Tom Christiansen Audio HPA-1 Headphone Amp Review

[solderdude]

In small q'ties the price is higher (Tom won't buy them in large q'ties most likely)

When one has a 1000 units made this means an investment of $ 12,000 extra.
Every $ counts and most bulk manufacturers do want to sell something new every few years or so as well.

Tom's design is not limited in this way and simply uses high quality parts instead of skimping on everything buying stuff that works 'good enough' for a few years.

 

[Nango]

Given the feedback @tomchr you could have asked twice the price for the HPA-1 ............ Those who buy it can be really happy!!!

If you included a 10 yrs warranty for certain parts like the pot etc (or something like "free cleaning treatment & revision" every 8 yrs or so) so one could be sure it lasts for the decade I think even $2.000 would have been reasonable.

 

[restorer-john]

but.. I mean it's only $12 difference?
does RK97 perform way worst than RK271?

Thankfully, HPA-1 uses RK271 and has an additional support bracket for the volume pot. I am not sure but I can imagine the support bracket for volume pot cost $10 a piece . (I am guessing here)

$12 difference translates to a significant difference at the other end.

The RK-097 is an adequate general purpose pot. The RK-271 is a superior pot. It tracks better, lasts longer, feels way better, is stronger, can take bumps and knocks, general abuse and rarely becomes noisy. Tom has likely commissioned particularly well tracking (taper to taper) pots at a significant (>$12 diiference for guaranteed X.XdB gang error) additional cost to him.

The bracket supporting both the headphone jack and the pot means your amplifier will take normal day to day use, and abuse, in its stride.

You know those times when you stand up quickly, the headphone cable is around the chair leg and the HPA-1 is yanked sideways, flies off the desk and swings by the headphone cable/jack precariously. Instead of contacting Tom and making up a story about "it was always like that from new...honest", you'll thank yourself for buying something well made that can handle normal usage.

It also allows the pot and headphone jack to be secured and discretely mounted behind the front escutcheon.

 

[graz_lag]

... You know those times when you stand up quickly, the headphone cable is around the chair leg and the HPA-1 is yanked sideways, flies off the desk and swings by the headphone cable/jack precariously ...

Indeed ... A long headphones' cable ... it's going to be there sooner or later ... if you like to wheel around ...
I solved the potential issue by sleeving my cables with some plumbing foam sleeves from Armacell, 3/8" ID.
A cheap but efficient solution, with - en plus, that 'my-friends-jaw-dropping' terrific esoteric look!
HaHaHa!

 

[JJB70]

I'm a big enthusiast of high build quality, and actually find it a more compelling reason to pay more for higher end audio than florid prose about lifting veils or measured performance which is so far beyond my capacity to discern as to be meaningless. That's why I'd happily buy Accuphase, Benchmark or other gear built to very high standards and why I've never regretted buying my Sony ES set up. The satisfaction provided by high quality is still there long after you realise all those claims about SQ or measured performance going to the far end of a fart really doesn't mean much.

However, I also think it is worth saying that short life and poor customer service are not a natural corollary of value engineering and lower cost products. I remember Nwavguy was always upfront in saying that if you wanted a headphone amp to outlast you then spend the money for something like a Violectric and that the O2 was about high performance at modest cost, however plenty of O2 amplifiers have proven to be pretty durable and long lived and some companies at the lower end of the price spectrum such as JDS have a first class reputation for product support. There are certainly cheap products that are trash can fodder and which I wouldn't expect to last long, but there are also lower cost items that are genuinely good products.

 

[vkvedam]

It's a wonderful amp but for some of us who live in the UK and EU it would end up costing dearly unless UK strikes a trade deal with Canada

 

[raindance]

Nice to see a solidly engineered amp. Brave, too, having an internal power supply

The Alps Blue Velvet has been my go to pot for years. They track well and are quiet. The only time they get slightly scratchy is when there's residual DC on them.

What about safety ground? The tab on the IEC mains connector appears to not be connected.

 

[solderdude]

I suspect the 3rd prong is also present on the PCB side (so 3 solder pins, L, N, Gnd), judging from the middle trace from the socket going to the chassis.
Both SMPS are double isolated (medical grade) so aren't connected to ground anywhere.

 

[trl]

I think I installed about 50 pcs of blue Alps 2x10k/log without a single issue. In DIY world, we do not have to look at price that much but we request for high quality and parameters.

http://pmacura.cz/disprefet_s.jpg

I love your care for grounding the potentiometer, quite a good catch to minimize the noise when you touch it.

 

[trl]

Here is a detailed picture of amplifier inside:
View attachment 42813
Source: https://www.tomchr.com/products/hpa-1

We still need it full size, right?

 

[tomchr]

Here is a detailed picture of amplifier inside:
View attachment 42813
Source: https://www.tomchr.com/products/hpa-1

That's a picture of the early prototype actually. The production version is even cleaner. I should update that picture.

Tom

 

[tomchr]

What about safety ground? The tab on the IEC mains connector appears to not be connected.

I suspect the 3rd prong is also present on the PCB side (so 3 solder pins, L, N, Gnd), judging from the middle trace from the socket going to the chassis.

It is indeed. The centre pin from the IEC socket goes to a 6 mm diameter solid stainless steel standoff that's pressed into the aluminum chassis, thereby grounding the chassis.

Tom

 

[trl]

Great performer indeed, as expected actually...congrats!

Anything about the CF opamps from under the HS1 heatsink?
Or at least something about what opamps were used there. generally?
Inverted or non-inverted circuit?

Basically, we're all expecting an update on the part:
"The block diagram of the HPA-1 is illustrated below.

[IMAGE TO COME]"

If everything is balanced from the XLR plugs to the potentiometer, what do you think about moving further and get another version with a 4-gang pot. and XLR plug as well? Or the button-switches need to get replaced too? It's only 50...100 EUR more, or am I wrong (without the added R&D and case costs)?

 

[tomchr]

The output stage is inverting with a gain of -1 V/V. The input stage is inverting and there's a buffer between the volume pot and the output stage.

I drew the block diagram while I flew to Toronto for vacation on Friday, but realized I missed some details, so I'll touch it up on my return flight tomorrow.

Tom

 

[tomchr]

If everything is balanced from the XLR plugs to the potentiometer, what do you think about moving further and get another version with a 4-gang pot. and XLR plug as well? Or the button-switches need to get replaced too? It's only 50...100 EUR more, or am I wrong (without the added R&D and case costs)?

What would you say would be a reasonable price for such an amp?

Tom

 

[Doodski]

Now for the power supply. The Mean Well MPM-15-15. A nice solution from the medical grade parts bin
https://www.meanwell.com/productPdf.aspx?i=838
https://www.mouser.ca/ProductDetail...aalG5TUgGqTPUILE6OS6gAorkF%2bNjOyewXT80lmVg==
https://www.meanwell-web.com/en-gb/ac-dc-single-output-medical-encapsulated-power-mpm--15--15

 

[tomchr]

They're rock solid supplies. They're well spec'ed and Mean Well provides excellent customer service. The alternative was to use the same Chinese transformer vendor that Schiit uses for their amps. I wasn't confident enough in the quality to buy the minimum quantity of 500...

Tom

 

[dachada]

Now for the power supply. The Mean Well MPM-15-15. A nice solution from the medical grade parts bin
https://www.meanwell.com/productPdf.aspx?i=838
https://www.mouser.ca/ProductDetail/MEAN-WELL/MPM-15-15?qs=sGAEpiMZZMuWiaalG5TUgGqTPUILE6OS6gAorkF%2bNjOyewXT80lmVg==
https://www.meanwell-web.com/en-gb/ac-dc-single-output-medical-encapsulated-power-mpm--15--15

yes nice. I going to build a new PS for my phono preamp using this MPM-15-15 and adding a ultralow noise LDO

 

[trl]

What would you say would be a reasonable price for such an amp?

Tom

That would probably need a dedicated voting pool I guess, but as long as is cheaper than HP-1 I don't see any issues with whatever price will be.

This headamp has a one of a kind design, it's not something copied from the datasheet or from a similar schematic, so R&D and novelty comee up with a price.

 

[LLL]

I have known Tom for decades; we were grad school classmates at UW in Electrical Engineering, we even had the same adviser. This kind of performance does not shock me a bit when it comes to Tom; it's kind of expected. He is one of the top analog engineers in the world, and for him to dedicate that level of knowledge and experience to bring a state-of-the-art headphone amplifier to the world is truly a gift.

Besides, he is someone with the highest level of integrity, and I know anyone who will buy this will both be enjoying this piece of equipment for decades (if not a century), and will be well taken care of.

Well done, Tom!