[jiiteepee]

Hi

Maybe not an issue but, ...

recording from LP using higher resolution (88.2kHz/96kHz) brings up some weird frequency spike @ around 33.6kHz (more exact fr shown in picture behind the link).

What is this ? Does it come from vinyl production process, cartridge, turntable, E-MU (Hi-Z inputs), USB port/path, software, ....? All I know, it's not the RIAA filter since I can test and have already tested this.

http://jiiteepee.fortunecity.com/tes...-high-res.html

Any suggestions?

jiitee

 

[utilisateur]

I have no real idea were it might come from
but
Did you check if it occurs at higher sampling frequencies aswell?

 

[Budgie]

Whats it sound like??



(just kidding...)

 

[Tarkovsky]

My guess is that's rf comming from a hard disk, computer monitor, or poor quality power supply. Either way I'd personally cut everything from 24k up. Imagine the needle of your deck moving 33.578 thousand times a second, isn't happening.

 

[Tarkovsky]

Also just noticed you aren't using a subsonic filter. Why's that?

 

[jiiteepee]

Quote:

Originally Posted by Budgie /img/forum/go_quote.gif Whats it sound like?? (just kidding...)

Fortunately the level is not very high (otherwise, it could be heard I guess ... meaning aren't the 1st octave backwards ~16.5kHz and the 2nd ~8.3kHz).


Quote:

Originally Posted by Tarkovsky /img/forum/go_quote.gif Also just noticed you aren't using a subsonic filter. Why's that?

Just forgot to tick the selection box ....

jiitee

 

[Tarkovsky]

Ah I thought I was in for some sort of vinyl revelation!

 

[infinitesymphony]

That is strange... Does it happen with all of your LPs? What kind of phono preamplifier are you using?

Quote:

Originally Posted by Tarkovsky /img/forum/go_quote.gif Either way I'd personally cut everything from 24k up. Imagine the needle of your deck moving 33.578 thousand times a second, isn't happening.

jiiteepee's graph shows information past 40 kHz. Why not keep it?

 

[jiiteepee]

Quote:

Originally Posted by infinitesymphony /img/forum/go_quote.gif That is strange... Does it happen with all of your LPs? What kind of phono preamplifier are you using? ...

Need to test this more now in this weekend (using higher sample rate, w/ some other LP's and couple other recording software as well). As it's exactly the same frequency with both 88.2kHz and 96 kHz, I still believe it is coming from some external source.

Actually, E-MU Hi-Z input stage is the only pre-amp there in my connection in this case ... RIAA EQ is done through software filter (really HQ, 3rd-5th order IIR filters I made just for RIAA) and I have tested already that filters are not the culprit.

jiitee

 

[utilisateur]

Please report back as soon as you have more infos!

I'm planning to do basicaly the same 0404DAC->FIR RIAA but my impression was the micpre in the 0404 is not on par.

 

[infinitesymphony]

Quote:

Originally Posted by jiiteepee /img/forum/go_quote.gif Need to test this more now in this weekend (using higher sample rate, w/ some other LP's and couple other recording software as well). As it's exactly the same frequency with both 88.2kHz and 96 kHz, I still believe it is coming from some external source. Actually, E-MU Hi-Z input stage is the only pre-amp there in my connection in this case ... RIAA EQ is done through software filter (really HQ, 3rd-5th order IIR filters I made just for RIAA) and I have tested already that filters are not the culprit. jiitee

Yeah, it would almost have to be from an external source... I've never seen a spectrograph of an LP with such a noticeable steady high-frequency tone.

A little OT, but is your software RIAA EQ available for download? (It seems like I remember you posting about this a while back, but can't remember.)

 

[jcx]

total software RIAA isn't technically a good idea

you really want a low noise preamp suited to your cartridge type with at least one pole roll-off in analog to allow the use of decent gain and preserve high frequency overload margin without wasting S/N on one end or the other of the frequency range

 

[jiiteepee]

Quote:

Originally Posted by jcx /img/forum/go_quote.gif total software RIAA isn't technically a good idea you really want a low noise preamp suited to your cartridge type with at least one pole roll-off in analog to allow the use of decent gain and preserve high frequency overload margin without wasting S/N on one end or the other of the frequency range

... but it's working in practice.

Yes, the matched pre-amp (flat) is a minimum requirement with software RIAA to get excellent results ... what I'm testing here is just how's the quality when using plain Hi-Z inputs found on 0404 USB (no software gain is needed and also you don't need to max the input levels on E-MU either ... ~50% gain seem to be enough). The only problem so far is the unmatching connection impedance/capacitance.



jiitee

 

[jiiteepee]

Quote:

Originally Posted by infinitesymphony /img/forum/go_quote.gif Yeah, it would almost have to be from an external source... I've never seen a spectrograph of an LP with such a noticeable steady high-frequency tone. A little OT, but is your software RIAA EQ available for download? (It seems like I remember you posting about this a while back, but can't remember.)

IIRC, I gave two versions out at that time (basic 44.1kHz version and 48kHz w/ recording option and some instructions on gaining the filter internally) based on Cycling '74 Max/MSP ... the nearly final version I'm using is not given out (yet) since I have not have time to finalize it (GUI, couple filters not integrated yet, etc.). You'll find links by searching here on this sub forum.

jiitee

 

[Bizzel]

Some HDTVs have a horizontal refresh rate of around 33.5kHZ (while the vertical is a more modest 60hz). Could that have something to do with it?