GSSL HELP THREAD!!!

[frazzman]

Thanks Greg.

Looks like my switch for switchable HPF cap will work fine. This looks like a pretty quick and easy way to implement an SC HPF. I haven't finished building the rev 11 circuit but I wired up the switch and measured capacitance at each position and it was all good. I left out the 40hz position for now...
The math fails me when it comes to calculating the required value, Gyraf or Harpo or other mathematically-ept members able to provide required cap value for 40hz HPF ? Much appreciated

I am not smart enough to determine the impedance at the HPF point, but I think Jakob said to expect 10K.

You can use this calculator to find the corner frequency.

Looks like 400nF should give you 40Hz, but empirical testing never hurts

http://www.sengpielaudio.com/calculator-RCpad.htm

Gustav

Thanks Gustav. Looks like you got to the same point as me, I couldn't work out R at HPF either...

However in saying that, by virtue of "reverse engineering" - Jacob already posted the 3 cap values I used. He said 220nf gives you 80hz HP, so using the calculator - for the corner freq to be 80hz and the cap value is 0.22uf - R has to be ~9000R - which gives you 80.38hz.

So for 40hz - ideal cap value is 0.44uf which gives you 40.19hz with R @ 9k. I don't think that cap value exists, with nearest alternative (0.47uf?) you get 37.63hz. With 0.4uf you get 44.21hz. Same deal I guess!

Thanks for your help

 

[Harpo]

Speaking of the HPF, I've been wanting to implement a simple passive one on an older GSSL board I have, and now I see there is one on the new PCBs, I understand how it works, but I have a question. If the schematic is more or less like the old GSSL, it looks like the HPF is after the sidechain VCA, whereas the old "super SC" circuits were put in prior to the VCA I think.  I like how the new way is simple and I'm hoping the end result is the same since it's before rectification?  Can anyone confirm?

Dimitri, use as internal HPF will work similar to the 'super sidechain' board (this SCF board is a filter board, not a 2nd.sidechain board such as the turbo, that could be used FI for the GSSL), but this onboard HPF spot is better not to be used as external insert (missing DC blocking cap before rectification) and sure not to be used as external key input (missing the voltage dropping sidechain-VCA loop).
Just for simplicity see edited/updated corresponding schematic for the current pcb layout.

 

[Harpo]

The math fails me when it comes to calculating the required value, Gyraf or Harpo or other mathematically-ept members able to provide required cap value for 40hz HPF ? Much appreciated

-3dB HPF is at 1/(2*PI()*R*C) with R in ohm and C in Farad.
Value of R are the two 20K resistors going to the virtual ground nodes of the TL074-pins2+13 in parallel=10000 ohm.
For 40Hz and solving for C (in Farad) is 1/(2*PI()*10000*40)
or solving for C (in uF) is 1000000/(2*PI()*10000*40)
or solving for C (in nF) is 1000000000/(2*PI()*10000*40)
or solving for C (in pF) is 1000000000000/(2*PI()*10000*40)
giving 397.887nF (maybe use 220nF||180nF or 330nF||68nF)

 

[mitsos]

OK, that's where I thought it was = a cap in series with the 22uF, cutting the coupling cap value creates the HPF?  If one were to use an external sidechain input along with this HPF, the sidechain is done like before, at the 47K resistors, and the still works... pretty cool. thanks for the clarification. 

 

[Gustav]

Thanks Greg.

Looks like my switch for switchable HPF cap will work fine. This looks like a pretty quick and easy way to implement an SC HPF. I haven't finished building the rev 11 circuit but I wired up the switch and measured capacitance at each position and it was all good. I left out the 40hz position for now...
The math fails me when it comes to calculating the required value, Gyraf or Harpo or other mathematically-ept members able to provide required cap value for 40hz HPF ? Much appreciated

I am not smart enough to determine the impedance at the HPF point, but I think Jakob said to expect 10K.

You can use this calculator to find the corner frequency.

Looks like 400nF should give you 40Hz, but empirical testing never hurts

http://www.sengpielaudio.com/calculator-RCpad.htm

Gustav

Thanks Gustav. Looks like you got to the same point as me, I couldn't work out R at HPF either...

However in saying that, by virtue of "reverse engineering" - Jacob already posted the 3 cap values I used. He said 220nf gives you 80hz HP, so using the calculator - for the corner freq to be 80hz and the cap value is 0.22uf - R has to be ~9000R - which gives you 80.38hz.

So for 40hz - ideal cap value is 0.44uf which gives you 40.19hz with R @ 9k. I don't think that cap value exists, with nearest alternative (0.47uf?) you get 37.63hz. With 0.4uf you get 44.21hz. Same deal I guess!

Thanks for your help

I doubt it will make a difference being that precise, but if that is your goal, remember the corner frequency is at -3dB.

And use caps in parallel, as suggested by Harpo

Gustav

 

[frazzman]

Thanks Greg.

Looks like my switch for switchable HPF cap will work fine. This looks like a pretty quick and easy way to implement an SC HPF. I haven't finished building the rev 11 circuit but I wired up the switch and measured capacitance at each position and it was all good. I left out the 40hz position for now...
The math fails me when it comes to calculating the required value, Gyraf or Harpo or other mathematically-ept members able to provide required cap value for 40hz HPF ? Much appreciated

I am not smart enough to determine the impedance at the HPF point, but I think Jakob said to expect 10K.

You can use this calculator to find the corner frequency.

Looks like 400nF should give you 40Hz, but empirical testing never hurts

http://www.sengpielaudio.com/calculator-RCpad.htm

Gustav

Thanks Gustav. Looks like you got to the same point as me, I couldn't work out R at HPF either...

However in saying that, by virtue of "reverse engineering" - Jacob already posted the 3 cap values I used. He said 220nf gives you 80hz HP, so using the calculator - for the corner freq to be 80hz and the cap value is 0.22uf - R has to be ~9000R - which gives you 80.38hz.

So for 40hz - ideal cap value is 0.44uf which gives you 40.19hz with R @ 9k. I don't think that cap value exists, with nearest alternative (0.47uf?) you get 37.63hz. With 0.4uf you get 44.21hz. Same deal I guess!

Thanks for your help

I doubt it will make a difference being that precise, but if that is your goal, remember the corner frequency is at -3dB.

And use caps in parallel, as suggested by Harpo

Gustav

Thanks Gustav & Harpo for your input.

As far as off the shelf values go, 390nF will get me there with actual freq calculated at 40.81hz where HPF R is 10k. Pretty cool... I'm going to go with a 6 pos switch - off, 40hz, 80hz, 160hz, 300hz, 500hz
A great and simple addition!

 

[weiss]

New Gssl is up and running. But still can't figure out how to power my meter..  toroid secondaries?

Specifications:
Full Deflection: 1mA DC
Internal Resistance: 600 ohms
Light: 2 white LEDs 5.6-7.6V

weiss

 

[berkleystudios]

New Gssl is up and running. But still can't figure out how to power my meter..  toroid secondaries?

Specifications:
Full Deflection: 1mA DC
Internal Resistance: 600 ohms
Light: 2 white LEDs 5.6-7.6V

There are connections of the faceplate pcb

 

[Gustav]

New Gssl is up and running. But still can't figure out how to power my meter..  toroid secondaries?

Specifications:
Full Deflection: 1mA DC
Internal Resistance: 600 ohms
Light: 2 white LEDs 5.6-7.6V

For the light - yes, you would do it from the toroid secondaries via a power resistor.

For the metering, there are connections on the back of the control PCB.

Gustav

 

[weiss]

thanks! 10k resistor and it works like a charm

weiss

 

[darkus]

Hi! Just completed my build. Well, its missing the meter (still waiting it to arrive from Hairball Audio)

Anyway i decided to test if the unit works as it should. My PSU voltages are correct and both switches light up (im using the nrg pushbuttons from Frank Röllen) and the unit passes clean signal, but it does not compress and the front controls have no effect. VCA´s and IC´s are correctly in their sockets.

Does anyone know whats wrong? Does the panel meter really need to be in circuit for the unit to work?

And yeh, it passes the signal but it does nothing alltho the switches work as they should and wiring is triple checked its ok.

 

[weiss]

Same problem here! And today something really weird happened on top of it: both of my 10 ohms resistors near the big capacitors started to burn..

i have no clue what to do, all my connections are well soldered and i have triple checked my 10 pin connector, my ic's and the other wiring.. :-\ the day before only my original audio signal went through, today i cannot even press the power button without burning down my unit, what's going on?

weiss

 

[darkus]

EDIT: Ok so my GSSL works now and it compresses but i had to jump the makeup gain near the pot connetion. So the makeup is in the circuit even in bypass. Im using the NRG pushbuttons from frontpanels.de file:///Users/markussuomela/Downloads/SSL_switch_wiring%20(1).pdf

As you can see in that pic the makeup pot is not in circuit. Is there a way i can make it work with these typo of switches?

 

[weiss]

EDIT: Ok so my GSSL works now and it compresses but i had to jump the makeup gain near the pot connetion. So the makeup is in the circuit even in bypass. Im using the NRG pushbuttons from frontpanels.de file:///Users/markussuomela/Downloads/SSL_switch_wiring%20(1).pdf

As you can see in that pic the makeup pot is not in circuit. Is there a way i can make it work with these typo of switches?

hi darkus, could you explain which points to jump? using the same push buttons

weiss

 

[darkus]

Look at the wiring file from frontpanels.de ..... there is a spot next to the 750k resistor. jump that. then your makeup gain will work. But it will have its effect even on bypass.
I had to reverse my On and Off wires to the bypass switch to make the compressor work when the switch is pushed in.

I now discovered that the makeup gain works like this on the original unit too.... might have to use a relay to make the makeup gain effective only when compression is set to in

 

[weiss]

Look at the wiring file from frontpanels.de ..... there is a spot next to the 750k resistor. jump that. then your makeup gain will work. But it will have its effect even on bypass.
I had to reverse my On and Off wires to the bypass switch to make the compressor work when the switch is pushed in.

ah nice find, mate! already thought of that when i wired the buttons..

I now discovered that the makeup gain works like this on the original unit too.... might have to use a relay to make the makeup gain effective only when compression is set to in

That sounds nice, makes perfect sense to me!

But still help needed on my burnt 10 ohms resistors. There are no shorts and every part is soldered the correct way. Even after i replaced them, they started to burn again. Which parts could cause such error? One of the rectifiers? damaged IC?

weiss

 

[Gustav]

Same problem here! And today something really weird happened on top of it: both of my 10 ohms resistors near the big capacitors started to burn..

You added the meter light in the meantime.

Which power transformer are you using?

Gustav

 

[weiss]

Unfortunately the meter is not the problem. I removed the cables and yet the resistors get damaged. Using a  2x15V toroid with 240V mains.

weiss

 

[Gustav]

Unfortunately the meter is not the problem. I removed the cables and yet the resistors get damaged. Using a  2x15V toroid with 240V mains.

weiss

I was looking for the current rating for your transformer, since it might have put a strain on the circuit, if your meter light pushed the total draw over the top.

If thats not the case, look for shorts. Did you desolder the secondaries at any point when you were adding the meter lights? May be the first place to look for shorts, if you put them back after.

Do you have a picture?

Gustav

 

[weiss]

Unfortunately the meter is not the problem. I removed the cables and yet the resistors get damaged. Using a  2x15V toroid with 240V mains.

weiss

I was looking for the current rating for your transformer, since it might have put a strain on the circuit, if your meter light pushed the total draw over the top.

If thats not the case, look for shorts. Did you desolder the secondaries at any point when you were adding the meter lights? May be the first place to look for shorts, if you put them back after.

Do you have a picture?

Gustav

Thanks for the help, just for clarification: i tried to power the compressor one time with and one time without meter connected. Both times, the two resistors started to burn. And i did not solder the secondaries, but added all cables to a screw terminal for easy connecting. So here are some pictures..