GSSL HELP THREAD!!!

[Ricardus]

Its red? I thought I packed white in there now, but must have forgotten to change it many moons ago.

you can position it on top and use a hot glue gun to glue it in there, you can drill a hole in the meter to position it, or whatever you like.

Gustav

Yeah, it's red. I was wondering about that. I guess I'll replace it with white.

 

[Beeswax]

I'm getting more compression on the right side.  It isn't volume in the program material as I ran it through another compressor to test.  Thoughts on this?

 

[Gustav]

I'm getting more compression on the right side.  It isn't volume in the program material as I ran it through another compressor to test.  Thoughts on this?

Are you getting more compression, or are the levels uneven, even with no compression?

If you are in fact getting more compression, did you install the turbo or something?

Gustav

 

[gyraf]

..please, this is not a chat for online-solving problems without the need for digging into the underlying electronics.

You need to do some work for yourself, otherwise the whole idea of a help thread that other builders can use will be void. Read through this thread to find similar symptoms, try similar remedies to what is proposed as solutions.

Then, if none of those works, report back here with the symptoms ant the list of solutions that you already tried, and what results you had from that.

Then it will make sense trying to help you - otherwise we're just cluttering up this whole thread with one-time-solutions

/Jakob E.

 

[ateshk]

Hi,
My GSSL works just fine but I see there is a peak at 50hz at -90db. Its not audible but Its there in the spectrum analyser when there is no audio running through the unit. It looks like there are some harmonics also in the higher frequencies. why do u think this is happening? I have the ERC board too to filter the power after transformer. Thanks.

 

[gyraf]

If its not audible, why bother?

 

[ateshk]

If its not audible, why bother?

So, is this a common issue?
I am using it but I want to fix it if it is possible.

 

[gyraf]

Are you used to interpret measurement systems like your spectrum analyzer? That is, do you know exactly what it tells you, are you sure you're measuring correctly regarding terminations etc.?

/Jakob E.

 

[Harpo]

Hi,
My GSSL works just fine but I see there is a peak at 50hz at -90db. Its not audible but Its there in the spectrum analyser when there is no audio running through the unit. It looks like there are some harmonics also in the higher frequencies. why do u think this is happening? I have the ERC board too to filter the power after transformer. Thanks.

Looks like induced hum at mains frequency. Rotating the mains transformer for least inducing hum might help. Distance is your friend. Greatest inducing field for usual is where the secondary wires come out of the assumed toroidal transformer. A halogen lamp shining above your gssl with lid open can cause this as well.

 

[ateshk]

Are you used to interpret measurement systems like your spectrum analyzer? That is, do you know exactly what it tells you, are you sure you're measuring correctly regarding terminations etc.?

/Jakob E.

I dont check the units with that analyser on ableton live. I was working and checking the song with an analyser and when the song stops I noticed the hum. So, after that I eventually check the other units as I work with them. I have this hum/peak at 50hz only in GSSL and in 1 channel of an EQ unit that I have built. Its not audible for the EQ also. Maybe its the transformer as someone mentioned in a post below.

 

[ateshk]

Looks like induced hum at mains frequency. Rotating the mains transformer for least inducing hum might help. Distance is your friend. Greatest inducing field for usual is where the secondary wires come out of the assumed toroidal transformer. A halogen lamp shining above your gssl with lid open can cause this as well.

I have attached the picture. Can you tell if this is a tight layout? transformer too close to circuitry?

 

[living sounds]

Make sure the + and - connections are wired correctly to pin 2 and 3.

Also, make sure pin 1 at each of the input and output XLR connectors directly connects to the chassis then and there. It should be enough to use a small wire to solder the pin to a screw that holds the connector in the cassis.

The mains safety earth should be bolted to the chassis close to the mains inlet.

The only connection between chassis and audio ground should be at the input of the ERC board, where it should go right down and be bolted to the chassis. Make sure that veroboard ERC board is wired correctly, same goes for the transformer primaries and secondaries.

Where does the green cable in your foto lead to? I would lose it and follow my above wiring guide. The shield connection goes through the chassis, which is connected only at these points: power inlet earth connector, ERC filter input, CLR pin, pin 1 of each XLR connector.


Check that the voltage after the filter board is sufficiently high to account for the regulator's voltage drop.

Check the power lines with a voltmeter and a scope, sometimes regulators are faulty.

If all of this doesn't help there might be a fault in the circuit somewhere on the board that is inducing hum. Is it the same for both channels?


From my experience with GSSL's (I've got 4) the ERC board and proper grounding procedure is enough to keep the hum below the noise floor. The transformer should not be a problem at the distance it is placed in the picture.

 

[ateshk]

Make sure the + and - connections are wired correctly to pin 2 and 3.

Also, make sure pin 1 at each of the input and output XLR connectors directly connects to the chassis then and there. It should be enough to use a small wire to solder the pin to a screw that holds the connector in the cassis.

The mains safety earth should be bolted to the chassis close to the mains inlet.

The only connection between chassis and audio ground should be at the input of the ERC board, where it should go right down and be bolted to the chassis. Make sure that veroboard ERC board is wired correctly, same goes for the transformer primaries and secondaries.

Where does the green cable in your foto lead to? I would lose it and follow my above wiring guide. The shield connection goes through the chassis, which is connected only at these points: power inlet earth connector, ERC filter input, CLR pin, pin 1 of each XLR connector.


Check that the voltage after the filter board is sufficiently high to account for the regulator's voltage drop.

Check the power lines with a voltmeter and a scope, sometimes regulators are faulty.

If all of this doesn't help there might be a fault in the circuit somewhere on the board that is inducing hum. Is it the same for both channels?


From my experience with GSSL's (I've got 4) the ERC board and proper grounding procedure is enough to keep the hum below the noise floor. The transformer should not be a problem at the distance it is placed in the picture.

Thanks for the detailed explanation.
I did everything here. All Pin 1 connected to chassis. Bolted with the earth from mains inlet. CRC board ground is now connected to Chassis at the bolt. I Check the voltages and find out that 7815 was not working properly so I replaced it. But, The hum is still there. Is there any schematic or a link to a schematic for the proper CRC board for GSSL? Is it also connected to main at some point? Inpult voltages on CRC board are 22V ac and output are +27.1V and -27.8V DC. Is this normal or am I missing something here?

 

[living sounds]

Thanks for the detailed explanation.
I did everything here. All Pin 1 connected to chassis. Bolted with the earth from mains inlet. CRC board ground is now connected to Chassis at the bolt. I Check the voltages and find out that 7815 was not working properly so I replaced it. But, The hum is still there. Is there any schematic or a link to a schematic for the proper CRC board for GSSL? Is it also connected to main at some point? Inpult voltages on CRC board are 22V ac and output are +27.1V and -27.8V DC. Is this normal or am I missing something here?

Something is probably wrong at the input of the CRC board.

I can't see what kind of transformer you are using. For +/- 15VDC a center tapped dual 15V trafo will be fine. A dual 22V trafo would be excessive and force the regulators to produce a lot of heat. With the CRC board an 18V trafo might be best, since there needs to be sufficient voltage for the regulator to drop some.

You need a transformer with two identical secondary windings. If you don't have a drawing for the trafo, connect one wire from one secondary to one wire of the other secondary. Measure the voltage across the other two ends of the secondaries. If you measure a very low voltage and you connect those ends to each other, the windings will be in parallel, but if you measure about 30 volts, the wires you've already connected will be the center tap of a 15 - 0 - 15 secondary.

Take a look at the image. The blue connection between 4 and 5 is your ground and goes to the ground connection of the input side of the CRC board. The other two wires (3 and 6) go to the other two inputs of the CRC board.

 

[hydroheinz]

hi...

i have a noise problem with my gssl (rev12)

erverything works fine, but there is a audible noise on both channels...
i searched alot the in the help thread and tried alot of things but i cant find the failure...

i use the cool audio 2181 and changed the 1m Resistor (Rsym)  to 150 k ( https://www.coolaudio.com/docs/COOLAUDIO_V2181_DATASHEET.pdf)

- i did Star Grounding
- i put a filter pcb between the transformer and the pcb (CRC Board)
- i put a jumper between pin 1 and 8 of the vca`s and getting a clear signal with no noise...

i read post #8283 and he said that the 2181 and the 2180 is the same chip.... so i tried to use the 2181 as pretrimmed ones and lifted the 150k (RSYm) resistor so that i have no connection between the distortion trimmer and pin 4 of the vca`s ...and all noise is gone but now i have a distorted output :-(

so i think i get the noise from the distortion trimmers ....what could now be the problem ? i have +15V and -15 V on the legs of the trimmer

i  get only clear not distorted sound when the trimmer is set nearly to the middle position (0,88V) ....but with the noise...!
when i move to - it is getting distored but no noise and when i move to + i got no sound

i hope you can help me...this is one of the last things in my box of shame which still is not working... i tried to find the failure for a long time but now i think i am near to it... the noise comes from the distortion trimmer side but why ?


thank you ..Heinz

 

[Script]

Don't know those ICs. Maybe not fully compatible ? Price is almost the same as proper THATs.

Did you do all adjustments when implementing the VCA (change) ? You have checked Matt Fisher's table ?

http://diy.fischerworks.com/gssl_vca.shtml

 

[gyraf]

what type of noise? at what gain (check with known size input signal)

 

[hydroheinz]

Don't know those ICs. Maybe not fully compatible ? Price is almost the same as proper THATs.

Did you do all adjustments when implementing the VCA (change) ? You have checked Matt Fisher's table ?

http://diy.fischerworks.com/gssl_vca.shtml

it should be nearly the same as the THAT vca`s...
i did all the changes from Matts sheet.... only the Rsym resistor is changed to 150K for the cool Audio VCA`s
( https://www.coolaudio.com/docs/COOLAUDIO_V2181_DATASHEET.pdf )

what type of noise? at what gain (check with known size input signal)

i would say it is pink noise.... i dont know if i measure it right but it is at -70db 

in my test i send a sine wave from my pc with -24db out and read also -24db on my spectrum meter on the input so i think that should be right?

it is definitly audible :-(

 

[Harpo]

You probably need some luck that your VCA's survived...

- i put a jumper between pin 1 and 8 of the vca`s and getting a clear signal with no noise...

...with the VCA removed ?, else you are shorting out the VCA with internally fighting input-/output-currents as the VCA itself is inverting.

i read post #8283 and he said that the 2181 and the 2180 is the same chip.... so i tried to use the 2181 as pretrimmed ones and lifted the 150k (RSYm) resistor so that i have no connection between the distortion trimmer and pin 4 of the vca`s ...and all noise is gone but now i have a distorted output :-(

that post refers to THAT2181 and THAT2180. The CoolAudio V2181 is NOT the same (FI no internal resistor between pins2/4,...). For your CoolAudio V2181, you'd need the 51R resistor as the shunt part of the 150K voltage divider in order to adjust the SYM-port for a max.range of [ +/-15V / (150000R+51R) * 51R = +/-0.005V = +/-5mV ]. You fed the VCA's SYM-port with +/-15V instead.
Maybe you got lucky an the VCA's could stand this abuse...

ps.: Fig.10 of the CoolAudio V2181 datasheet mistakenly shows a junction above the -15VDC supply, joining -15V with Ec+ and the inverting opamp stage.

 

[hydroheinz]

that post refers to THAT2181 and THAT2180. The CoolAudio V2181 is NOT the same (FI no internal resistor to pin2,...). For your CoolAudio V2181, you'd need the 51R resistor as the shunt part of the 150K voltage divider in order to adjust the SYM-port for a max.range of [ +/-15V / (150000R+51R) * 51R = +/-0.005V = +/-5mV ]. You fed the VCA's SYM-port with +/-15V instead.
Maybe you got lucky an the VCA's could stand this abuse...

ps.: Fig.10 of the CoolAudio V2181 datasheet mistakenly shows a junction above the -15VDC supply, joining -15V with Ec+ and the inverting opamp stage.

YES!!!!  now it is working and quiet as it schould.. .... there is no more noise and no distortion and  the VCA`s are still alive

thank you...i am really happy now..!!

but i could test it only with 47Ω becasue i had no 51Ω Resistors...
do i have to change them or is it not so important?



thank you ......Heinz