Topic: HDSP 9632 Hiss

Hi, I have an HDSP 9632 with a AO4S expansion board. I have them connected using XLR cables to a power amp as part of a 5.1 home cinema set-up.

On all channels I'm getting hiss on the tweeters. I've been looking at replacing the cards with a processor but when I started investigating I learned that there might be a "fix".

The hiss changes volume when I change the gain settings in the Hammerfall settings. It gets louder with +4 and louder again with +10 settings. I have the XLR breakout box checked.

Should this noise be present? Is it just the usual noise floor of a PC that I'm hearing?
Would a modified card fix the issue? Is there any way to tell if the card has been modified already (I read something about green dots)? If the serial number of corrected cards is logged I can provide that.

Lastly, is an HDSPe quieter than an HDSP? I've no reason to think it would be, I just want to ask.

Any other suggestions would be welcomed.

Thanks in advance


Re: HDSP 9632 Hiss

No comments from anyone in support? Should the card be completely silent, or is hiss to be expected?


Re: HDSP 9632 Hiss

This is a ground loop problem. You could remove the ground connection on the TRS plug that goes into the AO4S (try with one cable only to see if that really helps), or whereever it causes a change.

Matthias Carstens

Re: HDSP 9632 Hiss

Thanks for the response. If it's a ground loop then connecting everything (PC and Amp) to the same outlet should remove it, right? I'll try that.

I've had ground loops before and they're usually a buzz rather than a hiss. It sounds like a high noise floor. I'll try reconnecting things though. I can also try using unbalanced to see if that resolves things.

It's on all channels, the LR stereo out from the main card, as well as from the additional board.

Thanks for the response though, and Merry Christmas!

Re: HDSP 9632 Hiss

I assume you have isolated the RME soundcard from the computer chassis?

Meaning that you cover the metal bracket of card with electrical tape etc.
Also use a plastic screw to fix the card bracket to the chassis (if your computer chassis uses screws and not some other method like a clasp)

Re: HDSP 9632 Hiss

Nope, I haven't. Does that need doing on both the main board and the expansion board?
I do use screws. I'll see if I can find a plastic one, or just run it without a screw for a while, at least to see if that removes the issue.

Re: HDSP 9632 Hiss

Yes both or just let the second board float free.

Vincent, Amsterdam
HDSP9652+ADI-8AE  2X HDSP9632
Cubase pro10