GSSL HELP THREAD!!!

[Overmann]

Hi there,

Just a quick question:
I am missing a 120k resistor in my kit. I am wondering if I can use one of these:

https://www.kjell.com/no/produkter/elektro-og-verktoy/elektronikk/komponentsett/kjell-academy-motstandssortiment-1460-pk--p90435

I'm sorry if this is an offensively stupid question to anyone, but this is my first build that is not guitar boost pedal. I'm having fun so far, by the way! It's the specs of the ones I've linked to I am wondering about. Are those good for building audio equipment?

 

[gyraf]

Yes you can.
Also, you can use e.g. 100k+22k in series

Jakob E.

 

[Overmann]

Yes you can.
Also, you can use e.g. 100k+22k in series

Jakob E.

Great, Thanks! I already have 100k and 20k, so I won't have to buy this set to get the 120k then.
I can get back to work right away.

 

[Chader]

Hi everybody,

I have new insights on my mistake. I changed the transformer and measured the voltage at the end. I get the right tension on the end. Now I have installed the transformer and put it under tension.  One of the two 10 ohm resistors after the resitance bridge burned through.
I assumed a following error. So I replaced the resistance and what can I say. This burned again.
Can one help me? All components are in the right place.

Thanks
Sebastian

 

[Potato Cakes]

Hi everybody,

I have new insights on my mistake. I changed the transformer and measured the voltage at the end. I get the right tension on the end. Now I have installed the transformer and put it under tension.  One of the two 10 ohm resistors after the resitance bridge burned through.
I assumed a following error. So I replaced the resistance and what can I say. This burned again.
Can one help me? All components are in the right place.

Thanks
Sebastian

Are they all oriented correctly? Op amps/ICs backwards will do this. A solder bridge will do this. And a component not in the right place will do this.

Thanks!

Paul

 

[Chader]

Good morning,

All components are on the right place. The op‘s are correctly. I will check the ic‘s and solder Bridge these evening. The resistor is in the part for the power supply , right? So the failure must be in these part ?!

Thanks
Sebastian

 

[Gustav]

Good morning,

All components are on the right place. The op‘s are correctly. I will check the ic‘s and solder Bridge these evening. The resistor is in the part for the power supply , right? So the failure must be in these part ?!

Thanks
Sebastian

The 10R is part of a filter in the power supply.

A burn-out on it will occur if your current draw is excessive.

There can be a number of reasons for this, but a short circuit somewhere, a misplaced IC, a cap oriented the wrong way in the PSU section, or misplaced regulators could all cause this to happen.

Remove all ICs, then check if your supply voltages hold. If they do, place one IC at a time and check.

Could you show a few pictures of your build? Both top side with visible component placement, and bottom side to see the solder work?

Edit:Just saw Paul gave the exact same answer...carry on!

Gustav

 

[rivermAn]

hi, finished mounting all components but the sound that comes out of the device is incredibly distorted and the controls on the front panel don't seem to do anything to change the sound.  If I input a low volume signal, there is no sound. if I keep turning the volume up, the sound eventually goes full tilt into overdrive, clipping the input to my digital interface, without anything in between.
I have noticed that if i remove the ne5534s in the DBX 202 emulation stages, the distortion for each respective channel disappears and the output of the unit (for each channel) is reflective of the volume in the input.  For example, if I turn up the left input channel, the left output channel increases in volume. But the output is still very much louder than the input, and again the controls on the front panel do nothing to affect the sound or volume.
I did find a problem earlier on...the -12v rail was being shunted to GND because of a mis-solder. I fixed this one up and now all of the voltages are reading correctly. I've also been over the board and checked that all components are in the correct places, and that the balanced inputs are wired correctly.
Does anyone have any ideas? Was thinking of replacing all of the ICs..tried already to replace the NE5534s but no luck. I'd really like to understand more about what is causing the distortion and why the controls do nothing to affect the sound.
Thanks 

 

[Potato Cakes]

Check all your voltages with the ICs pulled. Then again with them in.

More than likely there is a bad/missing solder connection around your output ICs if the signal level is on maximum stun. Likely same for your VCA ICs. And pretty much any other problem here, including my first GSSL build.

Thanks!

Paul

 

[rivermAn]

Many thanks Paul!
I checked the voltages and they look ok..there are some slight deviations:

With all ICs removed, voltages are as expected.

With all ICS in, there are some slight deviations. TL074 is showing 22v across the rails (should expect 24v, right?). Also the THAT2181 that is used in only the Sidechain component (not the VCA emulation circuits) is showing 10v instead of the expected 12v between pin 7 and pin 2/6. Upon closer inspection there is a 5k1 resistor feeding pin 7 which could account for the voltage drop...but I can't see this 5k1 resistor on the schematic, which makes me anxious about using the schematic to diagnose problems.

To check the input/output components, I removed the THAT2181 chips and connected pins 1 and 8 (input and output). To my delight, it appears that both channels are outputting audio at the same levels as input, without distortion! The distortion is only present when I connect the THAT2181 chips. So I think that the input/output stages are ok.

My understanding of VCA emulation circuit is that the NE5534 modulates the output of the THAT2181. When I remove NE55334, the THAT2181 seems to boost the output signal by maybe 10x or more (purely a guess here as I haven't checked the dB levels). Is this to be expected?

I will replace the TL074 chip tomorrow and let you know how I go.
In the meantime, if you have any other ideas please drop a line!
Thanks 

 

[rivermAn]

Hi again, no luck with the TL074 replacement.
So to clarify what I said yesterday, when I remove the TL072 and short pins 1 and 8 on the VCA in DBX202 emulation stages, it passes signal (with the THAT2181 VCA chips removed...).
Have been over the board many times to check for shorts.
It's true that the lorlin switches are symmetrical and can thus be mounted any way, correct?
I am finding that the voltages on pins 1 and 7 for the TL072, which control the threshold and makeup (I think that's right?) are not changing when I alter the positions of these pots.
My suspicion is that something is up with the sidechain stage.
When I keep the THAT2181 chips in but remove NE5534 from the DBX202 emulation stage, I find that the audio has a large output (many times amplified relative to the original input signal) and this behaviour is consistent across both channels.
I have tried swapping THAT2181 chips across left VCA/right VCA/sidechain with no luck.
So maybe they're all fried.
Can anyone suggest some tests to pinpoint the problem?
thanks !

 

[vixo]

Hi guys, dropping in at a pretty late stage on this thread so I apologise if this has been asked already...

I am debugging a GSSL kit with the super sidechain mod for a friend, the guy who built it sadly passed away. There is clearly something wrong in the envelope detection circuit, the ratio makes very little difference and behaves very strangely

However at the moment though im just trying to work out - what are all those resistors marked as %? I cant see any reference to them anywhere in the documents

 

[Gustav]

Hi guys, dropping in at a pretty late stage on this thread so I apologise if this has been asked already...

I am debugging a GSSL kit with the super sidechain mod for a friend, the guy who built it sadly passed away. There is clearly something wrong in the envelope detection circuit, the ratio makes very little difference and behaves very strangely

However at the moment though im just trying to work out - what are all those resistors marked as %? I cant see any reference to them anywhere in the documents

They are to be omitted, if you are using the 2180 VCAs.

Gustav

 

[vixo]

They are to be omitted, if you are using the 2180 VCAs.

Gustav

thanks! are there exceptions to that? this has some wire links and resistors in the place of some of those % resistors - see attached image

I fixed a few things and now it now all seems to work fine except the ratio - If i have a gain reduction of 5db at 2:1 ratio, then i change it to 4:1, i should increase to 7.5dB reduction, is this correct? Changing the gain ratio from 2:1 to 4:1 always REDUCES the gain reduction by about 2dB, whatever the original gain is..  i can't quite follow the logic of the design with the envelope being fed back to the VCA controlling the sidechain amplitude so I'm having trouble being able to say exactly how this circuit should work and troubleshooting it

 

[Gustav]

thanks! are there exceptions to that? this has some wire links and resistors in the place of some of those % resistors - see attached image

I fixed a few things and now it now all seems to work fine except the ratio - If i have a gain reduction of 5db at 2:1 ratio, then i change it to 4:1, i should increase to 7.5dB reduction, is this correct? Changing the gain ratio from 2:1 to 4:1 always REDUCES the gain reduction by about 2dB, whatever the original gain is..  i can't quite follow the logic of the design with the envelope being fed back to the VCA controlling the sidechain amplitude so I'm having trouble being able to say exactly how this circuit should work and troubleshooting it

I'd have to dig out the schematic to see what the marked jumpers/resistors are in circuit. It seems you are able to read a schematic, so you could do hat yourself. I would just cut them.

Ratio switch changes threshold as well as ratio...

Gustav

 

[vixo]

Ratio switch changes threshold as well as ratio...

ok, if that is the case if there is anyone who can give me an idea of how much the different ratio settings should change the dB attenuation?

 

[gyraf]

No simple answer to that, you need to read and understand the circuit. Alternatively read closely through this thread.

 

[liquidcolor]

I've just sent the SSL gerbers to a board house to start a new project now that i have some spare time (two young children.) The board house has informed me that the drill file is incorrect, all drill sizes are identical.  Is it correct that I've told them to manually input the sizes from Tools.txt? Anyone else have this problem? Thanks.

 

[gyraf]

Who made your ssl gerber files?

 

[Potato Cakes]

No simple answer to that, you need to read and understand the circuit. Alternatively read closely through this thread.

What Jakob said.

You will find that changing the ratio affects the threshold.

I've said too much!

Thanks!

Paul