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SSLtech

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Rochey and I have been working on a couple of developments for the GSSL, one of which -while not yet ready for announcement (a couple more weeks, we expect)- should significantly improve the performance. -As with the 'turbo', it's designed to be easily retrofittable to any existing GSSL, or incorporated into a new build.

I've been taking a long hard look at the GSSL's noise and distortion behaviour, and one annoying quirk of the GSSL has been hampering my measurements; You'd expect the GSSL to be at it's quietest when switched to 'bypass', and to distort the least when switched to 'bypass' (in reality it doesn't actually 'bypass' anything -it's really a "compression enable/disable" switch)... -But this is not what happens at all. -In actual fact the HIGHEST distortion figures for the GSSL are measured when the compression is DISABLED by the front panel switch.

But I've discovered what's happening, and how to make it stop. -And you can do it for FREE!!! -All it takes is popping the top, swapping a couple of wires and adding a third wire.

One of the two halves of the bypass switch (the part which only has TWO wires going to it) requires a slight modification.

Referring to this pdf:

On the component overlay (second page) two wires going to the "bypass switch" are marked "Defeat makeup when out". One connects to Pole 'A', and the second connects to contact A2.

Firstly, REVERSE these two wires. -If you (as I've done) noticed that it's just a simple "make" connection and possibly just connected them in no particular order, you need to make sure that the wire at the board end which is physocally CLOSEST to the 750K resistorneeds to be connected to the POLE (common contact) of the switch, and the other wire to the second contact.

Now, finally solder a wire to GROUND from the other contact "A1". -There's already a handy ground available at contact 1 of pole 'C' if you need it... ("C1" on the rotary switch as shown).

That's it.

Distortion in bypass is now a thing of the past. -I know that most people don't seem to care about distortion in bypass so long as the performance is unaffected while the unit is switched 'in', but I get distortion readings up to 0.755% worst case (when the unit is in 'bypass', ratio 10:1, threshold set to max) which drops to 0.007% on the unit currently on the bench with this modification.

It only takes a minute to do, and it fixes something which I've always found slightly bothersome, but which has now made my life MUCH easier.

Enjoy!

-Keith

 

SSLtech

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Bluzzi said:
Keith: Thanks for sharing that! .775 to .007 is quite the improvement!

Absolutely. -I couldn't dial in the symmetry adjustments properly with all that hash and nonsense in the signal when bypassed.

-All so much better now!

Keith
 

strangeandbouncy

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Aug 8, 2004
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West Sussex. UK
Hi Keith,


  I noticed something along these lines a while ago, and thought that there might be something wrong with my build, or perhaps something to do with the 2001 vca's . . . .

  i have to confess I actually LIKE this extra distortion, so that I sometimes leave it in circuit in Bypass for a bit of extra punch . . . and erm, noise as well!


  Thank you so much for bringing this to our attention, and I will be trying your mod, oh yes!


      Kindest regards,


  ANdyP
 

Jonkan

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Jun 7, 2004
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thanks for figuring this out! I was always wondering why the measurements were way off when in bypass. Have you tried lowering treshold aswell? On my unit this severely raises the distorsion in bypass mode.

Btw. Will any of the new mods you are working on work with an Ultimate Gssl with two pcbs like your original version?

/J

 

SSLtech

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Yep. -Exactly! -What you describe (the threshold setting affecting the distortion in bypass) becomes a thing of the past with this little mod.

-Andy, you can add a simple switch to remove the extra ground wire which you add, and you can have the switch make the unit alternate between 'clean-bypass' and 'buzzy-bypass' if you like.

Yes, both of our new bolt-on goodies will work with ANY existing GSSL, whether tuboed, 'ultimate' (dual GSSL) or any other version.

Keith
 

moamps

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Hi Keith,

I discussed GSSL-related noise issues in the bypass mode 4 years ago, when I suggested the very same thing:
http://www.groupdiy.com/index.php?topic=10812.msg127729#msg127729

Regards,
Milan

 

Harpo

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Rahden, Germany
Keith, good/better idea. Thanks for sharing.
Result seems to be similar to my previously posted approach by switching CV of audio VCAs to 0V to set these to a current in=current out condition and don't care of a still indicating gr-meter, as this status gets indicated by an additional LED.
minimalist bypass/LED schematic and hookup.

 

SSLtech

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moamps said:
I discussed GSSL-related noise issues in the bypass mode 4 years ago, when I suggested the very same thing:
http://www.groupdiy.com/index.php?topic=10812.msg127729#msg127729

Yes, I see that we've arrived at the precise same conclusion!

-I wish I'd have seen your post before 're-inventing the wheel' -it would have saved me some time!

None the less, this 'rediscovery' came as part of my desire to improve the performance in a few ways, and I'm glad that I fully investigated this and other issues.

Cheers,

Keith
 

Sarcastic Sound

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San Diego
ok ok ok... 

so the new release is "top secret"

I can respect that

But as I'm about to blow some big money on a FPE front panel for my dual gssl build (with turbo, of course)

Should I wait on ordering my front panel because of your new guinness development? As in should I wait because there is a switch of some sort that may (or may not) have to end up on the front panel? 

I dont think that would be giving too much away no?

My bank account would appreciate a hint  ;)
 

SSLtech

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One will not affect front panel, just improve cleanliness of sound.

The other will affect the metering, making another meter choice available. ;) (and a switch)

keith
 

audiophreak

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Oct 3, 2008
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Litchfield, CT. USA
Keith, THANKS !
         
   I'm just at the point were I'm connecting boards, pots and switch's.

      Just in time!   ;)

  Thanks again for the work and posting,, cant wait for the other mods  ;)

  Chip


 

blaisa09

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May 26, 2009
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Puerto Rico
SSLtech said:
One will not affect front panel, just improve cleanliness of sound.

The other will affect the metering, making another meter choice available. ;) (and a switch)

keith



Great stuff Keith! Greetings to everyone on the forum, this is my first post. I'm about to start my first GSSL w/turbo mod build and also considering adding the dual super side chain mod. I've been doing my homework reading up on the SSL Help thread (actually been about 2 month reading up!!!). I cant wait to see the new mods that are coming up! keep up the awesome work  ;D

BTW one quick question, i'm just about to order all the parts and i was wondering if it was better to use the THAT 2180 (pre trimmed) or the 2181 (and i do have a distortion meter to trim it here), is there a big difference in sound? Thanks for the great info.



John Blais
Puerto Rico
 
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