GSSL HELP THREAD!!!

[MeToo2]

Has any one used the "nte858m" op amp in place of the "tl072"?  I asked for the "tl072" at my local electronics store and was given the "nte858m". I didn't realize this till I arrived at home.  I've done a bit of research and it seems they are the same op amp, just made by different companies.  I also saw the "ne5532" was the same which I don't think is correct.  I just wanted to check here to see if anyone had problems using the "nte858m" in place of the "tl072".

TL072 and nte858m are not "the same op amp, just made by different companies". Don't know how you came to that conclusion.

They should be similar enough to work in this circuit (both low noise jfet with mostly similar data sheet characteristics). But they may not.

The nte858m is faster (higher bandwidth) and so they might oscillate in combination with the VCA chips, which are apparently quite picky about being driven by an inductive source.

You can certainly try them instead of a TL072 (assuming you've fitted DIP sockets). It shouldn't do any harm to try them out.


The NE5532 is very different from the nte858m.

They both might be black rectangles and have 8 pins & contain 2 amplifiers, but the NE5532 is bipolar, and can drive relatively low impedance loads directly.
You should really use a NE5532 where that is specified, and not try the nte858m as a substitute for those positions, as that is unlikely to work.

 

[wartornrex]

I do understand that there are schematics on how to hook up the switch.  Schematics that are pretty much jibber ish to me as I don't understand how to read it.  I'm assuming from your response that the VU meter goes to the input poles and the I/O of the left and right go to the output poles.  I thought this thread was for people to ask questions about things they don't understand so that's what I did.  I don't understand how to read the schematics so I asked.

??? 9 pages of a build manual with pics showing how to assemble and connect it for various configs (and without full schematic).
How about reading it 

How bout read what I wrote.  Every time I try to get an answer from this thread I get some condescending jerk with an opinion that has nothing to do with what I'm asking.  I'm done with this place and trying to get answers from people who forgot what it was like to learn something for the first time.  As for the 9 page manual, the pics of the hook ups for the switch is jibber ish to me like I said and I can't read it like I said.  I won't ask anymore questions here cause its like pulling teeth.  I'm sorry for trying to do this project and for asking questions here.  I'm surprised that more people don't get discouraged from trying to learn something new when they just try to ask a simple question.



To the person that answered my question about the op amp, thanks, after numerous questions here and getting insulted for not knowing as much as others, your the first to give me a straight forward answer.  Ill try the nte858m but I just ordered the tl072 I need.  I will NOT post the results here from using the nte858m compared to the tl072.

 

[Harpo]

I just finished my VU mod from expat audio and would like it to read the left and right outputs as well as gain reduction.  I'm a little confused about how to wire the switch.  Do I want to wire the output into the switch and then into the meter? Or do I wire it to the meter then take it to the switch?  I am very lost on this and if some one can explain how it is wired up I would be great full.

The expat build manual doesn't leave any of your questions unanswered how to connect your true VU-meter in series with a 3K9 to both switch poles and how to hook up your switch throw positions to L-in/L-out/R-in/R-out/Gr or other/less permutations.

I do understand that there are schematics on how to hook up the switch.  Schematics that are pretty much jibber ish to me as I don't understand how to read it.  I'm assuming from your response that the VU meter goes to the input poles and the I/O of the left and right go to the output poles.  I thought this thread was for people to ask questions about things they don't understand so that's what I did.  I don't understand how to read the schematics so I asked. 

How bout read what I wrote.  Every time I try to get an answer from this thread I get some condescending jerk with an opinion that has nothing to do with what I'm asking.

Thanks for your kind words. How bout read what I wrote.

I didn't tell you 'the VU meter goes to the input poles' but
'connect your true VU-meter in series with a 3K9 to both switch poles'.
Lets disassemble/translate this jibber ish.
'connect' -> bring physical parts together in a way there is a conducting path from one part to the other. Some solder and maybe a piece of wire if distance between these parts comes into play might be needed to get there.
'your true VU-meter' -> you will need a true VU-meter, not a 1 mA FSD (full scale deflecting) meter for this build to give you a visual for the amount of gain reduction or VU level in a dB scaled readout.
'in series with a 3K9' -> there will be a resistor with parts value 3900 ohm (same as 3.9 kilo ohm or 3K9 ohm) in between the conducting path from one point to the other.
'to both switch poles' -> a switch comming with at least two poles will be required to make it work. You connect to the common poles of this switch.
IE switch pole -> 3K9 resistor -> VU-meter terminal -> other side of VU-meter terminal -> other pole of switch. Order of parts doesn't matter in this series connected string. Compare this jibber ish with 1st.'schematic' from pg.8 of the build manual you refuse to read.

I didn't tell you 'the I/O of the left and right go to the output poles' but
'hook up your switch throw positions to L-in/L-out/R-in/R-out/Gr or other/less permutations'.
Up to now you didn't tell us what kind of switch you use. Wild guessing it might be a 2x6 lorlin type rotary switch (two switch poles, 6 possible switch throw positions per pole, number of positions might be limited to lesser than 6 positions by displacing the switches end-stop washer). This 2x6 rotary switch comes with a pole labeled 'A' and another pole labeled 'C', both located close to the switches center. Depending on step setting, pole 'A' connects to throw positions 1...6 and simultaneously pole 'C' connects to throw positions 7...12 when dialing from rotary switches full CCW to its full CW position. From your 'would like it to read the left and right outputs as well as gain reduction' you'd need at least 3 throw positions, so a 3x4 or 4x3 lorlin type switch could work as well as a 2P3T toggle or rocker switch. Lets keep it for the 1st.assumption 2x6 for now. For full CCW 1st.position showing left side output, connect GSSL L'+'out to throw pin 1 and connect L'-'out to throw pin 7. For 2nd.position showing right side output, connect GSSL R'+'out to throw pin 2 and connect R'-'out to throw pin 8. For 3rd.step position showing gain reduction, connect Expat VU-driver board component header X1 pin 1 to throw pin 3 and connect the other Expat VU-driver board component header X1 pin 2 to throw pin 9. Turn the rotary switch full CCW and displace the switches end-stop washer (below the fixing nut) to pos.3. Done. (At cost of length of wires from GSSL inputs to the same switch and displacing the end-stop washer to pos.5 your VU-meter could show input levels as well, but you didn't ask for this option).

I might have assumed wrong that, if you had built the GSSL up to this step, you might have noticed, there are different type of switches involved and you could tell one from another.

Please excuse, if I used the wrong coloured spoon again.

 

[rainton]

Hello again,

I ordered some caps and diodes for the anti latch-up fix and soldered them into place from the bottom side of the pcb.
But I'm afraid it didn't work for me - or I didn't do it correctly.
I was using (I think MeToo22's) picture from a couple of pages before that showed where everything has to go and since I didn't know how to do it exactly as it's shown there
I was looking for soldering joints nearby that made sense and soldered the parts into place - was that wrong?

Anyway - the latch-up problem still exists.

Also another strange problem occurred: My gssl has a rotary switch to switch it on which goes from "off" to "bypass" to "in"
So when I switch the unit on (and it's not latching up) - but still running in "bypass" mode, everything is fine.

But as soon as I switch it to "in" the gr-meter shows about 2 db gain reduction - even though the threshold pot is turned fully clockwise.
It also happens when there's no signal being fed to the compressor at all.
If I feed it with a sine wave I can also hear the compression shown by the gr-meter and when turning the threshold knob CCW it compresses more - as it should.

Meaning everything else is working.

So I thought I messed up something so I took out the pcb to check the soldering joints of my recently added diodes an did some resoldering to make sure all connections are good.

I switched on the comp again - and it worked perfectly. No 'strange 2db gain reduction without signal' anymore.

put the pcb back in checked again to make sure it' still working - AND AGAIN the same freakin problem!!

Any idea where to look? Please bare with me - I'm pretty new to DIY

Thanks!

 

[gyraf]

As mentioned somewhere else, I doubt that latch-up problems can be fixed with diodes. I'd recommend changing the regulator in question to a different brand.

Jakob E.

 

[rainton]

Yes I know Jakob, you already said that...
...I'll change the regulators.

But what about the second problem I have with the comp
giving me 2db of constant gain reduction even without feeding it with any signal at all? (see my post above)

I'll have to add I also wanted to convert the comp for use on unbalanced inserts and therefor found two things in this monster thread I should do:

1. disconnect the (-) from the output xlrs to prevent shorting them to ground
2. changing the 15k feedback  resistors to 27k to prevent the signal from dropping 6db

So, why I mention this now is: the first time I encountered the "2db-permanent-gain-reduction" problem was right after disconnecting the (-) from the output xlrs.

That made no sense to me...but after reconnecting the (-) it went back to normal - at least for a while...now it's there again.

 

[MeToo2]

Yes I know Jakob, you already said that...
...I'll change the regulators.

But what about the second problem I have with the comp
giving me 2db of constant gain reduction even without feeding it with any signal at all? (see my post above)

I'll have to add I also wanted to convert the comp for use on unbalanced inserts and therefor found two things in this monster thread I should do:

1. disconnect the (-) from the output xlrs to prevent shorting them to ground
2. changing the 15k feedback  resistors to 27k to prevent the signal from dropping 6db

So, why I mention this now is: the first time I encountered the "2db-permanent-gain-reduction" problem was right after disconnecting the (-) from the output xlrs.

That made no sense to me...but after reconnecting the (-) it went back to normal - at least for a while...now it's there again.

Re: the 2dB. Is the bypass switch wired as per the original schematic?

Dumb question: Is this not just simply because you have some make up gain set?
Have you tried varying the make up gain pot, and then switching bypass in or out to see if remains at 2dB loss.

 

[rainton]

Thanks MeToo2

Well it's not just a 2db loss of gain when switching in the comp - it's actual 2db of gain reduction happening - the meter shows it.

If unit is in "bypass" : meter shows "0"
as soon as I switch the comp to "in": meter shows "2" - and the signal gets reduced by about 2db.

But for this to happen it doesn't even matter wether there's signal going through the comp or not.
Even with disconnected XLRs it's the same thing

unit in bypass -> meter shows "0"
unit "in" -> meter shows "2"

As I said apart from that the comp works.
When I feed the comp a sine wave and turn the threshold knob counter clockwise I can hear and see the unit going more into compression
everything as it should...

 

[MeToo2]

Thanks MeToo2

Well it's not just a 2db loss of gain when switching in the comp - it's actual 2db of gain reduction happening - the meter shows it.

If unit is in "bypass" : meter shows "0"
as soon as I switch the comp to "in": meter shows "2" - and the signal gets reduced by about 2db.

But for this to happen it doesn't even matter wether there's signal going through the comp or not.
Even with disconnected XLRs it's the same thing

unit in bypass -> meter shows "0"
unit "in" -> meter shows "2"

As I said apart from that the comp works.
When I feed the comp a sine wave and turn the threshold knob counter clockwise I can hear and see the unit going more into compression
everything as it should...

Hmmm exactly 2dB compression measured externally, AND 2dB GR showing on the meter at no signal? Odd. Are you sure?

If it was 2dB on the meter then I'd suggest meter calibration.
If it was constant 2dB compression measured externally, but not the meter, I'd suggest the ratio of the feedback resistor on the NE5532 to the input resistor on the VCA in the signal chain.

Having both correlated would seem to suggest a constant -ve DC leakage / offset creeping in from the sidechain VCA (point C), that gets grounded when in bypass.
Maybe the ratio switch? Loose wiring at points A,B & C? Duff TL074?

What DC do you get at pin 1 and pin 14 of the TL074 with no signal, and then switching in and out of bypass?

 

[rainton]

Ok MeT002,

I found it 

Your hint about the ratio switch connection helped!

I have the turbo-board installed and one wire going from there to the ratio switch had no connection. resoldered it and now it works. Thank you!!

But also before I fixed the issue I checked the compression externally and I found out what shows to be 2b of compression on the comp's meter is only a little over 1db on my console.
To check it further  now that I fixed the issue I now fed the comp with a 1khz sine wave at 0dbU and turned the threshold knob ccw until the comp's meter read 6db of compression - but my console shows
the signal is being only reduced by about 4 db - so I guess I have to do some meter calibration...

Now the only two things I have left to do is
a) ordering new regulators from another brand that will hopefully fix my latch-up problems.

and

b) prepare my unit to be used on the unbalanced inserts of my console.

Is it correct -  what I found out in this thread in regards of doing b) is:
I have to change both of the 15k resistors highlighted in the attached pic to 27k
and disconnect the (-) from the outputs?

Would be great to know before I order the parts - just in case there's something else I have to be aware of...

 

[MeToo2]

Ok MeT002,

I found it 

Your hint about the ratio switch connection helped!

Good.

Is it correct -  what I found out in this thread in regards of doing b) is:
I have to change both of the 15k resistors highlighted in the attached pic to 27k
and disconnect the (-) from the outputs?

Would be great to know before I order the parts - just in case there's something else I have to be aware of...

FYI Changing those 15K to 27K resistors are effectively adding an extra slug of ~+6dB make up gain to the +ve phase, to compensate for the lack of any -ve phase signal (-6dB).

You could consider using a 22K resistor + a 10K multi-turn trim pot in series so you can fine tune the 0dB gain point on both channels. Or you could just play about with a couple of fixed value resistors in series to make around 27-33K until it's correct. Or you could just put in the 27K and your make up gain calibration might be slightly off. Some people worry about being 1dB out, but others don't. it's all good, and won't effect the compressing character at all.

 

[rainton]

Thanks MeToo2!
I really appreciate your help!

I think I will give your suggestion with a 22k resistor in series with a multi turn 10k trim pot a try
I'll report back...

 

[rainton]

Just to give you a quick heads up:

MeToo2 I did as you suggested and used 22k resistors in series with 10k multi turn trim pots to replace both of the 15k feedback resistors
to the GSSL on the unbalanced inserts of my console...

...and it worked like a charm! This way I could fine-tune each channel for unity gain. Thanks again MeToo2!!


The other problem - as mentioned in the post above - that the meter is not tracking correctly I tried to solve it by soldering a 5K trim pot
into place where the 2K resistor used to be so I could fine-tune that as well.

Now here I encountered a strange problem.
Event though I turned the multi turn trim pot fully CW so there's the full 5K used - I still couldn't get the meter to show the actual compression.
The meter always showed much more than what was actually happening compression wise.
Turning the trim pot fully CW helped me to bring the meter down a little in comparison to how it was before - but not far enough - it was still a couple of dbs off.

So I tried adding another 1K resistor in series and that helped - but still it was not quite there.
Then I changed the 1K res for a 2K in series with the trim pot and that made the meter track almost correctly.

But that is weird, right?  ???  I mean now there's 7K in there but actually 5K should be more than sufficient...
Is it my meter? I can show 10db gain reduction max.

 

[Harpo]

I mean now there's 7K in there but actually 5K should be more than sufficient...

...when using a 1mA FSD meter. Yours obviously has a higher sensivity (100uA...500uA meter). A shunt resistor across the meter terminals (have a look at the GSSL schematic) will reduce needle movement to a more expected behaviour.

 

[zebite]

Hey all !
I'm new here and in the DIY field, I decided to challenge myself with a GSSL build seeing as it is reputated "easy" and I'm eager to learn about electronics in the audio world.
So I got my pcb kit (I won't mention where from !), thinking for a first time go with a kit where all components are included... Error #1 turned out half the resistors where missing and out of that half, half of them displayed wrong accuracy upto 6/7%, missing capacitors... !
Well I eventualy got everything and soldered everything in.
I have a "minor" problem:
I've plugged the compressor into 2 tracks on my console via the inserts and notice that the audio works but I have roughly a 6db drop in volume in both channels.
Also the machine seems to be constantly in bypass mode: although the meter reads gain reduction and I can see that all the controls change the meters reactions I can not hear any of this in the audio path, when I bypass the meter stops working but the audio doesn't change.
I've checked and double checked all solder points (which I also did when soldering all components) and I can't seem to find anything wrong (obviously there is), I seem to have the correct voltages, I've also tried changing VCA's and op amps...
If some one has encountered the same problems it would be great to hear from you.
Thanks in advance.

 

[Olegarich]

Hello Diy family! I'm new in Diy world and currently making Gssl with That 2180B on Gustav Boards.

Before you answer, i read 150 pages of this thread (Jakob and other you are heroes)and fully understand that 90 % is bad soldering, orientation and that seems to be really true.

I finished my unit, and the audio passes threw but there is no compression: only controls that working is bypass and makeup.
Threshold - atack - ratio - release doing nothing. I saw some guys pretty similar problems. Solutions was:
1. Bad TL074
2. that 2180B not inserted propertly
3. Bad input wiring, L+R unphased that gives 0 to sidechain

I've tried all of this but nothing worked for me.
1. Voltages looks good. (15 -15 12 -12)
2. I'm getting signal in Sidechain VCA pin1 but not in TL074 pin7 or 14
3. I've been checking voltages op amps should get and everything look good.
4. checked orientations and resistors lot of times, cheked for shorts and bridges with multimeter, look good.

Any suggestions??? I would be pretty thankfull for a help.

I'm checking it with one input channel, still nothing. I've just bught a scope so i can check for signal.

 

[Olegarich]

ou by the way I did modes for That 2180B mentioned on Math's page

 

[Harpo]

Welcome.

...and soldered everything in.

The pcb (latest pcb revision is 9, so reading this thread from the beginning might relate to different pcb revisions or parts) has placeholders for various types of VCAs (they are all different to a more or lesser degree) and for some types of VCA you better would leave parts out or fit different parts values. We have no idea what parts/values you have fitted.

I've plugged the compressor into 2 tracks on my console via the inserts and notice that the audio works but I have roughly a 6db drop in volume in both channels.

Last fix for your 'problem' is described by MeToo2 on this current page, just scroll up a little. IE make the resistors in front of the audio-VCAs (27k) same value as the feedback resistors in the audio-VCA following current-to-voltage conversion stage (15k).

Also the machine seems to be constantly in bypass mode: although the meter reads gain reduction and I can see that all the controls change the meters reactions I can not hear any of this in the audio path, when I bypass the meter stops working but the audio doesn't change.

You put the bypass rotary switch endstop washer in after turning the switch full CCW?
Depending on audio-VCAs used, you have left out the 68Rs, connecting to VCA-pin4?
You double checked parts values and solder connections around the TL072?

 

[Harpo]

2. I'm getting signal in Sidechain VCA pin1...

Double check parts values around and solder connections at TL074-pins5,6,7.
Double check parts values around and solder connections at sidechain-VCA and you fitted this VCA with correct orientation (opposite of audio-VCAs).
Using a magnifying glass might help to spot a shorted connection to a neighbouring pin.
These VCAs are current-in/current-out devices. VCAs i/o connections are at a virtual ground node of the following opamp stage for current-to-voltage conversion and this opamp stage tries its best to hold its inverting- and non-inverting input at the same potential, 0V reference voltage because pin5 connects to this fixed potential.

 

[zebite]

Hello Harpo and thank you for your reply.

Sorry for the lack of information...
I'm using rev 9 with the THAT 2180 vca's with pin 4 bent off.
I have changed the 15k resistors in front of the audio vca's for 27k as noted in the schematics. So if I understand correctly you are saying change the 15k resistors connected to the output of the audio vca's (pin 8 ) to 27k ?
And as for the bypass switch I don't think (?) I have messed up the washer as the continuity is broken when bypassed reading on a multimeter ( I can't actually double check right at the moment because I don't have the machine with me, but will check as soon as). Same goes for values around TL072.
Excuse me for my ignorance and thanks again, it's a pleasure learning from all you guys.