GSSL HELP THREAD!!!

[mdmedia]

Thanks for the fast reply! It wast indeed just a wrong pair of wrong cables . So next time I will check the cables first!

 

[Bob1991]

Thanks Sunnys & ptron, will try it this week and share the results!

 

[synnys]

Not Sunnys, it's SynnyS

 

[Arnoid]

Hi there

I'm busy with finishing a GSSL
I measured the rails from the main pcb before putting in any IC's

I'm getting:
14,77V
-14,44V
&
11,67V
-11.43V

I now there's a 10% tolerance so the power is ok
But is it ok that the +  and - rail are not equal or close to equal?
Isn't it better to have 14,77 and -14,77 for the symmetry or doesn't this matter ?

 

[synnys]

12 volt goes to the control pcb

 

[Arnoid]

12 volt goes to the control pcb

???  you don't understand my question

I know you have -15V, 15V to drive the vca circuit and -12V, 12V for the control circuit
My question is does the voltage has to be symmetrical like 14,77v & -14,77V and 11,67V & -11,67V

Now the voltage regulator 7815 gives me 14,77V and the 7915 -14,44V so it's not perfect symmetrical

The 7812 gives me 11,67V and the 7912 -11.44V also not perfect symmetrical

Or isn't this important for the gssl ?

 

[Harpo]

Arnoid, its good enough to not blow things up. Measure again with load (your ICs) connected. Some regulators need a load connected for correct operation.

 

[Arnoid]

ok will check with IC's  I know it's good enough

But for certain (audio)application the psu needs to be symmetrical so that's why I asked the question if it's important for the gssl

 

[Harpo]

maybe (dunno of any at the moment). These opamps don't swing rail to rail. With a +/-15V supply, 553x might swing about +/-13V. A supply rail 0.5V low, the lower rail signal waveform might clip at 12.5V. This GSSL has a not cross-coupled output stage, so peak signal in a balanced outout config between XLR-pins2/3 might swing up to 26V or only up to 25V with your 0.5V low supply rail. Your concern might be focused on the next connected piece of gear when feeding/grilling this next stage with this 30.5dBu or only with 30.1dBu. YMMV.

 

[dirtyhanfri]

The Farnell box just arrived at home, as soon as I get home I'll start soldering some stuff...

I've read the WHOLE thread (lots of info, but one of the most borings big threads in the forum BTW) and also some of the threads about building troubles. I wish a straight forward build...

Pictures soon, of course.

 

[Arnoid]

I'm busy with the connections of the meter I use from hairball

On the control pcb you have +M and -M but  the voltage at this points are both around 11,44V is this correct
??? Shouldn't -M be a negative voltage?

Now I've connected +M with the + on my meter and the - of my meter to ground and the led is lighting up.(As in the schematic)

 

[Looksharp]

Hi again,
didn't notice before (too busy giggin'..) now I'm goin' to do some mix and I note that the volume of the right channel in both of my gssl finished a couple of months ago, are lower than the left channel (let's say 5 or 6 db)...this happen in "on" and bypass mode as well...
I used the 2181 vca in case it helps...
could someone please help me?
as I stated in my first post I am  an inexpert and do know very little about electronics...but I finished this project without any trouble..just noticed this issue while paying more attention...
thanks!
Luca

 

[kante1603]

Hi again,
didn't notice before (too busy giggin'..) now I'm goin' to do some mix and I note that the volume of the right channel in both of my gssl finished a couple of months ago, are lower than the left channel (let's say 5 or 6 db)...this happen in "on" and bypass mode as well...
I used the 2181 vca in case it helps...
could someone please help me?
as I stated in my first post I am  an inexpert and do know very little about electronics...but I finished this project without any trouble..just noticed this issue while paying more attention...
thanks!
Luca

Hi Luca,

have you swapped channels left to right and vice versa?This is to make sure that it is your compressors and not your cables running to and from the gssl(s).
It´s a bit strange that the issue is on both right channels.......
Anyway:A drop of 6dB usually indicates that your signal becomes unbalanced somewhere;this can be the cables or the debalancing or balancing stage.
If you can make sure that it is not the cables you should look for shorts or open connections on the inputs and outputs next.
You can measure things with a multimeter set to ohms.Measure both the pins 2 against pin1(ground) as pin 3 against pin 1(ground) on both in and output xlrs.
If there is something close to zero ohms then you have a short somewhere.If you get anything very high resistive (or your multimeter goes out of range) then you have an open connection.

But it looks more like a bad cable to me,check this first and then proceed with measuring.It doesn´t seem to be a biggie since you stated that it happens both in bypass or "on",so it´s not the processing path (vcas etc.).

Hope to have helped,

Udo.

 

[dirtyhanfri]

Farnell also has these cheap standard types:

order no 143509 - it's 100uA, but will work with a different meter resistor (20K in stead of 2k)

Jakob E.

Hi

I got the meter that Jacob talks about from Farnell, and I have a question. It goes from 0 to 10. When the needle is in 2 (i.e.) it means itś reducing 2 dbs or 20%?

Maybe it's a obvius question, but I couldn`t be sure about this...

Thanks in advance for the answers

 

[Looksharp]

It´s a bit strange that the issue is on both right channels.......




Udo.

hi Kante,
yestarday while swapping from one compressor to the other just confused me and made me think that this umbalance channel issue happened on both compressor...my mistake!
it actually happens only  in one compressor..the other one is ok...
do your suggestions works anyway in this case?
L

 

[kante1603]

Sure-your DMM doesn't care which of your units it is measuring,hahahaha....
So disconnect your audio cables and do the measuring as I mentioned in the last post.

Good luck and have a nice weekend,

Udo

 

[Arnoid]

On the control pcb you have +M and -M but  the voltage at this points are both around 11,44V is this correct
??? Shouldn't -M be a negative voltage?
As in the schematic)

Somebody can check this for me plz ?

 

[Harpo]

I'm busy with the connections of the meter I use from hairball

On the control pcb you have +M and -M but  the voltage at this points are both around 11,44V is this correct
??? Shouldn't -M be a negative voltage?

Now I've connected +M with the + on my meter and the - of my meter to ground and the led is lighting up.(As in the schematic)

M+ on control pcb is connected to the +input terminal of your current (not voltage) reading meter. This M+ is connected to gnd, as shown on schematic and when you follow this pcb trace.
M- on control pcb is connected to the -input terminal of your current reading meter.
This M- is connected to 'G' and its driving stage.
Dunno the hairball meter, but when your LED inside your meter is lighting up, you connected to the meters illumination terminals instead of your meter coil. I have no idea how this (missing the current limiting resistor) LED will light up with both ends connected to GND as you described it, other that you measured wrong or mixed up wires.
"As in the schematic" doesn't show your description, but as previously described and a 36V/20mA lamp (not LED) connected across the mains transformer secondary for meter illumination. Your LED inside your meter will probably be connected across +15V/0V or 0V/-15V with a current limiting resistor in between.

 

[dirtyhanfri]

Farnell also has these cheap standard types:

order no 143509 - it's 100uA, but will work with a different meter resistor (20K in stead of 2k)

Jakob E.

Hi

I got the meter that Jacob talks about from Farnell, and I have a question. It goes from 0 to 10. When the needle is in 2 (i.e.) it means itś reducing 2 dbs or 20%?

Maybe it's a obvius question, but I couldn`t be sure about this...

Thanks in advance for the answers

So stupid question even for being answered??

Thanks

 

[gyraf]

linear meter shows readout in dB directly (as these VCA's are dB/V devices)