Hi,

I've had an Audigy in my system for about 1 year and I've been very happy with the sound. Even if it isn't transparent, it's quite nice. However..

I recently downloaded a program, fg_lite.exe with the aim of testing my limits of my hearing. I found with the Audigy that I could only hear a tone sweep up to about 14.5k, which is quite weird because I'm only 23 although I have subjected myself to a lot of noise (I'm a DJ). Anyway, going above about 16k (I think) I started to hear some strange sounds.

So I downloaded a tone sweep in wav format and found that I could hear the same effect with that.

Now I have an Audigy 2 in my system as well (2 SB cards - obviously I don't have a VIA chipset ) and it's showing similar symptoms but at a higher frequency. It starts very suddenly at about 18.137khz or so.

So I'm wondering. First off, is this problem caused by the 44 -> 48khz resampling?

Secondly, can I avoid this if I resample the sweep (with a good program) to 48khz?

Thirdly, has anybody used the SSRC plugin with an Audigy 2? Does it improve the sound at all?

Cheers!

Hi dgover2,

This is an excellent question.. I can't answer all of this, but I think what you're hearing might be either:
- aliasing due to Audigy1/Audigy2 's resampling
- distorsion due to your speaker system

If someone has a more accurate answer, by the way I'd also like to know which SSRC settings are recommended for optimal use of an Audigy1 soundcard.

I'm currently resampling 44kHz,16bit => to => 96kHz, 24bit.

It's definitely not the speakers because it happens with 2 different Amp & Speaker Combos. 1 Technics SU-A707 with Electrovoice speakers, and 1 Yamaha AX-396 with B&W DM303 speakers. It also happens with my Sennheiser HD25SP headphones.

BTW - I think with the Audigy (1) you should resample to 16/48 because a 24/96 source is also resampled (down to 16/48) and loses some high frequency response, or so I read somewhere the other day.

The Audigy 2 fixes this.

In that case, may I suggest you play your WAVE file @ 48kHz.. and take account of it when calculating the maximum frequency you can hear ?


IMO, no matter what the Audigy1 natively handles (48kHz or 96kHz), there should be no drawback (quality-wise) with feeding it a 96kHz (instead of 48kHz) signal.
That is, assuming that the signal:
- was originally upsampled from 44.1kHz
- is not filtered during the process of conversion to 48kHz (=the conversion simply drops half the samples).

However, I'm a bit worried about the following:
Are you really sure the Audigy1 is 48kHz ? I mean, I can understand marketing cheats about the SNR (because of say, 24-bit mixing, and maybe dithering to 16 bits by H/W) but really, what about the sampling rate ? why should they handle only 48kHz when they have 96kHz DAC's ?

From the Soundblaster web site (http://www.soundblaster.com/products/audigy2/compare.asp)

Sound Blaster Quality: "Sound Blaster 24-bit ADVANCED HD. 24-bit/96khz" (obviously the software-side, marketing point of view)
Audio quality/bit Depth: "16-bit/48kHz" (really? is this the actual limit ?...)
DACs: 24-bit/96kHz (then.. what's the point of this ?)

This is very confusing !
Just to clear up the confusion, has someone actually measured if, when playing a 96kHz WAVE file with say, a 30kHz tone in it, something is actually happening in the analog output(s) ?

It would then be very easy to see whether the cutoff is @ 24kHz or 48kHz, wouldn't it ?

I can understand the point in using a 24-bit DAC (that would guarantee accuracy when mixing several 16-bit audio streams) - but WHY would they use 96kHz DAC's, if the digital source cannot be 96kHz in the first place ? Maybe it's 48kHz with 2x oversampling (right before the output D/A converters) ?

This is in contradiction with the audigy specifications at http://www.soundblaster.com/products/audigy/specs.asp

24-bit Digital-to-Analog conversion of digital sources at 48kHz to analog 5.1 speaker output

According to this datasheet, only the SPDIF in/out are 96 kHz, not the DACs.

Yep. Audigy 1 resamples everything to 16 bit/48 KHz, so better use 48 KHz wave files, or SSRC resampling to 48 KHz.

Audigy 2 resamples to 48 KHz everything below 48 KHz, and seems that does not resample 96 KHz and 192 KHz, so in this case, use wave files of 48, 96, 192 KHz or SSRC to them.

Thanks, these specs are precise and clear.
Now, since I'm using the 5.1 discrete digital output (to Megaworks 510D), I guess I can stay safely with 96kHz/24bit... and logically, an Audigy2 would make no difference for me :-)

Not sure... the link you gave states that the Audigy 2 is the only one to have Full support for Windows Media 9 24-bit/96khz 5.1 content
I don't know if it is only Windows Media related or if the Audigy1 only supports stereo 96 kHz digital, and not 5.1 96 kHz.

So can anybody tell me exactly what the strange sounds i hear at the high end of the tone sweep are caused by? It seems weird to me that resampling would cause such a thing, unless its *really* bad - and if it was that bad I would expect the Audigy to be a generally terrible card.

I think I'll try resampling a tone sweep to various bit-depths & sample rates to see if i can hear any difference.. and post the results if anybody is interested?

Sonogram of a sweep tone (red) with aliasing (green) : http://pageperso.aol.fr/lyonpio2001/pictur...es/aliasing.gif (45 kB)

Note the 22 050 Hz point, where it refects itself downwards, while a strong alias is still going down. The end of the sonogram is 32 000 Hz.

When you resample a tone beyond the nyquist bandwidth aliasing occurs. A 22051Hz tone sampled at 44100Hz will become a 22049Hz... and a (22050+n) Hz tone will become (22050-n) Hz (where 0<n<22050) . Proper procedure to prevent aliasing is to apply a lowpass filter before downsampling.

That's necessary, but not enough. The above sweep was pure. A bad resampling process generated all the aliases without anything above 22050 Hz in the two sections on the left.

I think I can.
Audigy2 uses better AC97 codec + better DACs = better frequency response of sound.
Math.

I just downloaded fb_lite and I can confirm these noises. I hear sounds up to roughly 18,1 KHz, but at a certain frequency, an additional tone with way lower frequency is noticable on my Audigy 1 (Windows XP, CreativeLabs' newest drivers). It changes it's frequency at the same time as the 'real' signal changes when I move the slider. Perhaps this tone is always there, while the 'real' tone is generated, but you can't hear it, because the 'real' tone's volume is much higher - until the hearing's recognition-curve (and that of my speakers) falls...

Regards, fileman.

Audigy2 uses the Sigmatel STAC9721 AC'97 codec , the same one used in the Live 5.1.... Better? Ummmm...... I doubt it.

A few people who owns a TBSC bought the A2, and even they commented on 3DSS forums how the TBSC sounds BETTER on music over the A2.

Definitly better than CT1297 or smthg used in Audigy1.