GSSL Turbo board complete!

[kilmister]

Howdy!

At first thanks to people who are designing all this cool stuff!
I'm planning to build few GSSLs with turbo boards. Because Expat Audio is out of boards and it's time learn how to etch own boards I tryed to find etching image for turbo board but couldn't find it. Does anyone have it?
Of course I can make my own board design with GSSL schematic but never done anything like that so I think it's better to use board designed by people who really know what they are doing

Chears,
Paavo

 

[Davo]

Hi Paavo,

You won't find a home etch of the turbo board, but Brian may have one in stock for ya:
http://diypartssupply.com/index.php?main_page=product_info&cPath=2&products_id=2

Cheers,
Dave

 

[kilmister]

Yeah,
I sent email and Briand told me it will take 4-5 weeks until new set of boards arrive.
Due I'm very inspired at the moment I don't have patience to wait that long  :

There's allways possibility I'll try to make my own pcb design. If I send picture here can people check it out or will I be banned rest of my life?

-Paavo

p.s. I made my first etching today since 1994. New crush'n'blend boards looks really cool for me  ;D

 

[bassculture]

hi

i've got 2 gssl w/ turbo & it's like having 2 comp in one !
great mod definitly.
i also got 2 super sidechain boards on each. turbo is switchable.

i'm actually re-morking on one to get it on the road with me.

i followed the instructions shown on the pdf to install turbo card.
when i switch back to normal mode, it compresses is 2 times more, as the SC circuit on the GSSL PCB receive 2 time more signal (L+R summed). i have to re-adjust treshold to compare.
that's annoying for a PA use to my taste.

the 47K are not anymore on the GGSL pcb, as they are 1 on the output of the SC boards (i use the original schemo from 12afael).
the output is like that : op amp out > 47uF > 47K
there's a trimmer to adjust output level so i get equal in/out.

so i thought using a DPDT switch instead of a SPDT for normal/oxford mode switching.
on the second pole, the switching to normal mode would insert a resistor between the output of the two sidechain boards and the input of the GSSL PCB sidechain circuit to get equal compression when switching between the two modes.

is that the right thing to do ?
should i get rid of the 47K on the output of the sidechain board also ?

which value should i use ?

 

[Harpo]

For a GSSL with TWO (2) sidechainfilterboards and a Turbo my approach would be something like this ugly scribble
I'd use a DPDT switch for the differing input resistor requirement in both scf-boards for unity gain behaviour:
- Turbo mode: a single 10K resistor (you can keep both already soldered 20K resistors when you wirelink the L+R input of this scf-board) for the upper scf-board input and both 20K for the lower scf-board which get switched in parallel by the 2nd pole of this switch).
- GSSL mode: upper scf-board and turbo not connected, lower scf-board 20K input resistors separately fed by L and R.

For a GSSL with ONE (1) sidechainfilterboard and a Turbo, same switch but you replace the upper scf-board with a 47K resistor.

Hope this making any sense.

Sidechainfilterboard (SCF) Rin resistors R12 and R13 are 20K resistors. Wiring the DPDT switch as shown will parallel these (2x 20K in parallel=10K) for the lower drawn SCF board (connecting to the GSSL sidechain VCA) in Turbo mode operation only. For the upper drawn SCF board you can either leave one resistor (R12 or R13) out and fit a 10K for the remaining spot or keep both at 20K but wire link the L+R input of this upper drawn SCF board. This set this SCF summing amp to unity gain with Rfb 10K (R15).
If your kinda music or program material is more center related, the Rin resistor values for a constant power calculation [1/sqrt(2)] might fit better, so use a 14K as Rin for the upper drawn SCF board and a 27K in series between SCF board L-in and the right switch pole (20K || 20K+27K) instead, so both SCF boards have voltage gain of 0.707 or -3dB each in Turbo mode.

 

[bassculture]

thanks harpo ! 

you do the switching before the sc boards. i do it after them.
i got one rotary switch for each SC board.
i allready replaced the 20K by 10K on the inputs as i use one input of each sc board.

if we consider doing it my way (i'm a little lazy... + i'd like to experiment with the 2 sc boards at different settings)

1- is there any problem changing the resistors at this point of the circuit ?
( i remember mesuring after the 47K was improper > value read = 0)

2 - is that make sense ?
when using turbo > one 23,5K (trimmer or two 47K parallel) at the output of each SC board
when summing SC out to GSSL pcb (gssl mode) > one 47K at the output of each SC board.

thanks

 

[Harpo]

1- is there any problem changing the resistors at this point of the circuit ?
( i remember mesuring after the 47K was improper > value read = 0)

2 - is that make sense ?
when using turbo > one 23,5K (trimmer or two 47K parallel) at the output of each SC board
when summing SC out to GSSL pcb (gssl mode) > one 47K at the output of each SC board.

I don't see a reason why not. Your approach is increasing current at input of sidechain VCA, mine does it at summing stage in front of the sc-filterboard(s). There are other spots to get there, like the 127K* for altering the sc-control voltage.
If you use a trimmer, take care of its initial setting to not exceed the limits of the VCA. A resistor for max.allowed current in series to this trimmer will help to prevent this.
> ( i remember mesuring after the 47K was improper > value read = 0)
Right. This spot is current in of the VCA with virtual ground connected to its output terminal and the 47K in front does the voltage to current conversion.

 

[bassculture]

... back to my soldering iron  ;D

thanks !

 

[haima]

just want to say, i finally got a chance to install a turbo board in my ol'GSSL - and BOY OH BOY! was that worth doing!

i made it switchable - glad i did, mainly so i can flick back and forth and compare how much better it is in turbo haha. the difference really is like night and day... quite amazing. i feel no need for a HPF in the side chain now! the turbo mode will be great for 2bus/subgroup compression, very tight.

before the mod i didn't really use the GSSL much, except in parallel "FX compression" duties - it's like a whole new compressor now.

great work gentlemen, cheers!

 

[tree]

Help! Doh!
Finally got around to getting a turbo board stuffed and installed here into one of the gssls i made with 202 vcas and am having problems.  Argh!
The unit only extremely compresses now - to the point where i can only even hear the original signal (very compressed) if threshold is set to 0, attck set to slower and release to faster settings. Meter pinning.
Same results when turbo is disconnected!!
Can anyone steer me toward a likely area i botched ???
Doubly frustrating as i'm in the middle of some important mixes - thought this looked like it'd be plug and play situation, Dang. I am short a valuable compressor.
Anyone?   :'(

 

[livingnote]

Oy. Picture of how you wired it?

 

[tree]

Hi Livingnote ... Have gone over the wiring again and again - it all looks right ( to me ) 
Wondering why it might behave this way now even when the turbo card is unplugged???
Would the lifted resistors on the main card do this, do you think? 

 

[tree]

will try and post pic of the lifted resistors ... can anyone confirm these are correct?
no apparent solder bridges underneath ...

 

[livingnote]

Ah - you don't pull the resistor entirely - you don't even lift it (the 100R one) - you just solder the wire
to one end of it while it is in-circuit. (iirc, the end that is not connected to the TL072). With that R out
both your sidechains don't have anything to teach them manners with and they just slam waaaay up there.

Edit - also, you don't kick the 47K out all the way, you leave its leg in where your cable is now and solder
the wire to the leg that is sticking up in the air.

Are you trying to make it switchable?

 

[haima]

just as an aside - in my opinion, don't bother making it switchable - i did, but it never moves from the turbo position... it just sounds better that way, smooth and solid. if you ask me, save yourself the trouble and just hard wire it in, and use the time saved to get on with another project, or have fun with your new compressor 

 

[tree]

Ah - you don't pull the resistor entirely - you don't even lift it (the 100R one) - you just solder the wire
to one end of it while it is in-circuit. (iirc, the end that is not connected to the TL072). With that R out
both your sidechains don't have anything to teach them manners with and they just slam waaaay up there.

Edit - also, you don't kick the 47K out all the way, you leave its leg in where your cable is now and solder
the wire to the leg that is sticking up in the air.

Are you trying to make it switchable?

Thanks Livingnote. Most helpful.
No, not intending to make switchable.
So forgive me, but please, just to super clarify (cause i'm feeling a bit like an idiot right now)  :

both the 100R and 47K keep all their legs connected to their intended location on the main board...
I am simply to put the 2 wires from the turbo into the designated mounting holes for the legs along with the legs and resolder leg and wire together into the mounting holes??
Thanks again...

 

[livingnote]

100R keeps both legs in board. Wire gets additionally soldered on the end of 100R that is not connected to TL072 output
(i.e. opposite the hole your wire is in on the pic)

You can just solder the wire to the bit of resistor leg on the top of the board if you care, or its pad on the bottom, whatever.
Don't need to try to stuff both wire and leg in hole

47K has one leg in board (in the hole where your wire is in the pic), one leg out. Leg that's out gets wire.

Oh and not quite evident in picture - your point C connection is made, right? Otherwise you'll have a standard GSSL that
only reacts to channel 1

 

[tree]

Great Help.
Thanks very much once again, Livingnote.

Man, was i way off on this one!
Musta been really speed reading those instructions!
Or maybe just one too many solder fumes around here..

 

[livingnote]

Yeah Wanting to get things done quick gets things done way off schedule...

 

[pietro_moog]

hi,

i'm currently making a GSSL w/ turbo with THAT 2181LA.

1/ correct me if i'm wrong :
on the Turbo board
> i have to remove 10K resistor next to VCA (beetween pin 3 & 5)
> i have to also remove 47R from pin 4 to ground

is there other changes to do on the turbo board for That 2181LA ?

i'm not sure :
i have changed the 3K9 to 5K1 for the audio VCA.
do i have to change 3K9 (to pin 5) to 5K1 in the sidechain circuit ?
and so on the turbo board ?



Nielsk >

I also had to reduce the value of the 12 feed resistors to supply the increased current demand

you mean the 10R before the 7912/7812 ?
if not, which resistors ?
what value work best ?

thanks

is this correct?
5k1 instead of 3k9,
no 10k
no 47Ω next 10k one
and that's it

thanks