ssl mod questions

been thinking about some mods and have a couple of questions for ya Jakob...

1) how would you modify the ratio to change the 10:1 to something much higher?...It would appear that this would involve changing the value of a resistor near the ratio rotary, but I can't figure out which one....

2) I tried modfiying the attack time to make it faster by reducing the value of the 820R resistor in the attack section, however I encountered a lot of distortion after doing it...I changed it to 100R..does not really seem to be usable...Is this distortion just from the VCA not being able to handle it or is there another reason (such as op amp quality) that causes this?

3)how does the 6.8u cap affect the auto release...If that was changed to a higher or lower value, what would be the result and how exactly does the auto release work?

4)why specifically tantalums in the release section? would it react differently with a different type of capacitor?

The design is great the way it is, but I like to tinker with things and also always curious about how things work.

thanks man...

Chris

hi chris,

1) :?:

2) distortion at fast release times is a "problem" of many other comps, too I think there is no way to avoid this... I'm using 330R with a 250k pot in series and it works well... but it's also dependent on the audio signal... you can "run" faster attack times without distortion, if your signal doesn't have too moch low frequencies...

3) :?:

4) I've hear tantalums are very "fast" maybe that's the reason...


cheers,
matthias

Hi Chris,

We have made these projects available for the DIY'ers in a version that is checked and tested. If you want to modify beyond that, you really need to do a lot of the work yourself. It's not always easy to ansver specific questions of the "what-if" type..

For your questions:

1 - The Ratio. Look at the schematic around the ratio switch - it does two things: first of all, it changes gain in the rectifier stage by altering the feedback resistor. This is the actual ratio. Second, it adds in a DC voltage to change threshold according to ratio in order to maintain the same average GR regardless of ratio setting.

It is these two functions you should work with.

2 - The attack/release times are implemented like in the original unit. As in any compressor, if you time your sidechain too fast, audio distortion will result. I think that Mr. Smart was just that - and did a good job on selecting the A/R timing. You could off course experiment with these values depending on your taste, but I think that you'll find that the ones chosen are quite a good selection.

3 - The 6u8 in the "Auto" release setting takes care of the "long" part of the auto release. The Auto release is just two timing systems stacked, so that you for short transitions of the threshold have a short release, but after long-lasting compression there is a much slower release. It's the latter that is timed by the 6u8 tantalum.

4 - Tantalums are used because you want low leakage and low changing of capacitance over time. You could use polyesters, but these would be very large.

Happy modding!

Jakob E.

Hi! I would love to make an GSSL clone but would like it dual mono...so I would like to compress each side independenly....is for the 2bus ...so I don't mind if the controlleres are linked but I want each side to be compressed independenly.

Any link of the schematic?

Thanks!!

Hi! I would love to make an GSSL clone but would like it dual mono...so I would like to compress each side independenly....is for the 2bus ...so I don't mind if the controlleres are linked but I want each side to be compressed independenly.

Click to expand...

Build two of them. use just one channel on each .....

[quote author="MrZpliff"]Build two of them. use just one channel on each ..... [/quote]
Amen.

He speek the troof.

Keith

Hello,

not shure which thread to take, but as it is a modification....


can i power the GSSL comp directly with a +-15V switched PSU ?
just omitting all the PSU stuff and solder in V+ and  V- where the 7815/7915 feed their Voltage to the Board ?
I don't like to handle with voltages stuff higher than +-15V and i just could take the same PSUs i use for my modularsynth.
---> Traco Power 1515D ( +-15V, 1,3Ah, no probs with those in my Synth )


HC

Yes you can do it as described.

Though switched PSUs and low noise-floors sometimes present a challenge.

If you're thinking a switch-mode just for economy/availability reasons, I'd suggest that a transformer and the other few parts needed to do it as originally laid out by Jakob shouldn't be TOO expensive. -The VCAs seem to be prone to current noise, and a switched-mode power supply in the same box might possibly produce lousy figures...

...although the only way to KNOW is to build it.

If you're thinking 'economic option', I'd say that the tried-and-tested certainty of the 'standard' design might outweigh any cost savings, which wouldn't be enormous anyway.

Keith

From an economic view i think it would be cheaper to build it as thought on the original layout.
It's just the fear to handle high voltages and to do anything wrong on one side,
and on the other the GSSL will be built anyway into Modularformat ( one 19"  3HE Eurorack ).
On this one there's an economic point. I have a free Rack allready and i have the habit to build in this Format
This way  i'm also free to put it directly into my Modularsynth if i whish
Thanks Keith,

HC

i already made 2 GSSL.
with turbo & SIDEch boards - i love them

i'll use 1 for touring w/ a band next year.
i would get rid of switching attack & release.

is it possible to replace attack switch by a pot ?
should a 250K or 300K log pot + 820R in series will do ?

and release also (+ a switch to get auto mode) ?
should a 1M log pot + 180K in parallel with a U47 cap will do ?

i didn't find anything on the subject althought it seems to me to be a fairly evident mod.

please tell me if there's no tricky hidden problem so i can try it.

thanks

CHK312 said:

On this one there's an economic point. I have a free Rack allready and i have the habit to build in this Format
This way  i'm also free to put it directly into my Modularsynth if i whish
Thanks Keith,

HC

Click to expand...

I built my GSSL in modular format as well (SSL 5k format in my case), and I powered mine from the PSU of my console (+18/0/-18 voltagerails). I put all the components on the pcb just like using an external transformer (so including the diodebridge, regulators and caps). So, instead of applying 18/0/18 VAC, I apply +18/0/-18 V DC. The reason why I placed the components in full, is simply because maybe I want to put the compressor in a 19" enclosure one day.

helterbelter said:

CHK312 said:

On this one there's an economic point. I have a free Rack allready and i have the habit to build in this Format
This way  i'm also free to put it directly into my Modularsynth if i whish
Thanks Keith,

HC

Click to expand...

I built my GSSL in modular format as well (SSL 5k format in my case), and I powered mine from the PSU of my console (+18/0/-18 voltagerails). I put all the components on the pcb just like using an external transformer (so including the diodebridge, regulators and caps). So, instead of applying 18/0/18 VAC, I apply +18/0/-18 V DC. The reason why I placed the components in full, is simply because maybe I want to put the compressor in a 19" enclosure one day.

Click to expand...

I'm doing something similar, but with 22 channels of gssl and a Power One supply.  It's a beast!

Good lord John,  Pics or STFU~ :-*