New 'ultimate' SSL buss comp clone ;-)

[Rob Flinn]

Kevin

That looks really good. Glad it worked out so well !!

 

[Sleeper]

I'd like to try and simplify an earlier question.
I see keith and rob have 4 -202** vcas-in signal amp positions
khstudio has only 2-202**vcas in use

I get why you need 2 sidechain circuits to do the oxford style summing.

Since building two detectors and sidechains meant using two boards; I decided to go one step further. The VCAs I used are the 202XT's, which are each composed of 8 x SIL VCAs for noise reasons. Since they are all used in the same pole, I built the second channel in each and polarity-flipped the signal through it, re-inverting at the end, to re-sum back in the same polarity. (You have to remove one sidechan-summing resistor to prevent the signal nulling...)

The signal thus passes through the VCAs in opposite polarity, and some of the residual VCA distortion is thus canceled. -This is how the SSL 9000 J and K series console center section buss compressor does it: the "Superanalogue" version... except that they do it with half as many VCAs in each pole, since it's getting a little expensive by that point!

2. Link Left + input to right – input on both boards
3. Link right + input to left – input on both boards
4. Do steps 2 & 3 above to the outputs of both boards.

Am I right to think this won't help, and might actually make things worse if the vca's aren't really really close to one another to begin with?

Kelly

 

[SSLtech]

:thumb: :thumb: :thumb: :thumb: :thumb:
Hey, it looks REALLY neat with only half the components stuffed in each! -Well done, Kevin!

:guinness: :guinness: :guinness: :guinness: :guinness:
[quote author="Sleeper"]Am I right to think this won't help, and might actually make things worse if the vca's aren't really really close to one another to begin with?

Kelly[/quote]
I can't answer that question with any absolute authority unless you're specific about the 'aren't really close' part...

-However, it's very UNlikely to make things worse, unless the two devices had the same problem but in completely opposing poles... does that make sense? -In other words, for the problems to reinforce with polarity reversed, they would have to be in opposition to begin with.

-Of course, if you combine completely dissimilar VCAs with totally different traits, you should end up with some of the traits of both VCAs, but each reduced by half. -Is that "worse"? I shouldn't think so, but it's not what I was going for, anyhow.

Keith

 

[Rob Flinn]

[quote author="Sleeper"]

Am I right to think this won't help, and might actually make things worse if the vca's aren't really really close to one another to begin with?

Kelly[/quote]

I tried to trim my ultimate on the same distortion meter that I used to trim my Gyraf version of the GSSL. The distortion was so low that I couldn't trim it & when I added the op amps to use both 202xt's it couldn't measure any distortion at all.

With my gyraf version the meter did show a figure for distortion. But maybe I just got lucky with well matched VCA's. Who knows ?

 

[Sleeper]

Hi Keith,

You just had to come up with something better didn't you.:razz:


I had the idea, at least for an hour or so last week, of a mixed VCA solution... 202s on 1 board and 2181s on the other but that was just me trying to cheap out at the last minute.
F* it, I'm throwing all the 202s I have at this bad child.

I think maybe a better idea in the long run is to sort out the vca build. Mouser carries THAT components now, including 2180s and 2181s
so it's suddenly gotten much easier to DIY.

trolling posts. I should really get to work...
It looked like JLM has a VCA board... I emailed them last week, but I haven't heard back yet. If anyone can help with VCA pcb info, that would kick ass.
Kelly

 

[Sleeper]

IRC pricing looks better than mouser's.

 

[SSLtech]

Rob, I know it's been said before, but that cat of yours is righteous.

Keef

 

[Sorr]

Who are IRC?

 

[Greg]

Internet lingo...

IIRC => If I recall correctly

... I think.

 

[rodabod]

[quote author="Sorr"]Who are IRC?[/quote]

Hmmm..... I can't remember... :razz:

 

[Sleeper]

I knew two minutes ago, but I had to walk 20 feet and pet the cat and the phone is ringing, so if something doesn't sound right it probably isn't. :?

 

[khstudio]

Here is a hook-up diagram I used to make it easier to see where everything goes (& doesn't go)

If you only use 2 MAIN VCA's - you can load JUST the left sides of the board.
This Pic shows the parts to leave OUT!

Kevin

 

[Rob Flinn]

Kevin

Where you have drawn the + & - 12v supplies from the slave main to switch pcb. Was there something in the thread about taking both supplies from the master set of boards, because minor differences in regulated voltages can cause a problem.

Keith

-I reckon you don't need those ±12V links, in fact having them means that if either regulator has a slightly differenct notion of what is precisely 12 volts, there could be a noise issue... try removing them (assuming that you have the slave ratio board fed it's ±12V from the main slave board, of course!) and seeing if it shill works... it should, and since you won't have the two regulator outputs connected directly to each other, there should be no chance of a "fight"...

I seem to remember having a problem without the 12v's connected, & bearing in mind Keiths advice above took them both from the master set of boards so they would be the same for both channels. Maybe I should have tried removing them when I finally got the thing working as he suggests. Could you try this out since mine is getting a battering at the studio & I don't want to remove it unless I need to ?

Maybe someone could explain the point of these psu links ?? Since that is part of a feedback loop I can't see what they do ???

 

[SSLtech]

[quote author="Rob Flinn"]...since mine is getting a battering at the studio & I don't want to remove it unless I need to...[/quote]
That's a problem with this version: Once it goes into a rack, it can never come out, because someone's ALWAYS using it!!!

Keef

 

[khstudio]

[quote author="Rob Flinn"]Kevin

Where you have drawn the + & - 12v supplies from the slave main to switch pcb. Was there something in the thread about taking both supplies from the master set of boards, because minor differences in regulated voltages can cause a problem.
[/quote]

Well the 12v has to come from somewhere & I thought I read to hook it up there... :? ???

Keith,
what's the word on this 12v hook-up :?:
Also, did you get my email... didn't here back from you yet?

Kevin

 

[SSLtech]

Haven't checked my home email in 3 or 4 days... M<A<D busy in the evenings at the moment...

I like the drawing, it looks good from memory, and so much easier to grasp than a page of words...! :thumb:

Keith

 

[Rob Flinn]

[quote author="Rob Flinn"]Kevin

Well the 12v has to come from somewhere & I thought I read to hook it up there... :? ???
Kevin

The instructions say to link the + & -12v points on both switch boards. But, anyway is it possible you could try removing the power links to the slave switch board & see what happens. If it works OK then it would be useful to know. I think when I was having problems that was one thing I did to sort things, but I never tried it without when I got all functions of the unit working!

 

[timmygrimm]

Forgive my stupidity, but did you guys build these vca pcbs which sit atop the main pcb? I understand it is a number of vcas working together (with an opamp?), but it goes unmentioned in the build instructions.

Tim

 

[khstudio]

[quote author="khstudio"][quote author="Rob Flinn"]Kevin

Well the 12v has to come from somewhere & I thought I read to hook it up there... :? ???
Kevin

The instructions say to link the + & -12v points on both switch boards. But, anyway is it possible you could try removing the power links to the slave switch board & see what happens. If it works OK then it would be useful to know. I think when I was having problems that was one thing I did to sort things, but I never tried it without when I got all functions of the unit working![/quote]

Dude, it must be an optical illusion :shock:

Look at the pic again... the switch PCB's ( + & -) are linked :wink:

You can't JUST link the Switch PCB's 12v - you'd have NO Power. I have a perfectly working unit at this point & those pics I posted are exactly how I did it.

Kevin

 

[khstudio]

[quote author="timmygrimm"]Forgive my stupidity, but did you guys build these vca pcbs which sit atop the main pcb? I understand it is a number of vcas working together (with an opamp?), but it goes unmentioned in the build instructions.

Tim[/quote]

No. They are Pre-built version made by DBX. You don't HAVE to use them to have a great sounding compressor with the new 218x series VCA's available.
Get some pre-trimmed 2180 A or B's and you'll be happy.

Kevin