GSSL HELP THREAD!!!

[gyraf]

I had a PCB rev#11 from pcbgrinder which has a connector called "* HPF" for which I did not find any documentation.

Good tracing!

I'm still working on the documentation for the new board.

The "* HPF"  connector on the new revision GSSL pcb is for easily inserting a sidechain filter. If you don't want a sidechain filter, just short this connector. If you short it with a (preferably switchable) capacitor, you have a sidechain highpass filter: 220nF=80Hz, 100nF=160Hz, and 68nF=300Hz.

jakob E.

 

[synnys]

Good tracing!

I'm still working on the documentation for the new board.

jakob E.

How about all the components that are marked with %, can those be left out completely when using a pre-trimmed 2180?
is the 7812 marked with an * optional?
Is the connection between SSC and mainboard the same as in rev#9? where do 'pot a' and 'pot b' go now?
there used to be a 127k resistor near the sidechain vca, it's now 120k*, how come?

cheers,

ruben

 

[gyraf]

How about all the components that are marked with %, can those be left out completely when using a pre-trimmed 2180?
is the 7812 marked with an * optional?
Is the connection between SSC and mainboard the same as in rev#9? where do 'pot a' and 'pot b' go now?
there used to be a 127k resistor near the sidechain vca, it's now 120k*, how come?

Attached GSSL_11.pdf

- The new three-pin connector at TL074 to be shorted if no sidechain filter is used.
- 7812* and 22u* optional (for light+relay power)
- parts marked % omitted for pre-trimmed VCA
- board interconnections are the same as always. 1:1.
- 120K instead of 127K is updated value (but changes very little)



Jakob E.

 

[synnys]

Attached GSSL_11.pdf

- The new three-pin connector at TL074 to be shorted if no sidechain filter is used.

i reckon it can also be shorted when using the supersidechain board?

and thanks for the pdf!

 

[voitto]

Hello,
I've just completed a GSSL as my first project, now I'm considering replacing the 50k linear threshold and makeup gain pots with 12 and 24 position stepped switches respectively.

Is this as simple as using x11 4.7k resistors (for the 12 pos) and x23 2.2k (for the 24pos) in series or are there other things I'd need to take into consideration?

 

[fripholm]

Hi guys,
I'm planning on adding the super sidechain board to my Gssl and I have a question about the external input to the board.

Does it accept an external audio signal "as is" or does it need a dedicated amplifier before the circuit?

 

[gyraf]

Hi guys,
I'm planning on adding the super sidechain board to my Gssl and I have a question about the external input to the board.
Does it accept an external audio signal "as is" or does it need a dedicated amplifier before the circuit?

Yes, you can use it as an external sidechain input. Input impedance ca. 10KOhm.

Hello,
I've just completed a GSSL as my first project, now I'm considering replacing the 50k linear threshold and makeup gain pots with 12 and 24 position stepped switches respectively.
Is this as simple as using x11 4.7k resistors (for the 12 pos) and x23 2.2k (for the 24pos) in series or are there other things I'd need to take into consideration?

Yes, it's that simple.

Jakob E.

 

[emanuele.stragliotto]

Dear friends, I just finished building my first GSSL. It worked fine but when I installed everything in the case I had this problem ... The 10R resistance continues to burn...any suggestions. I'm not very practical in electronics and this is my first experiment ...
thanks...Lele

 

[Harpo]

The 10R resistance continues to burn...any suggestions.

remove the short between 79L12 and the cap located between 78L12 and 79L12 ?

 

[emanuele.stragliotto]

Thanks Harpo, now everything works fine ... But I still have a "hum" problem...guess in the otputs because without the inputs cables connected it remains...any ideas? Thanks

 

[Harpo]

But I still have a "hum" problem...guess in the otputs because without the inputs cables connected it remains...any ideas? Thanks

Depending on "hum" frequency 50/60Hz or 100/120Hz (please update your profile with your location data) this will be induced hum from your mains transformer (twist turn the transformer for least emitted garbage at mains frequency and distance is your friend) or ground loop(s) showing up at double mains frequency. Twist wire pairs between XLR-pins2/3 and input connection on pcb, so the line receivers can cancel out common mode induced garbage. When using shielded mic cable between XLRs and pcb, connect shield only at one side. All XLR-pin1 connect to your always safety ground connected metal/conducting enclosure in the shortest possible way. Join 0V reference voltage (FI transformers secondary winding center tap connection) with safety ground in exactly one spot. (Breaking this single 0V/safety ground connection would be a ground lift). Use non-conductive standoffs or fit an insulation washer between metal standoffs and trace side of pcb where a trace/standoff could make an additional connection to your case.

 

[RedRabbit]

Hi Everyone,
Very excited to join the forum here. I've been building and repairing equipment for years, but this will be my first "pro audio" box from the ground up.
Had a few questions before I started...

1. I have an original PCB that still has all of the markings for use with 2150 chips. I was curious what the proper resistor compliment was in the VCAs using the modern production THAT chips.
http://fucanay.fischerworks.com/diy/images/gssl/gssl_vca.html Is this information correct?

2. I have a bunch of polystyrene caps left over from other projects and have most of the values needed for the ceramics. Is it okay to use the styrenes for this?

3. I'm purchasing a bunch of Carnhill Transformers from Audio Maintenance for EZ1290 preamps I'm building and was curious if there is a Carnhill toroidal that would work well for this project.
http://www.audiomaintenance.com/acatalog/Power_Transformers_and_Chokes.html

4. I have a drill press and can easily bore holes of any diameter. However, cutting square holes I can't do by myself. Is there an appropriate meter that will fit in a round hole that can fit a 1U enclosure?

Thanks in advance!

 

[gyraf]

Welcome, RedRabbit1

Most of your questions can be answered by reading this board, particularly this thread.

Jakob E.

 

[emanuele.stragliotto]

Thanks again Harpo...I've checked all but nothing changed. Disconnecting the inputs connector the noise does not change, maybe I have to check the outputs capacitors...Another strange fact is that often switching the unit on nothing happens...trying again it powers up correctly...???

 

[Harpo]

I've checked all but nothing changed. Disconnecting the inputs connector the noise does not change, maybe I have to check the outputs capacitors

A pic showing some details of your build might help us to spot a source for your noise.

Another strange fact is that often switching the unit on nothing happens...trying again it powers up correctly...???

Voltage regulator(s) latching at startup. There are 4 different voltage rails in the GSSL, the LED is only showing the +12V rail operating. When fault shows up next time, measure each supply rail to identify the faulty one and replace this voltage regulator (could be 7815, 7915, 78L12, 79L12) with same target value type from different brand. Some manufacturers (FI TexasInstruments for UA78Lxx, pg.14, figure 6) advise to use clamp diodes between 0V reference voltage and regulator output to prevent output polarity reversals during startup. Have a look at my anti-latchup fix I posted some time ago, how to apply these diodes for the GSSL. This fix worked for some but not all builds that suffer from this fault.

 

[phancak]

You need quality power supply for your GSSL?
Benefits:
Small ripple
None hum
Precise adjustment of output voltage + -15/12V
Separate a supply for relays and light

 

[gyraf]

PSU noise is generally not a problem in the GSSL if dimensioned and built correct

The new board (rev#11) has aux. 12V for relay and light.

Jakob E.

 

[emanuele.stragliotto]

Yesterday evening I brought the gear in my studio where I have a voltage stabilizer for all the studio gears and the GSSL works great...only that normal "windy" noise when the make up gain is all up...I've tried to put in on a drum bus and sounds really cool...love it...next days I'm going to do more tests...So thanks for all the advices!!!

 

[jwhmca]

The "* HPF"  connector on the new revision GSSL pcb is for easily inserting a sidechain filter. If you don't want a sidechain filter, just short this connector. If you short it with a (preferably switchable) capacitor, you have a sidechain highpass filter: 220nF=80Hz, 100nF=160Hz, and 68nF=300Hz.

jakob E.

Just a capacitor? If so, why does the Super Side Chain circuit use the opamps? For the Sidechain input?

 

[gyraf]

Yes, just a capacitor.

Gives you a -6dB/oct cutoff, which I consider nice for sc. hpf.

"Thrust", a -3dB/oct filter is probably also possible with the use of 3-4 resistors and capacitors in parallel. Haven't calculated this yet.

You can also inject an external sidechain at this point (into the capacitor, NOT into the opamp).

Jakob E.