Skyraider,
with a decent soundcard (not luxury or expensive, just a decent
one) you should be able to check that there is nothing seriously
wrong with the frequency response and also check the tone
controls. You will probably find that the soundcard drops one
of a few dB towards 20Hz and towards 20kHz, although that
need not be the case. If you check first what response you get
with loopback, that is soundcard out directly to soundcard in,
you can check this and compensate for it. If you know the
soundcard drops 1 dB at 20kHz from this test, and then when
testing the amplifier you get a 3dB drop, then the amplifier
drops 2dB. That was just an example, of course.
You also mentioned checking for oscillations previously. That
is not possible. Oscillations (almost) always happen at
frequencies much higher than the audio band, so a souncard
can't detect that. You need an oscilloscope for that.
with a decent soundcard (not luxury or expensive, just a decent
one) you should be able to check that there is nothing seriously
wrong with the frequency response and also check the tone
controls. You will probably find that the soundcard drops one
of a few dB towards 20Hz and towards 20kHz, although that
need not be the case. If you check first what response you get
with loopback, that is soundcard out directly to soundcard in,
you can check this and compensate for it. If you know the
soundcard drops 1 dB at 20kHz from this test, and then when
testing the amplifier you get a 3dB drop, then the amplifier
drops 2dB. That was just an example, of course.
You also mentioned checking for oscillations previously. That
is not possible. Oscillations (almost) always happen at
frequencies much higher than the audio band, so a souncard
can't detect that. You need an oscilloscope for that.
Skyraider, there are many reasons amplifiers sound different ,some well understood and others more mysterious. The interesting thing about amplifier design is trying to work out what's important and how decisions about topology and component choice affect perceived sound quality.
I think the illusion of a 3D soundstage has a lot to do with a systems ability to reproduce extremely low level information, this gives a sense of 'air', space, depth and ermm... 'realness'
I think the illusion of a 3D soundstage has a lot to do with a systems ability to reproduce extremely low level information, this gives a sense of 'air', space, depth and ermm... 'realness'
Hi Guys,
I've been using RMAA with a kit soundcard preamp (with gain adjustable from .01 to 10) and an Audigy platinum2 ZS soundcard. The card itself is very flat, with low distortion, If you want to look at what nasty things I have uncovered in my amp using this stuff (Plus TruRTA as a scope) check out this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=24321&highlight=wintermute
Note that the html versions of the reports aren't quite as revealing as the originals (especially since they are comparing one thing against another, and it allways seems to choose the good curve not the bad one), One channel is playing up, and when you see the freq response curve it's pretty obvious there is something seriously wrong with it.
In the end I found that if I created a 44Khz 16Bit WAV file of the RMAA test tones, and burned it to an audio CD, I got even better distortion results (using my Marantz DV18) edit compared to the loopback test on the sound card. So I started testing using the cd (I was getting the oscillation problem mentioned earlier in the thread and that solved it).
Current state is I'm about to order replacement caps for all the electros and film caps.
Below is a screen grab of one of the latest tests I did, with the DV18 as the source.
Tony.
I've been using RMAA with a kit soundcard preamp (with gain adjustable from .01 to 10) and an Audigy platinum2 ZS soundcard. The card itself is very flat, with low distortion, If you want to look at what nasty things I have uncovered in my amp using this stuff (Plus TruRTA as a scope) check out this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=24321&highlight=wintermute
Note that the html versions of the reports aren't quite as revealing as the originals (especially since they are comparing one thing against another, and it allways seems to choose the good curve not the bad one), One channel is playing up, and when you see the freq response curve it's pretty obvious there is something seriously wrong with it.
In the end I found that if I created a 44Khz 16Bit WAV file of the RMAA test tones, and burned it to an audio CD, I got even better distortion results (using my Marantz DV18) edit compared to the loopback test on the sound card. So I started testing using the cd (I was getting the oscillation problem mentioned earlier in the thread and that solved it).
Current state is I'm about to order replacement caps for all the electros and film caps.
Below is a screen grab of one of the latest tests I did, with the DV18 as the source.
Tony.
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