How to measure frequency response with a PC? - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 25th March 2007, 09:21 PM   #1
diyAudio Member
 
Join Date: Jan 2005
Location: Argentina
Default How to measure frequency responce with pc

Hi people,

I'm trying to measure the F.R. of my tube amp (Help modifiying schematic) and I cant make TrueRTA work.

I tried with NVIDIA SoundStorm sound card an Sound Blaster Audigy 2 ZS. I cant calibrate the sound card to have a plain frequency response to start measurements.

I don't know what is my mistake.

Sound Controls (both cards tested):
recording: line input selected, at MAXIUM
playback: wave and master at maxium, line input muted (To avoid oscillations)
Loop cable conected between line in and line out.
I also checked and no "audio effect" is ON.

Any clue? Any other program to use?
  Reply With Quote
Old 25th March 2007, 09:46 PM   #2
diyAudio Member
 
Gold_xyz's Avatar
 
Join Date: Dec 2005
Location: Italy
Hi

Try an oscilloscope/spectrum analyzer from this site
http://digilander.libero.it/hsoft/

Link download : http://digilander.libero.it/hsoft/VA.zip
(with continous spectrum )
__________________
My English originates from here
  Reply With Quote
Old 25th March 2007, 11:39 PM   #3
diyAudio Member
 
Join Date: Jun 2003
Location: Portugal
This can be useful too .

http://www.usb-instruments.com/oscillo_stingray.html
  Reply With Quote
Old 26th March 2007, 01:35 AM   #4
diyAudio Member
 
Join Date: Jan 2005
Location: Argentina
Quote:
Originally posted by Gold_xyz
Hi

Try an oscilloscope/spectrum analyzer from this site
http://digilander.libero.it/hsoft/

Link download : http://digilander.libero.it/hsoft/VA.zip
(with continous spectrum )

Thanks for your reply!!!!

I've downloaded the program. I'm trying to calibrate it. Wave generator is configured as Sweep. After a few loops, the graph shows the frequency response of the sound card:

Click the image to open in full size.

Is there any way to "flat" it to correct the response of the sound card?

thanks
Jorge.
  Reply With Quote
Old 26th March 2007, 07:42 AM   #5
diyAudio Member
 
KimBOlesen's Avatar
 
Join Date: Aug 2005
Send a message via MSN to KimBOlesen
Hi

try this -> http://audio.rightmark.org/products/rmaa.shtml with this program you can subtract the soundcard data from your amp's data.

Best regards Kim Olesen
__________________
Best regards Kim Olesen
  Reply With Quote
Old 26th March 2007, 12:12 PM   #6
diyAudio Member
 
Join Date: Jan 2005
Location: Argentina
Quote:
Originally posted by KimBOlesen
Hi

try this -> http://audio.rightmark.org/products/rmaa.shtml with this program you can subtract the soundcard data from your amp's data.

Best regards Kim Olesen

Wowww that program seems to be really nice!! thanks!! I will try it. thanks!!!!

Jorge.
  Reply With Quote
Old 26th March 2007, 12:33 PM   #7
Svein_B is offline Svein_B  Norway
diyAudio Member
 
Join Date: Oct 2005
I often use ARTA, the speaker measurement program also for amplifier measurements.

- The Spectrum analyser is nice for measuring harmonic distortion, and it has built in tone generators.
- Compensation files can be loaded.
- FR measurement is OK, but most PC's fall short here with a limit of 20KHz. The same can be said for usefulness of any soundcard based oscilloscope.


Svein B.
  Reply With Quote
Old 26th March 2007, 01:02 PM   #8
diyAudio Member
 
Join Date: Mar 2007
Location: Canandaigua, NY USA
Zafira, I like VA quite a lot. If your sound card can sample higher than 44.1khz, you can test higher than 20khz. My inexpensive E-mu 0202 USB box supposedly can go to 192khz, though I haven't pushed it that far. Tests at 40khz (96khz sample) and more seem fine. I notice that your level is -60 db in the graph you attached. That's way down there- check your levels and 0dB setting. You might also find it interesting to use the pink noise source and set the analyzer for 1/3 octave or finer measurements. Handy when you move beyond the amp to the speakers.
  Reply With Quote
Old 26th March 2007, 11:33 PM   #9
nhuwar is offline nhuwar  United States
diyAudio Member
 
nhuwar's Avatar
 
Join Date: Jan 2007
Location: Cypress Texas
As far as hardware goes iIve been eyeballing this. ! channel o scope 400hz to 16 mhz spectrum analyzer.

http://www.velleman.be/ot/en/product/view/?id=348712

Nick
  Reply With Quote
Old 27th March 2007, 03:16 AM   #10
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
I believe if you are using line in and out and doing a loop back test the line input needs to be unmuted - that is where the signal you are trying to measure is connected to.

There should be no oscillations with loopback connection and both input and outputs enabled.

Note that depending on level settings and sound card you may clip either the input or output, this should be fairly obvious if you get high thd numbers.. I generally run at no more than 90% of digital FS to get good results.

I use Arta and Audio Tester.
__________________
"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
Easiest software to measure the Frequency Response -_nando-_ Multi-Way 72 15th July 2007 05:21 PM
How to measure frequency response with PC? Emiel Multi-Way 8 3rd November 2005 05:09 PM
What software to MEASURE response Madmike2 Multi-Way 3 6th July 2005 08:19 AM
Doubts on Phase Response and Frequency Response dumrum Multi-Way 11 5th April 2004 10:39 AM


New To Site? Need Help?

All times are GMT. The time now is 05:24 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