SSL 4048G+ distortion on main outs - HELP !!! -

[quested]

Hello everybody

been looking at this fantastic forum for quite a while....
now I am in need of help with my 4048G+ console that' s showing 3 different issues :

1) randomly starts generating a very loud noise from one spk...L or R, sometimes both spk,
keeps doing this noise with all buckets switched off , just centre section on...console can stay
without doing it for days, then it goes...sometimes it stops after a minute or two...power cycling
both console and psu solves the problem for a while....please see attached video
(horrible quality otherwise too big for attachment... but audio is self explanatory)

2) all main outs are distorting, it started on L ch only now is on both, sending a 1khz tone from one ch
or directly injected in main buss gives same result...PRE and POST VCA INS are clean so I am using these
for mixing in these days sending clean signal directly to my LAVRY stereo external converter

3) probably related to 2 : all main outs show a heavy crosstalk...pleas see attached picture of waves meter in daw
with signal -18 dbfs recorded fully panned R....note absurd level of L ch !

btw....console is a 1997 4048G+, until now has been warking almost flawlessly,first owner was a film mixing facility that
requested some modifications directly from SSL (25-32 ch with film pan mk2 card) and custom bussing logic and path,
console has been fully recapped in centre section, replaced all pre op amps, has led vu, led cuts and
many other switches led bulbs, monitoring selection is made through a Martinsound matrix
(L/R + 5.1) and there is a distribution amp that makes a mono sum and a stereo sum of L C R S channels
(maybe could be involved in these issues ?)

I have cleaned contacts of 25 card in center section (it has all new caps) and I have replaced all ic...
tried also swapping hybrids in it with no success ...btw I ve 2 new hybrids not yet installed...

maybe something like this has already happened to some of you ?...
any kind of help would be much appreciated !

[xmax]

You are saying there is no problem with the post VCA send on the quad buss?
And the problem is on both the monitor and main outs? Can you turn off the
extra 5.1 distribution amp to trouble shoot?

[quested]

Hi xmax thanks for your help

the distortion and the crosstalk have been solved. The problem was caused by an impedance load from a small jbl loudspeaker
connected to EXTERNAL inputs (STEREO IN 1 L/R of the patchbay)...after a mix we left the spk connected and that was causing this issue...
the spk was supposed to have an internal balncing circuit as it is a mono spk but with a stereo input (minijack....kinda mobile stuff usefull for real life listening check)...as soon as we disconnected this little spk this issues had gone.

unfortunately the noise (see attached video) is still there

Anyway, to answer your question just in case someone else should have issues like these in the future :

PRE and POST VCA INSERTS where clean both from distortion and crosstalk so I was able to mix from these outputs patched directly to
any of the EXTERNAL TO MONITOR inputs.

Your question about the distribution amp was correct as it has been the most investigated....but we found out that our console has a passive sum of the outputs
(that is : C / L / R / S / C+L / R+S / M) instead of a real distribution card....we searched all the possible places where this card could be installed also following the advices of our ssl tech (unfortunately he was not available in these days) but the card it's definately nowhere in our console...testing and comparing the impedance for the various outputs in patchbay has given proof of that.

[quested]

Regarding the noise, it's still there and while we found that with the centre section on and all the buckets off it is louder and can be stimulated to happen quite frequently, in the regular use with everything powered on it is much more random and lighter.

Even with a tech fisically present in studio we should just hope that the noise shows up in that precise moment and that lasts enough time to investigate....unless the  cause of it is found out regardless his appearance...

Our ssl tech is sure about the cause being related to the 025 card in centre section (card is recapped, all IC replaced, all hybrid cards replaced or exchanged)

Another tech has suggested the cause may be related to power unit(s) and/or changeover issues

Both techs are talented and experienced guys....this lets me think this issue wont be an easy one....!!!

[xmax]

Yes it is your PSU buy Atomic Instrument! 

Next time the noise happens dead patch the VCA return.
So we can see where it is coming from.

As for the distortion caused from the JBL, I have seen this type of thing happen
with a (turned off) converter normalled to the main outs.

[quested]

eh...I know Atomic....it is interesting but as we are based in Italy
the final cost at the moment is a bit out of reach...btw regarding
the power consumption benefits of Atomic these are less interesting for us
as we have a big fotovoltaic system that helps with the electricity bill
and our console's PSUs are of the last generation kind so we switch the beast
on/off every day with almost no issues...

I will try the VCA insert returns dead patching and post results

[xmax]

Yes we realize they can be very expensive overseas and in general.
We try to keep the prices as low as possible, considering the products
our units replace costed as much as 8-10 times our price.
Some examples: A second back up system for a
J or K console, SSL charged $80,000! The Cost of 2 661's and
a change-over was around $17,000 (maybe more).

In addition of keeping our cost as low as possible, we also offer
special deals and now free shipping! So if you ever do need our
PSU, hopefully this helps "soften the blow". Cheers! N