decent soundcard for measuremets - Page 3 - diyAudio
Go Back   Home > Forums > Design & Build > Equipment & Tools

Equipment & Tools From test equipment to hand tools

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 9th February 2013, 11:16 PM   #21
Telstar is offline Telstar  Italy
diyAudio Member
 
Join Date: Dec 2007
Location: Italy
Quote:
Originally Posted by tvrgeek View Post
Ah, that external PCI slot. I almost forgot about them. I guess most everything is built into laptops these days, so the need went away. I did not know there were sound cards that used them.
Yep, and I know only pci-e internal to pci (external) devices. Nothing with usb input, but the cost would make an usb "soundard" cheaper, especially a second hand 0404.

Quote:
Not much on mods, mostly because we use these things for lo-fi, like speaker measurements.
Still more and more people uses them to measure distortion of sources and amplifiers.

Quote:
I suspect if the truth be told, the digital portion of these boxes is not the problem. The power supply and analog is what needs work.
For my needs, all commonly used sigma-delta ADC have problematic HF noise from about 30khz, making it unusable to see extended harmonic spectra from any signal higher than 1khz.
I have yet to check the one that ESS made in 2011.
The power supply problem can be easily resolved using an external 5V regulated psu or batteries. Ideally, both the generator and the soundcard should be battery-powered. The "on" time makes this a non-issue.

Quote:
I still have my HP analog generator on the bench. Sometimes it is just plain handy.
Which one? I'm trying to find a 239A in Europe (and later mod it). No luck so far, i'll have to get it overseas.
__________________
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
  Reply With Quote
Old 10th February 2013, 01:28 AM   #22
tvrgeek is offline tvrgeek  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Md
A stock sound card is plenty good for setting bias, but for measuring distortion of solid state, not even close. They are also fine for measuring distortion of drivers. Even 192K sample rate is not close enough to look for amplifier stability problems. You need a real scope for that.

HP 209A. In it's low distortion mode, it is about .1% so really no better than the PC. Nothing beats it for sweeping around trying to find out what is buzzing in a room. ( I have a spring inside one window jam that resonates.) For doing real amplifier work, you need real laboratory equipment. I just run it through Spice, build it, listen and hope for the best. If someone wants to drop off a few hundred grand, maybe I could build a better test bench. Let's face it, a modern op-amp has about as much distortion as a metal film resistor. This is serious lab measurement range. By serious, I mean go talk to the folks at LBL or CERN.

For those of you who think they can do laboratory measurements with a $95 sound card, let me remind you the basic rule of thumb is that the totaltality of the test system must be ten times better than what you are testing. Go ahead, try and build that ADC or DAC with .00001% distortion. Heck, I want to see the caps you would use! Oh yea, when that measurement reads out a value like Qes of 2.12345, just use 2.1 You are not losing anything real. The air density changes more than that during the day. Remember what you are measuring.
  Reply With Quote
Old 10th February 2013, 02:16 AM   #23
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
Quote:
Originally Posted by tvrgeek View Post
A stock sound card is plenty good for setting bias, but for measuring distortion of solid state, not even close. They are also fine for measuring distortion of drivers. Even 192K sample rate is not close enough to look for amplifier stability problems. You need a real scope for that.

HP 209A. In it's low distortion mode, it is about .1% so really no better than the PC. Nothing beats it for sweeping around trying to find out what is buzzing in a room. ( I have a spring inside one window jam that resonates.) For doing real amplifier work, you need real laboratory equipment. I just run it through Spice, build it, listen and hope for the best. If someone wants to drop off a few hundred grand, maybe I could build a better test bench. Let's face it, a modern op-amp has about as much distortion as a metal film resistor. This is serious lab measurement range. By serious, I mean go talk to the folks at LBL or CERN.

For those of you who think they can do laboratory measurements with a $95 sound card, let me remind you the basic rule of thumb is that the totaltality of the test system must be ten times better than what you are testing. Go ahead, try and build that ADC or DAC with .00001% distortion. Heck, I want to see the caps you would use! Oh yea, when that measurement reads out a value like Qes of 2.12345, just use 2.1 You are not losing anything real. The air density changes more than that during the day. Remember what you are measuring.
You obviously don't build with tubes, you don't need a .00001% distortion ADC to dial in a tube design. I think agood asynchronous USB adc/dac could be built for a few hundred bucks that could esily compete with something like the expensive dScope. Would be a handy tool.
  Reply With Quote
Old 10th February 2013, 03:47 AM   #24
tvrgeek is offline tvrgeek  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Md
Actually regal, yes I have built with tubes. And yes, they do have so much distortion I could have used my PC for most of it The sound card is really great for setting the bias by measuring the distortion rather than just the current. In this case, balance by voltmeter got the distortion down to about 3%. Using the spectrum analyzer I got it below 2% at 6W. Not much help setting the bias on my FET amps which model in the .0001 range.

Tube amps don't have quite the problems you need to track down like a good fast FET amp will, so looking for stability issues at 200K is not a problem. 90K might be good enough for you. Hey, if you think you can better DScope, have at it.

So, something as simple as my Profire, 192K-24 bit would have the resolution if it had low enough distortion. Just build a box with a high quality gain/attenuation and safety clamps to use as probes. JFet inputs could even be high enough inputs to use conventional scope probes. What you won't get is the kind of resolution, buffering, and of course software as you do buying one. I wish my Zelscope could run at 192. It has the features, delayed sweep, triggering etc. The sound card is not the hard part.
  Reply With Quote
Old 10th February 2013, 01:39 PM   #25
Telstar is offline Telstar  Italy
diyAudio Member
 
Join Date: Dec 2007
Location: Italy
Quote:
Originally Posted by tvrgeek View Post
A stock sound card is plenty good for setting bias, but for measuring distortion of solid state, not even close. They are also fine for measuring distortion of drivers. Even 192K sample rate is not close enough to look for amplifier stability problems. You need a real scope for that.
Whoah, nobody wants to replace a (50Mhz+) scope here.
For some SS gear a card like the EMU is enough, and anyway better than nothing at all. Not for DACs and some line-level gear, though.

Quote:
HP 209A. In it's low distortion mode, it is about .1% so really no better than the PC.
I wouldn't use it stock. Modded, it can become sub-ppm. Search for 339A in this forum.

Quote:
The basic rule of thumb is that the totaltality of the test system must be ten times better than what you are testing.
This is correct. I'm aiming for -130dB and will settle for -120.
__________________
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
  Reply With Quote
Old 10th February 2013, 07:24 PM   #26
tvrgeek is offline tvrgeek  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Md
I dumped my EMU 1616m due to driver memory leak problems. If you motherboard does not have an on-board video, you may be OK. Other that that, it was a great box. Very confusing software because it did "everything" for the home recording set. Oh yea, the input impedance on the "line in" was very low. I had to add buffers ( battery powered of course) for the "reference" feed. The M-Audio Profire works fine without them.

My noise floor for my M-Audio Profire is about 120 dB, rising to about 90 at 20K. Battling some power line noise. Turns out in the last few years my trusty old Rotel bench amp has gotten very noisy. Time for a power supply rebuild with modern caps, hexfred diodes, and I am sure I can clean up the dress a bit. I lowered the noise floor in my DH-120 by 18 dB this way. Any way, If I get the whole thing back below 90 dB 20 to 20, I am in good shape for speaker building. Getting a test bench to actually have 130 dB floor is no easy feat. You may need a bank of power line conditioners, a ground plane, shielded power lines within 10 feet or so. 120 may be do-able with only hard work. You may need an opto-isolator between the PC and the acquisition box. Anyone make a USB isolator? Should not be too hard to do. Then feed what you can from batteries. Even things like the phantom power for my mic was too noisy, so it is not battery powered.

It is said the DCX A-2-D is pretty good, and they have a PCM link output, but no idea what software that could feed. Above the emu and M-audio, you are going to real instrumentation or studio stuff. Start adding zeros to the price.
  Reply With Quote
Old 10th February 2013, 10:03 PM   #27
diyAudio Member
 
Join Date: Feb 2003
Location: West Coast of Norway
Creative is coming with a new zxr model. Containing the pcm4220 adc chip. Looks all right. Will buy and test it when it is out.

An interesting video..

Newegg TV: Creative Sound Blaster Z-Series Audio Cards Interview - YouTube
  Reply With Quote
Old 10th February 2013, 10:21 PM   #28
Telstar is offline Telstar  Italy
diyAudio Member
 
Join Date: Dec 2007
Location: Italy
it's internal only (= psu interference are a sure thing), and creative drivers are usually much worse than e-mu ones.
__________________
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
  Reply With Quote
Old 19th February 2013, 12:42 AM   #29
ra7 is offline ra7  United States
diyAudio Member
 
Join Date: Feb 2009
Blog Entries: 1
FYI.

I asked about a USB interface for audio measurements to Ivo (ARTA author) and he recommended either one of the RME interfaces (expensive) or the EMU 0204 (cheap). He mentioned that neither is good enough to measure very low distortion (<0.0003%) found in modern opamps and DACs. But they are sufficient for most SS amps and definitely loudspeakers.
  Reply With Quote
Old 19th February 2013, 10:14 AM   #30
Telstar is offline Telstar  Italy
diyAudio Member
 
Join Date: Dec 2007
Location: Italy
Nothing new, unfortunately.
Here I can find quite easily an emu 0404 used at the price of a 0204 new. And i'll probably take one.
__________________
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
  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
looking for a decent enclosure dannycelluk Chip Amps 4 5th January 2010 10:38 PM
R2904/700000 measuremets file...... ermes Multi-Way 6 2nd August 2005 09:10 PM
Is This a Decent Setup?? TheNoodPoopler Car Audio 11 21st May 2004 01:50 AM
decent pc soundcard with multiple outputs? zag0r Digital Source 6 10th May 2004 05:00 PM
Need a decent kit Konnan101 Solid State 4 5th February 2004 07:02 PM


New To Site? Need Help?

All times are GMT. The time now is 02:59 AM.


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