DM 4800 distortion in TDIF expansion cards

[Hans Christian]

Hello all,
I have the following setup on my DM 4800:
- MOTU 2408 mkIII to 3 built in TDIF connectors on DM 4800
- MOTU 2408 mkIII to TDIF expansion cards in slots 2 and 4
- Firewire Card in slot 1
- Analog Expansion card in slot 3

Problem:
I am getting a distorted signal on the TDIF expansion cards during playback. Playing back through internal TDIFs (ch. 1-24) is fine, but switching to one of the cards in the expansion slots (ch. 25 and higher) distorts the signal. Both TDIF cards act the same way. I swapped cables and interfaces to eliminate those possibilities. Is there a problem using all of these cards together? Any other ideas?

 

[Arjan P]

What's your recording medium? Who is clock master? How does a DAW with IF-FW integrate?

 

[Hans Christian]

Hi Arjan,
Recording medium is DP 8.07 on a Mac OS 10.7
Clock master is a Black Lion external clock (problem also persists if I use the DM 4800 as a Master Clock).
The IF-FW is connected to FW 400 port on computer. Problem persists even if that connection is removed.
Also, if I play iTunes through one of those cards it also distorts.

The IF-FW integrates beautifully with the built in 24 TDIF channels on the board and both input streams show up in DP. It gives me 56 (32+24) channels at standard resolution, which is great. But in Hi-res (88.2 or 96K) I am losing half the TDIF channel count, and since Firewire has a ton of latency I cannot monitor through it while tracking a whole band. The goal is to activate all TDIF channels on the DM 4800 so that I have 20 channels in a hi-res tracking situation.
As you can see, I am not using the built-in pres or A/Ds on the DM 4800 except for drums. The "Input Bypass" method discussed elsewhere is too complicated for me and I also like to print EQ/comp for some drums.
Your thoughts are welcome. Thank you.

 

[Hans Christian]

BTW, I contacted TASCAM Tech Support via email about this and am awaiting a reply. Can't find a telephone number for them anymore.

 

[captdan]

"Can't find a telephone number..............."

323-726-0303 ext. 617 (M-F, 8am-5pm Pacific).

Website: http://tascam.com/contact/support/

"..'Input Bypass'.....too complicated...."

It's really not that difficult. I'd say it's actually easier than the DIRect method.

RE: Latency - If you're using your DM (not DP) as the monitoring tool,
there is no latency whatsoever.

CaptDan

 

[Hans Christian]

Hi CaptDan,
thank you. And if you happen to have a link to the routing of the Input Bypass setup I will look at it again and see if this might work. But the TDIF Expansion Card issue is still bugging me. Any thoughts on that?

 

[captdan]

Here's something that might help. Perhaps it's a bit basic, but it could explain some of what's involved:

http://www.tascamforums.com/threads/dm-routing-zen.634/

As for the audio distortion, I'm pretty much clueless. I've never used TDIF in my setup, but several people here do. Off the top of my head it sounds like something's getting overloaded in the signal chain. Could be anything from operator error (you ) to a hardware failure of some kind. Sorry can't be much more help with that.

CaptDan

 

[TascMan]

I have a 2408 MKIII as well. It sounds like either one of two things are happening.

The 2408 has settings for +4 or -10 operation. If you have yours set to -10 and your input signals are coming from a +4 source, you might hear distortion. There is also an "auto" setting where it will automatically determine the input level and set it accordingly. That's worked well for me.

But I would guess your distortion is a clocking issue. If you have a Black Lion external clock in the system, and want to use it, you could try this... Set the DM to clock externally from the Black Lion via Word Clock (BNC), but don't hook up either 2408 to the black lion. For each 2408, select "DIGITAL" as your clock source, and they will clock from the clock signal embedded in the TDIF signal, coming from the DM which is already clocked to the black Lion.

 

[Hans Christian]

Thanks for the feedback,
I wish it was operator error- can't find it yet. Played with the clocking issues and tried different scenarios. Also looked into the level matching issue. So far no leads. Since this is not crucial to the operation of my studio I am spreading out the research over several days, so that I keep getting some work done. If I have news I will post them here. Thanks again.

 

[Hans Christian]

Positive discovery (at least in low sample rate setting)
I seemed to have solved the problem by connecting the second 2408 to my Black Lion Master clock instead of my first 2408 (which send its audio to the internal TDIF ports of the 4800). You were right in assuming that it was a clocking issue (and it sounded like it). So, the discovery is that whichever 2408 is connected to the Expansion Slot TDIF Cards has to be the interface connected to the Master Clock. Not sure why this is.

It is possible to simultaneously use Firewire and TDIF cards in DP (under 'configure Hardware driver' you can select IF-FW and PCI 424 drivers by holding down the command button). Gives you lots of ins and outs!

However, the TDIF Expansion Cards in the 4800 don't work in hi-sample rates. I get white noise, and under 'Digital'/slot 2 I can see the sample rate oscillating between 48 and 96K. Hmm. Somehow they don't get clocking in hi sample rate mode.

 

[TascMan]

Are you aware that you cannot get a full channel count over TDIF at higher resolutions? You will have to pair your TDIF channels to record over TDIF at higher sample rates. This is a limitation of TDIF and many other digital connections. Basically, when you are operating at the higher sample rates, each TDIF output will now take up two channels over TDIF. This is referred to as the SMux protocol. So, if you want to record at 88.2 or 96Khz, you can only use every other channel over your TDIF cable. So, let's say you have your TDIF hooked up, coming from your 2408MKIII and you want to record from your 2408, through your TDIF into the DM. Well you will only be able to hook into input channels 1,3,5,7 on the 2408. In the DM you would assign your TDIF inputs as 1,2,3,4. There won't be a 5,6,7,8. TDIF Channel 1 will actually be 1 and 2, channel 2 will actually be 3 and 4, channel 3 will actually be 5 and 6, channel 4 will be 7 and 8. Wasn't sure if you knew this or not.

 

[Hans Christian]

Yes, thank you. I am well aware of this. Actually, you loose channels 5-8 for every 8 channel group.

Talked to TASCAM yesterday and they suggested a possible TDIF cable mismatch that might cause this distortion problem, which sounds like a severe clocking issue. I have to get back to this another time, it is such a time sucker to deal with. The system is working well at standard sample rates, and as long as I don't use the expansion TDIF cards. Bummer.

 

[TascMan]

Actually, you loose channels 5-8 for every 8 channel group.

Yes, which is what I wrote here...

There won't be a 5,6,7,8. TDIF Channel 1 will actually be 1 and 2, channel 2 will actually be 3 and 4, channel 3 will actually be 5 and 6, channel 4 will be 7 and 8. Wasn't sure if you knew this or not.

So, another obvious question then...are you using a real TDIF cable? TDIF pinouts are different than standard d-sub 25.

 

[TascMan]

Please disregard last question. You obviously are.

I noticed you said that you are using the PCI 424 card. I run my 2408 in standalone mode, in and out of the DM, without the PCI card. This may be your issue. The 2408 that is hooked into your PCI card would be trying to get it's clock signal from the 424 card.
NTM, using two different interfaces at the same time means bypassing the ASIO drivers for the DM. Not good, and can cause timing distortions.

 

[Hans Christian]

Thanks TascMan, you obviously are very knowledgable. Will look at my TDIF cables and try to remember where I got them from. As for your second point- have not noticed any timing issues. When you duplicate audio tracks and run them side by side on a FW and a TDIF output they match in quality and phase. I was very impressed by that feature.

 

[Hans Christian]

The 2408 is getting its clock info through a BNC cable from the DM4800 which is the Master Clock.

 

[RedBus]

Please contact TASCAM support with the description of the problem and the exact firmware version displayed - we'll be able to tell if you need a slot motherboard replacement.

 

[Hans Christian]

Thanks RedBus. I left a message with tech support at Tascam.