Topic: 9652 + ADI-8 DS Headroom problem

Hello,

I'm trying to figure out why I have some distortion happening on my system while there should be plenty of headroom with these setup. Manual says +9dB at +4dBu.

I send a test generator signal out from cubase at -0.2dB
Signal goes via ADAT to the ADI-8
ADI-8 connected to an API 5500 EQ
Back to ADI-8 and Cubase.

With this test signal, as soon as I clip the input (on totalmix) there is distortion. Doesn't really seem to matter where I gain the signal up, the input seems to be where the clipping appears.
I'm not sure if this comes from the ADI-8 or the 9652 though.
I would want to be able to use this extra available headroom, first to not have to pay too strict attention while using outboard FX and check all the time if there is clipping. And second I heard many times that analog devices are meant to be used with some extra output gain to give more character.

I'm no expert though, could anyone assist me on what could cause the problem here, or how to make a more accurate test if needed...

Thanks

Re: 9652 + ADI-8 DS Headroom problem

-0.2dBWhat are you sending out?

Re: 9652 + ADI-8 DS Headroom problem

Headroom applies to analog connections. If you clip the AD converter, you will have distortion immediately. Totalmix shows you the digital input level...


Regards
Daniel Fuchs
RME

Re: 9652 + ADI-8 DS Headroom problem

Manual says +9dB at +4dBu. (are you sure? for the mk1 the rme site says +13db for +4db)
This also goes for the output so you are sending your -0.2db sine out at close to +9db so almost clipping. Any slight gain increase will send it into clipping.

Vincent, Amsterdam
https://soundcloud.com/thesecretworld
HDSP9652 ADI-8AE HDSP9632
Cubase pro 9

Re: 9652 + ADI-8 DS Headroom problem

Headroom applies to analog connections. If you clip the AD converter, you will have distortion immediately. Totalmix shows you the digital input level...

Ok I think this is what is unclear to me, manual says :

Reference   0 dBFS @     Headroom
Lo Gain      +19 dBu      15 dB
+4 dBu      +13 dBu       9 dB
-10 dBV     +2 dBV        12 dB

I thought that meant I have a margin of 9dB above 0dBFS before actually clipping the input... and then take the level down digitally either on totalmix or in the DAW without having distortion.

I'm sorry, I probably have to go to dB conversion school.
So no signal can go over 0dBFS (hardware input on Totalmix) without distortion. If I understood it right.

Re: 9652 + ADI-8 DS Headroom problem

Yup this is info for analogue referenced systems (mixers) to +4db.
You could set outputs to +4db and inputs to Lo gain, then you have an extra 6db of headroom going out from the Adi to fx and back in.

Vincent, Amsterdam
https://soundcloud.com/thesecretworld
HDSP9652 ADI-8AE HDSP9632
Cubase pro 9

Re: 9652 + ADI-8 DS Headroom problem

Ok thanks, got it !
I was thinking though that these converters were able to handle input levels that would then be converted above 0dBFS, like in the DAWS internally. You can for example take a signal, put it +50db above 0dBFS, then back down -50 and the signal is still clean.
I knew this wouldn't exactly apply with the A/D D/A, but thought it could handle some margin.

8 (edited by vinark 2018-09-14 13:36:21)

Re: 9652 + ADI-8 DS Headroom problem

Exactly the opposite, converters can never handle anything above 0dfs. That is why it is called db full sample. Full is full. It is a standard not related to any electrical/analogue level. It is in fact the only absolute standard.
But if your mixer clips at 4dbu you do have some headroom with the +4dbu setting, that is what it is for, but since digital came it is all very different since in the past it was about managing noise and distortion (To low or to high levels), now it is about noise and clipping!

Vincent, Amsterdam
https://soundcloud.com/thesecretworld
HDSP9652 ADI-8AE HDSP9632
Cubase pro 9

9 (edited by lebarde 2018-09-14 16:16:12)

Re: 9652 + ADI-8 DS Headroom problem

Thanks for your time and explanations... will dig further to understand it completely. At least I know all seems to be behaving as it should in my setup.