Calibrating the G-SSL with THAT2181 - share thread !!!

[mathflan]

Hi guys!

I have a problem

On my SSL when I put no compression, threshold at +20 and I put Make up at 0, the sound when the compressor is active is lower than when the comp is bypass

do you know where this problem come from??

 

[Purusha]

[quote author="Greg"]Thanks Roger. I don't even remember which version of the 202 I put in there. I will say; however, that the one with the 202s and WIMAs is hands down the best of the 5 SSLs I've made. So I might not go muck with it even if it's off spec. But I am curious just for kicks.[/quote]

I've been hearing this WIMA name over and over again. Which caps are you referring to? Is it difficult to find them? I plan to put only the best things inside eventually. OK, maybe 202 will be difficult to find but you never know. :grin:

[quote author="Chris"]First I have to point out that these aren't my mods. In fact, I cut and pasted from earlier in this thread. [/quote]

I meant the mods you used in your G-SSL. BTW thanks for such precise measurements. It would be nice to see the same thing with 4:1 and 10:1 settings too. :thumb:

[quote author="Chris"]When I put together my chasis, I'll do the voltage measurement for you. [/quote]

Appreciated :thumb:

[quote author="RogerFoote"]Hey, one other thing to remember with 218xxx VCAs. You don't need that 10K resistor between pins 3 and 5 of the VCA. (As seen in Jakob's dbx 2150 to dbx 202 emulation schematic) This info was posted by someone from THAT, here on this BB.

Then the 3K9 from pin 5 to V- should be changed to aprox 5K (I used 4.75K and it works fine)[/quote]

This is a lot of new mods. Is it OK to just do it or will someone of you experts investigate this first? Those 10K are to be replaced with a jumper or just left out?

[quote author="Mathflan"] On my SSL when I put no compression, threshold at +20 and I put Make up at 0, the sound when the compressor is active is lower than when the comp is bypass

do you know where this problem come from?[/quote]

I had the same problem. Loss of 5.8dB and it was my soundcard. Check your input for +4dB and -10dB settings. I have settings to +4dB.[/quote]

 

[Greg]

For one of my SSLs, I used DBX 202s with WIMAs for the 100n poly caps and Nichicon PW electrolytics. Very nice IMO! Very nice midrange and round. It's nice on a drum buss and it can help tame a drummer who smashes the shit out of his cymbals, and adds some gusto to the drums... in general.

The WIMAs are more expensive and harder to find. And they're pysically bigger so they're a pain in the ass deal with in the GSSL.

Look here:
http://www.groupdiy.com/index.php?topic=7564&start=15

 

[Purusha]

Thank you both for the info :thumb:

I found some WIMAs in my local store. Would this be OK - POLY 0,1uF 100V 5% R5

(official name MKM2 WIMA) http://www.wima.com/navig/mkm2.htm

I wonder if 5% Wima caps sound much better than 10% Wimas? I found very cheap Wimas here http://futurlec.com/CapPolyester.shtml but they are all 10%.

Regarding the 202x. Is there any chance to make a small 100% clone on a small PCB of the same circuit?

 

[fucanay]

If Roger or anyone else wants to get the changed values and instructions together in one place, I can make a nice looking pdf/website and host it for everyone else to view. It seems a little all over the place right now.

What I propose is something for 2181LA/LB/LC, 2180LA/LB/LC, 215x, etc. I don't have all of that information, but I'd be willing to compile it into a central location.

I was thinking of something like this: http://fucanay.fischerworks.com/diy/gssl/gssl_test.html

If anyone wishes to help with this, let me know. Otherwise, I'll probably just start gathering the data slowly over time.

Matt

 

[Purusha]

Great idea! :thumb:

I could help but I think we have better experts here. Anyway, you can start from this thread. There is a lot of info for 2181 right here. Just take in consideration the different value changes of 1M resistor for LA, LB and LC.

Start to fill in the values and others will give suggestions or correct something if necessary.

 

[fucanay]

I'm going to start a new thread to generate some interest for this. It would be better to not have 2155,2180LA, etc. talk in the 2181LB thread.

hopefully, this will lead to a lot less confusion when newbies are building these, myself included.

Matt

 

[Greg]

hi Roger:
Just did a little tinkering with one of my GSSLs. The one with the 2180LBs in it. In the channel VCAs, I'm getting 228mV fully counter-clockwise with slowest attack. It measured 420mV at fastest attack. Then I did some testing at my typical operation. My measurements ranged from about 50-70mV. In fact, I have my meter set to fully deflect at 6dB compression because this comp is super aggressive in my opinion, so at 3 or 4dB I'm usually beginning to hear pumping. An 1176, on the other hand, is a different story... my point is that with 6dB compression, I'm not saturating the channel VCA (if I understand this correctly). And I double checked my ratios and they're still very close. So I'm thinking in my max operating range, everything is ok?

I haven't added my sidechain board yet, so when I do that I'll re-check this.

My GSSL with the 202s is loaned out at the moment, so I couldn't test that one.

Nice work and good info !!! :thumb:

 

[Purusha]

I'm getting 228mV fully counter-clockwise with slowest attack. It measured 420mV at fastest attack.

Isn't the 120mV the right or max voltage for G-SSL? Strange.

 

[Greg]

I'm not sure what you're saying...

But 120mV is the max input the VCAs can have before saturating... or I guess becomming non-linear. But in my max range of operation, I'm getting from 50-75mV, so in my operating range everything should be linear. And my ratios are good so everything is peachy as I see it. Does that makes sense to you?

I actually had to disconnect the meter to get the 200 to 400mV because I didn't want to peg it out.

Also, I actually tweaked the 1K going to the CV to adjust ratios. My summing resistors are 47K.

 

[tony dB]

Greg

Sorry for going a little aside of topic, but which of your 2 ssl' do you prefer?The 202 or the 2181 version?

Tony

 

[Greg]

I actually used the 2180LB. But to answer answer your question, I gotta go with the 202. Might not have as good of specs but I look to her 9 out of 10 times when I grab for a GSSL.

 

[Purusha]

Greg, so your actual voltage on 3rd leg is 50-70mV when your threshold is fully CCW? I am confused now.

Also, I actually tweaked the 1K going to the CV to adjust ratios. My summing resistors are 47K.

Which resistor would that be?

 

[Greg]

No, when I set the threshold to max, I get 200-400mV readings which will drive my channel VCAs into saturation; however, in the maximum range I'll ever operate my GSSL (ie max meter deflection), the highest voltage I get about 70-80mV. So in my range of operation, the VCA aren't being saturated... that's why the "range" of my ratios aren't screwed up.

I then fine tuned my ratios by adjusting the 1Ks connected to the CV pin on the channel VCAs (SSLTech's method). Look at the schematic it'll make more sense. But you don't need to do this since you adjusted the resistor in the sidechain as suggested by Steffen. "There's more than one way to skin a cat."

 

[j.hall]

[quote author="Emperor-TK"]
- replaced the 100K to 120K on the right of the TL074
I used 122K
[/quote]

just to clarify, i can turn my PCB four directions and get a different result on the location of this resistor. are we talking about the 100k that's in a stack with the 620k, 100k, and 220k?

if not, there is no other 100k resistor right next to the TLO74, there is however one right next to the TLO72.

 

[imo]

I'm pretty sure it is the top 100k, right above the 620k, according to the schem's..

 

[martthie_08]

There are a few minor updates regarding the THAT 2181LA calibration instructions on the website Volker is hosting. It was basically the results of looking into the "10K" resistor removal and "3K9 to 5K1" resistor swap modification posted by RogerFoote. It seems like a good idea, although I have not tested it, nor have I done any measurements on my GSSL yet.

you can find it at the same location, look here:
http://groupdiy.silentarts.net/martthie_08/gssl/index.html
and click onto "next page" at the bottom. Any comments are greatly welcome - I think this document might be a good source for people doing the "clean version" of this project, with the readily available 2181LA VCA.

cheers, Marten

 

[mathflan]

what does these mod improve( remove 10k resistor and change 3.9k to 5.1k resistor) on the SSL, correct ratio??

 

[Purusha]

[quote author="Greg"]No, when I set the threshold to max, I get 200-400mV readings which will drive my channel VCAs into saturation; however, in the maximum range I'll ever operate my GSSL (ie max meter deflection), the highest voltage I get about 70-80mV. So in my range of operation, the VCA aren't being saturated... that's why the "range" of my ratios aren't screwed up.[/quote]

Ok, this makes more sense to me now. Would it be bad to adjust the threshold in such a way that VCA would never go to saturation or that it would never compress more than the meter can show. In my case it would be around 13dB. If I have the meter scale set to max 13dB than it doesn't make sense to me that the compressor would go even 1dB further. Anyway the sound starts to saturate and compressor starts to sound useless to me soon after 10dB of GR. What do you think?

[quote author="Greg"]I then fine tuned my ratios by adjusting the 1Ks connected to the CV pin on the channel VCAs (SSLTech's method). Look at the schematic it'll make more sense. But you don't need to do this since you adjusted the resistor in the sidechain as suggested by Steffen. "There's more than one way to skin a cat."[/quote]

Thanks for clearing this.

 

[tony dB]

>>off topic <<

Cheers Greg!