GSSL HELP THREAD!!!

[Harpo]

Thank you very much for the indications HARPO, I am going to try to make the connections as you indicate,

Please again, tell us your type and model of your switch.
Could as well be a series LAS1-A from OnPow that comes with an option for AC/DC 220V with LED or AC 220V with neon lamp and additional required parts already built in. The pinout of the switch is differing from previously linked switches from C&K or NKK thou (switches common pole is an outer pin, not the center pin), hence knowing the manufacturer and type of switch is essential knowledge in order to get the corresponding datasheet for pinout or parts parameters/limitations.

I do not understand all the electronic terms you use because I am a simple fan of electronics, I know it is a lot of work and annoyance but could you draw how all this would be connected?

As long as you can't answer my previous simple requests, it wouldn't make much sense.

 

[Bernardo]

the switch has no mark,, has LA160 -16A written ,it is 2-position (self-locking), sunk position and normal position.
I have opened it and it only seems to have a bulb-shaped led with two contacts.
attached images.

in the central pins are the initials NC, NO, C

thank you.

https://drive.google.com/file/d/1gfJiRCdp40pFdpAGtjWcV103YHWW4zNq/view?usp=drivesdk

https://drive.google.com/file/d/1ZIUiy44jEbb_3Jtsyq3lbslCBAcrFDSD/view?usp=drivesdk

https://drive.google.com/file/d/1QTl4gBLErexk2fODXgrsMTDH28VP2v_n/view?usp=drivesdk

https://drive.google.com/file/d/1UZV0VNBexOc-c5r11O0rxzNSGrL9pJwK/view?usp=drivesdk

 

[Bernardo]

Hello everyone, I was finally able to solve the problem of the push buttons.
now I hope I have the last problem.
I want to put an HPF filter with various cutoff frequencies to the compressor.
Could someone please explain in a simple way what I need and how could it be assembled?
I've been doing some research and have found some filter sidechain plates.
is this correct?
I have always thought that the sidechain was a compression in relation to an external input signal not a high pass filter.
thank you

 

[living sounds]

I bought an ADT console this year and recapped and upgraded it. The console originally used DBX2150 VCAs, which I upgraded to THAT2181A. The owner of ADT, Gerd Jüngling, is a great guy, very knowledgable and generous with his time. He told me that his circuit didn't require any adaptation to account for the new VCAs and that his was the correct way to impliment them and that the one in the VCA datasheets was problematic. He also let me know that the 2180 (pre-trimmed variant) was the exact same chip as the 2181 (trimmable) version.

I was able to trim the VCAs on all my console's channels so that the harmonics were below the noise level. This prompted me to adapt the circuit in the GSSL the same way. I had never been able to tweak the distortion as low as I wanted with any of the chips in any of my GSSLs before, and the setting tended to drift. With changes applied however, as in the console I suceeded in getting distortion below the noise level in the compressor and have it stay there.

The main changes, aside from a slightly lower bias value (don't remove the resistor entirely) are bypass capacitors added to the THD trim and the bias voltage. It's also possible to trim the 2180 variant, just like Mr. Juengling suggested.

Attached are the necessary changes to be made to the circuit as well as the PCB overlay. As for the latter, I suggest to put the 47n bypass resistor between pins 2 and 4 below the PCB and the 10uf cap below the PCB as well.

 

[living sounds]

And here is the schematic with the changes. It should work for all THAT2180 and THAT2181 versions as well as DBX2150 and THAT2150 VCAs.

 

[FarisElek]

And here is the schematic with the changes. It should work for all THAT2180 and THAT2181 versions as well as DBX2150 and THAT2150 VCAs.

Wow amazing! I'll definitely try this out at some point. In the meantime, I wanted to ask. Is it normal for there to be a fair amount of distortion when in 10:1 ratio? I've never really used more than 4:1 before, but recently I was using it and noticed that in 1:10 crushing pretty hard that there is a good amount of distortion. I never really noticed it before because I tend to use 2:1 with 2-4db of compression.


Ryan

 

[living sounds]

Wow amazing! I'll definitely try this out at some point. In the meantime, I wanted to ask. Is it normal for there to be a fair amount of distortion when in 10:1 ratio? I've never really used more than 4:1 before, but recently I was using it and noticed that in 1:10 crushing pretty hard that there is a good amount of distortion. I never really noticed it before because I tend to use 2:1 with 2-4db of compression.


Ryan

Compression without distortion isn't really possible, so it might just be the normal reaction you're seeing. The GSSL also has some ideosyncracies like higher general distortion in bypass mode, I would have to check if ratio settings in a properly set up GSSL (correct resistors) at a level below the compression threshold made I difference, but I actually doubt it.

 

[FarisElek]

Good to know. It distorts pretty hard at 10:1 with high threshold but I wouldn't say it's ugly distortion. Maybe your advice will help a little with what I'm hearing.


Ryan

 

[living sounds]

Did you measure distortion? Clearly audible distortion would indicate a problem with the build.

 

[FarisElek]

I'm not sure what normal THD is for this device...but I was getting as high as .8% THD on 2:1 and 1% THD on 10:1 at 0db when crushing at max.

Somewhere along the build I heard that I should turn my trimmer resistors to about halfway because it didn't really matter for the 2181B VCA's. But I may have not understood. Gain reduction at at full threshold I just trimmed the THD from 1% down to .16%. Yikes! I knew something was off but yikes.

Most of the distortion is at Harmonic 1 which is 0.065% THD I'm using a 1khz tone at 0db.
Still seems high though. I've never measured THD so I may be doing something wrong.


Ryan

 

[living sounds]

I'm not sure what normal THD is for this device...but I was getting as high as .8% THD on 2:1 and 1% THD on 10:1 at 0db when crushing at max.

Somewhere along the build I heard that I should turn my trimmer resistors to about halfway because it didn't really matter for the 2181B VCA's. But I may have not understood. Gain reduction at at full threshold I just trimmed the THD from 1% down to .16%. Yikes! I knew something was off but yikes.

Most of the distortion is at Harmonic 1 which is 0.065% THD I'm using a 1khz tone at 0db.
Still seems high though. I've never measured THD so I may be doing something wrong.


Ryan

Again, if you are applying gain reduction (the needle moves) higher distortion is to be expected.

 

[FarisElek]

Ah! must've missed that. Then in that case I've still brought it down by more than half! I'm not getting the clearly audible distortion anymore. Didn't realize how important that potentiometer was in the case of the 2181B. It appears to be .003 after adjustment with no gain reduction.

Ryan

 

[gyraf]

..don't tell anyone but, if you listen carefully, you probably don't want to trim to lowest thd here. I know of at least one well-respected manufacturer that mis-trims on purpose to get a certain character that suits this circuit rather well..

the love for the 202C variant of this circuit is probably also about this

/Jakob E.

 

[absrec]

I just had something weird happen with my GSSL. I built it a couple years ago and have been enjoying using it. The compression has become erratic recently. Meaning, it will just randomly get sucked down like you’d expect if you had a surprise 808 sample in your mix, which I don’t.    I tried HP filters up to 400Hz but it still keeps happening. At first I thought the threshold was too low but when I raise it enough to get rid of this symptom, it doesn’t really compress much at all. Or at least I can’t hear that familiar character we all know and love. I’ve been trying to troubleshoot it but I can’t find anything suspicious. The ratio, attack and release seem to work otherwise. By that, I mean I can hear the expected change despite the audio bottoming out randomly.

All I can figure is it seems like the issue is not in the audio portion of the circuit. No matter what channel I run into or out of, it behaves the same. I hear it as well as see it on the meter which tells me that it has to be somewhere in the sidechain after the 47k “mixing resistors” at the input of the sidechain and the 1k mixing Rs  carrying the CV back to the audio path VCAs. I built it with the stock configuration...  no turbo mod, sidechain filters, etc. What’s really telling is that when I run a steady 1K tone into it and set it for a good bit of compression, the tone waivers in volume quite randomly. It seems to happen when more signal is presented to the sidechain. When it hits around 10db of GR seems to be when the random and severe action happens.  Even with slow release. The tone warbles around, sometimes gets louder... sometimes softer... just weird.

Anyway, I’m hoping this might ring a bell with someone since I’m getting a little frustrated trying to find a problem I don’t understand.  :-\    Can anyone suggest some things I could check for?

Thanks,
-Aaron

 

[gyraf]

check your +/-12v lines, these are references

then check voltage (variations) on your makeup pot

 

[absrec]

check your +/-12v lines, these are references

then check voltage (variations) on your makeup pot

Jakob, thank you so much for the reply.

The rails are +12.08 and -12.26 which seems fine. As far as variations on the makeup pot, I'm not sure what you mean. It is measuring pretty even throughout it's rotation. Approximate V from the wiper to GND are...

0% -              0V
25% -    +3.9V
50% - +5.45V
75% -        +8V
100% -  +12V

Now that I'm zoomed in a bit more, I can see that while the control voltage (at various points) is wavering at extreme levels, that wavering doesn't stop at lower levels. It just becomes more subtle. I didn't catch that originally. I can even even see it on my meter. The control voltage will vary roughly 200 - 400mV on an extreme setting and maybe 20-50mV on a moderate one. I thought I had been hearing things this whole time. Whatever that is is creating audible compression artifacts. SMH

 

[gyraf]

are voltages stable while audio is jumping?

 

[absrec]

are voltages stable while audio is jumping?

No. Everything was jumping.

It was a bad VCA. As I obsessed over it for a while, I started to feel like it had to be something with the VCA or something directly connected to it. I didn't base that on any concrete evidence, but rather a lack thereof. Process of elimination. Once I switched out the VCA, it sounded great like I remember.

Thanks for being my audience. I hope this helps someone find this problem quicker some day.

 

[FarisElek]

I wonder what caused the VCA to go bad.

 

[absrec]

I wonder what caused the VCA to go bad.

I think it was a solder bridge between pin 6&7. It’s a little embarrassing that I didn’t try to figure it out sooner. I had resorted to using the plugin version of that compressor in the box because I could tell something was just off.

One more question.... I know the unity gain mod (15k - 27k) has been discussed here a lot here. That interfaces level-wise with my other gear very well. However, I find that with a mix coming out of my console through a balanced +4 connection, I have to set the threshold in my GSSL way lower than I expected. I used to have a Smart C1 and with the same basic setup & levels, I kept the threshold at 12 o’clock and made adjustments into the compressor with my master fader to hit the sweet spot, which for me personally is usually around 4-6dB GR. I was looking at the pair of 47k Rs going to the SC and wondered if reducing them to maybe 22k would allow it to start compressing earlier, giving me more wiggle room.  I’ve since sold the C1 but I found the schematic by chance while cleaning my house and I see that it also uses 47k to the SC. Is there any reason you can think for such a large discrepancy between the two units?