GSSL HELP THREAD!!!

[orangerec]

Hi, I'm thinking of ordering Gssl boards from PCB Grinder (Gustav?) and including his Super S/C board. I'm also considering Expat Audio's Turbo board and their VU Meter Driver board to meter gain reduction, input and output. My question is, can I use all these optional boards without them creating a problem or interfering with themselves? Especially curious with the Turbo and the Super S/C boards. Anyone have an answer?

Thank you.

 

[damien]

can I use all these optional boards without them creating a problem or interfering with themselves? Especially curious with the Turbo and the Super S/C boards. Anyone have an answer?

Hello,
I use the turbo board and the super sidechain boards as well. you need 2 S/C boards if you want to use the turbo board, one for sidechain L and one for sidechain R.
Start building the regular GSSL to check if everyting is alright, then add the turbo board and finally the 2 S/C.
If you use the turbo board, Super Sidechain boards are definitely not mandatory.
I would go first with the turbo board and only if you are still thinking the compressor is over reacting to  the lo freq, go for it.

 

[orangerec]

Thank you Damien. I just read the instructions on the Expat Audio pdf for the Turbo board and they explain it just like you did. I'm going to do what you just mentioned; build the gssl, add the turbo board and I think I'll be just fine.

Cheers.

 

[Katash]

is gyraf.dk offline? =(

Have received my rack chassis today and wanted to finish this (which I haven't had time for a long while) and can't find the files..... schematics etc.

Are they somewhere else to download or could you send them to me?

Thanks!

 

[gyraf]

Yes, we seem to be offline. Hopefully it will be fixed today.

<-- If you see my logo load, we're back online

...aaaaaand we're back - 21.feb.

Jakob E.

 

[mg73]

I bought a pair of unpotted discrete DBX202 and are about to install them in my GSSL
but I can´t get rid of distortion and noise from them no matter how i set the dist trimmer.
I can see the the the shape of my test sine is changing on my scope
but its never get stable or symetric
It´s exactly the same issue with both VCA´s and all components on them seems to be fine.
Do you need to change anything else on the GSSL board?

All info I can find is that just to leave out all  components in the VCA area on the GSSL PCB
and put in the DBX 202 there instead.

 

[mokkinger]

VCAs are current devices (and these have a type number, so we're talking on the same subject). For now assuming, your audio-VCAs might be THAT2180 or THAT2181 in grade A, B or C.
Next step is checking the audio path for unity gain in bypass condition. Power down, pull your audio-VCAs out of their (hopefully fitted) socket and temporary jumper VCA sockets pin1/8 with a piece of wire, a paperclip or whatever else handy. Power on again, feed your left side Ch.input with a maybe +4dBu (1.228Vrms) sine signal at a frequency, your multimeter can handle (probably below 1kHz, 100Hz seems a safer bet), and measure voltage of your left Ch. audiosignal at input (between XLR-pins2/3). Same level should arrive at left side Ch.output between XLR-pins2/3 (but with inverted polarity because of the now missing audio-VCA).
If not, double check (22K) resistor values at input stage, (10K) at output inverter stage, the (27K) resistor in front of the audio-VCA and the (15K) feedback resistor in the I2V stage. With from schematic 15K/27K fitted, your output level will read a little (times 1.111 or +0.915dB) higher. If this buggers you, a 5K trimmer/rheostat in series with this 27K, trimmers initial value 3K, would give you the oportunity to tweak this for same i/o level. Keeping the 27K and substituting the 15K with 2* 27K in parallel (=13K5) would have the same effect without the trimming ability.
Repeat this procedure for the right side Ch. with same signal source (just switch the XLRs over) for same readout.
Power down, pull out the temporary jumpers and refit the pulled VCAs with their correct orientation and power on again.
This already might have fixed your level differences. If not, report back with a little more info (type of VCAs used, value of fitted SSCF input resistors, Aarhus/Oxford switch wiring, ...)

Hi Harpo,
I checked the GSSL last weekend as you explained it:
- the rails were okay, +-15V, 12V, all fine.
- checked the unity gain at bypass/without the VCAs, bridged pins 1&8: seems okay, not exactly unity but little more, as you described. I dont care if its exactly unity gain as long as its not too different... the level difference between L and R was now about 0.2Vrms (if I meassured it correct, still not 100% sure about  meassuring the Vrms with the multimeter... isnt it between pin 1 and pin2? do I need a balanced input signal to measure unity gain correct?)

After assembling back together the difference stayed that way, still not 100% equal L R, but way less than before

what seems really strange to me: when I use the comp as an insert on my master (inserts are unbalanced on my A&H ZED R16 board), the volume is a little lower in bypass mode than when I unplug the inserts - strange, as I measured the output a little louder (as you explained) than the input... might this be because of the unbalanced inserts? I might still miss some part of the logic...

thanks & regards,
mark
 

 

[Harpo]

..still not 100% sure about  meassuring the Vrms with the multimeter... isnt it between pin 1 and pin2? do I need a balanced input signal to measure unity gain correct?..

Only when you have XLR-pins1/3 linked. Have a look at the schematic. The balanced line receiver exclusivly operates the differential between NE5534-pins2/3, connecting to XLR-pins2/3 thru the 22K input resistors. Feeding the GSSL with an unbalanced source, you probably will have your XLR-pins1/3 (externally) jumpered by joining the cold wire end with cable shield at Shield of your TRS insert plug. (hot wire end goes to the Ring of your TRS insert plug) This has nothing to do with unity gain. Unity gain is level in = same level out.

what seems really strange to me: when I use the comp as an insert on my master (inserts are unbalanced on my A&H ZED R16 board), the volume is a little lower in bypass mode than when I unplug the inserts - strange, as I measured the output a little louder (as you explained) than the input... might this be because of the unbalanced inserts? I might still miss some part of the logic...

You only use XLR-pin2 on GSSL output for your unbalanced return (going to Tip of prementioned TRS insert plug, cable shield only one side connected), leaving XLR-pin3 unconnected (don't link XLR-pins1/3 at output. GSSL out is not floating balanced and you don't want to upset the output driving NE5532 by shorting its output to gnd). But connecting this way, you are missing +6dB from the last inverting stage. Easy fix. Make the feedback resistor in the I2V converter (15K from schematic) the same value as the resistor in front of the VCA (27K). From my previous post (2x 27K in parallel=13K5), you could even make this paralleling of the two 27K resistors switchable 27K/13K5 by lifting one of these resistor legs.

This has been beaten to death. A simple 'unbalanced' or '6dB' in the [Search within topic] would have given you the last 30 related questions/answers.

 

[ram75]

Yes, we seem to be offline. Hopefully it will be fixed today.

<-- If you see my logo load, we're back online

Jakob E.

Hey Jakob,

do you know when the site will be online?
cause i bought an unfinished gssl from someone and i'm kinda lost without any information or pdf about how to finish it

thank you

Philippe

 

[gyraf]

Try the wayback archive while we're down - it could take a few days still:

http://web.archive.org/petabox/20120224062529/http://gyraf.dk/gy_pd/gyraf_diy.html

Jakob E.

 

[gyraf]

..And we're back online...

Jakob E.

 

[thepraqtice]

have a few questions i was wondering if anyone can help with.

i'm at final wiring stages of gssl with turbo and 2x supersidechain + oxford/aarhus switch...

been looking around for a correct wiring diagram but cant really find anything conclusive. this seems to be the best diagram i've been able to find...

https://dl.dropbox.com/u/4364451/GSSL_turbo_ssc5.jpg

can anyone confirm if this is the correct wiring scheme for what i'm building?

do i parallel wire the +/- 15V and 0V connections for both supersidechain boards from the same points on main gssl board? or should i maybe wire the right sidechain to +/-15V points on right vca section and left sidechain to the +/-15V points on left vca section of gssl board and parallel 0V on both sidechain boards to pin1 on an xlr input?

also do i need to parallel wire the ext sidechain input, com, off, on, pot A, pot B, in led, in switch and meter led connections on both super sidechain boards?

many thanks

sam

 

[gyraf]

This help thread is for the basic version, I'm pretty sure that there are dedicated help threads for the add-ons as well.

Jakob E.

 

[Harpo]

I bought a pair of unpotted discrete DBX202 ...

unless someone hacksawed the modules, DBX202 come in a black housing, so your modules might not be type DBX202. The letter following the '202' (might be C,R,X,XT,...) will dictate the component changes needed on the GSSL board to adapt for the differing impedances, controlport laws or supply voltage and current requirements. They are all different.

 

[qwerty8787]

Hi everybody,

I'm still in trouble with my GSSL. Seems an endless nightmare.

My unit is:
GSSL + 2 SSC + Turbo.
2180LB used everywhere

The issues are two. One about distortion, the other about little GR at maximum settings.

1) when I set the Ratio @ 10, I get severe HF distortion as soon as the threshold is moved to get the meter kick in by just few db. On the scope the result is some HF modulation on the peaks. Like clipping, but the clipped part is oscillating at a higher frequency than the one of the sine input. With ratio 4 i get a similar behaviour, less strong. @ Ratio=2 i get only the rounded peaks, without oscillating thing.
What could be the reason of this?

2) If I put about 0dBu balanced at input, and set threshold at minimum setting, I get only about 8dB GR @ ratio=2, 4dB GR @ ratio=4, and less than 1dB @ ratio=10. I feel like the unit is not working properly. I expect to have more gain reduction at those levels. Note that I already putted the 47K resistor on threshold pot's leg. Maybe this problem is related to the distorting behaviour? Any advice?

Also I have doubts on resistor choice for the VCAs. By now i'm using 5.1K instead of 3.9K and the other resistors (68Ω, 2x10K, 1MΩ, 50k trim) are left out. 4th pin bent. I also tried to use in once channel a THAT2181LC putting in again those resistors+trim, with no difference respect to the other channel with 2180.

Any advice about my whole situation? thanks in advance

 

[beatnik]

i've got a problem with the threshold on my gssl.

it is way out of range.. if i send a -18dBFS signal into the compressor, even with the threshold pot fully clockwise i get about 5dB gain reduction.

i've built it with 2180 vcas and changed/left out all the resistors as indicated. added a super sidechain board wired per instructions.


i've done a lot of research and see many people report same problem about threshold sensitivity. many said to replace the 47K resistor from threshold pot to +12V rail. I tried 22K but that made no change.

i have no clue on what to do as next step. really hope someone will help

 

[gyraf]

if i send a -18dBFS signal into the compressor

dBFS does not tell us anything, it's only a relative measure for digital domain.

You need to measure level in dBu (or ac voltage) in order to know your actual analogue level.

Jakob E.

 

[beatnik]

Hello Jakob,

I've measured the signal. -18dBFS from my converters correspond to 305mV AC going into the compressor.

Pretty much around -8dBu... But the compression already kicks in even with threshold pot fully clockwise.

I guess there is some problem around the sidechain but I don't know how to figure out.

Maybe I try to disconnect the sidechain filter board and see what happens?

By the way, everything is sounding ok, just the threshold pot is out of range

 

[Harpo]

.. even with the threshold pot fully clockwise i get about 5dB gain reduction ..

gain reduction (only compressing loud passages) or less level out (-6dB from unbalanced out connection) ?

 

[beatnik]

on the return of the compressor I have 5dB difference between compression in or bypass.

and the meter shows gain reduction, so I think compression is happening and it's not just volume decrease

i tried to disconnect the super sidechain board and put the two 47K resiistors back on the main board, but what I got is there is even more gain reduction, about 10dB