GSSL HELP THREAD!!!
- Thread starter hairyandy
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Help Support GroupDIY Audio Forum:
Caps,
Trace audio signal through the unit as suggested somewhere in this thread.
The 78/7915 will get hot - but if they still give you the needed +/- 15V, then all is well. They will shut down temporarily if they get too hot - amd you'll notice that for sure
Jakob E.
Trace audio signal through the unit as suggested somewhere in this thread.
The 78/7915 will get hot - but if they still give you the needed +/- 15V, then all is well. They will shut down temporarily if they get too hot - amd you'll notice that for sure
Jakob E.
johnpinker
Member
I'm having soome GSSL issues and could use some help to figure out where to proceed in troubleshooting...
It passes audio and compresses (but way too much) and the threshold pot doesn't seem to have any effect.
I have been through this thread (but it is long enough where I might have missed something) and performed the standard checks. I.E. checking components and values, looking for solder bridges, etc. Supply voltages look good as well...
The treshold pot is getting what looks to be correct voltages... Turn it all the way up and I have -12v at the center leg and this does travel to the main board and appear at one side of the 220K connected to the TL072 (close to 0v on the other side).
Does anyone have any ideas of what to look at next or where to specifically trace things?
It passes audio and compresses (but way too much) and the threshold pot doesn't seem to have any effect.
I have been through this thread (but it is long enough where I might have missed something) and performed the standard checks. I.E. checking components and values, looking for solder bridges, etc. Supply voltages look good as well...
The treshold pot is getting what looks to be correct voltages... Turn it all the way up and I have -12v at the center leg and this does travel to the main board and appear at one side of the 220K connected to the TL072 (close to 0v on the other side).
Does anyone have any ideas of what to look at next or where to specifically trace things?
..trace voltages through the sidechain, to the sc vca.. a guess gould be a wrong resistor value..
johnpinker
Member
[quote author="gyraf"]..trace voltages through the sidechain, to the sc vca.. a guess gould be a wrong resistor value..[/quote]
Thanks... that's exactly what it was...
I'd already checked everything twice, but evidentally 3 times IS the charm...
Thanks... that's exactly what it was...
I'd already checked everything twice, but evidentally 3 times IS the charm...
tommypiper
Well-known member
Jakob,
I had to take a month away from this because it was so depressing.
OK, so now I'm testing again and I have to ask more questions.
http://i82.photobucket.com/albums/j243/tommypiper/GSSLSchemNumberParts.gif
I cut the CV at R10 just before it enters the audio VCA. The distortion immediately disappeared. (Yes, I'm using DBX 2001.) Toggled it on and off and it turned compression and distortion on and off. Make up gain had worked fine. So this means:
[quote author="gyraf"]
If all this is well, we now know that it's in the sidechain rectifier and timing that there is a problem. Jakob E.[/quote]
Yes.
[quote author="gyraf"]
The rectifier part simply makes a single-polarity signal from the incoming audio, and this is fed through a diode to a (tantalum) timing capacitor. Jakob E.[/quote]
Where is that timing capacitor? Do you mean one of the many caps in the Release circuit?
[quote author="gyraf"]A resistor in series with the diode decides attack time, and a resistor in parallel with the capacitor (to ground) decides release time. This A/R circuit forms kind of a low-pass filter which should even out any dirt (i.e. high-frequency content) from the sidechain CV voltage.Jakob E.[/quote]
Yes. On longer release settings the distortion goes away. This appears to confirm that it's AC or noise in the CV. The A/R circuit is filtering the noise, as you say.
[quote author="gyraf"]So you need to check what sort of voltages are present at the A/R capacitor - and to verify that this voltage is also present at the output of the high-Z buffer opamp that immideately follows the A/R circuit.E.[/quote]
Are you referring to connection point "D" on the schematic? And Pin 8 on the TL074? Can you be specific, please?
[quote author="gyraf"]In any case, check and recheck components, soldering, and inter-board connection - problem could very well be on the control board or in connection. Jakob E.[/quote]
Yes, I've been doing this 1,000 times over 5 months now and I can't find anything.
Can you, or someone, look at my posts on page 121 and please verify the voltages that I am seeing? I don't have access to a working unit, so I don't know what voltages I am supposed to see. What is right? What is wrong in those voltages?
I had to take a month away from this because it was so depressing.
OK, so now I'm testing again and I have to ask more questions.
http://i82.photobucket.com/albums/j243/tommypiper/GSSLSchemNumberParts.gif
I cut the CV at R10 just before it enters the audio VCA. The distortion immediately disappeared. (Yes, I'm using DBX 2001.) Toggled it on and off and it turned compression and distortion on and off. Make up gain had worked fine. So this means:
[quote author="gyraf"]
If all this is well, we now know that it's in the sidechain rectifier and timing that there is a problem. Jakob E.[/quote]
Yes.
[quote author="gyraf"]
The rectifier part simply makes a single-polarity signal from the incoming audio, and this is fed through a diode to a (tantalum) timing capacitor. Jakob E.[/quote]
Where is that timing capacitor? Do you mean one of the many caps in the Release circuit?
[quote author="gyraf"]A resistor in series with the diode decides attack time, and a resistor in parallel with the capacitor (to ground) decides release time. This A/R circuit forms kind of a low-pass filter which should even out any dirt (i.e. high-frequency content) from the sidechain CV voltage.Jakob E.[/quote]
Yes. On longer release settings the distortion goes away. This appears to confirm that it's AC or noise in the CV. The A/R circuit is filtering the noise, as you say.
[quote author="gyraf"]So you need to check what sort of voltages are present at the A/R capacitor - and to verify that this voltage is also present at the output of the high-Z buffer opamp that immideately follows the A/R circuit.E.[/quote]
Are you referring to connection point "D" on the schematic? And Pin 8 on the TL074? Can you be specific, please?
[quote author="gyraf"]In any case, check and recheck components, soldering, and inter-board connection - problem could very well be on the control board or in connection. Jakob E.[/quote]
Yes, I've been doing this 1,000 times over 5 months now and I can't find anything.
Can you, or someone, look at my posts on page 121 and please verify the voltages that I am seeing? I don't have access to a working unit, so I don't know what voltages I am supposed to see. What is right? What is wrong in those voltages?
yes. these tatalum caps gets charged (to a neg. voltage) through the diode in the sidechain, and then discharged over a set time by their associated parallel resistors.
In a compressor, there will always be distortion at relatively fast timing at relatively low frequencies. You're sure that this is not what you're measuring? What I mean is, you test the unit with music, not low-frequency tones, right?
When you measure at the timing capacitors, you should see a voltage that rises more-or-less instantly, and then fades out slowly. This is what shows at the meter as well. This voltage is added in with the makeup-gain voltage to control the VCA's.
Your problem should probably be found after the last diode in the sidechain rectifier, and before adding the timed signal to the threshold/makeup voltages. With the correct value components (and correct orientation of the tantalum caps!) error possibilities should be limited.
- double-check orientation and integrity of the diode just before the bypass switch.
- double-check wireing of the bypass switch.
- double-check value of the 3M3 resistor at the input of the timing buffer.
- double-check component values, orientation and wireing of the timing circuit.
There's still 95% chance that your problem is wrong component, orientation, wireing, or a pcb trace short. Check and recheck.
Jakob E.
dufo
Well-known member
I dont believe I have seen this problem, I think... :grin:
When increasing make up gain, in the LAST QUARTER of available gain on the knob the left output increases more than the right. The left ends up being higher by about 7db or so. However, up UNTIL the last bit of make up gain, both channels increase together the same.
Have done the 15K - 27 K job.
Triple checked for shorts.
Checked component values and orientation.
Changed make up pot 3 times.
Checked all wiring and changed out 5532's and 5534's.
Any ideas ?? Or can anyone confirm this happens to their unit? Thanks alot! :thumb:
When increasing make up gain, in the LAST QUARTER of available gain on the knob the left output increases more than the right. The left ends up being higher by about 7db or so. However, up UNTIL the last bit of make up gain, both channels increase together the same.
Have done the 15K - 27 K job.
Triple checked for shorts.
Checked component values and orientation.
Changed make up pot 3 times.
Checked all wiring and changed out 5532's and 5534's.
Any ideas ?? Or can anyone confirm this happens to their unit? Thanks alot! :thumb:
The sidechain is mono. The makeup-gain is mono, controlling both VCA's.
So your error must be at the audio vca sections, after sidechain processing. (only execption is if one of the output drivers don't work below a certain level - verify that both + and - outputs are working right on both channels)
Try swapping the two audio VCA's to check for their integrity. Then recheck all parts around the two audio VCA's, including their CV-driving 5534's - possibly measuring dc voltages at the control-voltage input at both.
Jakob E..
byoung
Well-known member
I've finished my SSL, seems to be working, but now I have a question. If I'm feeding the comp a sine wave 1000hz at 0db into the ssl, and I have the comp set at threshold of 0, and 1:2 ratio, fast release, fast attack, makeup set to 0, what should I be measuring in db at the output? I just want to be sure everything is as it should be.
Also take into account I have not done the unity mod and I have not added the 47K resistor to the the threshold pot(I'm sure those make a difference in the output)
But it would be nice to know also what the db measurement should be if I had those two mods(unity, 47k on threshold)?
Also take into account I have not done the unity mod and I have not added the 47K resistor to the the threshold pot(I'm sure those make a difference in the output)
But it would be nice to know also what the db measurement should be if I had those two mods(unity, 47k on threshold)?
tommypiper
Well-known member
Jakob,
I worked on it with the scope. I got some very strange readings with the scope and then things went to hell. I can post pictures on here if you like. I could see the distortion as jagged activity within the wave on short release setting. Longer release and it smoothed out. As expected.
But then I found that the ratio switch was effecting this more than the release. So I wondered, is the distortion coming from the ratio circuit?
I took many readings, and photos of the waveforms.
Finally worked my way upstream looking for a clean control voltage without distortion. I could not find it. Even at Pin 7 of the TLo74 there was distortion in the control voltage. The weird thing was, changing the ratio changed the distortion way up stream here at Pin 7! How can that be?? It's not in the circuit??
Double checking, making more readings, I tried to find a clean CV. I checked Pin 8 of the 2151 VCA, dead! Then I checked the audio path. Dead!
I turned off the sine wave. At this time I noticed the compressor meter was going from zero to full scale in a burst about every 2 seconds. I checked to see if I could hear it, nothing. Nothing on the scope either. The whole board went berzerk!
I can't find what is wrong. What makes the meter jump like that?
Voltages are OK all around the board, (except my 15 is spread from +14.7 to -15.2, half a volt apart, is that OK)?
I notice the meter is showing a small amount of gain reduction when power is on, with no signal. What the hell...? Then on the next power up it does the jumping to full scale thing again instead... ???
Any clues?
I no longer have a board that passes audio at all. I really don't understand why this board hates me so much. :evil: The guy who built it must have put a hex on it, or on me, because it has had over a dozen problems.
Can you suggest what to do to figure out how to get the board passing audio again? It seems to be a global problem on the board because of the meter freaking out, plus no audio, but all voltages are normal.
I'm in deep trouble.
I worked on it with the scope. I got some very strange readings with the scope and then things went to hell. I can post pictures on here if you like. I could see the distortion as jagged activity within the wave on short release setting. Longer release and it smoothed out. As expected.
But then I found that the ratio switch was effecting this more than the release. So I wondered, is the distortion coming from the ratio circuit?
I took many readings, and photos of the waveforms.
Finally worked my way upstream looking for a clean control voltage without distortion. I could not find it. Even at Pin 7 of the TLo74 there was distortion in the control voltage. The weird thing was, changing the ratio changed the distortion way up stream here at Pin 7! How can that be?? It's not in the circuit??
Double checking, making more readings, I tried to find a clean CV. I checked Pin 8 of the 2151 VCA, dead! Then I checked the audio path. Dead!
I turned off the sine wave. At this time I noticed the compressor meter was going from zero to full scale in a burst about every 2 seconds. I checked to see if I could hear it, nothing. Nothing on the scope either. The whole board went berzerk!
I can't find what is wrong. What makes the meter jump like that?
Voltages are OK all around the board, (except my 15 is spread from +14.7 to -15.2, half a volt apart, is that OK)?
I notice the meter is showing a small amount of gain reduction when power is on, with no signal. What the hell...? Then on the next power up it does the jumping to full scale thing again instead... ???
Any clues?
I no longer have a board that passes audio at all. I really don't understand why this board hates me so much. :evil: The guy who built it must have put a hex on it, or on me, because it has had over a dozen problems.
Can you suggest what to do to figure out how to get the board passing audio again? It seems to be a global problem on the board because of the meter freaking out, plus no audio, but all voltages are normal.
I'm in deep trouble.
To get the board passing audio, remove vca's (you socket'ed them, right?) and put in a wire from input to output pin. this bypasses vca's, and enables you to troubleshoot audio path.
- make sure that not only your +/-15V are alright, but also your +/-12V.
- there will always be some ac signal "on top" of your CV - it is just a matter of how much. slower attack/release decreases amount of ac riding on top of the CV - but will not completely remove it (unless timing is infinitely long)
- recheck integrity, value, and orientation of your timing tantalums
- recheck value of the 3M3 bias resistor at the timing buffer
- try reading the schematic and understanding what it does - there's a short explanation on the gyraf page. this will help you a lot in troubleshooting.
- find the VCA data sheets and application notes to get an understanding of how these work.
Jakob E.
- make sure that not only your +/-15V are alright, but also your +/-12V.
- there will always be some ac signal "on top" of your CV - it is just a matter of how much. slower attack/release decreases amount of ac riding on top of the CV - but will not completely remove it (unless timing is infinitely long)
- recheck integrity, value, and orientation of your timing tantalums
- recheck value of the 3M3 bias resistor at the timing buffer
- try reading the schematic and understanding what it does - there's a short explanation on the gyraf page. this will help you a lot in troubleshooting.
- find the VCA data sheets and application notes to get an understanding of how these work.
Jakob E.
JerryPbury
Well-known member
Hi,
I just finished populating my GSSL board and have a small issue. Anybody else using 202's and having a problem mounting them?
The holes are undersize but I can drill them out.
The bigger problem is the distortion trimmers being in the way.
Did you just mount them on the other side of the board (trimmers)?
I found this question asked by someone else in the help file but it was never answered.
I have seen several pictures of other people using the 202's but no comments as to mounting.
These are the older 202's, (no letter) the pins seem to be original but just not long enough to allow me to install without interfering with the trimmers.
Thanks,
Jerry
I just finished populating my GSSL board and have a small issue. Anybody else using 202's and having a problem mounting them?
The holes are undersize but I can drill them out.
The bigger problem is the distortion trimmers being in the way.
Did you just mount them on the other side of the board (trimmers)?
I found this question asked by someone else in the help file but it was never answered.
I have seen several pictures of other people using the 202's but no comments as to mounting.
These are the older 202's, (no letter) the pins seem to be original but just not long enough to allow me to install without interfering with the trimmers.
Thanks,
Jerry
Greg
Well-known member
I bought some pins and sockets... like the ones used for mounting discrete opamps. I also had to drill out the holes a little bit to get them to fit. Once the sockets are in place, it'll raise the VCAs above the trimmers.
matta
Well-known member
Hi Folks,
Well I have just built an SSL and all seems well in that it powers up, passes audio and compresses when switched in, so I guess there is 95% of the battle won right there... but... I'm getting a SLIGHT hum...
I have grounded it as per Jakob's recommendation, Pin 1's on the input XLR's go to my Star Ground, and the IEC Earth goes there as well, no other ground connections.
At first I thought it was the toroidal transformer so I took it out of the box, it still hums, I rotated it, it still hums... even tried a Ecore type... no go... hum is still there... It seems it isn't a ground related hum as it's peak is around 100Hz.
I've uploaded a clip here: http://www.matt-allison.com/diy/ssl/SSL_Hum.wav (1.1MB)
It starts off with the the unit bypassed and then switched in with Make-Up Gain FULL (+20dB) and then swept back down to -0dB. No signal was present and it connected to my balanced patch bay into the +4dBu input on my Digi002R with the faders set to 0dB and bounced down at that as well.
I have modded the board to be set at unity with the 27K Resistors in place of the 15K's and also done the mod RE the THAT sub datasheet and using 2180LB's.
The hum/noise is present on the outputs even without the ratio board connected...
I've seen some folks comment on hum issues before and it seems there was never a definitive answer or come back RE this issue. I know of one Forum member who built a dedicated PSU and it solved the issue, I'm just wondering if anyone has come up against this as well...
Do you just live with it? Or have you been able to lower it? I'm guessing it PSU related? There is no extra load on the PSU, no LED's connected etc and all voltages check out fine... just weird...
Anyone care to try replicate my test and see if this happens to you as well?
Any suggestions, ideas or tips?
Cheers
Matt
Well I have just built an SSL and all seems well in that it powers up, passes audio and compresses when switched in, so I guess there is 95% of the battle won right there... but... I'm getting a SLIGHT hum...
I have grounded it as per Jakob's recommendation, Pin 1's on the input XLR's go to my Star Ground, and the IEC Earth goes there as well, no other ground connections.
At first I thought it was the toroidal transformer so I took it out of the box, it still hums, I rotated it, it still hums... even tried a Ecore type... no go... hum is still there... It seems it isn't a ground related hum as it's peak is around 100Hz.
I've uploaded a clip here: http://www.matt-allison.com/diy/ssl/SSL_Hum.wav (1.1MB)
It starts off with the the unit bypassed and then switched in with Make-Up Gain FULL (+20dB) and then swept back down to -0dB. No signal was present and it connected to my balanced patch bay into the +4dBu input on my Digi002R with the faders set to 0dB and bounced down at that as well.
I have modded the board to be set at unity with the 27K Resistors in place of the 15K's and also done the mod RE the THAT sub datasheet and using 2180LB's.
The hum/noise is present on the outputs even without the ratio board connected...
I've seen some folks comment on hum issues before and it seems there was never a definitive answer or come back RE this issue. I know of one Forum member who built a dedicated PSU and it solved the issue, I'm just wondering if anyone has come up against this as well...
Do you just live with it? Or have you been able to lower it? I'm guessing it PSU related? There is no extra load on the PSU, no LED's connected etc and all voltages check out fine... just weird...
Anyone care to try replicate my test and see if this happens to you as well?
Any suggestions, ideas or tips?
Cheers
Matt
Greg
Well-known member
matta:
My first hunch is PSU ripple... you measure that yet?
My first hunch is PSU ripple... you measure that yet?
matta
Well-known member
Hey Greg,
Thanks for the heads up. I suspect this as well... only problem is BOTH units respond in the same way? Is there typically a problem with PSU ripple on the GSSL's?
Have you had to change anything on your units to lower the ripple? What would be the best way to check the ripple, I'll be honest and say though I've got a scope, I've not tried to check for DC ripple before... any advise?
Cheers
Matt
Thanks for the heads up. I suspect this as well... only problem is BOTH units respond in the same way? Is there typically a problem with PSU ripple on the GSSL's?
Have you had to change anything on your units to lower the ripple? What would be the best way to check the ripple, I'll be honest and say though I've got a scope, I've not tried to check for DC ripple before... any advise?
Cheers
Matt
tommypiper
Well-known member
Jakob,
I had a bad +15v regulator, that's why the board freaked out last week. Strange, it's the third regulator to go out... And they all broke to put out negative voltage... (I hope I didn't destroy my dbx 2001s.)
Does it matter what caps to use for the big PS 1000/35v? I have Nichicon audio caps there because I didn't have the ones I normally use in power supplies. Any working audio cap should be fine there, right? I'm just wondering why my 15v regulators are switching polarity... ?
A design question: I am showing +12.8 on Pins 1 and 8 of the 5534. These pins are NOT shown on the schematic. Is it correct to have voltage on them?
My friend Matt had +12 on Pin 1 and -12 on Pin 8, 5534s. Is that correct?
I am showing + on BOTH pins. Which is correct?
And it's +.8v higher than my 12v rail. :?
(It's not a 12v rails problem, as I have + and -12v showing fine on the rest of the board. Also, these voltages on Pins 1 & 8 only show when the chips are in place. There is no voltage in the naked sockets on Pins 1 & 8. So this must mean the chips are passing the voltage on to these pins? Do I have the correct polarities?)
My board is hexed.
I had a bad +15v regulator, that's why the board freaked out last week. Strange, it's the third regulator to go out... And they all broke to put out negative voltage... (I hope I didn't destroy my dbx 2001s.)
Does it matter what caps to use for the big PS 1000/35v? I have Nichicon audio caps there because I didn't have the ones I normally use in power supplies. Any working audio cap should be fine there, right? I'm just wondering why my 15v regulators are switching polarity... ?
A design question: I am showing +12.8 on Pins 1 and 8 of the 5534. These pins are NOT shown on the schematic. Is it correct to have voltage on them?
My friend Matt had +12 on Pin 1 and -12 on Pin 8, 5534s. Is that correct?
I am showing + on BOTH pins. Which is correct?
And it's +.8v higher than my 12v rail. :?
(It's not a 12v rails problem, as I have + and -12v showing fine on the rest of the board. Also, these voltages on Pins 1 & 8 only show when the chips are in place. There is no voltage in the naked sockets on Pins 1 & 8. So this must mean the chips are passing the voltage on to these pins? Do I have the correct polarities?)
My board is hexed.
Tommy,
Pins 1 and 8 on the 5534's are compensation pins (look up the data sheet!) and should be ignored if not used.
For the 7815 regulator, as mentioned before: stay away from the type named TS7815.
7815 does not change to negative (it can't) - you just see the normally-working -15V dragging it down through the consuming circuits.
Jakob E.
Pins 1 and 8 on the 5534's are compensation pins (look up the data sheet!) and should be ignored if not used.
For the 7815 regulator, as mentioned before: stay away from the type named TS7815.
7815 does not change to negative (it can't) - you just see the normally-working -15V dragging it down through the consuming circuits.
Jakob E.
