GSSL HELP THREAD!!!

[thedug]

My ssl is cose to working. Only the left ch. is acting funny.
It pretty much has 0 output.

The left ch. 5534 show unity gain. 1.3volts in and 1.3 volts out.
I swapped 5534s and teh problem stayed on the left channel.

What is wierd is that the meter reads the same with the same signal on either input.

I didn't really see any signal on the 5532 on ch. 1

d./

 

[gyraf]

[quote author="thedug"]What is wierd is that the meter reads the same with the same signal on either input.
[/quote]

Which means that the input circuits and the sidechain are working well.

Your problem can be found in the vca or output section in the silent channel.

Jakob E.

 

[thedug]

So I shouldn't get hung up on the unity gain on the 5534?

Should I keep tracking the signal through the "signal path" part?

d./

 

[radiance]

My second SSL clone is passing audio, but way too loud, to the point that it distorts. It is not compressing but the make up pot seems to work (a few db extra gain, that's all) and the threshold seems to do the same thing as the make up pot. In bypass mode the ssl still distorts but both the make up and threshold pot don't affect the volume (that's a good thing I suppose..).

I did check the following:
When both VCA's are removed and pin 1 is wired to pin 8 the ssl passes audio OK (it's not distorting) so I guess the input and output sections are OK.

I swapped all chips to my working ssl and they all seem to be OK.

All diodes are working (desoldered and tested them) and put in the right way.

So far I can't find any short's.

Meassured almost all resistors but could not find anything wrong.

I'm really clueless about what is wrong.
Thanks in advance.

 

[thedug]

Ok....

After much probing with my oscope, I couldn't really understand this...

I decided to swap the vcas to see what would happen. Well the problem with 0 output followed the vca. So.. it appears that I have a vca.

But upon tracing the circuit I found a few interesting things.

1) the 1k signal I was sending in went through the input stage to teh 15k resister, but then on the other side of the 15k at pin 1 of the 2150, it disappeared!
2) the signal didn't show on any pins of the 5532 until pin 7, the output!

Last, I had some more vcas that I had ordered for building other units, these are the 2180s I seemed to remember that you didn't want to mismatch the channel vca so I put in 2 2180s and left the sidechain a 2150. Is this ok?

BTW: The unit seems to work. If I turn the threshold all the way down, the VU pegs and I get a saw wave. Does this sound right?

d./

 

[thedug]

[quote author="gyraf"]

When using the trimmerless 2180, simply leave out the trimmers (and possibly the two 1M resistors between trimmer and VCA)

[/quote]

Hey, I just poped in 2180LB, can I remove the distortion trim too?

Looks like just taking the 1M resister out would disable it. Is it advised to take the trimmer out too?


Also, I just found this thread on the pricing, http://www.groupdiy.com/index.php?topic=379&postdays=0&postorder=asc&highlight=2180&start=30

The LA is quite a bit more expensive than teh LB. Is it preferable?

 

[gyraf]

[quote author="thedug"] ..1) the 1k signal I was sending in went through the input stage to teh 15k resister, but then on the other side of the 15k at pin 1 of the 2150, it disappeared!
2) the signal didn't show on any pins of the 5532 until pin 7, the output![/quote]

The 2150-series VCA's are current-in current-out devices. No voltage change on it's input and output termonals when it's working correctly

BTW: The unit seems to work. If I turn the threshold all the way down, the VU pegs and I get a saw wave. Does this sound right?

No. Check for shorts to pot wiper either on the main or the control board.

[quote author="thedug"]Hey, I just poped in 2180LB, can I remove the distortion trim too? Looks like just taking the 1M resister out would disable it. Is it advised to take the trimmer out too?
[/quote]

No need to remove the trimmer, just the 1M resistor.

The LA is quite a bit more expensive than teh LB. Is it preferable?

Not much. Depends on your ambitions. I get no audible difference - but inb theory it should be better.

 

[thedug]

[quote author="gyraf"]
The 2150-series VCA's are current-in current-out devices. No voltage change on it's input and output termonals when it's working correctly
[/quote]

So is there a way to "trace" through "virtual ground" stuff? Is there a way to know this? Cuz I was sure something was wrong last night.. ;P I.E. What distinguishes that something is a current-in current-out device

[quote author="gyraf"]
No. Check for shorts to pot wiper either on the main or the control board.
[/quote]
Actually, no shorts, but I did realize that I had the release set to position 6, only letting the release be pos. 1-5 got rid of the saw. Now, the pegged meter is prolly cuz it is a VU meter... See my next post about sourcing a VU that will work.

Also, it was really mind opening to watch the oscope as I changed the threshold with slow release/attack. Pretty cool.

Also, is it ok to use a 2180 in the audio section and a 2150 in the sidechain, or should I try to make them all the same?

 

[thedug]

The vu meter I have was sourced by a friend, it is the sifam AL19, which is a vu meter. Could this be causing my problems?

The thing is too big anyway, would this meter work?
Mouser Part: 541-ME-DMA-001

NRG's scale looks nice. Does anybody have a scale for the rectangular style vu?

 

[radiance]

[quote author="radiance"]My second SSL clone is passing audio, but way too loud, to the point that it distorts. It is not compressing but the make up pot seems to work (a few db extra gain, that's all) and the threshold seems to do the same thing as the make up pot. In bypass mode the ssl still distorts but both the make up and threshold pot don't affect the volume (that's a good thing I suppose..).

I did check the following:
When both VCA's are removed and pin 1 is wired to pin 8 the ssl passes audio OK (it's not distorting) so I guess the input and output sections are OK.

I swapped all chips to my working ssl and they all seem to be OK.

All diodes are working (desoldered and tested them) and put in the right way.

So far I can't find any short's.

Meassured almost all resistors but could not find anything wrong.

I'm really clueless about what is wrong.
Thanks in advance.[/quote]

I forgot to mention that the +15v/-15v and +12v/-12v are all there so the power suply seems to be OK.

 

[gyraf]

Radiance,

Try tracing the signal through the sidechain - and look out for wrong-value resistors..

Jakob E.

 

[radiance]

I meassured all the resistors in the sidechain and their values where OK.

I also meassured the pins off both the TL072 and the TL074 for DC with no signal present and in bypass mode.
I got these values:

TL072

Pin 1=3,4v DC
Pin 7=4,1v DC


TL074

Pin 1=0,177v DC
Pin 7=0v DC
Pin 8=0,0013v DC
Pin 14=0,37v DC

At point C in the circuit I meassured 0,039v DC.

 

[gyraf]

Rad,

Look through - and try to understand - the schematic. There's a circuit description on the gyraf page.

This will help you a lot with troubleshooting

TL072 pin1 changes with threshold + signal level
TLo72 pin7 changes with makeup + signal level

TL074 pin14 changes with ratio + signal level

Jakob E.

 

[radiance]

Thanks Jakob, and I found the problem.
It happened to be a short between pin 2 and 6 of the TL072.
What I did not understand was why I was getting DC at pin 7 from the TL072 while the unit was in bypass mode and there was no make up bridge. I starded to meassure continuity between the pins from the TL072 and found the problem.
This nearly drove me nuts so I'm very happy the problem is solved.
During the proces I fried one VCA but I really don't care right now.

Thanks!

 

[gyraf]

I'm happy we got that sorted...!

:thumb:

Jakob E.

 

[thedug]

Is it ok to us 2180s in the audio section and a 2150 in the sidechain?

If so, are there any drawbacks to doing this?

 

[gyraf]

Yes it is.

- I think we've already answered this earlier..?

Jakob E.

 

[PabloJn]

about the +/- input connection difference between schematic and pcb ...

[quote author="gyraf"]Pablo,

Don't worry about that - it's a minor schematic error.

The PCB's are known working.

Jakob E.[/quote]

Are you sure the error is not in the pcb :?:

my ssl clone is phase reversed if I connect the inputs as in the pcb is marked...

if I sum the dry input with the signal throught the compressor in bypass I have a null signal...


I have another problem: my ssl clone gain up a +6 db in bypass.
I'm working balanced.

Is it ok :?:

 

[gyraf]

Yes, I'm sure there's not an error on the pcb.

Jakob E.

 

[keithcamilleri]

hi guys,

has anyone got or had a problem with an ssl phasing? One of my ssls is phasing, I've redone the exact same wiring as the one working ok but the problem is still there. Was wondering if anyone had a problem like this... :roll:


cheers