Listening Impressions: HifiMAN HM-801 Balanced Amp Module vs. ST Amp Module v.2.0
Preface
The goal of this post is to attempt to compare key performance aspects of the new balanced amp module vs. the latest version of the standard (single-ended) amp module (known as the ST module) included with the HM-801. Since the gain structure of the v.2.0 of the ST amp has been revised to accommodate most IEMs as well as standard headphones without any audible hiss, the optional, IEM-only GAME adapter module is not included in this comparison.
Test Equipment
- HM-801 with 32GB Kingston SDHC card
- HM-801 ST module v.2.0 and optional Balanced Amp Module
- HifiMAN HE-500R (modified version of the HE-500 hardwired with Whiplash TWag V2 Reference cable, fully balanced XLR4 termination)
- JH Audio JH13Pro customs w./TRRS-terminated balanced Eclipse OM replacement cable (for balanced amp module) as well as TRS-terminated single-ended Eclipse OM replacement cable (for ST amp module)
- Adapters: custom TRRS male-to-XLR4 TWag v2 female adapter (for bal. amp module) and a combination of TRS-XLR3 balanced+XLR3-XLR4 balanced TWag v2 adapters (for ST module)
- Burn-in time: 200 hrs each amp module using the ISO-Tek System Rejuvenation CD “Small Equipment” session. The interconnects and headphones/IEMs have all been burned in far exceeding their manufacturer’s recommendations.
Evaluation Music
Tracks from the following 24/96 mastered albums have been used in this evaluation purchased from HDTracks without any additional conversion in native FLAC format:
Evaluation Methodology
As much I would have liked to follow a more real-time A/B switched testing method, the fact that the balanced module assembly does require replacing the two tiny screws holding the modified cover in place did introduce a 30-40 second delay between listening sessions switching from the ST amp and back. Luckily the differences between the two modules have been substantial enough where I feel comfortable publishing my impressions, subjective they may be.
Test One - Full-sized Headphones - HE-500R
The HE-500s are one of my all-time favorite non-electrostatic headphones and I was looking forward evaluating this particular, heavily modified version with the HM-801 in balanced output mode. That is because this is really the only way to experience all these have to offer.
Listening to the HE-500R using the ST module is not without merits, as the ST has a very pleasing tonal balance. Unfortunately, it doesn’t quite have enough power to muster the necessary voltage swings to drive the HE-500Rs to their full potential even at max volume. Almost, but not quite at the level to push them to their limit. The soundstage and depth is nowhere near as pronounced as it could be. Instrument separation also suffers a bit. Clearly, more efficient headphones such as HifiMAN’s own HE-300s and the Sennheiser HD600s could be easily and effectively driven by this configuration in terms of raw power output. But no matter what, an excellent source as the HM-801 is, truly deserves a balanced analog output stage to make it complete.
Swapping the amp modules and switching to the new balanced module requires very brief listening to fully appreciate what the upgrade cost buys you in terms of SQ enhancements. Here are the highlights:
- Imaging. The difference is quite pronounced, especially with the HE-500Rs. The spatial imaging is significantly extended along both the x and y axis; the soundstage becomes both wider and deeper.
- Power. While I do not recall the exact specs between the ST and the balanced module, the balanced module makes driving the HE-500Rs effortless. By that I mean it does so with a punch. Attacks are much sharper and even though the HE-500s are not the fastest cans on the block, the overall dynamics are much more satisfying and more consistent with similar performance characteristics those of balanced desktop amplifier/source combos.
- Instrument separation. The synergy between the neutrality of the HM-801 digital source coupled with the balanced amp module compliments the HE-500Rs midrange emphasis by slightly flattening the performance curve and infusing some extra detail between most instruments. This is evident in both reference recordings, but quite frequently surface during the Natalie Merchant “Tigerlily” tracks with acoustic guitar compliments. They are projected with a definite air around them, clearly distinguishable from the other accompaniments as opposed to somewhat fused in together.
- Bass and treble extensions. The improvement in these aspect of sonic excellence is relatively minor, but I believe it is still there and worth mentioning. In essence, the balanced amplifier is able to deliver cleaner, crisper treble and tighter bass with a slightly more pronounced, yet smoother texture without sacrificing midrange performance; a key selling point of the HE-500s.
Test Two - IEMs - JH13 Pros (TWag Eclipse recabled)
I’m going to take some literary license and make relatively short work of this one. Essentially, anyone who spent time listening to IEMs paired with portable balanced amps such as the RSA SR71B or the iBasso PB1 or PB2 could attest to this. Most IEMs I’ve listened to containing a passive crossover circuitry are not really capable of benefiting fully of balanced amplification the way balanced full-sized headphones such as the HE-500Rs can, because for some reason they are unable to effectively project the Y or depth aspect of imaging. The X is no problem, but it’s just how that technology works, I suppose.
The only exception I have encountered so far is the JH-3A/16 active crossover/DSP system.
So, how do the JH13 Pros benefit from pairing out of the balanced amp module of the HM-801? Essentially the same way as the HE-500s above with the differentiation being that the overall SQ of the JH13 Pros are more linear than that of the HE-500Rs. What’s nice with the amp module is that it’s equally capable of driving these sensitive customs without any noticeable hiss--minus the very faint overdrive at zero volume level I have described during
my earlier unboxing post--yet it can scale up extremely well to drive the HE-500Rs, if not the HE-6s. That is quite a useful performance curve for most people, methinks. With the balanced TRRS-terminated balanced HifiMAN cable included as part of the balanced amp upgrade kit, one can enjoy a pair of HE-500s or other headphones at home and switch to IEMs on the go, having to invest just one extra cable (or reterminate an existing balanced IEM cable using the supplied TRRS connector).
Summary
In closing, I think it comes as no surprise that I highly recommend this particular upgrade to HM-801 owners, provided the cost of any additional cabling or retermination needed to take advantage of the balanced amplification is within budget. Although the cost is not insignificant compared to the GAME adapter, its versatility in being able to support full-sized headphones as well as IEMs, plus the added extras the kit includes makes it somewhat of a bargain in my book. It is certainly more cost-effective and convenient than springing for an external balanced portable amplifier and interconnects. The sonic improvements alone breathe new life into the HM-801 platform and incorporating the balanced amplification features is done in a way that should effectively replace both existing amp modules with this single offering without hardly ever a need to switch while transitioning between headphones and IEMs.
Not sure if Head-Direct is planning to sell the balanced amp module as a bundle for new customers, but I would welcome such an arrangement. And I would also like to see a custom case offered at least as an option that incorporates a cutout for the TRRS socket bump-out in the back of the case to protect the player while on the go. Other than that, the new upgrade kit should please just about everyone who is considering investing into one of the best sounding portable platforms capable of natively rendering 24/96 high-resolution audio out of a single, well-engineered unit.
