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Firestone Audio Fireye HDB & DAB -- Portable Balanced Amps/DACs

post #1 of 10
Thread Starter 

Firestone Audio is really stepping up its game these days, with increasingly higher-end products, like the Tobby/Bobby.

 

As a followup to their previous HD offerings, they're coming out portable balanced amplifiers: the HDB amp and DAB combination DAC/amp.

 

These pictures were posted on their Facebook Page:

 

* *

 

Looks like they're using the Kobiconn/RSA/ALO 4-pin connector, which is a nice choice for portable.

 

Apparently, they're not skimping on parts quality, using PCOCC wire for the battery hookup; while details are sparse about the DAB, after asking around with people in the know, I've heard that it uses a WM8741 and supports DSD decoding as well as Android OTG support.

 

The HDB looks to be a fully-differential design with a pair of LME49724 as buffers and TPA6120 as voltage amplifiers.

 

* *

 

The outward design seems to be an evolution of the Fireye HD, which is nice. The volume knob looks chunkier/solid and the plugs are no longer recessed, which makes connectivity better. I also like that it has a three step gain stage.

 

If these units can perform on par or better than the current balanced products from ALO and/or RSA, then they'll present themselves to be a pretty good value, especially with DSD support on the DAB, which is a rare feature only seen on single-ended products so far like the iFi Nano iDSD and the new upcoming portables from Korg and JVC.

 

Hopefully, both will start off at a reasonable cost, as I think Firestone products are plagued with unstable pricing. They set different prices for different markets. It'll be affordable here in Taiwan (from what I've heard, price in New Taiwan Dollars translates to around $300 and $350 USD for the HDB and DAB, respectively), as FSA always gives the local market preferred pricing, but who knows how much they'll price it for foreign markets.


Edited by tomscy2000 - 11/12/13 at 7:01pm
post #2 of 10
Thread Starter 

Had a brief listen to a pre-production Fireye HDB through balanced outputs --- quite impressive. FSA is getting serious --- apparently, they're revamping their desktop products once again --- better enclosures, and even a CD player? Hmm. @project86, can you get on this? haha...

post #3 of 10

Judging from the PCB picture, it would seem that LME49724 is for gain or single-to-differential converter. while TPA6120 is for buffer / driver,  I don't see any inductor on the TPA6120 output so it likely has the 10ohm output impedance. I was hoping FireStone can avoid that (high OI) this time.

post #4 of 10
Thread Starter 
Quote:
Originally Posted by ClieOS View Post  Judging from the PCB picture, it would seem that LME49724 is for gain or single-to-differential converter. while TPA6120 is for buffer / driver,  I don't see any inductor on the TPA6120 output so it likely has the 10ohm output impedance. I was hoping FireStone can avoid that (high OI) this time.


Yeah, that's likely still the main problem. IEMs won't be ideal. It'd be very interesting to see how on-ears perform with it too, though. And overall, it's a nice looking package that has been improved over the Fireye HD. Personally, I'm more interested in the DAB model.

post #5 of 10

Hi - sorry if I sound newby - but what is the difference between the HDB and a DAB (what is a DAB??)

 

The homepage of Firestone (firestone-audio.com) only shows the HDB - I cannot see any differentiation.

 

Thx

post #6 of 10
Thread Starter 
Quote:
Originally Posted by AlterSack View Post
 

Hi - sorry if I sound newby - but what is the difference between the HDB and a DAB (what is a DAB??)

 

The homepage of Firestone (firestone-audio.com) only shows the HDB - I cannot see any differentiation.


The HDB is a portable amp only with balanced output, so it doesn't have D/A conversion capability. In other words, it only has analog input, just like a conventional amplifier. Conversely, the DAB is a portable DAC/amp with balanced output, and accepts digital input from PC and/or Android. I don't think the DAB is released yet, because I haven't heard anything from them about it. So I can only assume they're still working on it, while the HDB is already released to the public.

post #7 of 10

Thx - I was basivally wondering what "DAB" meant as an abbreviation ...

 

DAC = Digital Analog Converter

DAP = Digital Audio Player

DAB = Digital Analog Balanced Converter ???

 

and btw - can anybody confirm that the output impedance will be 10 ohm? I didin#t find it on the specs sheet


Edited by AlterSack - 4/4/14 at 2:21am
post #8 of 10
Thread Starter 
Quote:
Originally Posted by AlterSack View Post
 

Thx - I was basivally wondering what "DAB" meant as an abbreviation ...

 

DAC = Digital Analog Converter

DAP = Digital Audio Player

DAB = Digital Analog Balanced Converter ???

 

and btw - can anybody confirm that the output impedance will be 10 ohm? I didin#t find it on the specs sheet

 

Well, the extra 'B' does stand for balanced, while the 'HD' and 'DA' are holdovers from the previous generation of portable amps from them.

 

I assume that 'HD' stands for "high definition", while 'DA' stands for "digital-to-analog".

 

The HDB likely has 10 ohms of output impedance because it uses the TPA6120A2 as the output amplification chip. The TI reference board for the TPA6120A2 requires a 10 ohm resistor across the output in order to prevent instability and damage to headphones. The older HD also used the TPA6120A2, and it definitely had 10 ohms of OI.

 

Also, I used a pre-production HDB with the UERM, which is sensitive to output impedance mismatches to input impedance, and it because slightly, but noticeably darker, pointing to a high likelihood of it having 10 ohms output impedance because the UERM tends to get darker with increased OI. I've told Firestone about peoples' concerns with output impedance, but I don't know if they plan to make any alterations.

 

However, the HDB, even through the single-ended output, is noticeably better sounding than its HD predecessor.

 

I do know that the DAB is going to have completely different output topology from the HDB, so it won't be using the TPA6120A2. However, it's anyone's guess right now what it'll be. All I know is that they plan on using the Wolfson WM8741 for D/A conversion, and that the USB receiver will support both Android OTG (up to what I assume is 24/96) and asynchronous PC transfer (up to 24/192).

post #9 of 10

Thx :smile:

post #10 of 10

Could not anybode help me solve circuit diagram SE input to Balanced out by LME49724, please ?

As is it in this amp....

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