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4K,6K,8K Series / Quad to Cues
« Last post by Mixerman on December 16, 2018, 03:30:33 PM »
I replaced a light bulb on the Quad to Cues switch. After that the Quad to Cues did not work. Maybe it is the switch that got broken during the replacement... :-\  Someone who have replaced that switch before? Maybe it is an issue with a card in the centre section? It seems like a hazle to replace the switch, so maybe it is an idea to just short the switch on the card? Some one who got some ideas?


4K,6K,8K Series / 4k Maintenance plan and advice
« Last post by tko on December 16, 2018, 09:48:37 AM »
Hi all,

Thanks for a fantastic site and info, I've spent many hours reading other owners/users incredible journeys making cool alterations and owning the SSL DIY attitude!

I'm starting this thread to lean on all your amazing knowledge as I am located in NZ and there is literally NO SSL techs. I have a solid understanding of electronics and can solder. I've wired many studios and build a bunch of 1176's, mics and way too many bantam patch bays.

I have introduced my desk before but I'll go again - My SSL is the Ex-Real World 4k. It's a thing of beauty to me. It was cut down by Alan Smart to 24 and has been absolutely amazing to use, it's made a lot of albums and literally recorded hundreds of drums sessions and mixed over 1000 songs. I've tried mixing itb and I can't do it. I need to see 0dbvu and have those EQ's right there.

About 6-9 months ago I began to get some intermittent issues which have progressively gotten worse. EQs engaged killing channels or losing lows etc, compressors distorting, Channels returns with no signal etc.

I originally posted a Q here:,1371.0.html

But after some research (on this site) I've decided that after almost 9yrs of every day use and no real maintenance (as none seemed to be required other than bulbs and scratchy switches) it's time look at all the faults and give my 4k a full overhaul and start a programme of maintenance for the long term, while making sure I am doing everything right to look after her. I have 6 weeks off with no sessions booked, so I'm going to get stuck into it. There are also some minor issues that have been there since I purchased which I want to fix too, no VU lamps work for example.

I'm initially looking for suggestions on things I should do that might fix any simple issues such as bad card seating or general tips that can be easy fixes. I think its good place to start this journey with. And also anything I should look out for on the channels.

Of note:

1. The desk was moved 2 yrs ago and the issues started a little after that. When I moved to the new location 2016 the movers lost the rear panels and I never thought much of it. But I actually just found them buried in my lock up. So if that has contributed to heat inconsistency please let me know. I do intend to put them back on with this work.
2. I have already ordered a full set up Caps from Recycled Audio (just incase) and enough LEDS to replace the cut/solo lights.

This is what I am considering so far:

3. I read on another thread (,675.msg4547.html#msg4547) that suggested making an excel spreadsheet to document issues, so I can do that first.
4. I have 3 buckets so once all faults are documented power them down and one channel at a time remove all cards clean all cards connectors with Isopropyl, clean all switches with contact cleaner.
3. Re power up 1 bucket with my riser card re check documented issues and then come back to here for my next steps?

Thanks all for any help!

TKO - The Armoury - Wellington NZ.

P.S Here's a pic...

4K,6K,8K Series / Re: SSL 4k dynamics card, what part is this?
« Last post by amillar on December 14, 2018, 10:08:47 PM »
Seems like the AAZ17 is a relatively long recovery (350nS) diode.  The only sub I could find was AAZ15.

I can't see that causing a problem! Many thanks for the suggestion.

(And Hi Pascal, nice to hear from you again!  :) )
4K,6K,8K Series / Re: SSL Calibration and Tone Oscillator questions
« Last post by Chris Simon on December 14, 2018, 09:30:21 PM »
I'd say it depends on how you're measuring, and where. The on-board oscillator should measure +4dBu (1.228 V) when measured on the other end of the bantam cable; if it doesn't, then adjust that first. Now, if that same patch cable is patched to a line in, you'll measure 0dBu (0.775 V) at the insert send, as the level is reduced internally. That same signal, with the channel VCA fader at the "0" mark, will drive the Quad bus to a level somewhat lower level than 0vu on the Quad meters; I've never actually seen documentation that says what that level is supposed to be. Remember that the Quad bus would be overloaded in a hurry if any individual channel was able to drive the bus at unity gain.

Do not trust your meter. If it's a typical non-audio multimeter, the response may be a little better at 100 Hz, but not as good as the classic Fluke 8060A (I have one myself). Don't trust the Pro Tools oscillator, as it's response is different in Peak and RMS modes. Don't trust your interfaces until they're calibrated, inputs and outputs. I believe the industry standard is -18dBFS = +4dBm, so confirm that an external signal that's known to be 1.228 V will drive the Pro Tools inputs to -18 when in calibration mode.

Don't worry. It may turn out your system is just fine, but without proper test equipment you can't be sure.
4K,6K,8K Series / Re: SSL Calibration and Tone Oscillator questions
« Last post by MarconeMusic on December 14, 2018, 06:58:02 PM »
Hey Andy! Thanks for the reply.

Im using a basic tech shop meter. Velleman dvm850bl
Its not a great one.
I did, during my testing, use a 1K tone, but tried to use the 440 and 220 for the exact reason you mentioned.

All results were the same.  0.8 v
4K,6K,8K Series / Re: SSL 4k dynamics card, what part is this?
« Last post by gertius on December 14, 2018, 03:53:46 PM »
Thank you Andy and Pascal for your replies!

Andy, the background info youve given seems to be spot on.
I have in the meantime compared AAZ17 vs AA133 (those I have in another card), and the sound output is the same.
So it really seems that only the type of diode is important, but not so much the voltage/current rating.

4K,6K,8K Series / Re: SSL 4k dynamics card, what part is this?
« Last post by pascal.verdet on December 14, 2018, 03:48:48 PM »
Seems like the AAZ17 is a relatively long recovery (350nS) diode.  The only sub I could find was AAZ15.
4K,6K,8K Series / Re: SSL Calibration and Tone Oscillator questions
« Last post by amillar on December 14, 2018, 02:38:05 PM »
First question is what sort of meter you are using! Most meters don't work brilliantly at 1kHz, something like a Fluke 8060 (my personal favourite) will be fine. Worth trying different frequencies to see what happens.

Yes, you're right that 1.226V is +4dBu in SSL terminology.

After that - welcome to the 4k gain structure! 30 years ago I could have explained to you for hours and hours what was going on...but certainly the gain structure of the 611 compared to the 651 inserts does take some getting your head around - it is not obvious at all. I think what you are seeing is what it's supposed to do, but I may be wrong.


4K,6K,8K Series / Re: SSL 4k dynamics card, what part is this?
« Last post by amillar on December 14, 2018, 02:14:54 PM »
The type of that diode is important, not the voltage / current rating so much as the "curve" the diode gives to the dynamics response. It wasn't fitted to the very early 10 cards, it was added sometime around 1980? It was certainly there by 1984.

So the main thing is that it needs to be a germanium diode, not a schottky. That said, I think on the 9k I did use a schottky because we couldn't buy germaniums any more.

They may well have changed case style, and I vaguely remember I changed the type of diode in the late 80s because the AAZ17s became obsolete?? We wouldn't have bothered updating the circuit diagram for that. 

Basically if you need to replace them try to find AAZ17s if you can.

The glass case was a PITA. If you try adjusting up the dynamics card presets under (for example) fluorescent lights you find it behaves very strangely, those diodes are light sensitive. I remember trying to set up a 4k with the 611s on extender cards inside a BBC mobile studio (one of only two studio installations we ever did ourselves) and it took me ages to work out why when I put them back in the desk the dynamics were out of cal again...



EDIT: I've just found my 9k circuits, and I did use an AAZ17. So I guess should be that in all 10 cards as well. But different manufacturers may well have used different case styles, we really struggled to buy these so would have changed manufacturer occasionally.
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