EMU 0404 Sound Card - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 21st May 2008, 11:05 PM   #1
diyAudio Member
 
Join Date: Mar 2007
Default EMU 0404 Sound Card

I am getting barely any sound from the output with the output analog stage bypassed on my EMU 0404 soundcard. I tied V- and ground together and V+ to form an unbalanced output from the AK4395 chip. I removed the buffering opamp in the process, but the final stage opamp is still in place. What am I doing wrong? Do I need to remove the final opamp? Is balanced to unbalanced hooked up differently then I thought? Please give me some words of wisdom.
  Reply With Quote
Old 22nd May 2008, 02:55 AM   #2
diyAudio Member
 
benchtester's Avatar
 
Join Date: Apr 2007
Location: Oakland, Calif.
Here is the datasheet for the AKM chip:

http://www.asahi-kasei.co.jp/akm/en/...k4395_f01e.pdf

It does looks like the output is voltage signal, but I am not sure. A lot of DAC have current signal outputs, so the first op amp on the output is a current to voltage (I-V) converter.

In Figure 12 of the data sheet they show a low pass output filter which also serves to convert from balanced to single-ended. I think it would be less risky than tyeing the negative side to ground.
  Reply With Quote
Old 22nd May 2008, 09:51 PM   #3
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
You can't tie the Analog output - to ground you are effectively shorting half of the output circuitry and depending on protection arrangements in the dac op-amps you may have already toasted the dac chip. Using only one of the dac outputs exacts a 6dB amplitude penalty and also results in higher overall distortion and noise because the common mode component on the outputs is no longer cancelled. Your best bet would be to use a much better op-amp and perhaps resistors in the balanced to unbalanced diff amp circuit that follows the dac.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 23rd May 2008, 03:45 AM   #4
diyAudio Member
 
Join Date: Mar 2007
So you are saying this dac chip is not a voltage output chip, otherwise it would work. How come I hear stories of people bypassing the output stage completely like the modwright mods with a tube buffer on the transport. I know this uses almost the same chip AK4396 rather than the AK4395. Could I use just a resistor on the output to change the output from current to voltage? Thanks
  Reply With Quote
Old 23rd May 2008, 04:04 AM   #5
SunRa is offline SunRa  Romania
diyAudio Member
 
Join Date: Aug 2004
Location: Romania
AK4395 is a voltage output device. If you really want balance to unbalance without using an op-amp, nothing stops you to use a tube circuit like the modwright mods!
  Reply With Quote
Old 23rd May 2008, 04:46 PM   #6
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
It's voltage output not current.. You don't short voltage sources to ground because the current in theory is unlimited, in practice it is the wrong thing to do because at best you invoke current limiting in the output stage of the internal op-amp, at worst you exceed its thermal limitations and current capability and possibly destroy it. Current outputs can be shorted to ground as the current is inherently limited and doing so should not change the operating conditions of the dac driving it.

Using the single output is suboptimum for all the reasons I stated in my previous post.

You can also use a small audio 1:1 transformer to do the conversion, balanced input on one side from both outputs of the chip to unbalanced output on the other. A 600ohm:600 ohm transformer might work fine, better still would be a 1:1 designed for a higher impedance like several K. I use this approach to take the balanced outputs of the THS4131 in my homebrew dac and convert to unbalanced output to my pre-amp. The THS4131 can drive very low impedances however, and I bet such is not necessarily the case for the ones in the AKM dac IC.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
PC sound card sound chips kaluchka Chip Amps 6 20th June 2011 03:48 PM
FS: E-mu 0404 USB external sound card Jack Hidley Swap Meet 2 14th March 2008 01:00 AM
What Sound Card for PC T&M primalsea Multi-Way 3 8th February 2006 02:08 AM
DAC/ Sound card argonrepublic Digital Source 0 11th July 2005 03:39 AM
USB Sound Card GianLorenzo Parts 3 16th February 2005 06:33 AM


New To Site? Need Help?

All times are GMT. The time now is 02:21 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2