Thanks for your awesome review/input!
Ill gladly take it off your hands 
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…and you’re local - I could save up on the shipping cost. I’ll let you know if it comes down to that, you’ll have the right of first refusal.
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Nice choice. 
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I’m sure you mean Serbia 
Still, I did not realize it’s not the Serbian manufacturer that produces the “normal” headphone output, which limits the amount of changes Raal can add as mods. Inferring from the sound quality differences reported, I dare guess that Raal mods HSA-1a by changing the 4-pin XLR jack to female, changing the pinout to “normal” headphones, then adding resistors in signal path to better mate to “normal” headphones. Depending on the value and quality of resistors added, it may not work so well with some headphones vs. others depending on headphones’ impedance/sensitivity, etc.
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Hahaha you’re right and I typed that “in my head” but my keyboard got smart. Lol
As far as I know, the mods were done here in the US and I don’t know what the process entails for the internal components.
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It is in units shipping now.
Units that had already been shipped were modified in the US, but all new units are built with both outputs at the factory.
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This is great news! I hope that you get one of those units.
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Finally … I have my HSA-1a back … complete with the updates to support driving conventional headphone (which are a standard, factory, part of all units ordered as of about a month ago).
Performance with the SR1a is unchanged … best I’ve heard them this side of $10K+ speaker amplification.
And too early to say how performance is with conventional headphones, other than there is some added warmth and richness there (with step-baffle compensation turned OFF).
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I’ve managed several hours listening with the HSA-1a since it returned. After a quick validation that it’s performance with the SR1a is the same as the original unit I’ve had, I focused the rest of my time so far on using it with conventional headphones (quick “with my morning coffee” picture for provenance in the early Seattle morning).
Initial impressions … (again, driving conventional headphones form the normal 4-pin XLR output with step-baffle compensation turned OFF - since you don’t need it for normal cans)*:
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Overall signature is slightly warm with some added tonal richness.
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Tone/weight reminds me of the EC Black Widow, while other technicalities bring the Violectric V281 to mind (but without the dark presentation).
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Punchy delivery with impressive, and visceral, slam/impact - think Schiit Mjolnir 2 or Phonitor X (or good speaker amps feeding an HE6).
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Low-end is capable of excellent growl and rumble, but remains tuneful and tight.
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Very smooth overall presentation.
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No noise/hiss nor hum, even with my lowest-impedance, most sensitive, conventional headphones (dynamic and planar)**. Being solid-state, you wouldn’t generally expect any different, but it is very common to encounter such when driving headphones with speaker amplifiers, which is what the HSA-1a began life as.
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Some very minor low-volume channel imbalance (not heard via the SR1a at all) with very efficient cans. It’s completely gone well before reaching anything like a listenable volume … and before the volume dial passes the “10” (1 for other amps) position. But you’re probably not going to want to use IEMs with this.
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Audible click when switching between XLR/RCA inputs***. Louder in the right channel, but not loud enough to be worrisome in regards to hearing nor, probably, headphones, but I would personally be inclined to disconnect them before switching inputs.
*Despite effectively being out of time to do more in the online audio world, I am still planning on reviewing this unit, and probably finishing up a couple of other pending reviews.
**One exception; with both XLR and RCA connections in use, some very low-level hiss (about -90 dB) was audible using the Focal Stellia when the volume was turned up to maximum and no music was playing. Back the volume off even a fraction, and this disappeared completely.
***Very minor compared to the transients you get from, say, either version of the RNHP or the Fidelice Precision DAC.
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Still listening, evaluating … writing up notes … but a couple of things stand out here …
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If you were the type that wanted to stick a tube pre-amp or buffer ahead of the SR1a somewhere (e.g. maybe a Saga+ or Freya+ or iTube 2 (etc.) in front of a Jotunheim “R”), I strongly suspect the HSA-1a will cure you of that desire.
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This thing kicks like the proverbial mule. Currently running it with the Vérité Closed and it is a pulse (and temple) pounding tour-de-force. Same thing earlier with both the LCD-4 and RAD-0, and, well, the whole ZMF line-up … especially the Eikon with it’s bio-cellulose driver … holy shit …
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Hi, I am interested to do the same when I get mine but I am very new to audio. Do you use tools with metrics in order to analyze this or is this a subjective test? Your SR1a burn-in phase should have been completed for its sound not to change in the time being, right? or maybe you stopped listening to it while waiting your HSA-1a to return?
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Both.
I’ve had my set of SR1a for a year now, and they’ve got >2,000 hours on them, so yes they’re more than burned in by this point … and were before the first HSA-1a showed up.
So there was no break in listening to them, I was just running them off my big Chord stack (including Étude → SR1a interface) while the HSA-1a was away. And sometimes off the Jotunheim R.
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It’s still early days with the conventional headphone output, but it’s performing at a higher level than I had expected.
I think for a primary SR1a user, where the SR1a is their choice for critical/active listening, the HSA-1a is the obvious step up from the Jotunheim R. With the benefit that the HSA-1a will deliver a high-quality listening experience with conventional headphones for other listening purposes.
And I don’t mean to suggest the HSA-1a isn’t suitable for critical listening with conventional cans. It very much is. It might not quite match, say, the Phonitor X (or HPA4 or Moon NEO 430HA) for ultimate transparency, detail and micro-dynamic resolution, but the RAAL unit kicks/slams with the best of them, has a lovely rich tone, and is thoroughly captivating all the same.
For critical listening/reviewing* with dynamic or planar cans, I would still put the Phonitor X ahead of the HSA-1a. And if the majority of my non-critical listening time were with such headphones, I’d also likely go with the Phonitor X to drive them (paired with a Jotunheim R with the Phonitor X to service the SR1a).
While subject to revision with more listening, and as I pair up more regular cans with it, right now I’d say the HSA-1a is a 110% solution for the SR1a (even if you have no other headphones at all), and an 85-90% solution for conventional dynamic/planar cans (higher if you want something that hits hard).
It’s the best I’ve heard the SR1a this side of $10K+ speaker amplifiers and does away with the desire for tubes in the chain (due to its tonal weight and richness). Which makes the pricing attractive right there. And then you get what I would effectively describe as something similar to a Mjolnir 2 or Black Widow (different aspects of each) as part of the package too, which makes it very hard to ignore. Even if those focused on absolute quality are likely still going to also want a dedicated conventional headphone amplifier.
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Oh, and if it is not already obvious … and just in case I don’t get my formal review finished of the updated HSA-1a before I am no longer around …
I did BUY the unit I have now, so it is no longer a demo unit.
(Hopefully I’ll have time to test it with the Abyss Phi TC, Susvara and some speakers before I depart …).
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Thanks so much for making the time to do this for the forum!
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I knew you would! 
Congrats!! As you usually say in your reviews, this is the ultimate endorsement of how good you think the unit being reviewed is.
It’s a great unit. The performance driving conventional headphones leaves a sense of “lacking something” mostly due to the super high performance of the ribbon side. The difference between the two sides is very noticeable for people like me that had high expectations based on what I heard on the ribbon side.
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Then maybe the difference could be greater depending on the type of music and recording?
@Torq could you please advise me specific tools and/or softwares to have objective measurments for my SR1a?