GSSL HELP THREAD!!!

[Siegfried Meier]

Quick queston...

This GSSL I just finished, it works great with my bantam patchbays and AVID 192's.  However, I hooked it up to a 003 as a hardware insert and it seems that there's some kind of impedance thing happening, as no level will get into or out of it.

What are they doing in the 003?  They call it "impedance balanced", but is this the same as electronically balanced?  If I patch a DI in between, it works correctly.  Any clue what's wrong and how to fix it?

I admit I don't know the details of a 003 insert so I could well be wrong here. Sounds more to me like a basic cable or routing issue. If there was an issue with balancing I'd either expect a horrible earth hum loop, or 6dB of loss (due to the -ve phase portion being tied to ground or chassis) at either mismatch point. Have you checked which combination of TRS is in use on the 003 for send and return on the insert? And also the nominal levels? Normally send would be on the tip, and return on the ring, with sleeve as ground: but not always. You can obviously check that with a simple multimeter on AC Volts after passing a tone through the path if you don't have access to a scope.

The unit went to a friend of mine.  But last night he called me and said he hooked up a passive DI and it made it work somehow...so I too suspect cabling to be the issue.  Also, he said after 10 minutes of using the DI's, chn 2 blew up and is now hissing with no signal running through...so I have no idea what the hell he did.  He's gonna have to bring the whole thing back here for me to test.

If it worked with a 192 and a bantam patchbay, why in gods name would it not work on his 003??

Semi pro junk!

 

[Harpo]

a question about the meter.

would be ok a DC meter 0-150 mA?

the gssl specifies for 1mA, but there is a way to adapt another meter, like this one?

getting a meter with 1mA fsd will be a lot cheaper than building an additional driving stage for this 150mA full scale deflection meter and modifying/upsizing the psu accordingly. A TL07x will not drive this load. If it is only used to fill a hole in a frontpanel, just put it in, but don't expect the needle to move by a noticable degree.

 

[beatnik]

thanks harpo, i'll pass on this and look for another one

 

[mitsos]

revisited my GSSL last night after having it boxed up for a month (moved house recently). I remember that last time I tried using it I had only hissy crap on one channel but last night it worked perfectly. weird? anyway, guess I'll wait for it to happen again.

I did a bit of searching through some related threads and found the jensen transformer in/out mod, where Roger Foote is quoted as saying (I added the bold):
[quote author="RogerFoote"]I did a pair with JT-11 's on the input and outputs. They sound amazingly smooth and quiet. You can hear most difference with input iron because (I assume) of error in the electronically balanced inputs. Not knocking the input structure, but there is a silkiness and less grainy quality with input iron. The output iron kicks ass too, making the unit even quieter because of better matching between the GSSL and the next stage.[/quote]
[/quote]
I read another post saying something similar abotu the input section but can't find it right now. Anyone care to comment? Is this "problem" just people who don't like ye olde 553x opamps or something else? I've heard that some "upgrade" to OPA604s and such in there for example.  I like the sound of mine but I feel there is a bit more hissy/buzzy noise than I'd like (especially when turning up the makeup).  I'll try and run some tests over the weekend to get some actual numbers but just thought I'd throw this out there for comments.

cheers!

 

[MeToo2]

revisited my GSSL last night after having it boxed up for a month (moved house recently). I remember that last time I tried using it I had only hissy crap on one channel but last night it worked perfectly. weird? anyway, guess I'll wait for it to happen again.

I did a bit of searching through some related threads and found the jensen transformer in/out mod, where Roger Foote is quoted as saying (I added the bold):
[quote author="RogerFoote"]I did a pair with JT-11 's on the input and outputs. They sound amazingly smooth and quiet. You can hear most difference with input iron because (I assume) of error in the electronically balanced inputs. Not knocking the input structure, but there is a silkiness and less grainy quality with input iron. The output iron kicks ass too, making the unit even quieter because of better matching between the GSSL and the next stage.

I read another post saying something similar abotu the input section but can't find it right now. Anyone care to comment? Is this "problem" just people who don't like ye olde 553x opamps or something else? I've heard that some "upgrade" to OPA604s and such in there for example.  I like the sound of mine but I feel there is a bit more hissy/buzzy noise than I'd like (especially when turning up the makeup).  I'll try and run some tests over the weekend to get some actual numbers but just thought I'd throw this out there for comments.

cheers!
[/quote]
Without knowing exactly what the mod was, and what was driving the GSSL it's difficult to make any sensible comment. Loading could be a huge factor. As for hiss, I would suspect that would largely be sourced by the VCA (transistor junction noise in the gain cell) and not by the op amp. This is wild speculation on my part as I haven't measured this particular difference, but one of the basic trade offs in the choice of biassing an analogue VCA's is distortion versus noise floor. Higher current = relatively less noise, but higher distortion. On paper the 5532 has lower (input) noise than an OPA2604, but I'm sure there'll now be a gush of Top Trumps style "X is the best op amp" reactions, as the OPA2604 has higher bandwidth and slew rates. Horses for courses I say. It would be easy enough and not too expensive to plug in an OPA604/OPA2604 in place of the NE5534/2 (assuming you've socketed these) and see what you think yourself. This is DIY.

 

[mitsos]

Sorry, I should have posted the link, not just the quote. It's kind of academic, I mean, I'm pretty happy with the comp, but after I saw comments from RogerF and (I think) nrgrecording (frank?) at his forum saying the input stage is not that great. Both people that have been pretty well respected around here, so it made me curious.

Like I said, I should meaasure this to be sure there is no other underlying problem, but it seems to work fine.

Anyway, the transformer mod is basically 1:1 Jensens on in and output, there is a copy of Bill Whitlock's comments a couple posts down:

http://www.groupdiy.com/index.php?topic=8174.0

The quote from RogerF is on page two. I normally don't think these things make THAT much difference (at least not to my ears) but RF was pretty well respcted while he was here so I figured he might be on to something. 

Thanks for the comments! Appreciated!

 

[Bob1991]

I've got my GSSL finally (some kind of) working. After hours of fault-finding, the threshold section seemed to be the only part left. So i disconnected the wire that goes from the threshold pot to the the TL072, and, tada! there's compression  ;D. With the threshold potmeter turned full clockwise/or counterclockwise I only have a range going from +- 8,8 volts to 12 volts (measuring the output of the potmeter), so that 8,8 volt is preventing the compressor from compressing..

Havent fixed it completely, but now i know where to look for a fault.. i think..

Hadn't mounted that threshold 47k resistor - is this one necessary?

 

[Bob1991]

So i mounted that threshold 47k resistor, and the GSSL is compressing  :-X

Strange.. but as long as it works 

 

[USIEL]

Hi guys ,

I've just finished building my gssl  , but there is  something wrong with the + 12V rail
On the 78L12 input is 23V ...but 0V on the output  , replaced the 78L12 .....but that didn't change anything
Can  a 78L12 have "startup" problems  or is it better to check something else

any help is highly appreciated


usiel

 

[gyraf]

+12V line is probably shorted to ground somewhere...

Jakob E.

 

[poctop]

Is there anybody out there that has valid  part number for those -12v and -15V  regulator ,
it seems that everyting mentionned in thosessssss BOM are obsolete
Let me know,

thanks,
Dan

 

[USIEL]

+12V line is probably shorted to ground somewhere...

Jakob E.

Jakob,

checked it with a magnifying glass and a  flashlight this time ...  there was a short between 2 pins on the tl074!

Thank you sooo much !

 

[ptron]

hey i got a question!! regarding noise coming from my build...
to get rid of it i put a wire from the star ground to the meter leg (left right doesnt matter it still takes out the noise.) weird thing is as follows: EDIT: (actually noise stops with both legs but meter dont work when i connect negative to ground)

i try measuring voltages without that bridge and i get nothing from voltage lines.. when i put the wire suddenly all my voltages are great...
weird no?

i dont know what it means...

anyways thanks in advance there is no problem with my gssl its just curiosity. maybe i did something wrong and its still time to fix before all blows up!

 

[jordan s]

Back in August last year I bought a "complete, fully functional" GSSL off of someone from the TapeOp forum. User 12strang10. After months of battling with the guy, he finally sent me the unit with mostly populated boards and some really shoddy solder work. I had to undo his wiring and wire it all from scratch, replace incorrect parts and do a lot of checking with a fine tooth comb. I finally finished and plugged it up.

Seems like voltage is stopping at the rectifier. Then I realized that he installed both rectifiers so I removed the one near the onboard transformer area as I'm using an external transformer with the molex connectors. Same problem still. I've checked for all the proper parts, all the orientation of polarized components and checked for shorts to ground in the PSU section with a meter. I have a proper 18v going into each side of the rectifier but I'm getting something like 0.5v and -1.5v out of the it. Should I assume that the rectifier is damaged from trying to run the unit with both rectifiers installed?

 

[mitsos]

sounds like the rectifier is fried, but not from having two in place... shouldn't make a difference.

I'd replace the rectifier and check again, make sure you check DC voltages are OK before isntalling the ICs.

crappy deal with that guy.. I hope you got a discount  :

 

[AudioguyII]

Hello,

First off, thanks to all the great people and their valuable insight to help us build these fantastic units.

I've just finished stuffing 2 pairs of Super Sidechain boards, apparently I needed 2 per GSSL with turbo board installed.

Can someone please point me in the right direction on how to wire the 2 X SSC , turbo and Gssl?

thanks again!!!!

 

[Hank Dussen]

All the info is probably in this thread:
http://www.groupdiy.com/index.php?topic=18017.0

 

[jordan s]

Well, I got it to power on but it's not really functional in any way. All kinds of weird stuff is going on. For one, it doesn't seem to be compressing at all. The meter is completely pegged when not in bypass. Threshold pot does nothing. The release switch makes loud popping noises when switching and worst of all, it's making very loud scratchy, static noises. Also, one side is coming through a lot louder than the other. I don't even know where to begin with this. I've checked my wiring, all resistors, polarity of all polarized parts. Any ideas?

Update*, I swapped the 2180 VCA's in the VCA section with some 2181. Now it's compressing seemingly randomly, jumping all over the place, sometimes completely lowering the whole signal. The controls seem to have an effect on how it's compressing but not the desired effect. Now that I've got this all wired and I have all the expensive parts, I might just populate a new set of boards and swap them in. I could probably do it in an evening, who knows how long it could take to trouble shoot this. These boards have been in the hands of several novice builders before me and there's no telling what the issue is. At least I can keep track of myself when I populate the boards and be extremely through.

 

[ncoak]

be sure to note the info here if you're swapping vca's
http://diy.fischerworks.com/gssl_vca.shtml

 

[MikeClev]

Now it's compressing seemingly randomly, jumping all over the place, sometimes completely lowering the whole signal. The controls seem to have an effect on how it's compressing but not the desired effect.

Sounds like bad solder joints conducting one second and going open the next. Also I had jumpy crazy controls when I had a wrong size resistor in my 'threshold pot wiper to opamp' spot.