Audiophile 2496 Frequency Response Problem

A

Autist

New member
Below is the frequency response graph from the Rightmark analysis that I did on my AP 2496. I disconnected all of the case fans, turned the CPU fan down very low and moved the card further away from the graphics card but have been unable to get any better results (they remain consistent through every test).

All tests were done line out to line in.

Frequency Response Chart

This is the summary from the test:

Frequency response (from 40 Hz to 15 kHz), dB: +5.19, -2.31 Poor
Noise level, dB (A): -97.0 Excellent
Dynamic range, dB (A): 96.0 Excellent
THD, %: 0.0007 Excellent
IMD, %: 0.0046 Excellent
Stereo crosstalk, dB: -97.2 Excellent
IMD at 10 kHz, %: 0.0051 Excellent

Does anyone have any idea what the problem is, since I have ruled out case fans and the CPU fan (as much as possible without actually removing the fan or slowing it down so much that it is ineffective)? My friend thinks that perhaps the card is bad. Also, the large "hill" on the bass end side of the graph that starts around 350Hz does show up in spectrum analyzers when working in a DAW (even without recording anything through the analog inputs) and I have been unable to get rid of it.

System Specs:

Amd Althon XP 2400 (2Ghz)
1.5 GB DDR RAM
Asus A7n8x Deluxe Mobo
Ati Radeon 9100 graphics card
400w power supply
Windows XP Pro

Also, on-board audio has been disabled in the bios since I originally installed the AP 2496.
 
Autist,

> Below is the frequency response graph <

That graph clearly shows comb filtering in the numerous peaks and nulls that appear to get closer as the frequency increases. Comb filtering sounds like a phaser of flanger effect. Do you hear that effect in stuff you record or play back?

> All tests were done line out to line in. <

Maybe you something set wrong in the 2496's control panel routing? I'm certain this is not the correct response for a 2496 sound card, and this problem usually occurs when there's a delayed feedback path from the output back to the input. Which is why I suspect the monitor routing. Or some sort of software input monitoring gone awry.

--Ethan
 
Possibly try it with an internal loopback rather than an external loopback--I imagine if the problem is a bad card this would reveal something?

i.e.:
Set the patchbay router H/W Out 1/2 to Monitor mixer.
In the monitor mixer have both Master Volume and Wave Out 1/2 up, with the other volumes down.
Run RMAA with output as M-Audio Delta 1/2 and input as M-Audio Delta Mon. Mixer.

I noticed that if my DMA Buffer size was very low then the "Adjust audio I/O" in RMAA thought that there was channel leakage, but the tests still gave good results.

With this internal loopback I got frequency response results which looked ruler flat up to approx. 20kHz then dropped of, for 32 bit (float) at 96kHz (and even looked reasonably flat at 8bit 44.1kHz).
 
Thanks for the replies and the help!

I changed the patchbay/router settings to:

H/W Out 1/2 from Monitor Mixer to Wav Out 1/2
H/W Out S/PDIF from WavOut S/PDIF to Monitor Mixer

It seems that when I use the original settings I encounter the problem, but once I change them the problem is resolved.

These are the latest test results:

Frequency response (from 40 Hz to 15 kHz), dB: +0.02, -0.06 Excellent
Noise level, dB (A): -97.4 Excellent
Dynamic range, dB (A): 96.8 Excellent
THD, %: 0.0010 Excellent
IMD, %: 0.0048 Excellent
Stereo crosstalk, dB: -97.6 Excellent
IMD at 10 kHz, %: 0.0051 Excellent

I haven't tried it in Cakewalk with an FFT display yet, but hopefull that will look OK now as well.

Thanks again!

EDIT: There was no audible effect such as phasing, or flanging when the settings were producing the bad results.
 
Excellent!

I think somehow going though the monitor mixer you were ending up with the input for RMAA being a mix of an external loopback and an internal loopback--or rather, that's the only thing I tried which gave a similar kind of result for the frequency response.
 
I experimented some more and found that I get the bad results whenever I set the H/W Out 1/2 to Monitor Mixer.

Anyhow, now that I got all that fixed I can't seem to get Cakewalk HS XL to work with the AP2496 in ASIO mode, it keeps defaulting to GuitarPort and grays out all AP stuff. Oh well, I had it working befre, I just forgot what I did to get it to work. :o
 
You must log in or register to reply here.
Back
Top