general aspects regarding hardware performances

[gabsson]

Hello,

I need to buy a laptop to run my shows live. I have a desktop system already, it works fine but I would need to get something as powerful on a laptop.

There are a few point that stuck me a bit in my choices and I wish some of you might help to understand those.

First : number of core, speed.

are ALSA and JACK making a important use of multi threads processors.
How the takt affect the DSP capacity

Second : USB audio interface

How Jack manage USB 1, 2 and 3, does it make a difference regarding the latency.

Third : RAM

How much Ram might be used by ALSA and JACK. What does the RAM capacity impact on.

fourth : SSD hard drive

Are ubuntu system and most specifically KX studio distribution make an optimized use of the SSD technology.

As you might understand, the answer of those question would help me a lot to measure the amount and the quality of my investment which, I believe might be a case of interest for a lot of us.

best regards from Berlin

[dbp]

are ALSA and JACK making a important use of multi threads processors.
How the takt affect the DSP capacity

ALSA and JACK are not high in CPU consumption, unless you are using chains of ALSA plug devices with numerous of conversions.
CPU consumption mainly comes from software mixing (VST / LADSPA plugin etc).

How Jack manage USB 1, 2 and 3, does it make a difference regarding the latency.

JACK does not interface with hardware directly, it rely on ALSA.
Some user report instability / jitter in USB 2.x and resolved when enforcing to USB 1.x
I would suggest searching the exact model to see if someone has found problem.

How much Ram might be used by ALSA and JACK. What does the RAM capacity impact on.

In the scale of around 100MB. No need to worry for a 2GB+ RAM computer.

Are ubuntu system and most specifically KX studio distribution make an optimized use of the SSD technology.

Define optimize is tricky. You can set few configurations to take great advantage from SSD, but need to do a lot to squeeze its full power.

[gabsson]

This is the result of what I learned so far, which might interest people looking for laptop for DSP purposes. The number of core and furthermore the number of thread that might be handled is very relevant. If you use a lot different application in the meantime, a large number of thread will share the load and reduce accordingly the global cpu load.
regarding USB, I gave up on that since I've been able to use the mini PCI slot on a thinkpad laptop to connect a Firewire 800 card that works perfectly under ffado.
What I can say is that it is definitely possible to build a power full digital audio studio relying on a laptop on linux which is quite a good news as far as i'm concerned.

[CrocoDuck]

Hi there! I recently purchased an Entroware Apollo 1000 (now discontinued in favor of the Apollo 2000, even sexier) and I am very happy with it. I still have to put it under heavy tests but it works already very good after few optimization for either recording and lowlatency effect processing (at least for what I am used to do, which basically is Guitarix + Calf + Hydrogen + Qtractor sort of thing). If you go to my blog (in signature) you will find the review and a brief explanation on how I set up the SSD optimization (with related documentation). There is also a link to the output of

Code: Select all

lspci -vnn

so that you can see in great detail the hardware inside. I hope that helps in choosing your laptop.

This could be interesting as well for you.

[asbak]

Crocoduck, does the Entroware have separate usb busses?

[gabsson]

Now there is something that puzzle me, where does the DSP capacity comes from, is it the sound card?

[CrocoDuck]

According to the output of lspci -vnn and lsusb I would say that the busses are indeed separate:

Code: Select all

Bus 001 Device 002: ID 8087:8001 Intel Corp. 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 002 Device 002: ID 058f:3822 Alcor Micro Corp. 
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

The laptop audio capability is good: it got an output only Intel soundcard and an HDMI port that streams audio pretty well. These, however, are not optimal for live DSP. I use a Focusrite Scarlett 2i4 with it, hooked into the USB 2.0 port. My MIDI controller works pretty well in the USB 3.0 port.

[gabsson]

so in extent, if you want to be quite at ease with DSP load, you need to get a better audio interface that will also enable shorter latency time, is that correct?

[asbak]

so in extent, if you want to be quite at ease with DSP load, you need to get a better audio interface that will also enable shorter latency time, is that correct?

A soundcard must, amongst other things, be capable of low-latency operation if you want to play live.
On most typical 'prosumer' type sound cards the signal processing is done by the computer's CPU as far as I'm aware, not by the soundcard.

I think that the RME cards do their audio mixing internally, ie, that's taken care of by their own hardware. But let's say you're running some kind of softsynth or effects in jack, the CPU of the computer does the digital signal processing. (That's my understanding, so somebody please correct me if I'm wrong.)

So for the average person, in order to succeed they need

- a decent laptop
- with separate USB busses (refer to Crocoduck's post),
- at least 1 USB 2.0 port (or the ability to set USB 3 ports to USB 2 in BIOS because USB 3 and audio cards often cause problems)
- some kind of low-latency capable soundcard
- an Ubuntu type low-latency kernel or preferably (imo) a PREEMPT kernel (similar) or if you must, a RT Kernel
- some system tuning as per the guides
- fast harddrive/s, the faster the better
- properly configured jack settings
- disable unnecessary services & cronjobs and anything which eats up CPU time and causes unnecessary disk IO


Your particular case is a little bit different because you're using a firewire RME Fireface.
Issues with USB ports and low-latency audio cards (RME is low-latency capable) are already taken care of.

Just pay attention to the rest of the items and stay away from using Windows/Wine VSTS for live playing. (Too many potential reliability & performance issues using Wine/VST)

[CrocoDuck]

Yep, the sound card is needed to provide high (actually just higher) quality low latency AD/DA conversion. The internal sound card of most laptops is not optimal for music. Usually, it is a compromise: speech is what laptops are mostly used for and manufacturers want cheap components to keep costs at a minimum. So, preamps of internal sound cards are actually a bit low quality, especially the slew rate and passband are not optimal for music. Latency could be not that bad though. Another point is that internal general purpose sound cards do not accept instruments as inputs due to impedance issues. You could solve this with few electronic components, but it wouldn't solve the low quality preamps problem of the sound card. An external sound card solves these problems providing additional connectivity (midi ports, for example). Once the sound card translates the signals into numbers it is the computer doing all the work indeed. See the sound card as a "translator" between voltage signals and binary strings the computer can work on (and vice versa).

[Aleks]

I have a laptop with the following specs:

Intel Core i3, 1.8 GHz/3MB Cache
Intel HD Graphics VGA
4 GB DDR3-1600MHz RAM
2 x USB 2.0
1 x USB 3.0
HDMI

I'm thinking about buying a Focusrite Scarlet Solo (http://us.focusrite.com/usb-audio-inter ... ifications ) as a means to plug my guitar in it. I have tried one of those cheap USB cables (guitar link), which is USB 1.1 but with terrible results. Even with the buffer set to 512 samples, xruns are all over the place. For comparison, the built in generic sound card on my desktop runs with 128 samples, 2. 9 or something ms latency and 0 xruns, while playing videos on YouTube and using Rakarrack at the same time.

I have tried, everything, I even tried it with Open Box, disabled wifi, every optimization that I found on the net, it's still the same. So it must be the sound card, of course.

So my question is, would buying the Focusrite solve this problem? I'm opting for the cheapest solution, because frankly I don't need more. I don't use MIDI keyboards and interfaces, I'd just like to plug my guitar there, and practice and learn songs and transcribe songs and solos on my laptop, without bothering the neighbors and my family with obnoxious sounds .

The other option I'm considering is to ditch the digital modeling all together and to build an analog guitar preamp with cab sim, like Condor from ROG, and then a headphone amp with a simple mixer, where I could hook it up all together, and just use the laptop for listening and writing down the music.

[CrocoDuck]

So my question is, would buying the Focusrite solve this problem?

This isn't a question that it is easy to answer. My advice is to try before buy if you can. Chances are that the problem is in the USB bus instead of the sound card. That would yield again to the same problem. If you are after the cheapest I would advice to not buy Focusrite. After using my Scarlett 2i4 for my MSc project (I used it to acquire data for electro acoustic measurements) I came to the conclusion that it is a cheap device not significantly different from the sound cards having even half that price. I did not open it as I don't want to void the warranty, but the crosstalk between all the channels scrams "we wired cheap components in the cheapest way". Not sure what to point you to though, since the Scarlett got a superb Linux compatibility at least. I remember some people in this forums having luck with these sort of things. Maybe it is a good solution for you: if it doesn't work out well under Linux you still have an amp you can use. Have a good search online and in the forums to check the support status nowadays, as the article is a bit outdated.

[asbak]

There's also the Behringer UCG102 which is reported to work under Linux and it's cheap at around $30. That "Guitarlink" cable you tried could be some imitation or copy of the Behringer.

http://ubuntuforums.org/showthread.php? ... 7f12899649

Guys in that thread seem to have it working.

Anyway, there are a bunch of things which need to be configured correctly for soundcards to work properly.
USB soundcards & jack usually need to have the Periods/Buffer set to 3, and Frames/Period to something like 128 or 256 (it can go lower, but you increase the chances of getting xruns).

Mine's set like this as an example and it works ok:

/usr/bin/jackd -S -P89 -dalsa -r48000 -p128 -n3 -Xraw -D -Chw:U96k -Phw:U96k

[CrocoDuck]

This guy reported the UR-22 to work out of the box on Linux. Feels like a Scarlett 2i2 with higher sample rate (which is better, but not always you need it), price should be about the same.

[Aleks]

There's also the Behringer UCG102 which is reported to work under Linux and it's cheap at around $30. That "Guitarlink" cable you tried could be some imitation or copy of the Behringer.

http://ubuntuforums.org/showthread.php? ... 7f12899649

Guys in that thread seem to have it working.

Anyway, there are a bunch of things which need to be configured correctly for soundcards to work properly.
USB soundcards & jack usually need to have the Periods/Buffer set to 3, and Frames/Period to something like 128 or 256 (it can go lower, but you increase the chances of getting xruns).

Mine's set like this as an example and it works ok:

/usr/bin/jackd -S -P89 -dalsa -r48000 -p128 -n3 -Xraw -D -Chw:U96k -Phw:U96k

I gave a wrong information, it's not a guitar link, it is this one:

http://www.aliexpress.com/item/1pcs-3M- ... eb201560_9

Setting Periods/Buffer to 3 seems to help a bit, although xruns still occur. They use to come up in thousands, and now they are hundreds, so that quite an improvement. Maybe it can get better?

This is my lsusb output with the cable plugged in:

Code: Select all

Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 04f2:b469 Chicony Electronics Co., Ltd 
Bus 001 Device 005: ID 0489:e078 Foxconn / Hon Hai 
Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 002: ID 0d8c:0139 C-Media Electronics, Inc. 
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

I use Cadence for starting and setting Jack, and this is how it looks:

Selection_001.png (92.14 KiB) Viewed 1683 times

Selection_002.png (68.89 KiB) Viewed 1683 times

Also, in one of the previous posts was mentioned something about focing a USB 2.0 port to 1.1. How should I do that?