Whelp, the little Ultralite AVB didn't last long in my posession - i got greedy, and just "had to" upgrade from that to a "big boy" unit. Kinda had my sights set on something like a 1248, but with asking prices in the 900eu area, those were a bit of a no-go. For the most part, 828es's seemed to be in that same area, until one popped up on auction on eBay, from the Netherlands, for "just" 600eu (plus shipping). Coincidence or not, just as with the MOTU 8M a few years back, i ended up being the only bidder, so here we are...
A plentiful plethora, if you will, of ins & outs. Yes, very likely overkill for my usage scenario, at least for now, but i'm thinking futureproofing and so forth. That's my story, and i'm sticking to it!..
But let's pop the top off, shall we?
Well, the similarity to the 8M is no coincidence, they share a lot of DNA. Lots of similar building blocks, but this one's not quite so fully-packed, since it only has two mic preamps.
One slight novelty(?) is that the power supply is now less through-hole-based as before. The PWM on the primary side is now a surface-mount all-in-one, the diodes on the secondary are no longer those huge axial jobs, and the capacitor brands are changed. Same Hon-Kwang OEM though.
The core of this is a Power Integrations TOP269KG flyback controller, secondary diodes are Taiwan Semiconductor TSP10U60S, primary-side capacitors are Jamicon, while the secondary-side ones are... ehrm... "ZMCON". Green sleeving, white markings, GF series - might they be trying to mimic SamXon GF's, perhaps? Regardless, all of these are getting replaced, for peace of mind if nothing else.
Speaking of DNA commonalities with the 8M, the main processor board is literally completely identical, including the SKU number on the silkscreen. I won't bother re-typing (or even copy-pasting) that - if you're really curious, it'll only cost you one or two clicks. What's not in common though, is what seems to be a little factory "whoopsie".
Someone in assembly managed to thread in the screw that was meant to fasten the BNC "frame" to the rear panel, before attaching the rear panel, so... Something had to give... At least none of the bigger BGA's are nearby, so the odds for any actual damage should be minimal.
Diving into the audio circuitry, the mic preamp will likely look familiar too - the now "classic" Texas Instruments / Burr-Brown PGA2500, and some Rohm BA4580R's.
The analog inputs are handled by no less than three AKM AK5574EN 4-channel 32-bit ADC's. The two front inputs (buffered by a pair of National Semiconductor / Texas Instruments LME49724's), the talkback mic on the front panel and the LTC input go into one, and the eight line inputs on the back use the other two.
Before reaching the ADC's though, the line inputs go through some Rohm BA4580R's, a Cirrus Logic CS3318 8-channel analog volume control, some Texas Instruments NE5532 buffers and LME49724's
The DAC's are a pair of ESS ES9016S 32-bit 8-channel jobs. One of them handles the line outputs on the back, while the other drives the main output XLR's on the back, and the two headphone outputs on the front.
Speaking of the main outputs, a couple more BA4580R's drive those.
The headphone outputs are handled by a pair of Texas Instruments OPA1688's.
The biggest(?) chunk of silicon on the main board is an Altera / Intel MAX 10 10M02SCU169C8G FPGA, most likely used as I/O expander for the serial control buses for the DACs, ADC's, LCD's, taking in the signals from the buttons, encoders, and marshaling the audio data to and from the DSP on the processor board.
Moving on to power supply stuff... "Great", Lelon electrolytics... *shudder*
Glossing over that, an ST Microelectronics LD1117 regulator supplies 3.3V to whatever needs it on the audio board, while an OnSemi MC79M05 provides a -5V rail to opamps and the mic preamps.
The +5V rail to the mic preamps is cleaned up by a Nisshinbo NJM2846 regulator. Nearby, a TI TPS61081 boost-converter, complete with voltage multiplier on the output, provides the phantom power to the mic inputs.
I wouldn't have thought there was anything interesting on the front panel PCB, until i was turning it around trying to blow out a speck of dust trapped between one of the LCD's and the front window, when i noticed a BGA chip under the board and the displays. Interestingly enough, it's yet another Altera / Intel MAX 10 FPGA, same part number as on the audio board. I suppose it makes sense, to minimize the number of wires needed between the main board and the front panel, considering there are not one but two colour LCD's to animate and drive, as opposed to the monochrome ones we had seen up until now. The little QFN package nearby is a TI TLC5929 16-channel LED driver. When changing the brightness in the menu, that affects the LCD backlights, as well as the pad / 48V / A/B indicator brightnesses, which is a cute feature.
I might've missed (ok, i haven't bothered) documenting the odd little LDO regulator here and there, but the markings look like various Texas Instruments SOT23-5 / SOT-25 parts, so shouldn't be too hard to track down, and most of the voltages are either called out on the silkscreen, or can be easily deduced from the physical context.
The Lelons on the main board, as well as the caps on the PSU secondary all got replaced with low-ESR United ChemiCon 2200u/16v - i'm quite positive the stock ones had higher (or at least comparable) ESR, and since the PSU is rated for merely half an amp on the +/-8V outputs, the capacitance difference won't amount up to much. I'll stick with the reliability / longevity, thankyouverymuch.
Now all that's left is to start drilling holes in walls and floors, to run a CAT6 line down to the studio... someday...
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