# REVIEW: Firestone Audio Fireye HDB - New Balance



## Zelda

*REVIEW**: Firestone Audio Fireye HDB - *(feat. Panda Audio Amp-S and Hifiman HM-700)
 

 
 
*Specs*:
(From Firestone Audio site)
 
_* Power Structure: Built-in 4-Serial Li-polymer battery power supply_
_* Amplifier Structure: Class-AB amplifier_
_* Headphone Impedance: 16 ohm to 600 ohm_
_* Circuit Protection: Output short / temperature protection_
_* High / Medium / Low Gain_
_* Duration: Continuous using for more than 8hrs when fully charged_
_* Way of Charge: To charge via External Adaptor_
_* Charging Time: 2.5 Hours_
 
_Audio Performance (Output 2Vrms , Balance in, Balance out):_
_* Frequency Response (20Hz ~ 20kHz): +0.02dB ~ -0.3dB_
_* Noise Level: -112.0dB_
_* Dynamic Range: 111.3dB_
_* THD: 0.0004%_
_* Stereo Crosstalk: -110.2dB_
 
_Chips:_
_* Differential OPAmp: TI – LME49724_
_* Main OPAmp: TI - TPA6120_
 
_Connectivity:_
_* Charge Input: 2.0mm DC jack (24V/0.5A) *1_
_* Line Input: 3.5mm phone jack *1, Mini 4Pin phone jack *1_
_* Line Output: 3.5mm phone jack *1, Mini 4Pin phone jack *1_
 
_Weight/Size:_
_* Weight: 302g_
_* Net Weight: 194g_
_* Size (H*W*D): 171mm * 112mm * 80mm_
_* Net Size: 122mm * 62mm * 19mm_
 
*MSRP*: ~$300.
 
*Availability*: Only from some Chinese online stores.
 
*Warranty*: 2 years
 
*Official product page*:
http://www.firestone-audio.com/fireyehdb.html
 

 

 

 
 
 
 
*Packing & Accessories*:
Not much to say here. The new HDB comes in just a nice paper box. Inside you'll find a 4-pin to 3.5mm single-ended short cable, a DC 24V/0.5A adaptor and 3 extra DIY 4-pin plugs. The short cable is of excellent quality as expected from FSA cables. It would've been nicer if there was also a single-to-single cable as well, and at least a carrying pouch or case.
 
 

 

  
 

 
 
 
*Build & Design*:
Build quality is simply perfect. The whole amplifier is made of aluminum, rather thick and feels very sturdy. The gold painted volume knob is plastic and so are the 3 switches. In the front side we will find the Gain switch along with the volume knob and the two different headphone line outputs, single 3.5mm and 4-pin balanced ended. The single output can accept both TRS single and TRRS balanced plugs (such as Hifiman's in-ear models). At the rear side, the Power switch, the charge input and the both line inputs, 4-pin balanced and single 3.5mm, with a switch to change between the inputs, and the charging indicator LED. As for the 3 switches, they might be rather small, but not fragile. The Gain switch goes from Low (middle position) to Med (up) and Hi (down). Personally, I think it'd be more logical to put them in order rather than having the Low in the middle.
As for aesthetics, my credits to FSA for the simple yet elegant and beautiful design. Not the lightest weight unit, but easy to carry on the go nevertheless.
 

 

 

  
  
  
*Gain and Hiss*:
While there's no EQ/Bass Gain option switch like the one featured in the previous HD (non-balanced) model, instead of that, the HDB features a 3 level Gain option. The low gain is powerful enough for most sensitive earphones/headphones, while the High gain should be needed for really demanding ones.
Hiss was slightly noticed and only with very sensitive IEMs.
There's also a noticeable clicking sound when both starting and shutting the power switch. It could be annoying depending of the headphone in use, so it's recommended to start the amp before wearing the ear/headphones.
 
 
 
*Sound*:
So far everything looks good for the asking price, great and solid built quality and sleek design, with the necessary accessories pack (ok, it'd be better). But it'd be worthless if the sound quality didn't match the ~$300 price tag. Fortunately, I can confirm that FSA's new HDB balanced amp offers a beautiful and enjoyable full sound performance. Let's get into more details.
 
Gear used for the testing/reviewing process:
 
Input source (DAP):
SanDisk Clip+ (mainly), iPod Shuffle, Hifiman HM700
 
Interconnector cable:
Included balance-to-single input cable
 
Output:
IEMs:
Ostry KC06 (Silver), Hifiman RE-400 (Single version), Dunu DN-1000, Rock-It Sounds R-50M, Moe Audio SS01, Xiaomi Piston 2.0, and more.
Being a balanced amplifier, the HDB doesn't only supports 4-pin connections, but also Balanced TRRS 3.5mm ones, and so both Hifiman RE600(B) and RE400(B) were tested as well on their 'balanced' mode.
 
Earbuds and headphones:
SoundMagic HP200, Ubiquo ES703, ES903, Rock-it R-Lite and R-DJ (64Ohm).
 
The Panda Audio Amp-S as a reference amp (with stock LME49860 op-amp chip) and Hifiman HM700 were used for comparison as well.
 
*Part 1: Single Output*
The HDB presents a warm and very rich signature. A full and very deep sound, which is very enjoyable and truly immersive. It's not what you'd call a flat and linear reference or analytical amp for sure (that's something for the Amp-S or JDS O2, for example), but rather smooth and engaging, giving higher priority to great dynamics with a noticeable added fun factor. Simply put, it's just 'Musical'.
 
The bass is probably the first thing to be noticed. In short, it's *perfect*. It's very full and deep with incredible extension and excellent rumble. It doesn't offer a heavy-bass low-end, and in fact it's missing the Bass gain option that the previous HD model had; not a bad thing per se, but would've been nice to have. Despite the slight extra coloration, the quality is great, very tight with good speed (although slower when compared to the Amp-S).
As for the quantity, well, it'd depend on the output. It won't make warmer/bassier phones sound as a bass monster, instead will give them better control, speed and decay. The HDB tends to have a better synergy when paired with more mid-centered to brighter phones, as it adds the low end they can be missing.
 
The midrange is very rich and well textured. Neither more forward nor recessed, but it's given an extra thickness and sweetness that makes it much more enjoyable. Vocals, as well, may remain in a neutral position in the whole presentation, but come out much more natural and articulated; very catching and with much deeper emotion. Still, the mids are not the most open and effortless, again when compared to more analytical and brighter Amp-S. Yet, the HDB has the upper hand in terms of texture and 'musicality'.
 
As expected from a smooth and warmer amp, the highs aren't the highlight of the show. They are very well extended, but to a lesser degree when compared to the lows extension. Quantity wise the treble is not lacking but definitely smoothed down; which is not necessarily a bad characteristic. In fact, the HDB does a great job to tame down some of the extra harshness that trebly/brighter sets may have. It works great with the SoundMagic full size HP200 (which sounded quite edgy and aggressive through the Amp-S), or the TWFK based IEMs like the R-50 and DN-1000.
 
While not being a detail oriented amplifier, the HDB detail retrieval is nothing short of impressive. Instead of being thrown to the front, they are presented in a more dynamic and natural way. The stage is more than big; it's huge, very wide with amazing depth. Not just that, the depth this FSA new product offers is without a doubt of the best I've heard. Dynamics are excellent and both instrument and vocal well separated. Imaging is pretty good; not the best yet, but everything sounds well-positioned for a warmish signature.
 
*HM700 + HDB*:
As mentioned above, the HDB gave great results when paired with the Sandisk Clip+, as it's a very colorless DAP that shows no personal character. That's not the same case with the HM700. The new Hifiman DAP is already powerful enough and doesn't benefit from extra amping, and already has some very slight sense of warmth (just the typical from Hifiman's house). Not real improvement was found, aside of a bit of extra speed and depth.
This leads to...
 
*HDB (w/Clip+) VS HM700*:
Now, this is more interesting. While the HM700 has quite enough power to drive most my current gear, it's obvious that the HDB is the much more powerful as with the 3 levels of gain is meant to drive even 600ohm headphones. That aside, when it comes to sound signature, the HDB is noticeable warmer and stronger towards the low freq. with a much fuller and wider sound, giving a more "out-of-head" feeling. The HM700 in contrast, has a softer impact and leaner/thinner midrange but also more forward when no EQ is used. Vocals are more frontal and intimate on the HM700, while more even on the HDB. Even though, the Hifiman's EQ works as wonder and can achieve similar effect as the HDB. Still, the HDB will sound more spacious and much bigger with greater dynamic range; it can also be more aggressive (not in an offensive/annoying way). In the treble dept. the HM700 is brighter and more sparkly against the smoother and more rounded FSA HDB.
 
*HDB VS Amp-S*: AMP VS AMP
The two similar priced amplifiers are the contrast to each other.
In either Mode 1 or 2, the Amp-S offers incredible speed and clarity. Clarity and airiness are the strength of the Panda amplifier together with very tight bass, yet deep sub-bass. Obviously, it's much brighter on the upper end and less forgiving. Quite the opposite in both bass and treble dept. As for the midrange they perform great but also very different. While the Amp-S sounds more open, airy and effortless, the HDB wins in sweetness and emotion. In the end, it comes to personal tastes as always. 
 

  

  
 
 
*Best/Favorite Synergy*:
 
IEMs:
Rock-it Sounds R-50M:
Being a TWFK based earphone, the R-50M is obviously a very bright and clear set with a rather soft bass impact. When fed through the warm and smooth HDB, the results are quite nice. It tends to control the extra harshness these TWFK can have and add it a beautiful bass response. While it won't transform it in a bassy phone by any means, R-50M does sound more dynamic and richer through the midrange with a fuller overall tone.
 

  
 
 
Ostry KC06: (link)
So, how the well regarded great sounding KC06 matches together with the HDB.  Well, to be honest is simply...
	

	
	
		
		

		
			

















.....WOW!!! Yes, despite being the easiest to drive earphone I ever owned, the KC06 benefits a LOT from amping and the FSA HDB is no exception. These little and quite affordable in-ear set is taken to different and highest level (or should I say levels). First thing first, the bass is now REAL. The HM700 already improved the KC06 sound in this aspect, but the HDB makes a noticeable difference. While a un-amped Ostry has great bass control the quantities probably weren't enough. When plugged to this FSA, it's like listening to different and better beast. The mids as well sound much fuller and the whole sound is bigger, very spacious and incredible deep. And, the soundstage is rather huge with great dimensions. A perfect match indeed, regardless the HDB's retail price.
 

  
 
Hifiman RE-600:
Fortunately, the HDB is able to drive both single and balanced TRRS 3.5 ended earphones. Personally, I do think that RE-600 is needed to be driven in a 'balanced' configuration to show its true form. With the HM700 the RE-600 offers a perfect balance from low to highs with great extension in both ends. Like with the KC06, a similar result is achieved with the HDB. While, the RE-600 is the least light in bass from the Hifiman in-ear line, is more than amazing when listened with the HDB. The low end is substantially more convincing with very good rumble and deeper sub-bass reach. The midrange might show huge improvement in texture, but that's because the RE-600 is already perfect in this area; yet, the mids can be more enjoyable. The soundstage also feels wider.
 

  
 
 
Earbuds:
Ubiquo ES703: (link)
This is a pair of earbuds that I got to like a lot, usually used at home and quieter places. With the Sansa Clip+ alone the ES703 are already very enjoyable, but still are like earbuds. When used together with the HDB the results are more than impressive for just a ~$40-50 earbud. The ES703 start to sound similar to open cans, reminding me in a way to one of my favorites earbuds, the well known Yuin PK1.
 

  
 
 
Full size - Open cans:
SoundMagic HP200: (link)
This was probably my real test for the FSA HDB amplifier. The HP200 are a pair of headphones that I rarely use without amplification, not because being hard to drive, but simply they benefit a lot from a better source. With the HDB, the HP200's extra brightness is taken under control and don't show that certain edginess, even at the brightest tracks. I never found the bass to be light or missing in the HP200, and the HDB adds some extra power and rumble to low sub-bass. Mids are very good, smooth and rich, but not as open, clear or forward as with the Amp-S, especially on Mode-2 (flatter response of the amp).
 

  
 
*Conclusion* (so far for Part 1):
For their first balanced amplifier, Firestone Audio made a great product. A mix of excellent build quality, sleek design, and most importantly, superb sound, which is simply musically engaging. It has more than enough power, and the different balanced in/outputs make it a very versatile product. $300 is no little money, but a well worth buy, indeed. With the right matching equipment the HDB might take the music to another level.


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## twister6

You mentioned HM700 and KC06.  Are you driving these directly from balanced jack or through an adapter (balanced to regular)?  I do enjoy HM700 + RE400B a lot!!!, but that adapter is a real PITA and too flimsy.  I tried driving my other IEMs directly, but I hear hissing which also adds to a noise floor.  Curious because I'm waiting for KC06 and will be getting KC06A as well.  It's not an issue to use it with my X5, but slick portable factor of HM700 always draws me in, especially with included armband


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## DannyBai

Very comprehensive review Zelda. Thanks for bringing this amp to the communities attention. For $300, this thing packs some great features.


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## Makiah S

zelda said:


> *REVIEW**: Firestone Audio Fireye HDB - *(feat. Panda Audio Amp-S and Hifiman HM-700) 


Spoiler: Warning: Spoiler!






> *Specs*:
> (From Firestone Audio site)
> 
> _* Power Structure: Built-in 4-Serial Li-polymer battery power supply_
> ... 
  


 WHoa, nice a warm balanced amp in the $300 price range, looks like ibasso has some compietition!


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## Zelda

twister6 said:


> You mentioned HM700 and KC06.  Are you driving these directly from balanced jack or through an adapter (balanced to regular)?  I do enjoy HM700 + RE400B a lot!!!, but that adapter is a real PITA and too flimsy.  I tried driving my other IEMs directly, but I hear hissing which also adds to a noise floor.  Curious because I'm waiting for KC06 and will be getting KC06A as well.  It's not an issue to use it with my X5, but slick portable factor of HM700 always draws me in, especially with included armband


 
 Usually i use the KC06 directly through the balanced jack output (or with the balanced to regular, which works just as an extension for the kc06). Yes, there's some hiss. but again, the KC06 is very, very sensitive. sometimes i use it with the USB+Balanced adapter, which helps with hiss. although the volume needs a couple of steps more. the adapter itself doesn't bother me, as i just use the ostry at home for their lack of isolation.
 maybe you could get some impedance cable.
  
  


dannybai said:


> Very comprehensive review Zelda. Thanks for bringing this amp to the communities attention. For $300, this thing packs some great features.


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## tomscy2000

FYI, they're also releasing a Fireye DAB, which is an USB PC/OTG input DAC/amp that does 24/192 and DSD. Last I heard, they were going with the WM8741 for D/A conversion. Not sure about the analog stage. I can ask again where they're headed with it. Lately, they've been working on their USB power supply and Raspberry Pi-based wireless streaming dongle, so the DAB might come further down the line.
  
 I posted this a while ago here, but here's the schematic:
  



  
 The LME49724 allows for a fully differential design all the way through to the end, so this is a true balanced amp. Supposedly, they began this project because one of the FSA people who collected RSA amps opened up one of them (not sure which model) and discovered that it wasn't a truly balanced design, and so they set out to design their own.
  
 Anyway, you guys can see some high-quality components there: (Vishay?) MELF resistors, WIMA caps, and apparently even the Li-ion battery connection to the power supply uses thick gauge OCC wire to prevent unnecessary voltage loss.
  
 Specifically regarding IEMs, even though it's a very high-performance part, I'm not thrilled that they went with the TPA6120A2 because they tend to follow the reference recommendation of using 10 ohm output resistors, but if you don't mind the change to your earphone's FR, this amp is very high performance. Just for the HDB (and I assume the DAB), they've also begun selling balanced IEM cables (braid is UE-style --- the twisted-twisted pair pattern with a texture like the UE900's cable, and the connectors are proprietary overmolds) but I have no idea if they're planning to sell these cables overseas.


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## SDBiotek

It looks like yet another knock-off copy of a Ray Samuels Audio headphone amp. This time it may be the SR-71B Blackbird, but in a larger case and without the 3 levels of gain. I wonder how this one would sound in comparison.


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## Zelda

sdbiotek said:


> It looks like yet another knock-off copy of a Ray Samuels Audio headphone amp. This time it may be the SR-71B Blackbird, but in a larger case and *without the 3 levels of gain*. I wonder how this one would sound in comparison.


 
 you mean the HDB? it does have 3 levels


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## tomscy2000

sdbiotek said:


> It looks like yet another knock-off copy of a Ray Samuels Audio headphone amp. This time it may be the SR-71B Blackbird, but in a larger case and without the 3 levels of gain. I wonder how this one would sound in comparison.


 
  
 The topology is quite different from the SR-71B. The 71B uses separate opamp chains for voltage gain and current buffering. The HDB uses an integrated IC for both purposes. The only similarity is that they both have a differential gain input, but I believe the differential opamps used are different.
  
 So knock-off? No. Would you call all those ALO amps knock-offs of RSA amps as well, then?


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## SDBiotek

tomscy2000 said:


> The topology is quite different from the SR-71B. The 71B uses separate opamp chains for voltage gain and current buffering. The HDB uses an integrated IC for both purposes. The only similarity is that they both have a differential gain input, but I believe the differential opamps used are different.
> 
> So knock-off? No. Would you call all those ALO amps knock-offs of RSA amps as well, then?


 
  
  


zelda said:


> you mean the HDB? it does have 3 levels


 
 Sorry about that, you did mention the gain levels. I didn't notice the chassis markings until I pulled up your review from my computer (I originally read it on my phone).


tomscy2000 said:


> The topology is quite different from the SR-71B. The 71B uses separate opamp chains for voltage gain and current buffering. The HDB uses an integrated IC for both purposes. The only similarity is that they both have a differential gain input, but I believe the differential opamps used are different.
> 
> So knock-off? No. Would you call all those ALO amps knock-offs of RSA amps as well, then?


 
 I wasn't referring at any other amps, only this one, but I appreciate you taking the time to explain the topology differences.


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## wahsmoh

mshenay said:


> Spoiler: Warning: Spoiler!
> 
> 
> 
> ...


 
 I know!! I am subbed now. I have been looking for a badass portable amp for my Alpha Dogs so the next airplane flight won't be so boring : ]


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## Raidun

I am very new to the commune and this is my first post/activity. After reading you review I am inclined on buying this amp and it also fits my budget. A seller has it on sale for $330 on ebay including international shipping. Should I go for it? Or is it possible to get it for a cheaper amount? Help!


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## Zelda

raidun said:


> I am very new to the commune and this is my first post/activity. After reading you review I am inclined on buying this amp and it also fits my budget. A seller has it on sale for $330 on ebay including international shipping. Should I go for it? Or is it possible to get it for a cheaper amount? Help!


 
 I;m waiting for a reply from the seller regarding the price and availability. will update the OP asap


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## Raidun

zelda said:


> I;m waiting for a reply from the seller regarding the price and availability. will update the OP asap


 
 Also waiting for the next part of your review. Where does it stand against the Rx MK3 B+?


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## xxxfbsxxx

Its now offered for less than $300 and close to $200 on different site
Just wonder is it worth buying at this price
Any one have further impression? Thanks


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## osiris1

I think I may buy it at around $200. would be nice if Firestone sells them now instead.


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## stuzzyapple

Very in depth and informative thanks


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## MrBackup

Hello, I am interested to know where this amp can be purchased for less than $300 USD.


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## TigreNegrito

Just dropped for $180 for anyone interested!


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## Zelda

^ Yes, MassDrop have it for as low as $180 + s&h. great price!


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## talan7

I got mine off Massdrop for $180 something. This thing sounds more open than mojo. Awesome sound quality, definitely worth the price


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## Sound Eq

how does the old version that has bass boost compare to the new HDB


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## talan7

Sound Eq said:


> how does the old version that has bass boost compare to the new HDB



The old one has bass boost? Is it balanced?


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## Zelda

talan7 said:


> The old one has bass boost? Is it balanced?



the old model was the HD. had a bass gain, but not Balanced 4-pin output


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## malachidjl

Zelda, is still worth getting in your opinion?  Have you tried comparing with other amps recently?  Anything better for price and/or performance?


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## Zelda

malachidjl said:


> Zelda, is still worth getting in your opinion?  Have you tried comparing with other amps recently?  Anything better for price and/or performance?



what's the current price for the HDB?


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## talan7

$159 on Massdrop! Definitely worth it. Massdrop aint playing! They have xduoo xd05, fireye hdb and creative soundblaster e5 at the same time. I have all 3. Sound quality goes to fireye hdb, (only f you use balanced), power goes equally to xd-05 and soundblaster e5. Features definitely go to soundblaster, cool factor as well. I haven't used my soundblaster in almost a year. I'm going to listen to it and compare all 3 later today.


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## Zelda

that's a crazy deal on the HDB! fully balanced and 4-pin plug (input and output)
i could get an extra one for me


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## malachidjl

Thank you both!!!


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## AudioNewbi3

Can these drive the sennheiser hd600?


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## talan7 (May 15, 2017)

Yes, very well


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## AudioNewbi3

talan7 said:


> no, not good. Get the xduoo xd05 or creative soundblaster e5 for large cans


Ah I see I see Thanks for the reply mate!


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## malachidjl (May 14, 2017)

talan7 said:


> no, not good. Get the xduoo xd05 or creative soundblaster e5 for large cans



Have you tried the Fireye HDB with the HD600 or something similar to?  Just curious because Massdrop and their own website states this amp should be able to drive the HD600 "Headphone impedance: 16 – 600 ohm."


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## talan7

malachidjl said:


> Have you tried the Fireye HDB with the HD600 or something similar to?  Just curious because Massdrop and their own website states this amp should be able to drive the HD600 "Headphone impedance: 16 – 600 ohm."



I take it back. I just tested the fireye with my hd650 and lg v10. It drove it just fine. Granted I had my lg v10 cranked all the way up, but I got pretty good listening levels on med gain, high levels on high gain. Very open sounding, bass hit strong...no complaints here. As long as you have a good strong source, you should be ok.


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## talan7

AudioNewbi3 said:


> Can these drive the sennheiser hd600?



They drive hd650 very well. I misspoke earlier before testing. I used lg v10 phone, cranked all the way up with the fireye and got very good results


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## AudioNewbi3

Thanks for the info mate!


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## superuser1

Is the HDB available anywhere online? massdrop doesn't have it anymore.


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## LCMusicLover (Jun 23, 2017)

superuser1 said:


> Is the HDB available anywhere online? massdrop doesn't have it anymore.



It's back on, $159 w/ free shipping to USA.

I received mine today from the last drop (expected ship date of June 5 was missed by 9 days).

Build quality is nice, but I'll wait for burn-in to express opinions on SQ. I will say power seems ... substantial for a portable amp. Listening @ ~25%/low gain with my Monolith m1060s via balanced connection. Certainly not a hard-to-drive set, but clearly lots of headroom. 

One build comment: volume knob was loose, pulled off easily. There's a very small set screw that had to be tightened -- solved problem.


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## talan7

My knob came off almost immediately after I got mine. The screw came out. I re-screwed it back in with a touch of crazy glue. It's been fine since.


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