GSSL HELP THREAD!!!

[Guest]

[quote author="gyraf"]Hi Ju,

There's not much to do but to check and recheck components, orientation, pcb tracks, and powersupply distribution...

My meter was working when I first started testing, and now it is pegged ( and stays pegged). Ever run into this, and is there a way to "unpeg" it?

Sorry - I don't understand "Pegged"?

Jakob E.[/quote]
pegged - stuck where it is... on maximum...
I read this as fully stuck over to the right..?

 

[gyraf]

Aah - thanks.

If the meter is stuck all the way up, there may be a fault in it. Meters should have an end-stop that prevents this - try taking the meter apart and find and possibly re-set this endstop.

Jakob E.

 

[fum]

cool, that's the path I'm on, just wanted to make sure I wasn't missing a "better" way =)

ju

 

[axtrak]

Hi , i finished my first SLL Clone, one channel works fine, the other outputs only white noise. Where could i start to look for the problem? I checked the PCB, it all looks fine

 

[Greg]

[quote author="axtrak"]Hi , i finished my first SLL Clone, one channel works fine, the other outputs only white noise. Where could i start to look for the problem? I checked the PCB, it all looks fine[/quote]

Swap the VCAs (L to R) and (R to L) and see if the dead channel follows either VCA. I hope you socketed them. This way a VCA problem can be ruled out.

 

[mnats]

[quote author="frist44"]I used a 1ma lin scale meter from mouser. I'm just wondering if they resistor should be different because it barey moves during the most extreme compression. I know a couple other people have mentioned this meter, so I'm wondering if if requires a different size resistor.
http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=341715&e_categoryid=643&e_pcodeid=54101 [/quote]
I used the same meter and it works fine with the 2k resistor suggested for 1mA meters. Given the other problems you mentioned in the "SSL issues..." thread you started, the problem must lie elsewhere...

 

[gyraf]

Or it's simply a wrong resistor. Try measuring it (power off, and without meter connected)

 

[j.hall]

just got my sifam director 14 ppm's in.

the meters read 1 to 7, everything i have read here and on the net indicates they are true linear meters.


does this mean i can pick my value....2k for 20db range or 1k for 10 db range?

meter specs here:

http://www.nrgrecording.de/SIFAM_PPMsatcanford.co.uk.pdf



thanks for all the help,
j.hall

 

[gyraf]

Hall,

Yes, if it's a 1mA linear meter that should be right.

Jakob E.

 

[jensenmann]

Hi everybody
Since a few minuts I have two wonderfull working Gssl´s in my studio :thumb: :thumb: :thumb: :thumb:
They run with That 2181LA VCAs without Dist trim pots. The meters are Sifam EH30 Edgewise 0-1mA with customscale (0-20dB). It costed me around 160? each and took 6 weeks delivering time since it was a custom order. I´m sorry that I can´t provide any photos but you find the meter right there (german Sifam distributor): http://www.sibalco.de/indexho.html
They make the Gssl look really retro with Jakob´s frontpanel layout. :green:
Now its time to say big, big thank you to all you guys out there who helped me with asking qustions and answering them. Very special thanks to Jakob who gave us this (and not only this) project, provided us with infos, help, knowledge, fun, addiction... :thumb:
There is on thing to say about this community and it really comes from my heart: if the world would act like you guys are doing here in this community it would be a really better place to live. Thanx
Jens

 

[radiance]

Congrats Jensenmann!!

 

[Underthebigtree]

Hi good people -

I have completed a pair of GSSL's in a single case. One pair sounds perfect, and worked nearly flawlessly right out of the gate. The other pair has a gain problem, and is not compressing. Somewhere within the system, it is amplifying the signal into clipping. I've gone through it with a fine tooth comb, and cant find it - hopefully someone here can help.

Here are the facts:
1) The signal is fine leading into the 15K resistor before the DBX202 emulation circuit. I am actually using 27K's there for unity gain, but this hasn't changed the problem. I'm using Verbos' DBX chips.

2) The signal is amplified into distortion somewhere before pin 1 of the 5532 opamp (the output of the first half of the chip) leading out of the DBX circuit.

3) Between the 2 points above, I can't read the signal anywhere on my scope (not the greatest scope user), but that does narrow it down.

4) I've replaced all the dbx chips, the TL072, and the TL074 with the chips from the other unit. No change.

Any ideas would help a lot. Many thanks in advance!

Nick

 

[radiance]

Did you also replace the ne5534 from the dbx 202 emulation cicuit?
Also: within the dbx emulation circuit are two 1K resistors, check those two and also check the 15K near the ne 5532 in the output section.

 

[gyraf]

And compare the control voltages at the VCA - if there's a short around the VCA, gain could go high also..

 

[Underthebigtree]

Partial success!

The 5534, 1k's and15K mentioned were all fine. Found weird looking waveforms at pin 8 of the left and sidechain VCA chips, which led me to the TL074. Discovered a cold solder joint on the V- there, which must have led to some strange behavior. Repaired that, and the runaway gain problem is gone.

Sadly, not done yet. The unit is passing audio correctly, and makeup gain is working in non-bypass mode, but there is no compression at all, no meter movement, no change in level when moving threshold knob. I'll hunt through this thread to see if anyone else has had this problem. Otherwise, back to swapping chips and comparing the same signal between the 2 compressors until I figure it out.

Many thanks Jakob and Radiance!

 

[gyraf]

Depending on where the solder blob was at the TL074, that one could be fried. Try a new one. These are always good to have as spare parts..

Try tracing the sidechain signal through the SC VCA, the rectifier, and timing circuit.

Observe orientation of sidechain VCA!!!

Jakob E.

 

[Underthebigtree]

Nailed it (finally!)

It was 2 cold solder joints at the wiring harness on the main board wires that connect to the control panel board. It took way too long, and many blind alleys, to discover the problem, but I learned a lot in the process. Thanks, Jakob!

I'll post pix of the completed unit in the next couple of days.

Nick

 

[fum]

ok,

I'm trying to verify that these units are working properly, and am having some trouble seeing the output with the scope. When I hook it up to the crappy little b*ringer mixer on my bench ( says it's balanced in, but maybe it's "semi" balanced), I hear the output of the unit, but when I hook the scope up to it, I don't see anything.

Is there potentially a better way to test this, instead of plugging into a mixer?


Secondly, what kind of crosstalk, if any should I be seeing? There is none between Right in and Left out, but I got's lots between Left in and Right out.

Regards

ju

 

[Greg]

hi fum:

An oscilloscope would be a great way to test. Do you have one?
Input: waveform to pin 2, connect 1 and 3 together. Output: measure across pins 2 and 3.

And I don't think there should be any crosstalk b/w channels. I didn't have any on my unit.

 

[fum]

yup, I'm testing with an oscilliscope, connected pin 1&3, scoped pin 2 on output, same dealio.

I'm checkin connections, might have a solder blob, but there's definitely crosstalk from the input of 2 to the output of 1, but not vice versa

ju