GSSL HELP THREAD!!!

[capnspoony]

yep my sidechain wasn't being fed .. its fat and happy now ..

Thanks tommy!

im going to re read through your post and see if I can help at all .. My newbie qualities may get the better of me

-richie :thumb:

 

[tommypiper]

Cool! :grin: What was blocking it?

If you have a DMM, check what AC and DC readings you get with compression on (tell us how much compression approximately), using shortest release, at the places I mentioned. That will be interesting. Use a sine wave or some steady tone or steady audio (like a loop of applause or white noise or something if you don't have a sine wave).

If you also have a scope, take the readings at the same places I took them.

Cheers!

 

[Miguel]

Hello everybody,

I'm in the process of building a gssl (first audio build ever- hobby robot assembly is my maximum contact with practical electronics) and being the full-on newbie that I am, I was wondering: how difficult would it be to implement a headphone output? I would guess it would revolve around building a headphone amp.

If anybody could direct me somewhere I'd be grateful. I wanna make this the front end to my DAW.

And you guys seem to know it all.

I'm so glad I found The Lab.

Greetings,

Miguel.

 

[gyraf]

Hi Miguel,

Welcome to GroupDIY!

The SSL does not have enough spare power to supply a headphone amp. Better to build that separately.

Jakob E.

 

[tommypiper]

1) Is it normal for the waveform to move downwards and off the scope when applying make up gain? Is this some kind of DC offset?

2) With longer release settings the waveforms went flat. Is flat correct?

3) Should the CV be a flat signal on the scope? If so, then what is the waveform? Is the waveform leakage of AC through the rectifier?

4) If the waveform is leaking AC, or audio, then why is there no waveform at the output of Pin 8 of the sidechain master VCA?

5) Why is the waveform not present at the input of the TL074 on Pin 6, but it IS present on the first output of the TL074 on Pin 7????!!!

6) Does this mean the TLO74 is causing the distortion? Or there is another source of this waveform than the natural output of the sidechain VCA?????

7) Why does the waveform go flat when I lengthen the release setting even at test point "C" upstream of the A/R circuit?????

8) Is it normal to see the audio signal on Pin 7 of the TLO74?

9) Why does the distortion in the sine wave, visible at TL074 Pin 7, go away when I lengthen the release setting? How can the release effect the signal so far backwards in the circuit?

10) It would be going backwards through the rectifier and several stages of the TL074, (which I thought would act as buffers)! Is this possible?

 

[gyraf]

Hi Tommy,

Most of your questions requires that I open and measure on a unit -
which I don't have.

My guess is still that you have a mess-up in the Attack/release timing
circuit. look at the meter output on your scope. select dc-reading. at
the longest release, "auto", it should take 3-4 seconds for a
dc-voltage, generated by incoming audio, to return to zero from ca. -5V

tommypiper wrote:
> Do you not understand my questions? I'm trying to be clear.
>
> 1) Is it normal for the waveform to move downwards and off the scope when
> applying make up gain? Is this some kind of DC offset?
>

Not clear what waveform you mean. Sc-vca? main vca? unit output? Try
understanding the circuit - the makeup is voltage added to the cv-input
of the main vca's.

> 2) With longer release settings the waveforms went flat. Is flat correct?
>

Yes. That should be clear from looking at the schematic. Release changes
integrator timing.

> 3) Should the CV be a flat signal on the scope? If so, then what is the
> waveform? Is the waveform leakage of AC through the rectifier?
>

Yes and no. it will mainly b ea dc-voltage, but as the sidechain filter
is not infinitely steep, there will be an ac component whick is larger
with fast timing (which, again, is easy to see if you read the schematic)

> 4) If the waveform is leaking AC, or audio, then why is there no waveform at
> the output of Pin 8 of the sidechain master VCA?
>

Try understanding how the vca's work. there's good info on Groupdiy, and
there's a lot of info on THAT's homepage. VCA theory is not all that
simple to explain.

> 5) Why is the waveform not present at the input of the TL074 on Pin 6, but
> it IS present on the first output of the TL074 on Pin 7????!!!
>

Please read about inverting opamp amplifiers - they are current-in, that
is there is a "virtual ground" at the -input.

> 6) Does this mean the TLO74 is causing the distortion? Or there is another
> source of this waveform than the natural output of the sidechain VCA?????
>

no and no

> 7) Why does the waveform go flat when I lengthen the release setting even at
> test point "C" upstream of the A/R circuit?????
>

it's a matter of understanding the circuit - there is no "reverse
isolation" here.

> 8) Is it normal to see the audio signal on Pin 7 of the TLO74?
>

Again - read the circuit. Audio L+R are summed and sent through the
sidechain vca - so yes, it will be present at the output of the VCA I/V
converter opamp.

> 9) Why does the distortion in the sine wave, visible at TL074 Pin 7, go away
> when I lengthen the release setting? How can the release effect the signal
> so far backwards in the circuit?

feedback through cv to sc vca, modulating audio.

> 10) It would be going backwards through the rectifier and several stages of
> the TL074, (which I thought would act as buffers)! Is it possible for the
> signal to travel backwards in the circuit like this?

Try understanding the feedback-sidechain-character of this compressor

Jakob E.

 

[tree]

Hi All;
After a year or so, am back at building more Gssls.(#3&4!).
Will try not to be a pest.
I've reread all the previous pages and most Meta GSSL related to get back up to speed and am ordering parts (THANKS, GREG :thumb....

Haven't found a specific part# listed here yet for proper Lorlin mains ON and OFF and i remember that Jakob said to be careful here.... can someone confirm whether one of these might work?
http://www.mouser.com/catalog/627/1343.pdf

Thanks Much, Anyone.
Looking Forward;
scott

 

[gyraf]

Nope, none of those.
LORLIN RMS1016
Switch, rotary, 4A, 250V, DPNO

RS Components #316-800

Jakob E.

 

[tommypiper]

[quote author="gyraf"]Most of your questions requires that I open and measure on a unit -
which I don't have.[/quote]

Sorry, no, I wasn't asking for that. Just an understanding of the circuit is all that is needed to understand my questions. (My questions are mostly about how one thing downstream can effect something else upstream.) :grin:

> 1) Is it normal for the waveform to move downwards and off the scope when
> applying make up gain? Is this some kind of DC offset?
> [/quote]

[quote author="gyraf"]
Not clear what waveform you mean. Sc-vca? main vca? unit output?[/quote]
If you look at my post, I mentioned which waveforms behaved this way. (It's the first set of waveforms, measured after the make up gain portion of the circuit! :wink

So, I assume that is a normal DC offset behavoir of the CV?

> 2) With longer release settings the waveforms went flat. Is flat correct?
>

Yes. That should be clear from looking at the schematic. Release changes
integrator timing.

My point was, is the waveform itself normal, or abnormal, to be present? Waveforem present = distortion. Waveform absent = no distortion. Is the waveform supposed to be there, or not?

> 3) Should the CV be a flat signal on the scope? If so, then what is the
> waveform? Is the waveform leakage of AC through the rectifier?
>


Yes and no. it will mainly b ea dc-voltage, but as the sidechain filter
is not infinitely steep, there will be an ac component whick is larger
with fast timing (which, again, is easy to see if you read the schematic)

OK. But WHAT is the AC component?! Audio? Like the waveforms I saw?

> 4) If the waveform is leaking AC, or audio, then why is there no waveform at
> the output of Pin 8 of the sidechain master VCA?
>


Try understanding how the vca's work. there's good info on Groupdiy, and
there's a lot of info on THAT's homepage. VCA theory is not all that
simple to explain.

Perhaps I'm not being clear enough. If it's not audio, then where is the audio coming from which I see in the scope?

> 5) Why is the waveform not present at the input of the TL074 on Pin 6, but
> it IS present on the first output of the TL074 on Pin 7????!!!
>


Please read about inverting opamp amplifiers - they are current-in, that
is there is a "virtual ground" at the -input.

Are you saying the audio is entering the IC via ground?

> 7) Why does the waveform go flat when I lengthen the release setting even at
> test point "C" upstream of the A/R circuit?????
>


it's a matter of understanding the circuit - there is no "reverse
isolation" here.

OK. So why does the waveform go flat?

> 8) Is it normal to see the audio signal on Pin 7 of the TLO74?
>


Again - read the circuit. Audio L+R are summed and sent through the
sidechain vca - so yes, it will be present at the output of the VCA I/V
converter opamp.

Yes, I understand that. Then why, as you say the source of the audio is the L+R summation sent through the sidechain vca, is there no audio coming out of the sidechain vca?

> 9) Why does the distortion in the sine wave, visible at TL074 Pin 7, go away
> when I lengthen the release setting? How can the release effect the signal
> so far backwards in the circuit?

feedback through cv to sc vca, modulating audio.

What is that path, please? I don't see a feedback path.

> 10) It would be going backwards through the rectifier and several stages of
> the TL074, (which I thought would act as buffers)! Is it possible for the
> signal to travel backwards in the circuit like this?


Try understanding the feedback-sidechain-character of this compressor.

I am! :grin:

Everything makes sense, except for these odd behavoirs, thus my questions. What am I missing?

 

[tree]

Thanks Jakob!

:thumb:

 

[Miguel]

Ok, so scratch that. Thanks for the fast answer, Jakob.
This place ruuules.

Miguel.

 

[Axelerator]

So by now i´m just finishing my p2p-version of the ssl
i have started building at the rev 5 schemo from jakobs page and did all the changes i have recovered ... there is still one question left : the 10k resistor
going from the output 5532 to ground at pin 5...at first i build them in , then idiscovered a redrawn schemo with marked "errors" where it was marked and i swapped to 470r like the one at pin3..
later i read somebody telling the red values are the wrong ones so the 10k would be the right one?
so i downloaded the layout and placement files from jakobs page and there seems to be the 470r in ( i count 4 of them in the output section of the placement picture ) the rev.7 schemo in the same file says 10k still so i´m really confused...
i ´m just doing the switches and then i can fire it up (hope to see no fire indeed..!) . i will post some pictures of this little monster in which i spent way too much time...

so please can somebody tell me what to build in here



greets
axel

 

[Axelerator]

...another question about the hp-filter -mod : when i just want to use the filter (no ext sidechain) , can i let the additional buffer out and go direct between the 47k summing resistors and pin 1 of the control-vca or does the vca gets crazy with the capacitance of the filter ?
thanks again ...
axel

 

[gyraf]

[quote author="Axelerator"]the 10k resistor going from the output 5532 to ground at pin 5...at first i build them in , then idiscovered a redrawn schemo with marked "errors" where it was marked and i swapped to 470r like the one at pin3..later i read somebody telling the red values are the wrong ones so the 10k would be the right one?[/quote]

These resistor values doesn't matter in real-life - we would have been more specific about it if it was important. Anything from a short up to 100K will do fine here. Just stuff the pcb according to component overlay, and you'll be fine.

Jakob E.

 

[Axelerator]

ok thank you , jakob
-maybe you also spending way too much time with this projekt and this for years now , looking at all the answers you gave the community... but it seems like you still have some fun in helping newbs

my deep respect for this!

axel

 

[Axelerator]

Btw. , i used 25 volt types for the 22uf-decoupling-caps , should i change to 35 volt types because of -15+15 means 30 volts peak or do they never see full voltage -swing and i can leave them in

did not see this before...
axel

 

[gyraf]

..leave them in - no worries. They always refer to 0V anyway..

Jakob E.

 

[rbaker]

A small, petty question about regulators/voltages...

I've measured my voltages and I have -14.96 and +14.62 or so....I know that this is nearly fine and not really anything to worry about (the unit is sounding great) I changed to another one (same part no) and it's still the same. There's plenty of voltage going into it.

I saw earlier in the thread jakob said it might just depend on the brand of regulator. I have the one from greg's list---TI etc.

if that's the case, why when I paid for +15 am I getting +14.62? They are ripping me off by almost .4v! :shock:

Yeah I knowit's close enough...but out of curiousity, are there any brands/etc that I can expect that will give me a closer voltage, if I chose to be anal about that?

 

[Greg]

Off by 0.4V is roughly within 2.5%... If you want exact voltages, you'll need to go with the trimmable 317 and 337 and build some supporting circuitry. Though not necessary in my opinion. Enjoy the comp.

 

[tommypiper]

I'm still stuck. I've taken all the measurements and scope readings possible and asked questions as clearly as possible.... Hello?