RAAL-requisite HSA-1a - True Ribbon Headphone & Speaker Amp - Official Thread

It would be very helpful to know what you think about the AHB2 in comparison with the HSA-1a. Hope you can do it in the future.
Keep enjoying this combo !!

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I’lll put it this way …

I prefer the Jotunheim R over the AHB2 for driving the SR1a.

I prefer the HSA-1a over the Jotunheim R.

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I preferred the SPL s800 over the Jotunheim R. Looking forward to your continuing thoughts about the Raal Requisite HSA-1. I would certainly like to audition one with my SRA-1 earfield monitors.

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The SPL s800 is very good.

It’s definitely different, overall than the Jotunheim R. Though the s800/interface combination ultimately lacked a little separation and detail vs. the Jotunheim R direct when compared blind, the s800 had a bit more tonal weight and overall presence.

Compared to either the AHB2 was a bit lean, dry and sterile.

The HSA-1a, so far, is competing at a higher level than all three. Closer to, maybe exceeding, the Chord, Linn and other more exotic gear (with the interface). And the HSA-1a has the potential to be significantly more flexible than all of them, but I’ll say more about that in the near future.

Personal preferences are what they are, however; so it’s great that there are options.


When the current lockdown situation has ended here, I will see if Danny will send me an HSA-1 to audition with my Roon Nucleus / dCS Bartók Source. From your early observations, it seems to be the optimum pairing with the SR1-a’s. I very much appreciate your opinions and find that I am in accord when auditioning the same units. Many thanks, Ian.


Thanks for your answer .

So … there’s an interesting development with the HSA-1a, for which I’ll update the main post in a little bit, but in advance of that …

  • The HSA-1a has been updated to swap the 2nd headphone output for a conventional balanced headphone output, so that it can be used both to drive the SR1a and also any normal headphone (i.e. not electrostatic) cans as well*.

  • For super-hard to drive headphones, like the HE6(SE) and Susvara, there will also be an adapter cable in the box to allow it to power those properly.

So this turns the HSA-1a into an amplifier that can drive the SR1a, any normal headphone, pathologically hard-drive headphones AND speakers - all from one box!

I will be getting an updated unit in short order (likely this coming week), and that’s definitely a useful and, I think, broadly welcome addition!

Finally, anyone that ordered/received an HSA-1a already will get, or be able to get, the updated unit for no charge (if you need to return a unit for the update, shipping will be covered)!

*It’s not just a socket/wiring swap, there’s more to it than that.


Yup, this is a great move for Raal. :wave: The normal headphone output will probably bypass the circuitry needed to push extremely low impedance of Raal SR1a. Since the affordable Jot R already sounds great with low-impedance planars like Abyss with just socket swap, SR-1a’s normal output will probably sound great driving both low impedance AND high impedance 'phones.


Once an output stage has the ability to drive low-impedance loads, which is really about current and thermal limitations, there’s not really a need to bypass it for higher impedance loads.

You might bias it differently.

You might switch out some number of output devices (one way to increase current capability is to use spread the current load over more output devices, so that each only has to service a fraction of it - which tends to trade capacity for noise).

I suspect it’s more likely scaling (e.g. a different gain or attenuation structure) the output to be more in line with what conventional headphones actually require - both to get the most out of the output as well as to help protect one’s headphones.

We’ll see when it lands …

Either way, I’m excited about the possibilities … especially if it lets me run the same array of cans but with fewer boxes (and even more so if it winds up sounding better with the conventional headphones than my current solid-state amp).


is this even available? the real website doesn’t present it as an option. sounds almost compelling…

The HSA-1a is available to order, yes.

My understanding is that the updated version should start shipping at the end of the week (with due allowances for potential disruptions). That’s when I am expecting my updated unit to ship out (and that’ll be the version I am keeping as my personal purchase).

My assumption is that any orders placed now would be the updated unit, but I would check to be sure ahead of placing an order.

In this case, I think the press-shots and web-site info is trailing the product/engineering (which is a nice change).


thank you, @Torq - looking forward to it

The HSA-1a/SR1a combination has, again, consumed my listening time this week, excepting a bit on the deck with the Vérite Closed to enjoy the nice weather/view.

And that has allowed me to get my HSA-1a review completed, as far as possible, ahead of receiving the updated unit (with the 2nd output swapped to drive conventional headphones).

I’m champing at the bit to get the updated HSA-1a as, if its performance with conventional headphones is close to that of what it delivers with the HSA-1a, it’s going to mark another upheaval in my headphone systems and likely those of many others - especially those that had any reservations bout the SR1a vs. their normal collection.

Details will have to wait for my review … but at the end of my original SR1a review I said:

The RAAL-requisite SR1a rapidly established itself as my favorite headphone, ever … and I say that based on having heard every flagship can I know of (and on owning most of them). They are so good, they likely mark a major hiatus in my reviewing headphones.

I just don’t know where I would go from here …

I do, now …


This bloody thing has made me fall in love with the SR1a all over again … and I was never “out of love” with them in the first place … they’ve been utterly magnificent since the very first listen.

Had it all out on the deck, fed from the Hugo M-Scaler/Hugo TT 2 this morning … and probably should have taken pictures (maybe I’ll do that again here in a bit, if the weather holds … skies and water are very pretty right now, if heading towards “threatening”).

The HSA-1a/SR1a combination really does turn the SR1a up to “11”, maybe even “12”.

Due to all the virus-related lockdown stuff, our (work/lab) anechoic chamber is free this coming week, and I am seriously contemplating taking this rig into that and doing some super-critical listening (will likely take the Jotunheim R too if I do it at all). After all, it’s one thing listening in my now-unusually-quiet home (amazing how much quieter it is with NO traffic), and another entirely when the ambient noise level is <0 dBA …

With the Jotunheim R, and even the Chord Étude/Interface, I had contemplated, occasionally, adding a tube-buffer for some specific pieces/moods. I have NO desire to do that with the HSA-1a driving the SR1a.

Completely awesome …


I’m looking forward to seeing the updated model and hearing your thoughts on it! Also I really like this picture as it gives a good perspective of size and how it would sit on my desk potentially… If it is on par with the Phonitor XE, I may end up putting it and the Jotunheim R up for sale and consolidate my collection a little bit.


It’s a couple of inches narrower than the Phonitor X/XE, and about an inch and a half deeper, while being maybe a bit under half an inch less-tall, and 2 lbs heavier.

No pre-outs (which you don’t have on the XE anyway), but can, of course, drive efficient speakers.

Very real possibility it replaces my Phonitor X if the conventional headphone output measures up to the Phonitor X. Though I will miss the VU-meters and Matrix functions.


Not even the mighty AB-1266 Phi TC can do bass-resolution, texture and speed this well.

Yes, the Abyss is slightly more visceral and has a tad more impact on the low-end, and plays deeper (without EQ), but the difference isn’t that big (and barely discernible with EQ) …


What kind of EQ are you applying to these for regular use?

None, anymore.

Originally I had a sub-bass shelf applied, along with a bass lift. But with the Chord Étude/Interace or Jotunheim R that’s not been necessary. Less so, even then, with the HSA-1a.

EQ is only “needed” if you don’t like studio-neutral/true-neutral. And if/when you do apply EQ … there’s no other headphone on Earth that takes it as well, even to extreme levels.

If you’re a volumetric bass-head, you’ll probably want +3 to +6 dB under 33 Hz, and +1 to 3 dB from 33 Hz to 40 Hz … at which point you’re within 1, maybe 2% of a perfectly fitted AB-1266 Phi CC/TC.

But nothing you can do will bring the AB-1266 Phi TC, Susvara, LCD-4, HEDDphone or any other headphone, to the same level of articulation, detail, speed or textural nuance in the bass as the SR1a.


i think it will be hard to beat now and in the years to come