A new take on the GSSL (Pics Inside)

[matta]

And now for something... completely different... (Python fans?)

Here is my take on Jakob's GSSL design, sorry for the bad photos.

It has been a labour of love and I'm VERY happy with the way it all turned out!

I decided I wanted the heart of the GSSL and all it's DIY goodness but wanted a front panel design that looked a little different, somewhere between a DBX160A and a Distressor, which I then laid out and have Purusha to thank for making the cases... I had to take 5.... so I have a few more GSSL's to build over time, Hah hah!!!

I plan on building 2 for me and 2 for mates, who graciously covered all the costs of the units so mine ended up being free, at least parts wise! (WORD OF WARNING: DIY for non-profit sucks when you do it for other people, it takes a lot of time and time is money... in my case it works cause I was/am completely broke!) Another nice thing I thought of was putting a serial number on them so if it ever end up on the Bay I will know who the culprit its!!!

Right onto the build info...

I used THAT 2180LB trimmed VCA's all round and adapted the Jakob's circuit based on the THAT application note for substituting 218X series for 2150's. I also changed the 15K to 27K resistors to set the unit up for Unity Gain at +4dBu, and wrapped it up by lowering the Threshold sensitivity but replace the 100K resistor with a 120K.

You will also notice that there is no on board PSU. I REALLY struggled with this, to the point on insanity. I tried grounding it EVERY which way and no mater what I did I had a low hum, around 100Hz on the unit when the make-up gain was cranked up (it was constantly there, but got louder with the increased gain)... looked like a case of ripple on the PSU, since it wasn't ground hum... Neeno came to the rescue as he said he build 4 units and they all suffered from this, and both of my 2 did as well... the answer...

A separate PSU... I built one of MNAT's awesome bi-polar PSU's and removed the on board PSU parts, and jumped the board to feed it directly with regulated DC... low and behold, problem solved!

They say the proof is in the pudding, so here are some short before and after samples of what I'm talking about.

They were recorded into Pro Tools at +4dBu, fader set to 0dB and bounced down in the same fashion. The unit was switched in with the make-up gain all the way up (+20) and no audio passing through it.

The samples are REALLY short to keep the file size down so you may want to loop you sequencer to give you feel.

GSSL with On Board PSU (80kb)
GSSL with Off Board PSU (80kb)

I also decided to have a go at using RogerFoote's Pico Comp Meter, but built for the GSSL, we (Roger, Wayne and Myself) thrashed out how this could/would be done in the drawing board and I've come up with a parts overlay of the changes that need to be made if you want to have a go at this yourself, info is all here: http://www.groupdiy.com/index.php?topic=17162

Thanks to all who helped put this project together, most of all to our faithful and fearless designer/moderator Jakob for a fine project and for supporting the cause of DIY :thumb:

Cheers

Matt

 

[matthias]

wow! very nice design

 

[Lowfreq]

Matt, your units always look very tidy. :thumb:

Very neat wiring.

 

[gyraf]

That is very, very pretty!

Jakob E.

 

[mathflan]

Wow, I have exactly the same noise in my ssl,GSSL with On Board PSU (80kb)

I 'm happy to see after many times trying to resolve this hum that it's not come from my own construction.

I know that this hum is at very low volume when you put a 0db signal into the SSL but it's disturbing when you finalize a track..

therefore, very nice job, matt!

matt, do you have a link for the Mnat's PCB?

 

[Lowfreq]

Interesting, so the whole psu mounted off the board? Not just the transformer?

Mmmmm, at this stage I have both an onboard trasnformer and psu parts, that may be a problem once I get my unit going............

Getting it going is the harder part. ha ha :wink:
Oh well, back to reading the gssl thread..........................again.....

 

[mathflan]

ok I got the lonk for PSU :

http://www.geocities.com/m_natsume/psu.html

 

[Jonkan]

matta, You ROCK!

I cant believe how good you have gotten at this, considering the short time you have been doing it.

You keep spitting out amazing looking stuff, and im totally impressed.

/J

 

[Kid Squid]

Looks real fine matta :grin:

Steve :thumb:

 

[astrovic]

Matt - you keep putting out some seriously fine work. That's a superb effort.


Even better, the information and detail you provide alongside is fantastic. An example - I've currently got the front panel of my GSSL in the oven, baking on the lazertran. As a baking guide, I use your post where you summarised how to get the best results with lazertran. So thanks, mate - you've probably forgotten that post by now, but its still coming in handy :thumb: :thumb:

 

[mathflan]

matt , could you give me more informations about The PSU outboard, perhaps a layout...

Did you leave whole PSU stuff onboard, 79l12, 78l12... or just leave +15 and -15 volt Voltage Psu.

 

[jensenmann]

very nice design, indeed. Congrats!!!
:thumb:

 

[Purusha]

I already spoke with Matt today, but anyway. Very nice result. I like the knobs very much also. I used the same ones on my QUAD preamps.

Paka :thumb:

 

[KingKai]

Nicely done Matt !! :thumb:

Peace - Out, Irv

 

[matta]

Hey Guys.

Thanks for the support and kind words... this DIY thing is addictive :?

One day I'll take a shot of all my DIY work together, I'm amassing a fair amount of the stuff! LOL. I need to slow down to start USING it more instead of BUILDING it! Besides the custom rack jobs of modules I've bought I think I have a G1176, GSSL, Countless Green Pres, a pair of Hot Rodded Neve 1272 and waiting on my racked for my API 312's, it is all racking up... excuse the pun!

I know that this hum is at very low volume when you put a 0db signal into the SSL but it's disturbing when you finalize a track..

Yes, don't get me wrong... I'm sure for many applications it would be fine, since the input signal would be WAY louder than the noise. I am just being more and more conscious of noise in my DIY and getting it as low as possible esp for low level sources.

Interesting, so the whole PSU mounted off the board? Not just the transformer?

Yes, completely new PSU and off board transformer.

As a baking guide, I use your post where you summarised how to get the best results with lazertran. So thanks, mate - you've probably forgotten that post by now, but its still coming in handy

Thanks a lot. I am glad I can give back in some way to help others, I'm no EE, just a hack with a love and passion for learning and empowering others, that is why this place feels like home.

Did you leave whole PSU stuff onboard, 79l12, 78l12... or just leave +15 and -15 volt Voltage Psu

I removed the MAIN PSU, if you look at the schematic and board layout you will see the regulated +-15V rails feed the +-12V rails, so you need to jumper it in a way that the off board PSU still feeds those regs. I will in time post drawings of the mod... again I can't take credit for it, it Neeno's hard work that prevailed!

Cheers

Matt

 

[mathflan]

Ok matt, thanks.

I''ll try this mod and give feedbacks....

matt, is that th PSU from Mnat that you is different from the PSU onboard of the SSL.
I mean, Do I have just leave stuff of the main PSU to another board or I need to use the stuff of the Mnat PSU?

 

[Greg]

Nice work Matt... I really like the LED meter. If I ever build another, I think I'll try it out. :thumb:

Interesting PSU observations. I haven't noticed any noise at 100Hz on mine, but I know I didn't do any tests with the make-up gain cranked. At normal operation, everything is fine. Perhaps I'll dig a little and see if mine are behaving the same way.

Regardless, I don't see how an improved PSU can be a bad thing.

Relax and have a beer! :guinness:

 

[radiance]

Building a plain GSSL clone gives no hum. But when I tried to power a relay, a lamp, more relay's etc. etc. it always gave me hum problems.
The relays where powered by both the onboard or a separate power supply ,feeding of one or two secondaries of the power transformer, but nothing made any difference. Always hum. I'm going for this "off board" supply as well by my next gssl build.
Great job Matta :thumb:

 

[matta]

Interesting PSU observations. I haven't noticed any noise at 100Hz on mine, but I know I didn't do any tests with the make-up gain cranked. At normal operation, everything is fine. Perhaps I'll dig a little and see if mine are behaving the same way.

Regardless, I don't see how an improved PSU can be a bad thing

Hey Greg,

Thanks for the kind words. RE the hum, it is low, at -95dB, but louder than the noise/hiss of the make-up gain cranked by a few dB's. Some may not have an issue with it, I've just tried to lower it as best I can.

If you load up the samples you can hear the difference, it may or may not be quantifiable to make the changes, but for me it was.

I get pedantic about noise/hum and maybe the problem is I spend too much time TESTING the gear with 'non-real world' scenarios and not enough time making music!

The good thing about the separate PSU is that the extra juice is nice for feeding things like the LED meter and being trimable I can set the voltage and increase it to +-15V under load.

EDIT: To confirm the test was done with the standard GSSL build, no LED meter or ANY extra current draw, even without a power LED... I still got the slight hum.

Cheers

Matt

 

[mathflan]

like radiance, I have relay circuit, a power led and a Led for the bypass.

Matt or mnat, is it possible to have the schematic of this PSU.
:wink:


matt , so you use 317 and 337 Regulator or you have keep 78L15 and 79L15.