GSSL HELP THREAD!!!

[chrispbass]

hi again good people.
So I used up the LED output on the board to power an LED in my meter, meaning I'm taking power for my Power indicator LED from the unregulated supply after the rectifier.  My question is, how do I calculate the current limiting led that's required to put before the LED?  I don't know the rating of the led in my switch I'm afraid, but when I put a 9 volt battery across it it glows, not particularly brightly.
thanks in advance for your advice!

Basically, you need the operating voltage of the led and its current draw and the voltage of the supply you intend to use.

ohms law says V = I x R, rearranging you get R = V/I ...

in this case you subtract the forward voltage of the led, so  V(supply) - V(led) / I(led current) = your required resistor in ohms

e.g if your supply was 12V, your led operating voltage was 2.2V and your led draws 20mA (0.02A) you get

12-2.2/0.02 = 490 ohms so use closest value to 490 you have, best to go bigger rather than smaller.

You can check the wattage of resistor you need by squaring the current and multiplying by your resistor.

In this case = 0.02 x 0.02 x 490 = 0.196 watts ,so a 1/4 w 490 ohm resistor will suffice.

Try and find the data sheet for your switch, to get specs for led. Failing that, measure the current draw with a multimeter.

hope that helps!!

 

[Harpo]

..from the unregulated supply after the rectifier

Don't touch the 12V rail.
Assuming 15V Ac from one of your center tapped transformer, giving 15V*SQR(2)=about 21V raw DC after rectification.
(21V raw DC - depending on colour maybe 2V LED Vfwd) / 0.01A LED Ifwd= 1K9.
A 2K might fit without burning your retina.

 

[wthrelfall]

Thanks guys, working great!

 

[killjoy]

Hello GroupDIY, this is my first post! i just received my 2 PCB kits from PCBGrinder.com and am excited to get building! i have experience with building other things mostly firearms. this will be my first DIY eletronic piece so... i'm probably going to need some help!
   

 

[straypacket]

Hi all,
My GSSL boards are populated and I'm doing some voltage testing, matching the voltages on my board to those on the schematic in Jakob's PDF.

All looks OK to me, with two exceptions:

(1) I seem to be getting no voltage on my threshold potentiometer.  I can try to debug this, but the next issue is puzzling to me:

(2) The inset at the bottom of the schematic, for THAT2180/2181 substitution says I should be seeing +12 on pin 7 of the NE5534 and -12 on pin 4.  I am seeing +15/-15 (ish) on these pins

I have performed the resistor omissions and substitutions for the pre-trimmed VCAs (using 2180As).  Also, I am seeing +/-12 on the sidechain pins, per the test voltages printed on the PDF schematic, so I would think that the 12v regulators are OK ?

Would there be a set of clues I can look for to determine why these voltages are so off?  On a side note, I notice that the voltage measurements listed for the 202C/2150 are +/-15 ...  maybe there is a clue for me there? 

Here is a spreadsheet of the test voltages I measured:  https://docs.google.com/spreadsheet/ccc?key=0Aun7twHHx3oydDVTMmdTWHp6ZFNKaGM2eHItZHVnWFE

Any pointers would be appreciated.  If I debug it myself I will follow up.

EDIT:  A note on performance so far:  passes audio in bypass mode.  Switching compression in drops volume immediately, makeup gain and threshold seem to do nothing, and the attack control acts like a nifty distortion generator...  the more you click it clockwise, the more distortion you get   The LED pads will not power an LED - Measuring -11v on the round LED pad.

 

[spudstyle]

Hi guys,

Merry christmas

I got a problem with the BOM & PCB from PCB grinder (or other I think that's the same). In the BOM we have 9x100pf caps but on the PCB, I can see 10x100p caps... It's an error ?

 

[kenny]

Hi spudstyle,

http://www.groupdiy.com/index.php?topic=47.1140

"Mount the board as silk-screened, and you'll be fine."

You need all 10.

 

[spudstyle]

Ok, i'm not crazy thank you, i'll order a new cap after.

 

[spudstyle]

Hi all,

Wich software you use to design your front panel ? Not for holes but for scales & text ?

Thx.

 

[straypacket]

Rebuilt the entire control board... something on it was apparently the problem    because ... Holy smokes...  IT WORKS!!!  A couple more LEDs (and the driver circuits for them) and it's done.

How can I be expected to go to work on Monday?!?

Here's the album:
https://plus.google.com/photos/105419510319865834801/albums/5827643262218308065?authkey=CPLzztCruvCAYA

 

[damien]

Hello & happy new year to everybody!

I built a GSSL with 2x supersidechain  & Turbo board. I am struggling to find a bug on my GSSL.

All my voltages are alright on every boards, I triple checked them, they are all fine.(+-0.15V max to references)

I don't have any sound coming out from the RIGHT channel even if the bypass button is switched ON.
When I switch the compressor on, the left channel is compressed properly,but nothing is coming from the channel RIGHT, not even distortion...

This is what I tested with sine waves @0dBfs and white noise from DAW:

- IN & OUT connectors are ok.
- I flipped the input 5534 with no change, the RIGHT channel is not working even once IC are flipped. (5534 are both ok)
- I flipped the output 5532 with no change, the RIGHT channel is not working even once IC are flipped. (5532 are both ok)
- I flipped the 2 THAT 2080 with no change  (2080 are both ok)
- I checked all the solder points on the boards, they all seem to be fine

my Turbo board is connected to the R channel between the right SSC and the 100R return point.

Have you got an idea about how to start finding the issue properly?
What's really strange is that even in bypass mode, the RIGHT channel is still not working and does not provide any signal.

thanks a lot for your help

edit: I removed all connection to the 2x SSC and to the Turbo board and soldered back the 2x47K. The issue still occures. 100% sure it's coming from the main board.

 

[MeToo2]

Hello & happy new year to everybody!

I built a GSSL with 2x supersidechain  & Turbo board. I am struggling to find a bug on my GSSL.

All my voltages are alright on every boards, I triple checked them, they are all fine.(+-0.15V max to references)

I don't have any sound coming out from the RIGHT channel even if the bypass button is switched ON.
When I switch the compressor on, the left channel is compressed properly,but nothing is coming from the channel RIGHT, not even distortion...

This is what I tested with sine waves @0dBfs and white noise from DAW:

- IN & OUT connectors are ok.
- I flipped the input 5534 with no change, the RIGHT channel is not working even once IC are flipped. (5534 are both ok)
- I flipped the output 5532 with no change, the RIGHT channel is not working even once IC are flipped. (5532 are both ok)
- I flipped the 2 THAT 2080 with no change  (2080 are both ok)
- I checked all the solder points on the boards, they all seem to be fine

my Turbo board is connected to the R channel between the right SSC and the 100R return point.

Have you got an idea about how to start finding the issue properly?
What's really strange is that even in bypass mode, the RIGHT channel is still not working and does not provide any signal.

thanks a lot for your help

edit: I removed all connection to the 2x SSC and to the Turbo board and soldered back the 2x47K. The issue still occures. 100% sure it's coming from the main board.

OK Suggest you debug the main board before adding in the SSC & turbo boards. Please note that the "bypass" on the main GSSL board is NOT a true bypass connecting input to output. All it does is defeat the make up gain and compression gain controls: the signal still passes through the main chain (including the VCA's). Since you have access to a 0dB sine tone from your DAW, the obvious thing to do is to step through the circuit stage by stage starting at the input jack, and compare left and right channels using your voltmeter on AC volts setting. At one point, the left channel will show a reading and the right one won't. There is a fault just before that point.

 

[damien]

OK Suggest you debug the main board before adding in the SSC & turbo boards. Please note that the "bypass" on the main GSSL board is NOT a true bypass connecting input to output. All it does is defeat the make up gain and compression gain controls: the signal still passes through the main chain (including the VCA's). Since you have access to a 0dB sine tone from your DAW, the obvious thing to do is to step through the circuit stage by stage starting at the input jack, and compare left and right channels using your voltmeter on AC volts setting. At one point, the left channel will show a reading and the right one won't. There is a fault just before that point.

Thanks MeToo2,

I tested the paths L&R at every point from the input plug.
The values are matching, until the 27K before the VCA stage. The input stage is ok then.

between L input Hot point and just before the 27K I have the same value as on the R channel.

through the 27K resistors:

on L:
L hot pin to VCA in L : 1.4V ac
Grnd pin to VCA in L : 0V

on R:
R hot pin to VCA in R : 0.9V ac
Grnd pin to VCA in R : 0.3V ac

both 27K values are ok (27K & 26,95K)
continuity between 27K input to VCA in is ok on both channel.

I removed the turbo and SSC and soldered back the 47K's.

I really don't know what's happening, this may come from an other part of the VCA stage.

thanks for your help.

Damien

PS: I attached the diagram with voltages. around the 27K point.

 

[MeToo2]

OK Suggest you debug the main board before adding in the SSC & turbo boards. Please note that the "bypass" on the main GSSL board is NOT a true bypass connecting input to output. All it does is defeat the make up gain and compression gain controls: the signal still passes through the main chain (including the VCA's). Since you have access to a 0dB sine tone from your DAW, the obvious thing to do is to step through the circuit stage by stage starting at the input jack, and compare left and right channels using your voltmeter on AC volts setting. At one point, the left channel will show a reading and the right one won't. There is a fault just before that point.

Thanks MeToo2,

I tested the paths L&R at every point from the input plug.
The values are matching, until the 27K before the VCA stage. The input stage is ok then.

between L input Hot point and just before the 27K I have the same value as on the R channel.

through the 27K resistors:

on L:
L hot pin to VCA in L : 1.4V ac
Grnd pin to VCA in L : 0V

on R:
R hot pin to VCA in R : 0.9V ac
Grnd pin to VCA in R : 0.3V ac

both 27K values are ok (27K & 26,95K)
continuity between 27K input to VCA in is ok on both channel.

I removed the turbo and SSC and soldered back the 47K's.

I really don't know what's happening, this may come from an other part of the VCA stage.

thanks for your help.

Damien

PS: I attached the diagram with voltages. around the 27K point.

Hmmm does like your Right channel VCA then (or components around this area).

The input current should be identical on the channels when a mono signal is fed in. [the VCA is a current device]

Can you check that Voffset_in for the That 2181 VCA chip [pin 1] <±5mV DC when there is no signal?
That'll indicate whether it's biassing correctly.

Can you check the DC control voltages (CV pin3 of VCA) on the 2 channels are identical?
NB this may be very small and may be difficult to measure directly.

Check power to the VCA's [V+ pin 7 and V- @ pin 5 = set current]?

Output of VCA after conversion from current back to AC voltage [pin 1 of 5532] with signal present?

 

[damien]

ok I took voltages around the V- and V+.

V+ is ok. but V- is not.

I have:
-2,92V on channel L
-0.44V on channel R

so I checked the REAL values on the resistors and it seems that a pair of 10K on the Right channel are actually 120R

I will change it right away. thanks for the help. I have to check if I did not switch those 120R and  10K somewhere else. ( edit: I did, I put 10K instead of 120R on the 2 VCA stage).

thanks a lot for your help

 

[damien]

Thanks MeToo2 for the tips.

It's working now! I tested with sines/sweeps and music and everything is fine.

I still have a doubt on my meter.
Even without signal, if I set the threshold very high(max clockwise), and set the release @12:
the meter displays -8dB @ "1:2"
the meter displays -6dB @ "1:4"
the meter displays 0dB @ "1:10", that must be ok.

Anything wrong with my meter? compression even without signal seems a bit weird to me.

thanks

 

[MeToo2]

Thanks MeToo2 for the tips.

It's working now! I tested with sines/sweeps and music and everything is fine.

I still have a doubt on my meter.
Even without signal, if I set the threshold very high(max clockwise), and set the release @12:
the meter displays -8dB @ "1:2"
the meter displays -6dB @ "1:4"
the meter displays 0dB @ "1:10", that must be ok.

Anything wrong with my meter? compression even without signal seems a bit weird to me.

thanks

Your meter problem could probably be either the compression ratios are not working correctly OR that the meter scaling is simply incorrect for your specific brand of meter.

To find out, you can measure the slope of the compression in your DAW using two constant tones. Please note it is the slope you need to measure (using the difference of two tones with hi and lo amplitude) and be sure that you measure quite a distance from the compression knee.  So the ratio should be (GR tone hi - GR tone lo dB) / (amplitude tone in hi - amplitude tone in lo dB) NB The position of the compression knee may move when you change ratios. You will have to readjust the threshold pot every time you change the ratio switch. This is normal.

If it's the meter scaling, adjust the 4K7 for the zero offset (meter reads far right under no GR) and you may have to tweak the 330R scaling resistor to control how far it moves left under compression if your meter is not 1mA FSD.

If it's the real compression slopes measured in your DAW that are not working correctly, check the resistors around the TL074 and SW1 on the control board. There's also 5 diodes here that you have to have installed the correct way around.

I use the Expat Audio add-on VU meter board so that I can get a calibrated gain reduction meter reading in dB using a standard VU meter. That really tracks to within a 1dB of the real GR AFAIK on my build. Otherwise you'll have to calibrate yourself.

 

[damien]

Thanks for your tips MeToo2.
I started with your guidelines and double checked the diagram. I forgot the // 330R on the 100uA meter  :

thank you for everything.

 

[killjoy]

Quick question, I'm starting on the power source portion of my GSSL. Im to the point of ordering my IEC, and transformer. I'm going with the one mentioned on the first page of this thread the:
digikey part # TE62063-ND.

But its $40! is there a cheaper (but adequate) transformer option, or are all y'all paying about the same?

also, i found an IEC that has a power switch, and fuse holder attached. its Digikey part # Q300-ND
is this a viable option, or should i get the components seperate?

Thanks in Advance!!

 

[spudstyle]

Hi all, I need some help.

I'm tryinge my GSSL (without 1U case for the moment). I just use one channel for the test, so i've sound (and noise) ok... But I don't have any compression
Switchs don't change anything, threshold don't change sound but Make-up is working. Meter don't move but sometimes, when I cut power and re connect it, the sound disappear... I disconnect/reconnect... Sound come back and meter go to 8dB reduction without movement... I disconnect/reconnect... Meter back to 0dB... Very strange.

Do you have an idea ?