#58 Behringer FirePower FCA1616 teardown

Long time no see, eh? Well, what can you do when the new job's kicking you in the rear end? Regardless, new patient on the table this time around - A not-that-often-encountered Behringer audio interface (now discontinued, "obviously"). I took the gamble on it primarily because it was cheap, secondly because i wanted to take a peek under the hood, and somewhat connected to that, curious about if and what "magic mojo" might the touted Midas preamps contain.

Front panel's pretty fully packed - look at all the buttons and 3mm LED's! Not all just for show, though. Each of the four mic / instrument inputs has an input selection switch, a pad switch, a high-pass (aka low-cut) switch, and an individual phantom-power switch.

Quite busy around the back side as well. The four line inputs reside here, as well as, surprisingly enough, inserts for all eight analog inputs (the mic/instrument ones on the front, and the line inputs on the back), and all the digital ins & outs.

The format and the feature set remind me, to some extent, of the MOTU Traveler units (sans the stand-alone configurable mixer functionality), but with added analog inserts. Also, i may very well be wrong, but i can't seem to recall any other Firewire *and* USB connectable interfaces, outside the MOTU Hybrid lineup. On a brief research, it would appear these units require a power cycle to switch between the two connectivities, but anyway... I didn't exactly buy this to use as a "daily driver".

The eBay listing said it doesn't even power on, but the seller couldn't tell whether it was a power supply issue (external 12V 2A power brick), or within the unit itself. For the record, i did indeed stick to the mantra of "Don't turn it on, take it apaaaah't!", but i did venture plugging in the power brick. At least unloaded, puts out 12.03V, just as it should. Whether it can still maintain that under load, is a totally different story (as a local friend whose Scarlett 18i8 wall-wart i recapped last month, can attest).

That being said though, there's something rattling inside the casing. Could that perhaps be a clue? Off comes the top - drumroll, please...

Well, you don't see a yellow-soldermask board all that often. I think the only other time i have, in recent times, was in some internal photos of a Behringer amplifier, on a forum. Come to think of it, there was the odd PCI soundcard back in the day with orange(ish) soldermask... Ah, the "good old days" - simple(r) times...

Buuuut back to the task at hand. Spoiler alert - don't look on the left side of the board!

Glossing over the arguably... interesting area of the board, the main controller is an Archwave DM1500, and as one might expect, some DRAM (Micron MT48LC4M16A2 64Mbit / 8Mbyte SDRAM) and firmware flash (Macronix MX29LV320EBTI-70G 32Mbit / 4Mbyte) in the vicinity. Also, a near-classic TI TSB41AB1 is handling the physical / electrical interfacing to the Firewire connection. And last but not least, "below" all these is a small TLV0832 analog-to-digital converter - pretty sure this reads the "Mix Bal" and "Main Vol" potentiometers on the front panel and passes the data on to the brains of the operation.

Further on, we have the converter section, all Cirrus Logic equipped. The bigger chip is a CS42435 codec, containing four analog-to-digital converters and eight digital-to-analog converters. The two smaller ones are a pair of CS5340 A-D converters. Can't quite tell which are in charge of the front inputs and which handle the rear ones, but either way, one can be sure they haven't "interleaved" them.

Despite Behringer having a reputation for (nearly) bottom-of-the-barrel equipment, they haven't cheaped out too-too much, at least in this case. All the silicon looks to be name-brand, even the opamps. Most of them are SOIC8-packaged 4580's, but going by the font and the -R suffix, i'm reasonably sure they're Rohm BA4580RF's.

And now, we get to the mic preamps. Same opamps as mentioned above, and a somewhat familiar sight yet again - a pair of 2SA1268GR / KTA1268GR PNP transistors. Between these and the four slightly fatter 8mm diameter electrolytics in the area, this "smells" to me a lot like the "XMAX" preamps in the Presonus Audiobox 1818VSL from a while ago - in other words, a pretty classic circuit.

The board also contains four SIP9-packaged NJM4580L's, most likely to drive the two headphone outputs, given their proximity to the connectors for the cables going to that area. Once again, nothing space-age, but no no-name parts employed. On the other hand, though...

Umm... Yeah, i think i finally found the cause of the rattle mentioned near the beginning. Whoopsieee...

Surprise-surprise, power supply did a boo-boo. And, "of course", took the main PWM controller down with it.

So then, after the DC input jack, the two power lines go through a rectifier bridge made up of four diodes, gets filtered with the bigger electrolytic, then gets OR'd with two diodes - the other one, i suspect, being the power supply coming from the Firewire connection (when used / available). That then gets filtered by the destroyed capacitor (which used to be a 47uF 25V Decon SA).

The sadly deceased PWM controller, after some digging (due to half the marking being illegible due to the crater in it), turned out to be a LinearTech LTC1871. That, in turn, drives a FairchildSemi FDS3672 N-channel MOSFET, which then drives the flyback transformer. This creates the +/- analog supply rails for the opamps, as well as the phantom-power rail.

On the other side of the blown electrolytic is a Monolithic Power Systems MP1591DS step-down converter, which most likely handles the main digital power rail - my best guess would be 5V for the converters and likely LED driving (on the front panel), which then gets regulated down to 3.3v by the SOT223-packaged BCD Semiconductor AZ1117.

[To be continued...]