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Help fixing a Fucusrite Liquid saffire 56's preamps

Discussion in 'Studio Lounge' started by pcrecord, Oct 30, 2015.

  1. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    Yes, the mistake in focusrite name was intentional ;)
    I love my ISA preamps but this 56 was a pain from day 1, it went to the service center and return in the same condition.. At first it was just channel one, so I just accepted it to avoid loosing the unit 3months again...
    Now the problem occurs on more than one channel so here's the cry for help !

    I replaced it with a Fireface 800 but, I'd like to fix it and decide later if I sell it or keep it as a backup/input extension...

    The problem ;
    Preamps, will fall to near zero level after a bit random time and sometime at power up.
    In channels 5-8, this happens rarely, but in 1-4 it happens all the time.

    To make them work again, I need to put the volume to maximum and then the signal come back (with usual feedbacks if not carefull)

    If the unit would become stable after a while it could be fine.. but it's intermittent.. I could record a drum track and boom loose a channel in the middle of the song..
    I tried different cables, mics, with or without phantom power, I cleaned all the front controls and xlr connectors. name it I've tried it all.

    Now is the time to open it up and fix it or break it.. I'm handy with soldering and with a multimeter, I just need some direction as to where to look first.

    I thought about the powersupply but it's not all channels at the same time.. usually just one, then another..
    I thought about on board condenser, that might just empty themself..

    Saddly I can't find any schematics of the board to follow preamps circuits.
    I fear sending it to a repair shop because this is an random problem, it would cost me alot to let it stand on a bench.

    Any idea ???
    Thanks
     
  2. Boswell

    Boswell Moderator Distinguished Member

    It sounds to me like dry joints in a Friday afternoon unit.

    When the level jumps, is is just a gain change, or does the quality of the sound change as well? When you wind the gain up to get it back to the normal state, does the level recover suddenly or jump back? Does the technique work even if the output of the pre-amp is muted beforehand? Does percussive therapy have any effect?
     
    pcrecord likes this.
  3. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    No hitting it doesn't change anything..
    When the signal nearly go off, the sound is very faint and crappy.. I should try to record it..
    When the level go down (without touching the gain) it will not go back by itself, I'd need to push the gain to its near maximum or like in the mp3 hit on the mic. Then the sound suddenly comes back to normal and I need to put the gain back where it was to have the same levels.
    The defective signal often occur when I power up the 56... as if the preamp do not receive enough electricity and then if I push it the contact is made and the signal is back. . . then it can go off again after a few minutes..

    I hope you have a better picture of this problem.. Thanks for taking the time. ;)

     

    Attached Files:

  4. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    If it's a dry joint(s) where do I start ? the preamp signal path or power supply or everyone of them ?
     
  5. Boswell

    Boswell Moderator Distinguished Member

    The puzzle here is why there should be more than one channel affected at different times. With a single fault, either one channel only is affected or all channels in a group. For there to be output amplitude variations in several channels at different times implies a similar fault in several places, which does not seem likely. I wonder if the difference in behaviour between channels 1-4 and 5-8 is a clue? One way in which they grouped like that is in S/MUX ADAT.

    Do you have ways of getting signals out of the Saffire 56 other than through the computer interface? For example, can you route converted input channels to ADAT outputs? If that is possible, I assume routing ADAT inputs to the analog outputs is also possible, so connecting a lightpipe between the ADAT1 out and ADAT1 in would enable you to get a different view of the converted inputs. If you were to do that, do the signals that have done an ADAT round trip suffer the same amplitude fault as channels taken back to the computer via the FireWire interface?
     
    kmetal and pcrecord like this.
  6. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    The problem started with the channel 1 and it was only that one for a while...
    Thing to consider, I learned it was a floor demo for longer than the seller told me.. I think they had it for a few years as a mic test setup..
    The problem occur even in standalone mode and with the computer but signals still pass through the onboard digital mixer, so it's not strait in and out.. it goes through some dsp chip I guess.
    I started to redo all the joints I could redo.. All but the surface soldering which need a pool to do.
    The channel 5-8 are indeed more stable.. once I make them peak once.. the stay up a lot longer.. I should let them for a few hours and see if the shut down as well..
     
    kmetal likes this.
  7. DonnyThompson

    DonnyThompson Distinguished Member

    I'm following this thread with interest.
    Unfortunately, I have no advice to offer; certainly nothing that would even come close to what our beloved and wickedly intelligent Bos would suggest...

    ...but I am watching, lurking... :notworthy:
     
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  8. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    I'll try to finish the joints of the 2 main boards today and test the unit. It will still leave the power supply joints.
    After that, Could it be a defective capacitor ? I know cheap ones have been sold every where.. At least none of mine seems busted. (no round or leak tops...)
     
    kmetal likes this.
  9. kmetal

    kmetal Kyle P. Gushue Well-Known Member

    I also will be of little help but am watching closely. Caps tubes and power supplies are the most common things that I hear faulting out.
     
  10. Boswell

    Boswell Moderator Distinguished Member

    Marco - can you post a short section of the degraded sound from one of the channels? If it's very quiet, it may mean increasing the gain digitally by 40dB, but I would like to have a detailed look at the waveform. My suspicion is that the problem is happening in the digital domain.
     
  11. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    After a redo of all joints except surface mount chips, the problem vanished !! :)
    Just hope it's not coincidence and it's waiting to come back.. But I just left the unit running for 2 hours and it's still ok !

    I had a doubt about joints and capacitors for a while. I guess, I just needed the courage to do the work. Thanks a lot Bos.

    If you still want a wave file of the defective sound, I can provide it.. I saved it..

    Now the next question is, do I sell it in fear of the problem comming back (I'm looking for the Audient ASP800 and could use the money..)
    Or I keep it to complet my preamp list and forget about the Audient...
    What would you do ?
     
    kmetal likes this.
  12. kmetal

    kmetal Kyle P. Gushue Well-Known Member

    Sweet man! Back to life is a good thing. I was interested in the asp800 but 96k is its max sample rate, and that's a deal breaker for me. The asp is probably an upgrade in a reliability sense, but probably only a small upgrade in sonics. Seems like a fairly expensive 'even swap'. I'd try and get a little more out of the focusrite. That same money or a bit more you've added up could get you some cool stuff. A couple of 7th circle api clones would rip on your lock and snare. Maybe take that $800 and start a 500 series rack. A nice maag eq would add some life to those overheads by recipe. Pffft, and RND unit isn't far off from that range. Those are serious volume and tone knobs.
     
  13. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    It doesn't mather to me since I would use it with the FF800 converters. I already use my ADAT ports for my UA-470 on which goes 2 x ISA two and with 2 LA-610 on the list the ASP800 would just be there to complete the preamp count for the limited times I do a full band. While many still work in 44 or 48k, I feel that, working at 96k is already excellent. So 192 is not in my plans...

    I'll think about it K. I got the feeling the Audient preamps are better than the Saffire 56 but how much$$ better is the right question ! ;)
     
    kmetal likes this.
  14. Boswell

    Boswell Moderator Distinguished Member

    Glad you got it working again, Marco. For the problems you described, there must have been a whole area of the PCB that was not flowed properly at manufacture. Slap on the wrist for Focusrite. I wonder if they keep a watchful eye on this forum?
     
    kmetal likes this.
  15. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    I was in contact with them asking to orient my diagnosis but they ask that I send the unit to a repair center (the same one that kept it for 3 months last year without finding the problem)
    You can bet I'll send them an email saying what fixed the issue ...
     
    kmetal likes this.

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