GSSL CRC Board from Expat Audio

[SSLtech]

I'm pretty sure that Lukas used the 317/337 regulators, but that unit's on the bench at work, so it wouldn't be until tomorrow that I could confirm that.

Anyhow, yes likewise, with the CRC, the noise floor goes down so far that I measure a dynamic range well in excess of 100dB on the Expat test-mule. _Actually, I've had LM317 circuits (I use it the power supply which I designed to go with the SSL 9k for example) where they too have been noisy, and I've had to bypass the voltage sense pin with values greatly in excess of the data sheet's specified values, so I've definitely looked carefully at that side of things.

In fact somewhere here there's a thead where I was trying to trace down some noise on a 48V circuit, and it turned out to be the data-sheet implementation of the 317 which I'd made. -The 7818 which was on the same board was significantly outperforming it (by an order of magnitude, in fact!) and I knew that had to be wrong. -In the end, I was able to get them to behave similarly, but the 317 was not appreciably quieter than the 78/79 regulators when all was said and done.

Ever since then, I've been careful to measure rail noise and look at circuits' susceptibility to it.

Ah... I found the original thread: Link to the thread.

Keith

 

[stitch-o]

Mine is on the way.

Thanks Expataudio doods!! 

 

[ytsestef]

0.5A or higher... 50V or higher... make sure it's the package type called 'WOG' (which is the button-type) and you're golden.

The 3-button controller can be made to do more or less ANYTHING. You can choose from a menu of functions, such as sidechain high-pass/flat, external sidechain, compression on/off, hardwire bypass, turbo mode on/off (Oxford/Aarhus), or pretty much anything else which you can think of. You can even fit more than one board, and have more than three buttons, if you REALLY want to go crazy!  ;D

So, this means that the bridge rectifier that is used in the original gssl psu design will work just fine (Jakob's BOM says 1A/50V WOG round type)

As for "REALLY going crazy with the 3-button controller" is there any chance we will see an other version of the controller chip, preprogrammed in a way that when we enable a button the other two get disabled? I don't know what it's called in english, maybe "exclusive toggling" or something..

Like a ratio selector, for example: if the first button is enabled (2:1) and we press the second one (4:1) the first one gets disabled.

Just sharing ideas there, sorry for the offtopic!  ;D

 

[Rochey]

sure, that's possible. I need some time to code it up, but stay tuned.

/R

 

[livingnote]

It's a 78/79xx thing, separately we have the LED bus dangling off a 5V logic (never again)
because we had some voodoo concepts surrounding that back then which turned up
utter bull in practice. At least it makes nice and warm ITB

 

[dagoose]

ok, so today i veroboarded this filter and it seems to be working nicely!
I measured the noisefloor before and after but to bad i didn't measure it a bit more precise/more range because it looks now as if it is gone in total.  ;D

And this is a pic of my gssl with just a couple of mods..  8)

 

[Soeren_DK]

I received my CRC board today. Thanks.. Great service.
One question, can I leave the bridge Rectifier on the main board or should I remove it?

Cheers
Soren

 

[ytsestef]

I received my CRC board today. Thanks.. Great service.
One question, can I leave the bridge Rectifier on the main board or should I remove it?

Cheers
Soren

I have asked that question in the past so I may as well answer it now ;D
You can leave the bridge rectifier on the GSSL, there is no problem. 

 

[Soeren_DK]

I received my CRC board today. Thanks.. Great service.
One question, can I leave the bridge Rectifier on the main board or should I remove it?

Cheers
Soren

I have asked that question in the past so I may as well answer it now ;D
You can leave the bridge rectifier on the GSSL, there is no problem.  

Hehe.. Thanks. I just had to read two replies above to find the answer. Thats laziness. Sorry...
But thanks for answer the question again... :-[  

Cheers
Soren

 

[Soeren_DK]

Hi Rochey

Your CRC board really helped on my GSSL. Great work with the design and PCB's.
If you have problems with the hum buy this board and this will help.

Thanks.
Cheers
Soren

 

[Rochey]

I'm thrilled that it worked well for you.
many thanks for the kind words.

/R

 

[stitch-o]

And this is a pic of my gssl with just a couple of mods..  8)

Holy crap!
That's a serious box...

 

[stitch-o]

I have some 400v 1.5A bridge rectifiers here already. The package fits the throughholes: this will work fine right?

Cheers!

 

[Rochey]

FYI: CRC Boards are back in stock.
PTownkid will also be supplying kits very soon from http://www.diypartssupply.com

Cheers

/R

 

[Ptownkid]

Kit pre-order now on.

 

[SSLtech]

I have some 400v 1.5A bridge rectifiers here already. The package fits the throughholes: this will work fine right?

Cheers!

Yes. Perfectly.

Anything 500mA or higher, 50V or higher.

-And yes, you can leave the original bridge-rectifier in with no worries at all.

Keith

 

[pietro_moog]

hi guys!
i had a CRC board from Expat Audio, but resistors got burned and i destroyed it (while i was trying to change the resistors)

i wanna build one on a PC board. (i have the original to copy)
my question is:

the original has a few traces and the rest is ground. how can i make it?

thanks

 

[conleycd]

Two things...

Someone mentioned that they used 1000uf caps instead...  I'm not sure how 1000uf caps would work because I think this circuit creates a specific RC filter using a 10ohm resistor and 470uf cap.  I'm not sure how 3 serial RC filters work or what they end up filtering but... 1000uf caps would be filtering some different frequency.

Second... Keith..  do you think is an application for the CRC outside of the GSSL.  I mean - could this be a helpful power filter in general for critical demanding applications?

CC

 

[SSLtech]

Two things...

Someone mentioned that they used 1000uf caps instead...  I'm not sure how 1000uf caps would work because I think this circuit creates a specific RC filter using a 10ohm resistor and 470uf cap.  I'm not sure how 3 serial RC filters work or what they end up filtering but... 1000uf caps would be filtering some different frequency.

The filter is a low-pass, and not 'tuned' to 60/120Hz... it's tuned BELOW that number, to wipe out and utterly destroy any frequencies ABOVE it... (increasing efficiency at a theoretical 6dB/octave until practical consiterations define the limit) hence doubling the cap value would simply tune it lower, and it would do it's job even better... within practical limits, of course.

Second... Keith..  do you think is an application for the CRC outside of the GSSL.  I mean - could this be a helpful power filter in general for critical demanding applications?

CC

The GSSL is a current-sensitive design, since the VCA is actually a CURRENT amplifier, and it feeds an op-amp[input which is configured as a 'current-summing' node referred to 0V ground. If there's ANY current modulation happening around the ground reference, the recovery op-amp may reproduce it at the output as a voltage, since it's configured as a current-to-voltage convertor, immediately following the VCA.

As a result, the cyclic pushing-and-pulling of the incoming power being rectified on-board means that the current flowing in and out of the capacitors to charge and discharge both rail reservoirs runs the risk of finding a path which can modulate the voltage recovery op-amp's input.

This cyclic modulation would manifest itself as a cyclic voltage...which is where the hum comes from.

If you have another design which is proving hummy for similar reasons then -yes indeed- this might prove to be the cure (current consumption/rail impedance might dictate different R/C values, but basically the beauty of the design is that it is simple, and moves the 'heavy-lifting' of the AC current charging and discharging off-board, where it can do less damage.

By the time it comes on-board, almost all of the ripple is dissipated, and a much more steady, stable, linear flow results in almost no modulation of the current reference in the VCA's voltage recovery op-amp...

So what's the simple answer?

If you have a design which is exhibiting similar hum for the same reason, then yes. -It can work.

If your design doesn't exhibit such sensitivity, or isn't noisy, then it won't improve things all that much... you can't reduce hum much on a piece of gear which doesn't hum to begin with.

Keith

 

[strangeandbouncy]

HI,


  got myself a CRC board, and am just about to install it. I read that you can install it without removing the existing bridge rectifier. I am just unsure how! - as in positive/negative goes where on the rectifier? to the ac connections, or the +/- connections?


  sorry to ask such a basic question, just don't want to damage my VITAL compressor by mistake . .



    Kindest regards,



    ANdyP