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MOTU 828 mkII USB crackle
Old 17th December 2009
  #1
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MOTU 828 mkII USB crackle

Does anyone else have a problem with this interface crackling - mine is very new (just over the year's guarantee of course!), I used to have it hooked up to an iMac, and sure I didn't have this problem then. It's now hooked up to a Mac Pro, and I'm getting a REALLY annoying crackle. I've isolated it down to the MOTU - I can unplug everything going into it, power aside, and everything going out of it, but can still see on the meters that there is an intermittent noise. It's not all the time, and if I change MOTU settings (sample rate, clock source etc.) then it seems to go for a while. I run iTunes, Logic etc. through it. I've tried plugging it into a socket on its own, I've disconnected it from the internet, I use power over ethernet, so I've unplugged all that too - but nothing seems to fix it long term. Having said that, it's behaving extremely nicely right now. Can't find anything else on google about it, hope someone else has had similar probs, and has fixed! Thanks!
Old 17th December 2009
  #2
Gear Nut
 
RTFMPleez's Avatar
 

Is this a new Mac with Snow Leopard. If so, maybe you need a firmware update??
Old 17th December 2009 | Show parent
  #3
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Thanks! It's 10.5.8 - but the MOTU produces crackle when not attached to the Mac at all. I'm in quite an old house, and I imagine the electrics are not exactly modern, so wondering if that is a problem. Next step of diagnostics is to take the MOTU somewhere that I know has modern electrics, see if I can replicate there. Unless anyone knows different. Or do you think the firmware update is important anyway? Also, fairly sure I didn't have this problem attached to the iMac which was 10.4.something.
Old 17th December 2009 | Show parent
  #4
Gear Head
 

yeah, my 828 has been slowly breaking down over the years. first it was the backlight burning out, then about a year ago i encountered the similar crackling noise. i traced it down to one of the built in mic-pres. i tried to turn down the input volume on it, but the noise was on the channel internally. so, i opened up the cuemix and muted the channel, and although the noise is still there, i just don't hear it anymore. this solution can obviously be applied to any of the channels (so if you see your LED light up on channel 5 whenever a crackle happens, you know to mute that channel).

if your crackling is somewhere else in the machine, i wish you the best of luck. i tried calling MOTU for months and never got past a busy signal.
Old 17th December 2009 | Show parent
  #5
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RTFMPleez's Avatar
 

Well 10.4 would be tiger.

Do you have additional pre's attached to the 828 via lightpipe or S/PDIF?? Because sometimes when the clock is not synced you will hear crackle.
Old 17th December 2009 | Show parent
  #6
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Right now I've got nothing attached to the MOTU other than the Mac via USB (and I can unplug that and still get crackle). Excuse my ignorance, how do I sync the clock? If it's relevant, have attached the settings on the MOTU Audio Setup.
Attached Thumbnails
MOTU 828 mkII USB crackle-motu.jpg  
Old 29th December 2009 | Show parent
  #7
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FIXED!

Ha, I'm such a doofus - just checked the cuemix software and all the outputs were set to max, not sure why this wasn't sending out massive vol, but it wasn't - just an intermittent crackle, surprise surprise!

DOH!
Old 4th February 2010 | Show parent
  #8
Gear Head
same problem, same fix

I've notice a nasty crackling for the last couple of weeks and can see the input lights jump on mics inputs one and two (828mkii firewire). Opening Cuemix and dropping the volume all the way down on these channels fixed the problem. Didn't even realize I had those up.
Old 4th February 2010 | Show parent
  #9
Lives for gear
Quote:
Originally Posted by caotico View Post
I've notice a nasty crackling for the last couple of weeks and can see the input lights jump on mics inputs one and two (828mkii firewire). Opening Cuemix and dropping the volume all the way down on these channels fixed the problem. Didn't even realize I had those up.
same here. but doesn't really fix the problem, just mutes the crackle. Why the mic inputs crackle in the first place, i dont know. A cheaper interface, getting old i guess.
Old 27th February 2010 | Show parent
  #10
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LeeYoo's Avatar
 

Smile

Hi there. My first reply, so don't bite me if I do something wrong. My son has a Motu 828 mkII and he has got three problems with it, just like everybody else eventually. I used to be an electronics technician at parts level and he asked me to look at it. First of all, no backlight. This is a burned out led (smd sized), glued to the right hand side of the what used to be green lcd. Desolder the two wires, break it away and replace with a HIGH BRIGHTNESS 3mm green led. Can post details to complete this job. Secondly, the crackling mic inputs. I traced it down to the ANALOGUE part of the mic preamp. The crackle is already present on the outputs of the preamp, BEFORE it enters the A/D converter chip AK4528VF. Since eventually two mic. channels are affected, there must be a common problem. Electrolytic smd caps can do this, but none are used here. I had problems in the past with potentiometers and DC voltage on them. The metal inside them starts to migrate and makes a false track. I resoldered the 7 pins of the pots and the problem disappeared. This is not a fix, but a trial. Will keep you posted on this.
Old 28th February 2010 | Show parent
  #11
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LeeYoo's Avatar
 

Smile crackle, crackle, pop.

Three days without crackles (it used to do it every 5 minutes). It just started again in mic1. I have replaced the potentiometer board with 4 fixed resistors. If it is the pot. board, it should stop completely now. Will keep you posted..
Old 11th March 2010 | Show parent
  #12
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LeeYoo's Avatar
 

No more crackles

Hi guys,
This seems to have fixed it. I am now 99.9% sure it is the gain pot board. For you guys out there with the same problem, I am making a drop-in replacement. This is a small plug with some resistors that have the same value as the gain pot in a certain position (you choose). Can post you a set (no charge). This way you can see for yourself if it fixes the problem. You then can move on to finding a new gain pot board. Maybe I will look at manufacturing a board later. To clarify: this is to fix the problem in the mic inputs only. The one that goes away when you mute the mic inputs with the software! Not the squeel/crackle from the firewire/drivers. Replacing only needs a screwdriver, 10 minutes and half a brain. Will provide easy steps to complete.
Old 11th March 2010 | Show parent
  #13
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Kenton's Avatar
 

Quote:
Originally Posted by mcpf66 View Post
about a year ago i encountered the similar crackling noise. i traced it down to one of the built in mic-pres.
Exactly the same has happened to my 828 mkII within the last 3 months. I'll be getting my soldering iron out having read this thread......
Old 12th March 2010 | Show parent
  #14
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interesting lee yoo. i dont use my mic inputs very often as ive better outboard preamps i prefer, but it might be worth looking into your fix.
Old 12th March 2010 | Show parent
  #15
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LeeYoo's Avatar
 

Hi Guys,
Today I measured the resistance between the two tracks of one potentiometer. One channel was very high, as it should be, about 1000megohm. The other pot had an isolation resistance of only 11megohm. Not good. In the past, I had problems with other gear and double track potentiometers (on one wafer). The pins on pots are connected to the carbon track with silverglue. The pins on these double track pots are very close together. DC voltage on one of the tracks (2.5volt in my 828) and 0volt on the other, together with moisture, can cause the silverglue to migrate and make a false track between the pins inside the pot. Contact spray won't help here. Replacing is the only option. The problem is that the pots are special ones. one track is 20k, the other one is 2k AND they are reverse log (type C). Anybody out there that can supply them?
Old 14th March 2010 | Show parent
  #16
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LeeYoo's Avatar
 

DIY

This if for all of you slutz who want to try the fix for themselves.

Get a "header terminal strip" from your local electronics part store.
Jaycar Electronics - Search results HM3212
And some small resistors:
2x 180ohm and 2x1k8 for 75% gain and/or
2x 330ohm and 2x3k3 for 50% gain.
Note the 1:10 ratio. You can use any value from 0/0ohm to 2/20kohm.
Snap two sets of 4 pins from the strip.
Solder a 180ohm between pin 1 and 3 and a 1k8 between pin 2 and 4.
Solder them on the shortest pins and make another one.
Use the 330/3k3 set if you want 50% gain.
Unplug the power of the Motu and remove the top (3 screws).
Locate the pot board behind the mic sockets and remove the two screws that hold it in place. Lift it up to unplug it from its socket. Remove the knobs and wrigle it out of the front.
Plug in the thinghy's you made, making shure, the lowest value resistor (180ohm) is pointing to the closest corner. Make sure, the resistors are not touching each other. Close the unit and put the old parts in a ziplock. You might need them again.
Try the unit with the mic input software cranked up again.
Post your findings..
Old 17th March 2010 | Show parent
  #17
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LeeYoo's Avatar
 

DYI 2

This post if for you slutz, who want to replace the backlight themselves.

Don't start this if you haven't got some technical and soldering skills.

Remove the front panel from the unit. Don't forget the little srews next to the mic sockets and a nasty hook on the circuit board that locks the two boards together. Unplug the two plugs from the MAIN BOARD, not from the front. This plug has got less pins than holes, so you could make a mistake here, plugging it in again (like I did). Work on a clean surface, to prevent dust building up behind the perspex front. Remove the display (note that one screw has a plastic washer). Remove the solder on the two contacts, next to the display with a solder sucker, or with solder litze. Break away the very small strip with the smd led on it, by pulling on the desoldered wires. This is glued onto the side of a perspex sheet, that runs under the display. Buy a 3mm HIGH BRIGHTNESS green LED from your local electronics store. The green means the light, not the colour of the plastic. It should set you back close to US$5.00 , don't use a normal one. Cut off the shortest leg to 10-12mm (half an inch) and bend it 90 degrees. Tack this short leg to the bottom contact, making shure, the front of the led shines into the middle hole (indent) of the perspex plate under the display. You can see this by lifting the tin foil a bit. If it fits, cut off the other leg and solder it to the top contact. Stick a piece of black tape over the led to prevent the light bleeding into the neighbouring display. Assemble in reverse order.
Post your findings..
Old 18th March 2010 | Show parent
  #18
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hi LeeYoo and all,
thought i take the chance and drop in with my first post.
i own a motu 828 mk2 usb version. it started crackling quite a time ago, makes it almost useless for me. here it's not only the front mounted inputs that crackle- i use the rear in and outs as insert points for my daw. and those crackle too..
my first thought was about condensators too as i know them to be aging parts. didn't dare to open my motu yet.
LeeYoo- the rear inputs don't have any pots or movable parts. does this behaving make any sense referring to your investigations?
Old 18th March 2010 | Show parent
  #19
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Hi macke zwo,

There are TWO sources of crackle in a Motu 828, as far as I know.
This thread is about the crackle in the mic pre's, the one that goes away when you mute them with the software. The other crackle/whistle is software/computer based. There are threads about this as well. They address chipsets in your computer, PCI bus load, drivers, settings and even changing XP drivers to SP1 and hacking the registry. Some say Mac, others say PC. Not quite a computer expert, maybe others can help you here.

P.S. My son said that changing from IDE to SATA hard disks made a big difference.
Old 20th March 2010 | Show parent
  #20
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thanks LeeYoo, you're right- already found something about it. i bookmarked this thread anyway for future use... knock on wood though, yet everything fine with the gain pots here.
fwiw: i found the link to
Black Lion Audio | Home
around here. they offer mods for the 828, interesting read to me.
Old 21st March 2010 | Show parent
  #21
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LeeYoo's Avatar
 

Hi macke zwo,
Black Lion Audio seems to do a good job, upgrading your gear with better quality parts. But, your problem seems to be your computer, not the Motu. The computer can't keep up with the data stream, as far as I understand from all the posts I have read. Try to look in that direction first.
Old 21st May 2010 | Show parent
  #22
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LeeYoo's Avatar
 

Update:

Almost 3 months without any crackle. Must have fixed it..
Old 22nd May 2010 | Show parent
  #23
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leeyoo are you using the 828 mk2 USB or firewire? If usb where did you find the drivers?
Old 23rd May 2010 | Show parent
  #24
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LeeYoo's Avatar
 

Hi msm07.
Using Firewire here, but these posts have got nothing to do with USB, Firewire or drivers.
These posts are about a crackle in the front mic pre's only. The one that goes away by muting them. This is a hardware fix.
Please read posts carefully if this applies to your unit.
Old 23rd June 2010 | Show parent
  #25
Gear Nut
 

Just one crackling input

Hello,

I seem to have a similar problem. My input 1 crackles, and doesn't pass any audio other than crackling but input 2 is fine. I was just checking as i get the impression that your from leeyoo's early description that it might involve both inputs crackling.

Also is this a 'good as new fix' or does it leave fixed gain (just wondering about the 50 and 75% gain thing)

And how difficult a fix is this for someone with a soldering iron and only limited electronics experience.

Cheers

Phil
Old 24th June 2010 | Show parent
  #26
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LeeYoo's Avatar
 

Hi Phil.

The two mic inputs are separate inputs. If mic#1 crackles, mic#2 might still be ok. Just mute #1 with the software. It should stop.

When you read the posts carefully, you will understand, this is a semi-permanent fix. The problem lies in the guts of the front gain controls.

You can try if it is that by unplugging them from the main board (they are on a daughter board), and use a "fixed", non adjustable dummy control. A simple plug-in thinghy that imitates a gain setting of 75% (3 o'clock) of the original control. Leaving it in there will be the same as having the gain control always on 3/4.

Also, no soldering required. Just a screwdriver and half a brain.

And if it works, get another gain-pot board.
Old 28th June 2010 | Show parent
  #27
Here for the gear
 

Quote:
Originally Posted by LeeYoo View Post
This post if for you slutz, who want to replace the backlight themselves.

Don't start this if you haven't got some technical and soldering skills.

Remove the front panel from the unit. Don't forget the little srews next to the mic sockets and a nasty hook on the circuit board that locks the two boards together. Unplug the two plugs from the MAIN BOARD, not from the front. This plug has got less pins than holes, so you could make a mistake here, plugging it in again (like I did). Work on a clean surface, to prevent dust building up behind the perspex front. Remove the display (note that one screw has a plastic washer). Remove the solder on the two contacts, next to the display with a solder sucker, or with solder litze. Break away the very small strip with the smd led on it, by pulling on the desoldered wires. This is glued onto the side of a perspex sheet, that runs under the display. Buy a 3mm HIGH BRIGHTNESS green LED from your local electronics store. The green means the light, not the colour of the plastic. It should set you back close to US$5.00 , don't use a normal one. Cut off the shortest leg to 10-12mm (half an inch) and bend it 90 degrees. Tack this short leg to the bottom contact, making shure, the front of the led shines into the middle hole (indent) of the perspex plate under the display. You can see this by lifting the tin foil a bit. If it fits, cut off the other leg and solder it to the top contact. Stick a piece of black tape over the led to prevent the light bleeding into the neighbouring display. Assemble in reverse order.
Post your findings..
Hi Lee Yoo
I have been working with audio and recording and electronics for years as a hobby, which I really enjoy. I have a Motu 828 Mk II which seems to work OK, except that the backlight is not working on the LCD.

I followed your recommendations as above without to much hassle. Bit of a pain to fit the front panel back into the unit, but managed it. I noted that it is strange that there are two leads from the led via long pins that go back to the header plug, but they do not connect with anything on the header. They are basically not terminated with anything.

My problem is that I still have no backlight, and I have checked the long pins that come through the LCD board, and there is 0 volts to the LED. Otherwise the LCD panel is showing things as normal. Do you have any clues what might be amiss with 0 volts to the LED? I would really appreciate any comments that can put me on the right track.

Kindest regards,

zephyrmic
Old 28th June 2010 | Show parent
  #28
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LeeYoo's Avatar
 

Hi zephyrmic.

Don't have the unit here at the moment, but from what I remember, the two long pins connect to two wires (small plugs) from the black ribbon.

If you have unplugged the ribbon plug, it might be inserted wrong, as explained in the post. There are more holes in the plug than pins on the board.

The LED runs as far as I remember from a negative 12volt rail through a small ?180/220ohm? resistor on the edge of the main board, right behind the display.

If you are not in a hurry, I can give you pictures in a few days.
Old 28th June 2010 | Show parent
  #29
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Thanks for getting back to me. Just thought of a possible solution and tried it. I found that the ribbon cable from the LCD panel to the main board was back to front, that the header plug that had the two LED wires had to be put into the main board, and that the other end of the cable had to go to the LCD board. That's why I was getting 0 volts to the LED previously.

Also I identified on the LCD board that if I match the pink stripe on the ribbon cable - pin 1 - with the bottom of the header pins, so that the two spare sockets on the header plug are at the top, that is the right way to connect the plug.

So problem solved! Works like a charm! thumbsup

Kindest regards,

zephyrmic
Old 28th June 2010 | Show parent
  #30
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LeeYoo's Avatar
 

thumbsup
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