(NOT the official) SSL clone help

I've just built the ssl clone and I have a problem;

When I switch the bypass switch in, nothing happends to the sound. On the meter it looks like it should, If I change to a higher ratio I got higher response on the gain reduction.

I'm shure I've overlooked something in the sidechain or the wiring to the panel but I've gone through everytning several times and just cant find it.

Supply voltages are ok, and I have sound throug.

It should be said that when I first powered up, i had wired the trafo wrong. I've changed the 12V reg, seemed like they were broke.

I'm planning to build another, so I have spareparts for everything. Therefore I changed all the IC's. But the result is still the same..

Anyone??

Ole Henrik

Hi Ole,

Welcome to The Lab.

So you're getting sound through the unit in both channels in "compress" and "bypass" mode, but it's just not compressing the sound? What sort of input level are you sending to the input? Does the gain-reduction meter move in response to the level of audio, or does it just jump around randomly? What happens when you move the Threshold control down? Does it look like it alters the threshold (have a look at the meter when moving the Threshold control) And how did you wire the transformer wrong- did you get any smoke from any other part of the board- resistors, caps etc?

Lots of questions I know- but we need to know a bit more!

:grin:

Oh yes, and double check your resistor values around the sidechain and VCA's!

Mark

..and does the makeup-gain control work as it should?

Jakob E.

I actually had a similar problem when I built mine and it turned out I had put a 3.9M resistor instead of a 3.9K resisitor on the board I think....swapped it out and it worked.

try checking all your resistors

Thanx for the reply guys!

When I wired the trafo wrong, I swapped the one of the phases with the center pin. No smoke or smell or anything, voltages are correct so I suppose power supply is ok?

Im sending a standard +4db line in to the compressor, and when it comes out it looks like its amplified 6 db (just a gues on my bad protools meters)

The meter acts like it should, and its responding to the signal. When I turn the threshold pot against the clock, meter is responding more (larger swings to the right).

The makeup gain doesnt affect the level at all..

I'll check my resistors.


Ole Henrik

[quote author="Ole Henrik"]Im sending a standard +4db line in to the compressor, and when it comes out it looks like its amplified 6 db (just a gues on my bad protools meters)[/quote]

Regarding this statement, the SSL has 6dB gain. It you want unity gain, swap the 15K resistors before the DBX202/2150 Substitute Circuit with 27K resistors. It's marked on the schematic as 15K*.

It's also discussed here: http://www.groupdiy.com/index.php?topic=5356

Ole,

Check that you have your TL072 working right. You should have a voltage varying with signal level on both pin 1 and pin7. Threshold should vary one of these voltages also, and makeup should vary the other.

Jakob E.

Pin 1 is varying with threshold, pin 7 is 0v. Actually, if i bring in a signal its 0,08v and 0v without

Ole

Note, that the two opamps contained in the TL072 are switched with regard to the schematic.

If you have no DC control voltage at pin7, then this is your problem. Pin7 feeds control voltage to the two VCA's.

Check that you don't have a short from pin7 to ground.

Check that you don't have a short from pin6 to ground. This is the inverting input for the VCA-driving opamp.

You have a 100K resistor from TL074 pin8 to TL072 pin6. Check that this is correct and not shorting to anything.

You have a 620K resistor from the "makeup-gain" pot to TL072 pin6 (on the control panel. Check that this is correct and not shorting to anything.

If your meter moves, you have good signal at TL074 pin8. This means that you must have a short (to gnd?) somewhere around the TL072 - or the TL072 is not working. Try replacing it.

Jakob E.

Hi Jakob.

Tried to replacing the TL072 with the same result.

When I take out the TL072 and measure, I got 1142 ohms from pin 7 to gnd, and 1239 ohms from pin 6 to gnd. I guess this should be normal??

The 100 k isnt shorted to anything, at least not from its own conectors. When i mesure from its connectors to gnd its 1371 ohms on one and 1238 from the other. I lifted it up and I measured it to be exactly 100 k. When I measured between the conectors (with the 100k left out) I got 3,26 kohms

The 620 k isnt shorted to anything an when I lift it up I measured it to 620 k. When I measured it between its conectors its 937k ohms


Ole

You have a 100K resistor from TL074 pin8 to TL072 pin6.

At one end of this, you have the voltage varying with signal level, as this also drives the meter. We know this to be alright. At the other end of this resistor, you enter the inverting input of TL072, that is fed back with a 100K also. So any voltage present at TL074 pin8 should appear in inverted form at 072pin7

There is little that can go wrong here - check that you don't have a short e.g. from pin6 to pin7 on the 072. Maybe the 100pF is shorted? Or the 100K feedback resistor is wrong?

EDIT: 1239 ohms from pin 6 to gnd (if measured on the socket on the pcb, with no power on) is wrong. You should see nothing but the two 100K resistors and the 620K resistor from this point, so there should be something like 40-50K min. here..

Jakob E.

Ehhh

It turned out that the 100k between pin 6 and 7 on the 072 was a 100ohm.

Now everything's working perfect!!

Thank you so much Jakob!!!

Ole Henrik

:grin: :grin: :grin: :grin:

I love these threads. It seems like a wrong value resistor is the culprit a lot of the time! This is great stuff!

:guinness:

When I stuffed my GSSL, I definitely took my time when putting in the resistors. I measured, then re-measured every resistor, soldered it down, then checked between the resistor ends and another point on the board for continuity. Then I checked to make sure it wasn't shorting any nearby point that it wasn't suppossed to be connected to. As a result, and with a little luck, I didn't have any trouble.

It did take me a little bit longer to get all the components soldered down (probably a few extra hours), but that's better then trying to track down a wrong resistor value, especially since I'm color blind and have trouble distinguishing between the red and brown bands on a resistor, and sometimes yellow and orange.

Ole,

Great! I'm glad we got that sorted out!

Greg,

Yes, that is no doubt the best way to stuff pcb's - specially constructions that you're not quite familiar with.

:grin:

Jakob E.

Hi...


I'm having some problems here too...i tested pin 1 on the 072 and the threshold varied it between .002 and 3.0...or something like that.
At pin 7...12vdc...no variations with makeup...nothing at pin 8.

Attack switch makes a loud crack on the last position if jiggled...2 switches tried...

no compression...but signal is passing and make up works...nothing else
seems to work? lol Also...the overall level seems very low...i plugged the SSL into an insert and lost alot of level...

Any suggestions?

Thank you..

read through the "official" help thread. check, check, and check.

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!!

Please use the "official" help thread (look in the meta-meta) - this one is no good..

Jakob E.