"Clean" audio in Scope DSP

[Music Manic]

I was getting some odd sounds from a samples library I had which lead me to test Scope's DSP.

I used the control room and used a sine wav and Spectrogram to see what was happening to the audio path..

I started at 1kHz and all looked correct, then I tested it at between 15 and 16kHz ,where I was getting odd sounds. It seemed that there were some sidebands occuring rather than a pure single sine wave.

I will test it more but if I'm getting a side band or two at a certain frequency then God knows what else is being added to a harmonic signal.

Any views?

Thanks

[the19thbear]

uhh!! tell us more!

[garyb]

bad woofer?

something resonating in the room?

or something viewable on the scope?

[bassdude]

How are you actually testing this? How do you know you are not overloading the spectogram?

[the19thbear]

yes. please post a screemshot and explain more

[Music Manic]

Well here is the same sort of thing from my cheapo audio laptop card:
@ Gary - It's all internal Gary.

[garyb]

what and where is this measurement?

i'm not confrontational, just confused.

[Music Manic]

what and where is this measurement?

i'm not confrontational, just confused.

I didn't take it negatively Gary.

Ok, I set up a sine wave to pass through the audio drivers which is picked up by the spectrogram.

What I am asking is, why is the spectrogram showing sidebands when the sine wave is supposed to be a pure signal.

I tested this because I was getting some "fluttering" affect. I've just replaced the drivers and everything sounds as clear as a bell.Yes they were corrupt.

The wierd thing is that I still get the sidebands as a result. They are very bad in the Lows and lower mids and begin again at about 15.5kHz.

So my question is: What noise is being added to the audio signal?

I can't believe how bad the sound was and how flakey things got when the drivers were corrupted.

[garyb]

sure, corrupted code won't function correctly or at all...

the sine wav itself may not be very pure. it's hard to say what's happening from the info...

[tgstgs]

tricky thing a fft is;
there are no sidebands at all;

good vibes

[Music Manic]

tricky thing a fft is;
there are no sidebands at all;

good vibes

What's that noise that's showing though?

[Fede]

FFT approximation?
FFT should give different approximation with different sample block size (also different approx @ different frequencies)

cheers
Fede

[tgstgs]

i dont know spectograph;

but what i see (the bands around 100Hz or 1kHz) is a mathprobl. _ there is no noise!
the fft doesnt care about frequency its a mathmodel put on;
-------
use a higher N to get less 'noise' or apply a window before fft;
if interested do a search for _ julius von hann _ hanning window _ to get an idea

good vibes from vienna

[Neutron]

using rightmark audio analyzer i got "excellent" across the board with 24/44 with a16 plugged back in to itself.

[MD69]

Hi,

If you are getting a ringing metallic tone superimposed to your sound, there is a good chance that your scope have partly lost its synch.

change your sample clock (cycle from 44,1 to 96 then go back). There is a good chance it fail. In my config this is a symptom of a bad sitted STDM cable / board.


cheers

Michel

[Music Manic]

Hi,

If you are getting a ringing metallic tone superimposed to your sound, there is a good chance that your scope have partly lost its synch.

change your sample clock (cycle from 44,1 to 96 then go back). There is a good chance it fail. In my config this is a symptom of a bad sitted STDM cable / board.


cheers

Michel

Are things really that volatile?
So many things can go wrong..

[MD69]

Not that much (once or twice a year). One of my STDM connector get loose after a time (the one associated with the 1rst connector on the board) and exhibit this problem

cheers