From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jelle de Jong Subject: Stuttering 100mA and 500mA MaxPower usb audio investigation on bus powered and external powererd usb hubs Date: Sat, 08 Nov 2008 21:56:24 +0100 Message-ID: <4915FCF8.9040703@powercraft.nl> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from node02.cambriumhosting.nl (node02.cambriumhosting.nl [217.19.16.163]) by alsa0.perex.cz (Postfix) with ESMTP id 4DFCB10381E for ; Sat, 8 Nov 2008 21:55:25 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by node02.cambriumhosting.nl (Postfix) with ESMTP id 1411EB00017D for ; Sat, 8 Nov 2008 21:55:24 +0100 (CET) Received: from node02.cambriumhosting.nl ([127.0.0.1]) by localhost (node02.cambriumhosting.nl [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id djEr6PltSu3y for ; Sat, 8 Nov 2008 21:55:23 +0100 (CET) Received: from ashley.powercraft.nl (84-245-3-195.dsl.cambrium.nl [84.245.3.195]) by node02.cambriumhosting.nl (Postfix) with ESMTP id 850DFB000115 for ; Sat, 8 Nov 2008 21:55:23 +0100 (CET) Received: from [192.168.1.213] (unknown [192.168.1.213]) by ashley.powercraft.nl (Postfix) with ESMTPSA id CE18423BC331 for ; Sat, 8 Nov 2008 20:20:24 +0100 (CET) List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org Hello everybody, I have been testing several scenarios to find some glues why some usb audio devices did not fully work and gave stuttering sounds I found the following: usb devices define a max power attribute during there enumeration process. I have some usb devices that have this at 500mA and some that have this on 100mA. I also have some usb hubs that have external extra power supply and some that are only a hub with bus power. Here it comes: Make sure the 4 port usb hub is full with for example: - usb keyboard (100mA) - usb mouse (100mA) - usb audio (100mA or 500mA) - usb stick (200mA/500mA) - usb hub with external power (500mA MaxPower) (AC adapter delivers 1A) - usb hub without external power (100mA MaxPower) Make sure to use audio with several tones low tones (most dvds will do) When connecting a 100mA usb audio devices on a hub with external power it will give stuttering sound!! (most usb audo devices are 100mA and most hubs are external powered due to more then one usb stick) When connecting a 500mA usb audio device on a hub with external power it will work perfectly. When connecting a 100mA or a 500mA usb audio device on a hub without external power it will work perfectly. I have the idea there is something wrong with the power distribution system when using external powered usb hubs... Any ideas how to correctly address this problem/bug? Best regards, Jelle