GSSL Finished - Sounds bad :-(

[chrissugar]

Did you check the voltages for the 5532 pins?

chrissugar

 

[Hulk]

Yes I did check the voltage on the output 5532 and it had the values you stated so they should be ok right??

The SSL passes audio without any kind of distortion with the channel VCA's pin 1+8 connected so that's ok too - hmm this is getting really intersting!

 

[chrissugar]

Now we know that the ballanced input receivers and output drivers work properly. The problem is now isolated to the VCAs and the sidechain.
If both channels with the VCAs inserted in the sockets distort identically, it looks like the problem is from the sidechain. Hmm. All the chips from the sidechain are also soldered or socketed?

chrissugar

 

[chrissugar]

Are you sure you put the diodes (1n4148) in the sidechain in the right direction?
Put back the VCAs and measure votages at:

Ch1 VCA pin7 +15V
Ch1 5534 from DBX emulation circuit, pin7 +12V, pin4 -12V
Ch2 VCA pin7 +15V
Ch2 5534 from DBX emulation circuit, pin7 +12V, pin4 -12V

Sidechain VCA pin7 +12V
Sidechain TL074 pin4 +12V, pin11 -12V
Sidechain TL072 pin8 +12V, pin4 -12V

chrissugar

 

[Hulk]

I have tried to replace the 3 THAT2180lb's with 3 new ones but that does not make a difference.
Could it be the TL072 or TL074 that has to be replaced I'll measure them now!

 

[Hulk]

OK the sidechain VCA, TL072 and TL074 had the measures you stated so they must be ok!

The right and left channel VCA's pin 7 both had +15V but the two channel 5534 showed:

Right channel 5534:
pin 4: -15.11V
pin 7: +14.83V

Left channel 5534:
pin 4: -15.11V
pin 7: +14.83V

??

 

[chrissugar]

Oh, it is probably right, i don't have a SSL compressor at hand so I'm looking at the schematic and maybe on the PCB the 5534 have +15/-15V power.
Are you sure the diodes are in the right direction?

chrissugar

 

[chrissugar]

Forgot to say that if you changed the VCAs with some new ones and they behave identically it is clear that the problem is in the sidechain.

chrissugar

 

[Hulk]

hhmmm I have put in the diodes in the right direction this is strange. I have made two very short drum recordings (2 x 312KB mp3) - one with out the SSL and one with the SSL on the drum bus.

This is the version with out the SSL

This is the SSL version. The settings are:

Ratio: 4:1
Thres: 12 o'clock
Attack: 0.3 msec (position 2)
Release: 0.6 sec. (position 4)
No makeup
Gain Reduction on the meter is between 1-2.5 dB!!

The SSL version sound hideous :?

 

[matthias]

check the direction of the sidechain vca... !!
pin 1 is on the other side as pin one of the channel vcas !!!!!

 

[Hulk]

Hi Matthias

The sidechain vca is turned opposite of the channel vca's so that's not the problem - I running out of ideas - any suggestions??

 

[chrissugar]

I listened to the samples and it is clear that something is wrong.
If you rotate the threshold pot for no gain reduction the sound is still distorted? How it sounds if you put the switch in bypass?

chrissugar

 

[matthias]

you are using the 2180, did you left out the distortion trimmers??

 

[radiance]

Check for shorts between pin 2 and pin 6 of the TL072, somewhere near the 620K and the 100K resistor.
Once I had a very tiny short there which made the signal sound distortorted, a bit like yours....

 

[Hulk]

In bypass it sound ok no distortion.

If I go for faster attack it distorts even more so with slow attack and very little threshold it sound ok but then there not really much compression (if any) taking place!

 

[gyraf]

There is a wire link at the front-panel control board - just above where the cable to the main board connects. Make sure that this wire link is soldered in.

If that is not the problem, check control pcb for shorts, and chack cabling between pcb's..

Jakob E.

 

[Hulk]

I'm using 2180LB and I did not put any trimmer in but I put in all the resistors "around" the trimmer??

 

[gyraf]

The trimmers is not the problem if it sounds right in bypass..

 

[matthias]

sorry, I mixed up the numbers... the 2180 is already pretrimmed..

 

[Svart]

just a thought.. are you close by any of the other members of the forum? maybe you could send it to them for a second opinion? I ALWAYS have someone else look at my stuff if i have a hard time figuring out what is wrong.. sometimes it takes a new set of eyes to see the problem..


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