Long USB Solutions

[kittonian]

I found an active USB 2.0 extension cable I had laying around from Cables to Go and so far I seem to be up and running, perfectly stable. Thanks for the suggestions.

[Timo]

Apologies for the intrusion in your thread, Kittonian. (PMs sent to those concerned).

That really is good to hear, and no doubt a potentially useful tool for live use too. The kid in me is thinking "I wonder how many active USB cables you can hook up in series" for mammoth cable runs.

[kittonian]

Thought I'd give everyone an update. While the active USB 2.0 extension does work (sort of) it consistently loses communication with the system. To resolve this I have to unplug and reconnect the USB cable on the rear of the TI2. Beyond that it is not properly sync'ing the patch browser with the keyboard (i.e. names are not sync'ing up).

I had a long discussion with Access about what to do and their answer was "there's nothing you can do". They want you to use the shortest possible USB 2.0 cable with no hubs/extensions.

So, either I redesign my control room (not going to happen), I live with how it's working with the extension (not great), or every time I want to use the keyboard with the software control, I need to move the keyboard really close to the computer.

I love this thing so it might be worth it to pickup a TI2 desktop and put it on the floor next to the computer. Seems silly they can't figure out how to make it work over 25ft in stable form.

[MBTC]

Originally Posted by kittonian

Thought I'd give everyone an update. While the active USB 2.0 extension does work (sort of) it consistently loses communication with the system. To resolve this I have to unplug and reconnect the USB cable on the rear of the TI2. Beyond that it is not properly sync'ing the patch browser with the keyboard (i.e. names are not sync'ing up).

I had a long discussion with Access about what to do and their answer was "there's nothing you can do". They want you to use the shortest possible USB 2.0 cable with no hubs/extensions.

So, either I redesign my control room (not going to happen), I live with how it's working with the extension (not great), or every time I want to use the keyboard with the software control, I need to move the keyboard really close to the computer.

I love this thing so it might be worth it to pickup a TI2 desktop and put it on the floor next to the computer. Seems silly they can't figure out how to make it work over 25ft in stable form.

Bummer. I was happy to hear your initial story of success, and also quite surprised, but I opted out of indicating such due to some other issues going on in the forums and I was afraid I would be perceived as bashing Access on the USB cable length. Silently I was predicting this would not work out well long-term, and I'm disappointed to hear I was right.

The problem here, however is not in Access' implementation USB, it is the USB specification itself. There is no way you can increase the distance of a cable without increasing latency; it doesn't mean it won't work some of the time but in a latency intensive scenario like streaming audio, especially at USB 1.1, the odds seem not in favor of longer cords. The limitations of USB are much like cable delay properties of copper wire itself. There's some reading on the subject here if interested : http://en.wikipedia.org/wiki/USB#Cabling

[namnibor]

This might be a 'slight curve in road' but still on-topic with USB cable lengths. Very early Summer bought new USB audio interface that would have a lot of inputs, front level controls for each main input, and with future option of adding more via optical ADAT, which is the Focusrite Scarlett 18i20 (USB version of Sapphire 40), and to my surprise, they only included a 3 Foot USB A/B 2.0 cable with unit. It is A/C power dependant, not USB. Mind you, it's RACK MOUNTED, so not *everyone* is going to have their computer configuration to rack synths/equipment that crazy close! Plus, it's a full, one unit, and DEEP unit, and with majority of ins/outs on rear, only makes sense to have this in my top rack space, which is about forehead level of my sitting, 5.8' Anglo-Saxon self.
Yes, could place my tower DAW PC on top of desk beside it but not exactly ergonomic.
Both Sweetwater and Focusrite communications (both were very helpful) informed me at least with the 18i20, to *never* exceed 15 foot length and they know that 10 feet worked great with nothing added as far as latency, etc. So that's what I have done and the length of 10 feet is absolutely perfect with no negative effects on latency, perceived or otherwise.

Thought this would be germane as far as lengths of USB and my rather recent experience with studio nexus.

[kittonian]

First off a few corrections/updates:

1. The TI2 is USB 2.0 not 1.1
2. The max spec length of a single non-active USB 2.0 cable is 16.5ft
3. Active USB extensions are made so that the signal transmits over longer lengths without loss (at least the good ones). Will there be an increase in latency, perhaps, but it should be fairly negligible when we're only talking about 25ft (only 9ft over the max spec of non-active cabling).

That all being said, and having been in both the pro audio and technology industries for many years, I would say that it is the software that is the issue. I'll explain why.

• If I can plug in the USB cable with the extension and achieve flawless playback with no discernible increase in latency, why is it losing communication after not being used for a few hours?
• Why can I play the unit just fine, have it sync with the USB clock, and have it automatically (through the plug-in) pull up the correct patch(s) yet it won't show me the proper names in the software (but it will on the hardware)?

I truly love the Virus and when you have the TI2 close enough to the computer and on its own USB bus, at least with PT|HD, it works flawlessly. This is also one of the reasons we are an Access dealer. I own and use a TI2 Keyboard personally and wanted to ensure that the joy I get from this instrument is also offered to our customers.

My problem is that if one of the big plusses is going to be software integration, perhaps working on issues such as these would be in order. Most pro studios have a separate machine room where the length would need to be far greater than the 25ft I am dealing with. Even if Access came out with their own USB extension solution, that they developed with their software to ensure rock solid reliability, I would buy it in a heartbeat. At that point they could say, no 3rd party solutions will be supported, and honestly I wouldn't have an issue with that, even if their solution was a bit expensive.

[namnibor]

Originally Posted by kittonian

First off a few corrections/updates:

1. The TI2 is USB 2.0 not 1.1
2. The max spec length of a single non-active USB 2.0 cable is 16.5ft
3. Active USB extensions are made so that the signal transmits over longer lengths without loss (at least the good ones). Will there be an increase in latency, perhaps, but it should be fairly negligible when we're only talking about 25ft (only 9ft over the max spec of non-active cabling).

That all being said, and having been in both the pro audio and technology industries for many years, I would say that it is the software that is the issue. I'll explain why.

• If I can plug in the USB cable with the extension and achieve flawless playback with no discernible increase in latency, why is it losing communication after not being used for a few hours?
• Why can I play the unit just fine, have it sync with the USB clock, and have it automatically (through the plug-in) pull up the correct patch(s) yet it won't show me the proper names in the software (but it will on the hardware)?

I truly love the Virus and when you have the TI2 close enough to the computer and on its own USB bus, at least with PT|HD, it works flawlessly. This is also one of the reasons we are an Access dealer. I own and use a TI2 Keyboard personally and wanted to ensure that the joy I get from this instrument is also offered to our customers.

My problem is that if one of the big plusses is going to be software integration, perhaps working on issues such as these would be in order. Most pro studios have a separate machine room where the length would need to be far greater than the 25ft I am dealing with. Even if Access came out with their own USB extension solution, that they developed with their software to ensure rock solid reliability, I would buy it in a heartbeat. At that point they could say, no 3rd party solutions will be supported, and honestly I wouldn't have an issue with that, even if their solution was a bit expensive.

All good info! I also learned something from your post that I think via mal-informative posts about the Ti line, had always heard the whole Ti Line was USB 1.x and it never really made sense to me that in a version 2 (Ti2) they would continue to utilize lower bandwidth rather than USB 2.0....this makes me actually anticipate whatever Access releases next because by then there would be Ti2 or even a 'Polar' at a better used price when people tend to sell gear for the next best thing!!!
I did forget to add that Focusrite wanted to make sure I used a Ferrite USB cable and that was heavily shielded from outside crap, recommending me a particular Belkin cable, which really did not mind the $12. USD it cost on Newegg.com whereas in any big box store they wanted little more than twice that!!!
Love learning something new!

[MBTC]

Originally Posted by kittonian

First off a few corrections/updates:

1. The TI2 is USB 2.0 not 1.1

Actually Access touts it as a USB 2.0 compatible device that runs at 12Mbit data transfer rate, and that is the max data rate of USB 1.1 (a.k.a Full Speed mode, as opposed to Hi-Speed mode that USB 2.0 is capable of). This has been well discussed here and elsewhere.

But still, comments well taken and I do understand your point about potentially a software issue and it inexplicably working for a while and then stopping, and you very well may be right. The only thing I could say is that I have seen some USB devices (not synths necessarily) that do not behave well when the computer's power mode changes, for example powering down to a standby mode. It's a long shot but is it possible your system is in some way changing it's power state?

Interesting to me that a Virus dealer is highlighting the problems with software integration here. Perhaps you'll find more appreciation for your focus on this problem than I have. It is a big topic with me because I want to enter Virus ownership again but I keep waiting for a big announcement at NAMM to make a decision.

[Timo]

Originally Posted by MBTC

Actually Access touts it as a USB 2.0 compatible device that runs at 12Mbit data transfer rate, and that is the max data rate of USB 1.1 (a.k.a Full Speed mode, as opposed to Hi-Speed mode that USB 2.0 is capable of).

It's certainly confusing isn't it. Given that USB 2.0 is mainly available in two different chipsets - Full Speed (12Mbps) and High Speed (>480Mbps) - and that a USB 2.0 device with a Full Speed chipset cannot use the High Speed standard (due to requiring a different chipset), what in fact is the difference between USB 1.1 Full Speed and USB 2.0 Full Speed?

Both state they use the same bandwidth of 12Mbps and other similar specs. I wonder if the 2.0 standard added any additional back-end enhancements over 1.1 - such as hardware improvements, the way the data is handled, or error-correction or similar. I understand USB 1.1 fixed many problems that were present in the earlier 1.0.

As a layman, given that Access allow for 3 stereo audio outputs (6 mono outputs) at 16-bit 44.1KHz to be sent over USB...

44100 (sample rate) x 16 (bit depth) x 6 (discrete audio [mono] channels) = requires a bandwidth of 4,233,600 bits/second.

Tidying up, that's 4,233,600 / 1024 / 1024 = 4.0 Mbit/second.

I don't pretend to know much about how USB handles data, whether it is possible to use all the stated bandwidth available (12Mbps in the VirusTI case), but 4Mbits/s is well within the 12Mbit/s Full Speed standard of 1.1 and USB 2.0. In fact it still leaves 8Mbit/s available for Virus Control, MIDI bandwidth, error correction and anything else. On paper, at least, 12Mbps looks like it should be more than enough for the TI's current feature set.

If you started requiring multi-channel 96KHz @ 24-bit, that's a different kettle of fish, new hardware is required (USB 2.0 High Speed or USB 3). Virus TI mk3 material.

[MBTC]

To the best of my knowledge (and memory, since it's been a long time since I spent any time researching this), "Full Speed" refers to the mode (overall speed of throughput, basically) rather than being tied to a specific USB version; it's more or less a short cut to avoid saying "the mode that maxes out at 12mbps". USB 1.1 compatible devices can run in Full Speed, as can USB 2.0 and 3.0, and if they are running in that mode they are all said to be running at Full Speed.

That said, the upper throughput ceiling of each mode is just that -- it's an "up to" number, meaning that is where throughput would max out under absolutely pristine conditions. The average throughput for any operation on any given device is typically much less than the maximum for that mode. The only thing you see consistently in benchmarking articles is that throughput is significantly faster as the ceiling increases; in other words if you took something like a storage device or media player, and compared the same device at Full Speed to its throughput in High Speed, it might perform on average 4x-7x faster in High Speed (certainly enough to justify the upgrade, but not the 40x improvement that the specification implies on paper). I don't think I've ever seen a USB 2.0 High Speed device achieve anywhere near 480Mbps even though its fair to say the cable spec facilitates such speeds.

In other words the labeling of modes gives us a good relative measure, when all other things are equal, but load predictions are difficult to impossible, I'd say.

There are a number of things that can affect actual throughput, most notably (and easy to envision) is the idea of how fast can the sending device push the data down, and how fast can the receiving device receive it? Best analogy there is let's say you've got a really fast Internet connection like 50mbps and you're streaming a HD movie from some device, and it still pauses and buffers, even though 10mbps should be plenty for movie bandwidth. There can be other things like other devices in the house using bandwidth, server delays and your neighbors competing for bandwidth in some cases that affect the ability to stream the movie smoothly.

Things like the polling rate and technique the software uses to actually transfer data, handle timeouts, etc. add more variance.

In a real-time audio streaming scenario like a synth, I can imagine a number of other things that could get in the way, some of which you mentioned like MIDI bandwidth, which needs to travel both ways across the wire.

Then you have other factors that affect performance, for example how many bytes per transfer? We've been discussing mostly throughput here, without even talking about latency, and in many applications optimizing for throughput versus latency can almost be at odds with each other. For example lots of audio streaming seems to lend itself to more bytes per transfer, however for better latency I would think smaller packet sizes would be preferable.

Then of course you have factors that neither the source nor destination of data have full control over, for example the USB bus and its specific handling of other devices on same bus (this is one reason a dedicated USB card is never a bad idea IMO).

One thing that Access could do is create a software utility that runs on the PC or Mac host that "exercises" the connection, simulating a high-load audio and MIDI scenario, which would allow the user to test their connectivity/latency/throughput to the Virus. Just send a fully-loaded audio and MIDI stream and measure throughput and latency. This might not identify every possible problem, but it should eliminate lots, if not most scenarios, by removing the DAW configuration from the list of possible culprits, it would identify things like bad cables or USB hubs causing problems, problem with the Virus hardware itself, etc.