GSSL with VCAs using 8 x 2181

After numerous listening blind tests and A/B comparison of SSLTechs version of Jackobs GSSL, and the original mix bus compressor from the 4000 series console (manufactured in the 80's), made me come to a conclusion that the they sound different. Not only to my ears but to people who use this equipment on daily basis.
The main difference is that the GSSL is more open, more of the higher frequencies were observed, and the console compressor sounded "tighter", sort of gluing it a little better. Of course these are all subjective opinions!
I am sorry if I didn't explain this good enough, but putting sound into words has always been difficult for me.

Anyway, I started to search for an answer and after a lot of research I concluded that it must be the VCAs that make the difference in sound (I know that some people disagree with me). So I experimented for a long time, burning a couple of 2181s and I came up with a two designs using 4 and 8 21xx chips, like the THAT202R and THAT2002T which can be found in some x-logic units.

I found that the 8 x 2181 sounded almost identical as the original. This test was made by sending one signal to both, GSSL and the original unit, then inverting the signal which came from the GSSL and adding it to the non-inverted signal which was coming out of the original unit. The result was a silence which proved that sounds from each unit are almost identical!

Here is the pic of the vca...



sorry for the blurred picture but I had to make it in a hurry.
The vca is a bit large, I suppose it could have been made the same size as THAT2002T, but I didn't care.

Sound clips will be posted here as soon as I get the unit back from further testing.

Personally I like the Jackobs GSSL sound better.

Regards, Renx.

Nice one! Dit you match those resistors? I'm asking because on the 202 vca's I always see these resistor array's...
Could be done with matched resistors as well I guess....


:thumb:

See... here's a problem.

VCAs CAN and DO have an effect on the 'sound'.

...but they don't affect the nature of the compression. The 'difference' in the SSLtech 'ultimate' dual-sidechain version ONLY affects the NATURE of the compression, and even then ONLY in stereo.

So some people -and possibly yourself- are building one GSSL and then an SSLtech "ultimate" SSL, and noticing differences which go BEYOND the SSLtech sidechain difference, because they've used different types of VCA for each build.

Of course this is perfectly understandable, but I think I have an answer which will make EVERYBODY happy...

I'm hoping to announce it in a couple of weeks...

Keith

[quote author="SSLtech"]
Of course this is perfectly understandable, but I think I have an answer which will make EVERYBODY happy...

I'm hoping to announce it in a couple of weeks...

Keith[/quote]

oooh! pins and needles! pins and needles! can't wait keef! :green:
-grant

Well for one thing, I think I'll be selling a few dbx black 202Cs in case people want to taste the "old school flava"... watch the black market, or PM me if interested.

In addition, there will be a new 'product' which will make EVERYONE's life MUCh easier, and -hopefully- meet with the approval of renx and everyone else.

-Basically it's intended to give ABSOLUTE freedom in choice of VCA and sidechain topology.


Keith

radiance:
I did try to match them at the best of my abilities, but I don't think that +/- 1% would make any difference.

Keith:
I built your version of the compressor first, but both vcas used, were from GSSL, Jackobs emulation of dbx, and this was compared...

Another interesting thing, which I discovered by accident when all was still on a proto-board, is that you can unplug 4 thats and the thing would still work without major resistor replacements. The sound was little less "tight", but only half as expensive.

I am more interested in what would the difference be if the sidechain signal (after the sidechain vca) is not only full wave rectified but also "RMSed". And what would be the difference if one would use opa627 instead of 5534, and opa2604 insted of 5532, since these op amps are much faster (opa627 = 55V/us).
Sadly I don't have the time to try this, since I'm currently struggling with a power-amp I'm building.

Renx.

[quote author="SSLtech"]....I think I have an answer which will make EVERYBODY happy...

I'm hoping to announce it in a couple of weeks...

Keith[/quote]

:grin:

Glad I have not started building your Ultimate version yet...

About this anouncement: can I get rit of my two GSSL pcb sets :wink: ???? hint hint hint

[quote author="SSLtech"]Well for one thing, I think I'll be selling a few dbx black 202Cs in case people want to taste the "old school flava"... watch the black market, or PM me if interested.

In addition, there will be a new 'product' which will make EVERYONE's life MUCh easier, and -hopefully- meet with the approval of renx and everyone else.

-Basically it's intended to give ABSOLUTE freedom in choice of VCA and sidechain topology.


Keith[/quote]

Hello Keith - just trying to finish my USSL with sidechain built into an "Oxford " edition case from Purusha. There's quite a lot of chopping and changing and I think it's at the point where the PCB could do with being re-done. I've been discussing this with Tat (Purusha) and said I'd contact you with regards to hint's/tips on a new PCB.
Then I saw this post - have you already done a new PCB or is it just drop in VCAs? I've had a few thoughts on this one and it'd be a good one to get my past CAD experience back up to scratch, unless you already have done it!
If you can, please let me know - i don't want to be doing work that you may have already done!

Thanks for all your contributions to GroupDIY.

Mike Baker

ps. If it's warm in Florida, please send it over - it's BLOODY FREEZING in Manchester on a night time!!

Two things:

Firstly, as regards VCA sound, I've posted some dbx 202C's for sale in the black market. (Black-can, "old-skool" vcas).

Secondly the ultimate SSL project is getting close to completion. The PCB is designed, but I've got a surprise up my sleeve... I can't tell you much more because my 'PCB guy' is in Tokyo at the moment, and I have to wait until he's back next week to see if I can make any announcement, so I'm sorry to prolong the 'tease' a bit, but I hope you all understand.

This is going to be an easier, trouble-free version with NO complex documentation issues... but there's a VERY pleasant surprise for some people out there...

You'll see what I mean when it's announced. -I just need this mad British guy to get back from Tokyo and tell me when I can get my hands on the prototype!!! :twisted:

I promise, you'll LOVE it... it addresses EVERYONE'S issues.

Keith

[quote author="SSLtech"]Two things:

Firstly, as regards VCA sound, I've posted some dbx 202C's for sale in the black market. (Black-can, "old-skool" vcas).

Secondly the ultimate SSL project is getting close to completion. The PCB is designed, but I've got a surprise up my sleeve... I can't tell you much more because my 'PCB guy' is in Tokyo at the moment, and I have to wait until he's back next week to see if I can make any announcement, so I'm sorry to prolong the 'tease' a bit, but I hope you all understand.

This is going to be an easier, trouble-free version with NO complex documentation issues... but there's a VERY pleasant surprise for some people out there...

You'll see what I mean when it's announced. -I just need this mad British guy to get back from Tokyo and tell me when I can get my hands on the prototype!!! :twisted:

I promise, you'll LOVE it... it addresses EVERYONE'S issues.

Keith[/quote]


I was starting to go through my parts to start building another GSSL, but I guess I'm going to have to wait. Any rough guess on when a first batch of PCBs will be available? :sam:

Well, I'm back from Tokyo...

We should have proto's in one month or less, depending on when the boards get sent for fab.

Website and Paypal will be set up for orders. This has to be as automated as possible. I can't _stand_ manual organisation.

Keef -- you can let the cat out of the bag now if you like.

:wink:


BTW - PLEASE PLEASE PLEASE - NO PM's :sam:

[quote author="Rochey"]
Keef -- you can let the cat out of the bag now if you like.

:wink:
[/quote]

Please let it out. :roll:

Here's the deal: Everyone's got the "ultimate sidechain filter, the super-thrust sidechain...etc.

We'll be making available a 'conversion' PCB as a bolt-on to a GSSL. We're calling it the 'Turbo'.

The Turbo will be a PCB which will contain the second sidechain to allow the GSSL to work in EITHER 'Oxford' (SSL) mode or 'Aarhus' (GSSL) mode.

It will be small, affordable, a MUCH SIMPLER build than the current "two-full-PCB" way of doing it, and it will come with simple instructions explaining how to connect to the main unit, using three small header connectors.

It will be available in such a way that it can EASILY be bolted onto the GSSL which you built five years ago, or the GSSL which you're currently sourcing parts to build.

You'll be able to "bolt on" a turbo to ANY GSSL, and it will be compatible with any sidechain filter PCBs... you'll just need to add a second sidechain filter PCB for the turbo sidechain as well.

Just like with a car, bolting on a turbo will give you a VERY impressive performance upgrade!

Renx,
You'll be able to add the turbo to your favourite GSSL and enjoy entirely original performance with your favourite sounding VCA, and ALSO switch it to SSL turbo sidechain mode WITHOUT changing the signal path IN ANY WAY.

Keith

Mmmmmmm - intersting!
Keith - does this mean that the VCAs will work in single ended mode now that it will be back to 2 channels on one pcb? I still like the idea of dif vcas for distortion cancellation - still may be some CAD for me to do!

Hi Keith,
That sounds like a great idea.
It can be a bit painful to watch people struggle.

Mine's getting there, but only now that I really understand the circuit.
And now that I really understand my VCA's.
I had a few minor problems with the board interconnects.
i thought it was maybe the VCA's
I had to figure out a way to test 202c's to figure out that they were fine.
The super-ultimate with parallel VCAs and 2 boards is not the easiest thing to troubleshoot that's for sure.

I still have a small problem around one of the input sections. I may have blown a 55xx with all the probing and poking. thats an easy fix though.
Anyhow, I think I started off way in over my head on this one.
Dog paddling now.
Looks like you've come up with a life preserver.
Too late for me... I'll just have to build another one.
can I call the old one a superultimatessl?
Kelly

Struggling eh...do you mean people, or me? :green:

Great idea!!! If i cant get the original design two pcb ultimate running correctly, atleast theres some hope.

I just hope it will sound almost as good as the two board pcbs. I kinda like the idea of having the VCAs differentially connected. But maybe there wont be such a big difference between the versions. Afterall the sidechain changes are probably the most important thing about it.

I still dont understand why my box doesnt work correctly though..It should. I followed all the instructions to the letter, and hooked everything up exactly like kevin posted in his pictures, and his unit seems to be working fine.
/J

Hi Jonkan,
I was talking about myself, but you are clearly swimming in the same pool as I am so welcome aboard. I'll let you know if I figure out anything significant to your posts on the other thread. Good Luck.
and yeah, isn't it cool that there's hope no matter what.

Thanks! Id appreciate your help alot.

/J

Keef/Rochey - any developments yet :?:

PCBs are being manmufactured at the moment; I believe that we're expecting them THIS WEEK!

:grin:

I have a 'standard' SSL buss comp here waiting... just WAITING to be the recipient of the first 'Turbo' bolt-on.

:twisted:

Keith