amp shows it’s a very low noise floor.

HPA-1 driving the RAD0 brings solid clarity/detail, punch, and speed.

Today’s quick listen: Source: Qobuz -> DAC: Chord Cutest

  • Keb Mo “The Itch.”
  • Fleetwood Mac “Dreams Take 2.”
  • John Lee Hooker It Serves You Right to Suffer, Serves You Right to be Alone ( the Avener Rework)
  • Dusty Springfield " Son of Preacher Man."
  • Kaleo “Way Down We Go.”
  • Bob Dylan “Knockin On Heavens Door.”
  • Foy Vance "Make it Rain
  • Massive Attack, “Angel.”
  • Trentemoller “Chameleon.”
  • Parov Stelar “Jimmy’s Gang.”
  • The Piano Guys “Story of My Life.”
  • Dave Mathews, “Two Step.”
  • Louis Armstrong “Summertime.”
  • Gary Clark Jr “Bright Lights.”
  • Elmore James “Dust My Blues.”
  • Jimmy Hendrix “Hey Joe.”
  • John Lee Hooker “Jesse James.”
  • New Order “Dreams Never End.”
  • Biffy Clyro “Many of Horror.”

But really, it was the Dan Clark Audio Aeon Flow Open that started my search for better AMP/DAC to bring out the best of this headphone. It was this headphone that also leed me to find this forum. Plenty of power to drive them to a reasonable volume at less than noon on Volume Pot at low gain.

  • Wow Kaleo " Way Down We Go" was intimate, rich with detail, claps hit you with a punch. After wearing the Rad-0 you forget how light these cans are. Ben Howards, “Old Pine.” The opening guitar is heavenly leading beautiful harmonized vocals. Then ben vocal right there super intimate. sorry getting back to listening, less thinking.

I will leave you with the Chord Qutest + TCA HPA-1 combo is making me friends with the Aeon Flow again.



@Torq and @Resolve you guys might like this new solid-state amp. It would be great to see what you two think of it.

Tonight I dragged out the trouble children in my headphone line up.

  • Beyerdynamic DT-880 600 Ohm - did not have an issue driving them with the low gain setting, put in high gain and around 1 pm bass kicks you in “Cameleon,” they do not have rumble down my neck of HD-6XX or Focal Elex
  • Dan Clark Audio Aeon Flow Open 13 Ohm - The current monsters are tamed, I just started drifting off listening to the music, good detail, speed. And a lot more. This rig does well with darker headphones. Knocking on Heavens Door by Bob Dylan is like have first or second-row seats.

The Reference

  • HD-6XX With “Cameleon” engage high gain volume pot at noon bass extends to the top of my shoulder, Low gain is about 4 o’clock for the same feel. This combo really brings out the best of this headphone

The pack hunters

  • Focal Elex - sound great on this amp in low gain way too many songs. Cameleon, it starts rumbling hard little past 2 o’clock in low gain, feel at the bottom of the neck. Symbols are fast and tight
  • HIfiman Ananda a lot of great music that plays well with this, I did find a few songs where treble would poke out

The current King of the Pack

  • Rosson Audio RAD-0
    Keb’-Mo’. “Suitcase” is probably one of the best showcases for the headphone on this combo.
    Ben Howard " Old Pine"

Something has me going back to Aeon Flow Open’s with this combo…


It’s an interesting looking piece which, based on Tom’s prior work, I assume will measure and perform very well. I actually toyed with the idea of building his other new offering, the Neurochrome HP-2.

That said, I am unlikely to review the HPA-1 myself.

I have been trying to limit what I review to things that I might actually buy for my own rigs, and while I have made some exceptions there in the last year, and might in the future, those are going to be increasingly rare.

Now, if I come across one at a meet, or someone local picks one up, and I have the opportunity to hear it in appropriate circumstances, I’ll certainly give it a listen and post my thoughts there. But I wouldn’t trouble anyone to send me a unit to review, as I’m just not looking to spend that kind of time with any gear I am not looking at for myself.


Yes, it measures very well. Here is the Audio Precision APx525 Test Report for the TCA HPA-1 Prototype

Forgot to say the Qutest is running at 2Vrms outputs

To me, This would be a great augment to the RME DAC if you want more authority in your music, or you could go with an excellent desktop package with the Qutest/TCA HPA-1 combo and conserve desktop space. I wonder if it would give Hugo 2 a run for its money. You have a solid foundation to drive headphones like Dan Clark Aeon Flow’s, Rosson Audio RAD-0, HIfiman Ayra, HEDDphone. I am sure it would drive an Audeze LCD-4 as well.

I know you tried Geshelli Labs amp, I have 2.5 Pro here now. HPA-1 is a different class of build quality and authority in how projects music. Geshelli Labs feels thinner in its presentation. RAD-0 was playing Kaleo “Way Down We Go.” Shows the HPA-1 is more dynamic; the peaks reach higher. Also, the frequency peaks more focused with less bleed into adjacent frequencies. Transition speed peak ( Dynamic is greater) ability peak and quickly dampen is better

SPL also shows this behavior over Geshelli as expected. The Xduoo XD05 Plus ( my first backpack amp since its battery powered) is another 1 watt into 32 Ohm portable amp in my collection is the Qutest DAC makes a big difference driving it. It does not have the noise floor of HPA-1, but it is now musical at low gain.

@Torq, after trying a few more amps with the Qutest, it makes me appreciate the analog section of the Qutest how it drives an amp.

SPL Phoinitor X is still the king of the headroom; it is a little warmer than TCA. But it takes up a lot more space.


It probably wouldn’t be my personal pick to pair with the RME. Simply because there is considerably less expensive stuff available, that measures similarly (the differences are well below any feasible audible threshold) that retains balanced headphone drive, in a similar form-factor - as in for less than half the price.

Once enough power is available, I really haven’t found a difference with these types of high-feedback/feed-forward EC, monolithic-based designs. I couldn’t, for example, tell the Geshelli Archel 2 from the Schiit Magni Heresy in a blind test - as long as I wasn’t trying to dive difficult loads or pushing volume limits.

I expect the same would be true with a $300-$400 THX AAA amplifier and the HPA-1. And none of them (THX AAA or HPA-1) offer anything in terms of must-have features, or particularly likable/unlikeable aesthetics to me to warrant distinction on those grounds.

The Qutest already sounds indistinguishable from the Hugo 2 when both feed the same amplifier.

The Hugo 2 doesn’t have a conventional amplifier driving its headphone outputs - they’re actually the same connection as the RCA outputs on it. Its the same stage as on the Qutest, also, but just with three selectable fixed-level outputs.

So in theory, as ALL amplifiers add noise and distortion (in this case it’s below audible thresholds), the Hugo 2 vs. Hugo 2 -> HPA-1 should result in the Hugo 2 on its own yielding better measurements when it comes to driving headphones … but again not to the extent that they should be audible.

Hopefully! The Geshelli stuff is mounted in CoTS aluminum extrusions with printed/drilled plexiglass ends! I used to case little electronics projects like that myself, when I was 8.

And in terms of authority, both the Geshelli units are lower-power devices (the 2 in particular), so if the HPA-1 didn’t out do them I’d be surprised.

All good info for others, but this is really at the opposite end of the market I am interested in, which is why it falls off my potential review radar. I only covered the Geshelli because it had such good measurements and I was curious to see how it fared.


Thank @Torq. I understand when it comes to premium gear; it how I feel about Guitars. It is just a more enjoyable playing instrument from a boutique builder like Novo or Collings over mass-produced Guitar. Much better fit, finish and attention to key details. Guitar Amps are also similar. It took me a while to get to my guitar collection. I flipped through about 10 guitars to find the one that I could bond with. Each one has its own personality.

Also, you have an incredible collection of amps and headphones, a lot more experience with products in this space. which why many of ask you first.

For others, the new Geshelli 2.5 Pro is now 1 watt in 16 Ohms. Yes the build reminds me of Radio shack project I used to build as a kid as well.

Thanks again for the dialog.



Congrats on the new amp!

I have one coming my way, but its going on a “tour” starting up in Canada so it may be a few more weeks until I get it here to compare with the THX AAA I have. But we will do some subjective comparisons.

I am sure the amp performs flawlessly!

Have you done some level matched listening tests between the Phonitor and Toms amp? WIth all the fancy stuff on the Phonitor off I am very curious if one can really tell the difference in between the two?

Enjoy the music!

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Thank you, Alex; I normally leave all the fancy stuff off on the Phonitor. I need to build a dummy load box. Something like this so I can just put he Osciliscope on it. Need to update to 5-watt resistors.

Interesting how PowerCube adds additional layer of detail to Audio Precision analysis and goes a little deeper into how the amp will perform under load. I am sure if we tested all the 1-watt amps we find they all test different since each amp have different opamp and power supply design

How to test your new Audio Amplifier Design - PowerCube basics and example graphs

  • Published on January 3, 2019

Lars Ohlen

Lars Ohlen


Head of Design @ AudioGraph

1 article Follow

Lets see how our test systems can help you design your audio amplifiers. To understand the need of the PowerCube test, you must be aware of how a loudspeaker appears to the amplifier during dynamic conditions.

Why the PowerCube test?

It’s well known that an 8 ohms speaker for example, is nothing but 8 ohm at most frequencies. How far down against 1 ohm it goes depends on the specific loudspeaker. And we are not talking about the static impedance curve, but how the loudspeaker appears in a dynamic point of view. These examples below does not concern the loudspeaker, but the amplifier.

It’s assumed that you know that loudspeakers can produce severe load cases to an amplifier, which can be difficult to handle for the amplifier - and cause distortion and shut downs.

Example graphs and how to interpret them

This graph on the right will bring you up to speed in how to interpret all the information that the graphs contains. The PowerCube test is a dynamic test – it tests the amplifier’s dynamic output power capabilities

To quote one of our customers: “There are no faster way to check a new design - in five minutes we can see if it is stable, if the power supply works as intended - if the design works as a system”

Below you will find some example graphs to show y.ou what you can find when testing an amplifier.

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You need to check the USPTO database if there is a real issue, but it confused brand name, I did see a couple more amps that use HPA-1 in there name. Branding is an interesting exercice.

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For those who like to see measurements, I had asked him to measure low load for all the Dan Clark AEON FLOW users. He sees more power in the final product. I am fixed the numbers above.

I wanted to see how the Monoprice THX 887 sounds next to the TCA HPA-1.
For the test:

  • Qobuz for music source on Mac Book Pro via USB to both DAC’s, * Chord Qutest for RCA inputs
  • D90 for XLR input which both amps accept.

Single-ended it really not fair with the HPA-1 and the Audeze LCD-4 @ 200 Ohms it is a more powerful amp single-ended. The amp is at just past noon at normal listening level with no gain boost. THX 887 needs the volume pot all the way open at no gain boost to equal in moderate volume. THX at Gain Level 2 and little past 1 o’clock equalize the situation.

Another end of the spectrum Dan Clark Aeon Flow Open’s @13 Ohms ( “AFO”) which is more current dependent, HPA-1 at moderate volume around 11 o’clock on the volume pot and THX 887 is just past 1 o’clock to get to the same 60 average -73 dB. for the peak on Yosi Horikawa Bubbles.

Also played John Lee Hooker tune “Jessie James”
on the same settings with AFO headphones, with simular take away.

Also played the Keb Mo “itch”, on THX 887 really needs to be on Gain level 2 Single-Ended to match base output HPA-1 dynamic volume range without gain. HPA-1 amp does seem a bit more open, not compressed with the AFO’ headphones with no gain. Gain level 3 the issue was gone THX amp.

Note I need to use a little gold sharpie to make it easier to see where volume pot is set at on THX 887.

I have XLR and Single-ended cable for my Ronson RAD-0, so used XLR on cable on THX 887, and 1/4 Single-ended on HPA-1 amp. I walked away I prefer HPA-1 amp with these cans, with plenty of clean power with richer clarity on songs like Cure “Just Like Heaven” and John Mayer’s Clarity.

They are both great-sounding amplifiers, when I get my XLR cable for my LCD-4 I will go back and retest THX amp.

Note they now have more measurements on the HPA-1 amp at the website

I do need to measure taper of the Volume pots on the two amps, TCA HPA-1 seams linear, THX 887 maybe Log(audio) taper


I talked to Tom it is log based pot on HPA-1. I can pull the volume to full lock on RAD-0 with THX amp with no Gain lift. But HPA-1 will get way to loud to listen comfortably.

The gain on the HPA-1 from the published specs are: 1x and 12X.
The gain on the Monoprice THX AAA 887 are: .66x, 2.0 x and 6.6X

This makes comapring loudness settings with volume pot positons not as easy as one would think?

Jumping from 1x to 12x seems a bit wide, but we shall see next week. Its almost like the HPA-1 amp was desgined for Low and Hi impedance headphones with this gain scheme.

The least gain for the best overall listening experience is often the addage most of us follow and adhere to.

One thing that stands out with this and and the THX amp is the balanced output is not in the HPA-1 and I have read Tom’s description and his reasoning for this absence which makes sense to me but a lot of folks will still want this reagardless, there is engineering and there are customers that just want this feature good or bad. Also if you compare the specs of power out with the balanced well to most of us non-engineers it looks like the THX AAA has more power…


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I never boosted HPA-1. I find you do not need too, unlike the THX 887, with higher load headphones. It also why I was volume matching with SPL meter and Audio Spectrogram. It would have been helpful to have 1x mode on THX. Still .66x just means you need 1/3 more dial movement to equal 1x gain at a minimum. Once I get the load box built I put them on Oscilsocope.

Begins to tell a story

But ultimately, it not about speeds and feeds; it how happy it makes you listen to music you love. They both very good amplifiers to do just that.


I totally agree its about how happy it makes you to listen to the music you love…absolutley!

But these amps and their designers really tout and emphasize these measurements and the engineering that goes into them…so we can not ignore the claims when reviewing or comparing…

To me the numbers on both of these amps are prety spectacular for sure, but its not all about numbers for sure.

I am sitting here with a $79 B-Stock Schiit Magni 3, old technology with good but no where near the numbers that these amps have. BUT, I am smiling and tapping my feet and am amazed at the musical experience I am having this am with this “low” end amp…


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three pieces to test when you get your amp

Han Zimmer

Georges Bizet : Carmen (1964) - Callas Remastered

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