Noise from 688?

[Alex J Kramer]

Hi Fam,
How its going there?)))

Today I've start to mix an jazz album and mention(also producer and musicians) that weird annoying noise(see link). It's present on A B C busses with all channels muted so I decided to re-schedule mixing session and fix that. The biggest problem - I have no idea about what should I do and how.
Please help!


https://drive.google.com/file/d/1esSieLNsKN-b4dqEc-VdqFZKLlbAxiL5/view?usp=share_link

[radardoug2]

Well, your little video gives us no idea on what level the noise is at, and what you have connected, or anything. Get yourself a good milivoltmeter, and measure the signal to noise. Looking at graphical tools like you are is often unrealistic.

[tlamix]

Greetings,
You could try and float every channel to remove them from the A,B,C buss.
This will just verify that it is not a problem with one of the channels.
Float is the only way to remove the channels from the master busses.
Also, mute and turn down the level of the reverb returns.

When I mix, I float any channel that is not in use.
It reduces the noise floor significantly.

Good Luck.

[jimlfixit]

I have read these comments and regardless of any noise problems, the 688 early or later versions were not rarely meant for normal recording studios. The three stereo mix buses were designed for Music, Effects and Dialog for film and/or broadcast.
I built all the early ones at SSL (was there from 1980-87) with just a 681 sized panel and 3 big pcb's hanging off the back and also the later ones on the 6K consoles with the rack, a bit like the 651 centre section rack but smaller.
Both were designed by Trevor Stride at SSL, a design engineer who also designed some of the 5K series console Pan and compressor modules.
I also wired a unique  one off 4 buss 688 rack for a USA studio at SSL which involved a lot of mods to the back plane and I wonder where this is now in the USA?
Good luck with your noise problem and I can't help with that as I just wire things and am not technical.
Regards from Jim Lassen in Maidenhead, Bucks, UK

[Alex J Kramer]

Greetings,
You could try and float every channel to remove them from the A,B,C buss.
This will just verify that it is not a problem with one of the channels.
Float is the only way to remove the channels from the master busses.
Also, mute and turn down the level of the reverb returns.

When I mix, I float any channel that is not in use.
It reduces the noise floor significantly.

Good Luck.

Thnx a lot, tlamix!
I did that but the problem is still there.

Here's one possible reason(see attachment).
Is that some kind of mod?
Both '26 cards without c1 and c2

[horizonsound]

That's standard on the 6000 consoles. The mix bus amp is not used on the E26 cards.

Instead, there is effectively the same thing on each of the six E256 cards in the 688V section.

Anthony.