Studer 169/269

[nhaudio]

Hi,

I was wondering if any owner of a Studer 169 / 269 could tell me if their mixer is noisy?

On mine, I get this slight hum starting from 50hz at -78dB +-. the figure shown is with the master fader fully up. (the noise increases with the master fader not with the channel faders.) Is this a normal behaviour for a 169/269?

It seems quite noisy to me... I may be wrong, but in the mean time,

My thought was bad filtering in the PSU, I've redone the whole PSU unit (all capacitors, transistors and regulators). With my multimeter I don't see any ripple on the output (don't have a scope) and voltages are dead on.

I would imagine to look around the master section is the next step... But wanted to know first if the wisdom in this forum had any clue on where to look specifically if of course this is not how the Studer 169/269 sounds.

thank for the help

 

[Bo Deadly]

I've never owned  a mixer and probably never will but obviously it should not be that noisy. It could be because it's just super old and needs to be recapped. You could pull the master section out and replacing the 2-4 biggest supply filter caps and see if things improve. You can also try grounding signal input at some point just before the output like at some switch or cap (where there is no DC of course!). If that fixes (or improves things significantly), that would suggest something upstream. Divide and conquer.

Fortunately Studer service manuals are just about the best there ever was so that makes completely re-capping tolerable. Just get a hot air station, secure each board to some kind of fixture and just carefully remove all of the eletrolytics. Then just tally up and order new stuff. Mouser has a lot of axials so it might be worth ordering from them.

 

[nhaudio]

I've never owned  a mixer and probably never will but obviously it should not be that noisy. It could be because it's just super old and needs to be recapped. You could pull the master section out and replacing the 2-4 biggest supply filter caps and see if things improve. You can also try grounding signal input at some point just before the output like at some switch or cap (where there is no DC of course!). If that fixes (or improves things significantly), that would suggest something upstream. Divide and conquer.

Fortunately Studer service manuals are just about the best there ever was so that makes completely re-capping tolerable. Just get a hot air station, secure each board to some kind of fixture and just carefully remove all of the eletrolytics. Then just tally up and order new stuff. Mouser has a lot of axials so it might be worth ordering from them.

thanks for the reply... forgot to add that it has been fully recapped, all tantalum replaced and cleaned.

 

[synthiaks]

The 169 is not noisy

 

[zamproject]

Hello

Studer 169 user here (as bigger old sister)
There is definitely an issue somewhere, what PSU do you have ? ACDC onboard or DCDC version with external trafo ?
If the whole console is already recapped you have to look elsewhere...or double check caps orientation .
There is a mistake at service manual for one big axial in master section IIRC... so if you orientate by looking at service manual and not the original caps orientation you can reverse it...
Did all modules work as they should ? did both master show the same 50Hz harmonics ?

Best
Zam

 

[nhaudio]

Hey Sam,

thanks for the Reply,

I have the ACDC internal type. I've switched the cap's looking at the PCB. An error can always occur, but feel pretty good about the recap.
All modules work as they should*, I had to replace a few IC's on some but mostly everything is working fine except for one ch where I get a small oscillation high pitched when the fader is at infinity. Might remove this channel and see if it helps.

Yes both Masters show the same symptoms.
*when applying full gain on the mic input i get a the same hum but much lighter in the signal.
That's why I thought the PB was in the PSU.

what I didn't replace is the .1uF cap placed on the chassis. Do you think it could help. I don't think it's on the +15 -15v line... thoughts?

cheers,

Nico

 

[radardoug]

You need to determine whether you have a ground loop or a power supply problem.
First, disconnect all cables from the mixer except the power cord. Plug in a pair of headphones. Can you hear the noise in the headphones? If not, then you have a ground loop. Start plugging in the cables one at a time, monitoring the noise level.
Change grounding appropriately.

If you can still hear the noise with no cables connected, you have a power supply problem. This might relate to the supply being built in.

 

[nhaudio]

will try thanks

 

[nhaudio]

You need to determine whether you have a ground loop or a power supply problem.
First, disconnect all cables from the mixer except the power cord. Plug in a pair of headphones. Can you hear the noise in the headphones? If not, then you have a ground loop. Start plugging in the cables one at a time, monitoring the noise level.
Change grounding appropriately.

If you can still hear the noise with no cables connected, you have a power supply problem. This might relate to the supply being built in.

thanks for the tip. I does look like a ground loop!

Here's the frequencies without anything plugged in with the exception of the output. Even tough I'm still seeing some 50hz harmonics, I think it's pretty quiet. Do you guys think it's within Studer 169 standards now?

If any owner of a 169/269 could post its noise profile that'd be great.

thank again will keep you updated hunting for the loop.





Do you guys

 

[radardoug]

Are you sure you dont still have a ground loop to your test gear?
So when you listened with headphones, was it quiet?

 

[nhaudio]

it's on the headphones too.
I have to crank the headphone volume fully up to notice it, but it's there.

 

[nhaudio]

I removed all the channel modules leaving just the master section and now no 50hz at all on the headphones.

will hunt for the bad module.

I'm still wondering where the loop can be because the signal is from the console straight to the patch bay and every connector on the patch bay is grounded individually to the the incoming connector. There's no group grounding or similar. If you guys have any tips...

 

[radardoug]

Put the modules back in one at a time. My guess is you will put them all back in and the hum will come back. Which means it could be lack of filtering in the supply, or a bussing problem, which is not unusual in consoles. Your last graph looked pretty good, what was the overall noise level in dB? If it was -80 to -90 I wouldn't chase it. You then need to look at your external grounding. Are you using unbalanced circuits?

 

[Spino]

I removed all the channel modules leaving just the master section and now no 50hz at all on the headphones.

will hunt for the bad module.

I'm still wondering where the loop can be because the signal is from the console straight to the patch bay and every connector on the patch bay is grounded individually to the the incoming connector. There's no group grounding or similar. If you guys have any tips...

Not sure I understand how your patch bay is wired, but patch bays for sure could be the cause of the ground loop, I understand that every connector to the patch is also connected to ground at the patch? When they said disconnect any cable from the console, they were litterally meaning EVERY cable, you should have the 169 attached only to the AC cord. If the noise is gone, then it's a ground loop with something connected externally. If you still have noisy headphones, then remove one module at a time and see if it changes.

I used to work on a 169 some years ago and it was a very clean sounding console.  It also had pretty much transformers for every in and out, which usually remove/reduce ground loop problems, but you never know.

 

[nhaudio]

Not sure I understand how your patch bay is wired, but patch bays for sure could be the cause of the ground loop, I understand that every connector to the patch is also connected to ground at the patch? When they said disconnect any cable from the console, they were litterally meaning EVERY cable, you should have the 169 attached only to the AC cord. If the noise is gone, then it's a ground loop with something connected externally. If you still have noisy headphones, then remove one module at a time and see if it changes.

I used to work on a 169 some years ago and it was a very clean sounding console.  It also had pretty much transformers for every in and out, which usually remove/reduce ground loop problems, but you never know.

I think I have a mix of both. Some ground issue within the console and some ground loop within the patch bay.

I will rethink the patchbay organisation, but on discovering new things: I assumed that my monitor controller was balanced input, but it's not, and probably causing problems. An upgraded monitor controller is on its way.

Every single point in my patch has individual ground. Meaning the ground that come from the cable. There is no group ground or chassis ground. It's the Neutrik SPP L1 type.

As of right now, I have to start pulling back the modules to see which one cause the hum as with only the master section, I have absolutely no hum at all. Dead quiet.

Will keep you updated on my findings.

cheers

 

[zamproject]

As of right now, I have to start pulling back the modules to see which one cause the hum as with only the master section, I have absolutely no hum at all. Dead quiet.

Then it can look like one (or more) module is faulty and maybe draw to much current, pushing the PSU regulation.
You say early in this topic that DC voltage measure good, but did you check the current per rail ?

I assumed that my monitor controller was balanced input, but it's not, and probably causing problems. An upgraded monitor controller is on its way.

If the Studer is your studio center piece, the monitor section is not that bad in the console, and you have 3 external stereo input !
For more than one monitor parr, a single rotary lorlin (3P4T)can do the job .

Best
Zam

 

[nhaudio]

Thanks to all for the help on this project.

The mixer is dead quiet now after replacing the caps on the rails located on the chassis (it's a big .1 uf and some .022uf).
After replacing those the hum disappeared.

As other suggested, I do have a ground loop in the patchbay too, which I haven't find a solution yet. I've read a few post and articles about the subject. It seems that there is no one solution fits all answers. If anybody has any tip / good practice...

while continuing the restoration of the Studer, I get a pop every time I put a channel in solo or in mute. I know there is a circuit in charge of that and the fault is probably around there, any specific clue on where to look? (like I said before, the console is all recapped on electro and tantalum).

 

[Mc Cat]

Hello sir, I also have a 269 that is having the same noise master problem as yours. Can you send me a picture of the location of the 2 capacitors that I replaced? Thank you very much.

 

[13engrsapper]

None of our Studer stuff is noisy at all, must be an issue somewhere. Even their older stuff is very well thought out.