ULTRALITE crackling...

djencode · Post by **djencode** » Tue Apr 25, 2006 5:45 pm

Ok so here is my setup...

i have 2 computers, one pc laptop, one mac with 10.4.6 ppc, 2 ultralites to connect the 2 via coax s/pdif using monster wire. i then have my roland vsynth into the pc ultralite, then 6 outs from the pc ultralite to the mac ultralite (for the purpose of using different MIDI channels and different audio channels to have multiple vst's running using my laptop as an external plugin host)

now every once in a while
i'll get a crackle on all channels on both cards and audio will cease, this takes about 2 seconds then it continues what it was doing. i have the pc ultralite as the sync master for the duo, runnint at 44.1. then the mac ultralite is set to s/pdif for the sync source and is also set to 44.1. on the pc i have outs set to s/pdif and have main outs set on the mac.

anyone know why this is happening?

ALTOIDS · Post by **ALTOIDS** » Tue Apr 25, 2006 6:09 pm

Hi djencode,

Sounds like a pretty straight forward setup.

How about changing Samples Per Buffer size on PC?

What kind of FW connection have you established on PC side? Via a PCI FW card or to a built-in FW port?

If PCI FW card, do you have any other PCI card installed that may interfere the PCI bandwidth?

If built-in FW port, have you checked to see what type of FW chipset is being used on it (sounded like MOTU recommends Agere/Lucent or TI chipset FW cards such as Belkin F5U501)?

Good luck, and keep us posted.

djencode · Post by **djencode** » Tue Apr 25, 2006 6:12 pm

buffer size! brilliant never thought about that, i'll try that see if it helps, right now it's set at 256 so i'll bring it up to 512 and see if that fixes it, also i just swapped the sync so that mac is internal and pc is s/pdif let's see if that fixes it first, if it happens again i'll move on to the buffer size. as for the fw on the pc it's integrated , with the TI chipset so im lucky, although i might look into getting gold plated cable for it to increase conductivity. since i had to dig and steal the cable from my lacie drive...

edit : ok swapping the sync didn't fix it but it damn well lowered my noise floor on the s/pdif a hell of a lot so thats a plus, tried boosting the buffer, so far so good....

arth · Post by **arth** » Tue Apr 25, 2006 6:20 pm

I have noticed that there's a 1-2 second crackling sound whenever changing the sampling rate on the Ultralite. In your case, with 44.1 kHz selected, this could be the issue, if there's a sporadic 48 kHz signal on the SPDIF. Try running temporarily:
(a) without the SPDIF connected
and
(b) With SPDIF connected but the devices set to 48 kHz

If there's no crackling in those cases, this has narrowed down the culprit -- whatever is feeding a 48 kHz signal over the SPDIF cable.

I don't think there's any viable workaround for this problem, short of a firmware/driver change (MOTU could and probably should add some code that mutes the outputs when doing frequency changes, and zero the buffers on the driver side)

Regards,
--
*Art

djencode · Post by **djencode** » Tue Apr 25, 2006 7:19 pm

ok at 48khz the crackle has a tinny tone to it..and happens a bit more frequently. weird thing is before i bought my second ultralite i was still using a firewire 410, and no problems there...

edit : when it does it, it seems to be on the pc card first, so i bet it's a driver issue...but strange it didn't have the issue before, and this is the computer with the first ultralite....

djencode · Post by **djencode** » Fri Apr 28, 2006 11:55 am

still happening, any ideas?

djencode · Post by **djencode** » Sun Apr 30, 2006 12:50 pm

update : ok so i tried changing to gold plated firewire cables, and that hasn't resolved the issue at all

it seems the only fix it to up the buffer >.<

which seems odd when the buffer on the mac sits at 256 no problem, but it's gotta be 1024 on the pc