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Sunday, 13 October 2019

#55 Focusrite Scarlett 2i2 (1st gen) teardown & modding

I had fiddled with one of these a couple years back, but here's another chance to take a look inside a (1st gen) Focusrite Scarlett 2i2, their second-smallest USB audio interface of the range.





Two ins, two outs, pretty much all you need in order to get started with home-recording (of a higher quality level than using the on-board soundcard in your laptop or desktop, that is). 

Same chunky extruded aluminium housing as its larger brothers (the Scarlett 18i8 and, to some extent, the 18i20), which facilitates quite simple assembly and servicing. First part to come off is the rear panel, once the 1/4" jack socket nuts are removed, as well as three mounting screws.


Two internal clips undone, and the guts can slide out the front. Not terribly much on the inside, but then again, there's not all that much required nowadays.


A closer look with the front panel reveals a bit more of the internals, but the top daughterboard needs to come off as well.


The "main mover and shaker" is, once again an Xmos processor - this time around, an XS1-L8A-64-TQ128, same as one of the two chips in the 18i20, as it turns out. An SMSC (now Microchip) USB3343 interfaces the controller to the USB port. 


Where previously a Cirrus Logic CS2300 PLL clock generator was found, here it's a Microchip PL611 (the C1L95-marked 8-pin chip right next to the 26MHz quartz crystal). In the vicinity we also find two OnSemi NCP1521B step-down converters (GALRZM marking), and an OnSemi NCP303 voltage detector (SOERZJ marking), for keeping the processor in reset until its supply rail has stabilized.



The power supply section, apart from the two chips mentioned just above, there's a pair of Intersil / Renesas ISL97519A step-up regulators - one (U9) handling the generation of the +48V phantom-power, and the other one (U4) handling the analog supplies (+/-5V or 7V, i neglected to measure).



Even though this is the baby of the Scarlett range, they haven't skimped on components. Granted, partially due to economies of scale as well, no doubt. But the audio conversion is taken care of by a lone Cirrus Logic CS4272, just as in its bigger brothers.



On the analog side of things it's "business as usual" as well - NJM4565 opamps and NJM2122's as the adjustable preamplifiers. Unlike the bigger units though, the input switching is routed through an OnSemi MC74HC4066 quad SPST analog switch (as opposed to 4052/4053 multiplexers). I'd reckon that choice was made more out of board real-estate reasons rather than other considerations.

On to the modding stage then. One of the very few complaints regarding this first generation 2i2's was that, on the instrument input, the preamps reached clipping disappointingly soon, even with the gain adjustments at minimum, and especially when used with guitars with higher-output pickups. As mentioned right at the beginning, i had done a bit of tweaking on a 2i2 belonging to a guitarist bandmate, which helped things somewhat. At the very least, he's yet to complain about the issue, so i guess it must've worked well enough (at least for his guitars).


The NJM2122's in these preamps are wired as the two input opamps in a three-opamp instrumentation amplifier. The third opamp is one half of an NJM4565 (U18 in this case). The "Rgain" in the Wikipedia article is the gain adjustment potentiometer mounted on the top board, and accessible on the front panel, with a 470uF DC-blocking capacitor in series with it (to minimize the DC-offset on the outputs), as well as a 33 ohm resistor (to limit the maximum gain). "R1" are 10k (R94, R98, R96 and R89 on the board), R2 are 30k (R58, R59, R60 and R61), and R3 are 13k (R80, R81, R82 and R83).

All stock, with the gain controls at minimum, the input clipping indicators (red LEDs) come on when the input signal reaches around 3.6Vpp. With the above-mentioned resistor values, and the 20k gain potentiometer (which is actually a stereo 50k with the two sections wired in parallel), the minimum gain coming out of the NJM2122 is 2x. Through a bit of LTSpice simulation as well as messing with a couple resistor values, i managed to figure out that, by reducing the value of the 10k feedback resistors around each of the two halves of the NJM2122's, i could reduce the minimum gain there. Sure, that would then also limit the maximum gain available, but at least in these usage cases, that wouldn't be an issue (no ribbon mics in use, nor terribly insensitive dynamic mics used on quiet sources). 



Reducing the 10k's to 5k (by just piggybacking another pair of 10k's on top of the existing ones), the clipping point moved up to around 4.6Vpp; further reducing that to 3.3k (with yet another pair of 10k's) resulted in a clipping point around 5Vpp. That's a ~4dB increase in headroom - not stellar, but without totally reworking the preamp design, or increasing the power supply rails, it seemed like the best(?) way to go given the situation. This time around though, i had some 4.02k 0603-packaged resistors handy (the blue ones), which when parallelled with the stock 10k's came out close-enough to the 3.3k from the previously-determined tests, so that's what went in.

52 comments:

  1. Hola, Me puede ayudar en algo necesito los driver de audio ubs para mi focusriti 2i2 1ra gen. llevo muchos tiempo en eso y no lo es podido conseguir

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    1. First of all, i'm afraid i don't speak spanish, but fortunately there are online translators - you could try using one.

      Have you tried looking for a driver, for example, on the Focusrite website?

      Delete
  2. Hi! Can you help me? I have an 2i4 in my lab, the failure is in ch 2, there are a feedback circuit that switch between mic or line through the switchs on combo connector, i don´t understand why the Sleeve pin go to voltage divider with 47k resistors and a mosfet smd (markes MCW) transistor, and some stages of preamplification. The failure is a "pink noise", when plug a TS or TRS connector the noise disappear. Have you a circuit of this? I changed electrolytic caps, op-amps, the 4066 and nothing happen. Thanks and sorry for my english!

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    1. Which sleeve pin goes to that voltage divider? The connector has the pin that makes contact with the sleeve of the TS/TRS jack, and another pin that's the "sleeve switch". See the diagram in the drawing (lower right side):

      https://www.neutrik.com/media/8604/download/ncj10fi-h-4.pdf?v=1

      So the noise is present only when the XLR connection is active? What about when a microphone or some other signal source is connected? Or just when nothing is plugged in? And at what gain adjust level?

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  3. Hi, can you help me please? I have 2i2 first gen with.. I think it's XMOS chip failed, it eaten my brand new USB3343 chip twice with the same symptom of popping (burn) ULPI Supply (VDDIO) pin of USB3343 chip. XMOS chip itself even heatup with no USB3343 chip soldered.

    I'm not familiar with XMOS at all, is it need to reprogram? Or I can just replace it right away?

    Also, I don't think it's XS1-L8A-64-LQ64 or at least LQ64 code since it got 128 pin.

    Regards :D

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    1. That sounds really odd. But if the VDDIO gets toasted, it might be worth measuring the resistance to ground of the data bus pins (or better yet, the reverse-diode-drop between ground and the data pins). With the power off, of course.

      Not quite sure why, but it seems the photo of the Xmos chip area disappeared from here, but i've reattached it. Good catch, although the two chips may well be identical internally, just with more I/O pins "exposed". Oddly enough, the "8L6C5" marking is shared between the two packages... because logic. Turns out the actual part number is XS1-L8A-64-TQ128.

      I can't say for sure whether the chip itself needs any reprogramming, but i'm thinking it shouldn't - i quite doubt it contains anything but the factory bootloader and whatnot. I'd expect some sort of coloured dot or label on the chip, to show that it has been programmed, like for example the flash memory chip next to it (which contains the firmware).

      Delete
    2. Thank you for reply and bring some more info and advice, yes I agreed that it's really odd.

      Sorry for I'm not give additional info. I already tried measure resistance and diode test on ULPI pin and it show that the ULPI seem to be fine. All pin got very high resistance (Over 1Megaohm) and around 0.9V diode-drop, no short at all.

      Here's what happened, one day Scarlett just gone unable to start. I think computer recognize it as disc drive or something. Windows showed it unable to start because it door still opening... (What?). So I though it would be USB chip about to die so I do try to replace it.

      1. Attempt) When I replace USB chip for the first time. Computer recognize the Scarlett but for only 5 second then USB chip died. No heat, VDDIO not toast yet.

      2. Attempt) On second attempt with second chip, it react the same as computer will recognize for only 5 second or less then USB chip died again. So I do plug USB in for diagnostic for long time then VDDIO pop!. Now ULPI pin of USB chip shorted to ground

      3. Diag) After remove USB chip, measured with result of no short at all. But this time XMOS chip starting to get hot so fast.

      So I still has no idea if XMOS chip is really a root cause or not or I mess something up then it sum up to be a big mess.
      * I bought USB3343 from RS, it should be genuine one *

      Another odd thing is, mine XMOS has no any marking other than XMOS name, wafer number, and lot code. So thank you for clear me up on exact part number.

      I hope reprogramming is not require as you said, it will make it possible to fix.

      Delete
    3. That's a really interesting / odd sequence of events. Considering what's happened there, i'd almost start suspecting something in the power supply section as well.

      Is there any chance you can check the various voltage rails (+/-5v, 3.3v etc - test points are clearly marked on the board), maybe with the USB chip removed?

      Delete
    4. Hello Khron, I do remove USB chip then measure. 5Vusb and 3.3V seem to be fine, but U1 give out only 1 volt and U4 at Pin 5 give only few millivolt (USB ground as reference). No short circuit to USB ground, seem like something wrong with the U4?

      But as I try to trace U4 output, it mostly powering Opamp. How this going to affect the digital side?

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    5. U1 might be supposed to be the 1V regulator, to power the core of the Xmos controller. What voltage were you expecting to see there, if you say that's wrong?

      U4 has an "enable" pin, as you may or may not have noticed in the datasheet. For all i know, there might be some power monitoring circuitry somewhere, that shuts things down if it detects some voltages are way off.

      As i mentioned, i'm pretty sure most of the voltage rails in there have clearly marked test-points, don't they? I can see the 3.3v test point in one of my photos.

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    6. Yes, I measure 3.3V test point and it gave correct voltage.

      I will try to trace from enable pin to see if there is power monitoring circuitry and what's wrong with it.

      Delete
    7. Is that the only voltage test point available? No "VA"-marked ones? I don't have a 2i2 at hand, and it seems i haven't caught them in the photos i've taken.

      Delete
    8. I can't find VA marking in mine. Also U4 is controlled by XMOS chip directly and XMOS keep it disabled.

      Here is all test point I found
      TP1 - 3.3V, tested ok
      TP2 - U4 control signal, 3.3V present at all time.
      TP4 - Ground
      TP6 - 48V, tested ok
      TP7 - Ground
      TP8 - Ground

      I can't find where TP3 and TP5 is.

      And oh, I just notice that your and mine is 1st gen (mine S/N start with S) but we have quite different board layout.

      https://www.img.in.th/image/Yf4P29

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    9. Interesting... But i guess it's not shocking to have different revisions of a product, throughout its lifetime.

      It's tough to give such specific advice from a distance, so i'm not sure how much more help i can offer.

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  4. I have a scarlet 2i2 2nd gen which I accidentally put 40v rail of my power amp through the audio ground through the preamp which grounded through the scarlett USB and blew parts on the board including the USB ground trace on the board and my laptop. There are no visibly burned ics and I pulled the 5.2v zener (shorted) and now I get usb 5v to the regulators but I can't figure out what supplies high (reset circuit) to the "EN trace" which connects to EN pin of two regulators and the usb audio (xmos) chip.
    What did you find on the gen 1 unit?
    What controlled the output of the 3.3v regulator?

    Thanks for your help!

    ReplyDelete
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    1. "Blew parts on the board including the USB ground trace on the board and my laptop" - on one hand, i'm not even sure that's fixable anymore; on the other hand, i'm quite sure it's not worth fixing anymore.

      Not sure what i was supposed to "find on the gen 1 unit" - i wasn't exactly looking for anything, especially nothing like what you're asking.

      Delete
  5. Thanks! I just fixed one Scarlett 2i2 by replacing the USB3343. Your blog was really good source of information!

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    1. I'm glad to have been of help! And / but without Suomi accepting and welcoming me as nicely as it has, i'm not sure even this blog would've ever happened, not to mention all the "patients"...

      Delete
  6. Hi! Excellent post. Do you know where can I find a service manual for this card? I want to take the preamp section and feed a PCM2900 with it, bc I haven't been able to find other preamp for the pcm

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    1. There is none. But you're in luck, more or less - i did reverse-engineer the preamp section, to some extent, in order to try to make up for one of the greater criticisms / design missteps of this unit, namely, too little headroom on the instrument input.

      https://drive.google.com/file/d/1_nMGRzwDcgGZIiVSj9Uy-jFZaCasZeNg/view?usp=sharing

      Can't quite say if it's 1000000% accurate, you'll have to double-check it yourself probably, but i suppose it's more than nothing.

      And you'd want to feed the output of the preamps into a PCM2900 because.....? "Only" the signal-to-noise ratio of the 2900 is about 25dB WORSE than the CS4272.

      Delete
  7. Hello, I tried to repair my 2 i4. But I lost C39.C38.C40.C41.C42.C43.L12L13.L10. Do you have any relevant parameters? Forgive my English is not very good. Thank you

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    1. You might be ever so slightly lucky - i actually have a 1st gen AND a 2nd gen 2i4, both ready to be torn down and inspected. Which one do you have?

      Delete
    2. 在遇到您之前我以为我的声卡已经没救了,十分感谢您的帮助

      Delete
  8. Hellow! I have a scarlet 2i4 1 generation. The sound card just stopped being detected in the PC. The flash and the microcontroller are powered (3.3V, 1V, etc.) Nothing heats up abnormally, I think to start with the firmware, can you provide a dump from the same working card? thanks!

    ReplyDelete
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    1. You're actually in luck, at least partially. Currently i'm doing the write-up on the teardown and repair of a 2i4 gen2, but i also have a 2i4 gen1 that has issues, as well as a working 2i4 to dump the firmware from.

      Slight trouble is, i've recently moved house, and my programmer is... somewhere, yet to be found (again). But as soon as i do, i'll dump the firmware from the good 2i4 gen1, and i hope i'll remember to also post a link to it.

      Delete
    2. Sorry, I was wrong in the card model, not 2i4, but scarlet 2i2 1gen

      Delete
    3. Sorry, I was wrong in the card model, not 2i4, but scarlet 2i2 1gen
      I have a firmware that has been merged from a working scarlet 2i4 1gen soundcard. Here is a link to the archive with the firmware, there is a photo of the board, the minimum driver and a dump from the flash drive. If you share with me the firmware from 2i2 1gen, I will be very grateful to you.
      https://drive.google.com/file/d/1HhePYJVstOSB8UyC-x6Lm26onXqjiDyV/view?usp=sharing

      Delete
    4. I seem to have forgotten to dump the firmware from this 2i2 belonging to my friend, but i could ask to borrow it again for a few minutes.

      So you tried to run your 2i2 with the firmware from a 2i4, or..?

      Delete
    5. No, I have not tried it, but I will have no choice, if I do not find the firmware from 2i2, if it does not work correctly even after that, then at least I will be convinced that the hardware is a whole and the matter is only in the firmware.

      Delete
    6. If you still manage to merge the firmware from the 2i2 card, I will be very grateful.

      Delete
    7. Well, you're in luck - i managed to borrow my friend's 2i2 again, and dumped the firmware from it, so here it is.

      Delete
    8. Thank you! tomorrow I will start repairing, just in case I still ordered a processor and a yusb transceiver!

      Delete
    9. Good luck with that! I'm waiting to receive a new USB3343 for my 2i4 gen1, in the hopes it'll come back to life too.

      Delete
  9. Hello Khron,


    I really do appreciate your sharing of knowledge and what you have found in these gears. I have very limited knowledge in electronics. I had used my 1st gen 2i2 for quite some years since 2014. However, it stopped generating any sound even though it is still detectable when I plug into my PC. Strange thing is that it works when I turn on the live monitoring switch. Seems like the Analog to Digital Converter is burned? It would be so great if you could tell me what to look for and how to test the potential faulty parts since I have lost hope with the customer service. Thank you and appreciate it!!!

    ReplyDelete
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    1. Thanks for the kind words, first and foremost.

      Regarding your issue though... The converter is indeed one of the prime suspects, but certainly not the only one. To be able to make (more) completely sure, some oscilloscope propbing inside the unit would reveal more information.

      Delete
  10. Great Article! I'm planning on making my own audio interface. Did you happen to make a block diagram showing how all of the ICs you identified interact with each other? Do you know where I could find one?

    I'm getting into the nitty-gritty of what my allowable analog voltage ranges should be. Anything helps. Thanks!

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    1. Good luck with that. In the grand scheme of things, i'd say the analog voltage ranges are the LEAST of your issues...

      But, of course, that depends on what "audio interface" means to you.

      I don't mean to sound arrogant or anything, but most of the circuitry inside devices like these are a collection of more or less "standard" building blocks, on some occasions with a minor "twist" here and there. The "secret sauce" is in the firmware / drivers / software, though...

      Delete
  11. my 2i4 2nd gen sound card suffered a crash recently and it was no longer recognized on the PC. When I plug in the red LEDs light up when I press the buttons. So I decided to replace the xmos with a recovered xmos from a 2i2 2nd gen sound card. currently, the pc recognizes the connected 2i4. everything seems correct on the pc side but no sound signal comes out of the sound card. no sound through headphones, no sound from the monitoring outputs. although the phantom indicator lights up the microphone does not come on because the + 48V is not present at the XLR cable. The 3.3 v, 1v, and 5v are present on the test pins. I noticed that the different JRC 4565 are not powered. There is a problem with the power supply of these JRCs. Can someone help me solve this problem please?

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  12. Someone can help with 2i4 2nd gen electronic diagram please?

    ReplyDelete
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    1. Would it have been a better idea to post this in the 2i4 2nd gen teardown, perhaps? ;)

      Are you 100% sure the same chip model is used in both the 2i2 and 2i4 gen2? And how certain are you that no components flew off when you removed the original Xmos chip?

      Look through the datasheets of the power supply chips (all linked within the 2i4 gen2 teardown and see how each chip's enable input works (active high or low). If it's anything like the Saffire 6 USB, the digital supplies are "always on", but the analog supplies are activated by an output from the Xmos chip, possibly through a small SOT23-packaged MOSFET or two.

      Delete
  13. Scheme attached in post (http://forum.vegalab.ru/showthread.php?t=89889&p=2990782&viewfull=1#post2990782).

    ReplyDelete
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    1. Maybe that's true, but that's not my ch help to people who don't speak russian, or can even read cyrillic letters...

      Delete
  14. http://forum.vegalab.ru/attachment.php?attachmentid=411179&d=1638952178

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  15. Replies
    1. That's a great find! BUT... Once again, why post this on the 2i2 teardown, when there are blog articles here for the actual 2i4 (gen 1 AND 2)?

      Delete

  16. potresti aiutarmi, la mia interfaccia era così, collegando il cavo usb il led verde si accende e si spegne, windows non riconosce, l'interfaccia è la 2i4 foscusrite

    ReplyDelete
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    1. As you may or may not have noticed, nothing on this blog is written in anything else except english, so... Why imagine that i might happen to speak italian? Because i don't.

      But thanks to Google translate... How long does the green USB LED stay on, before it turns off again?

      Either way, it's difficult to guess what the problem is. Could be the USB PHY chip, could be a firmware issue, could be a power supply issue, or worst case, the Xmos controller itself.

      Delete
    2. forgive me, I didn't watch the language, forgive me, it stays 1 second at most, it's very fast.
      but thanks for the tip.

      Delete