[BUILD] STA LEVEL PCB OFFICIAL BUILD & HELP THREAD

[porkyman]

thank you. the cx2 is on the pcb pictured below.  another questio. which direction do the leds go ?  -  to outside pcb  is what i did. thanks.

 

[bernbrue]

Take 100N X2. It's listed in the bom for mains and extras.
Bernd

 

[kosi]

Hi everybody, mine is up and running !
I took it to my studio today and I'm extremely pleased with the sound.
I have to tackle 2 small problems:

1. I use the bypass board and  the relays hang, means, when I switch from bypass to "on", I get no sound. but when I tap with the fingers on the relays, it jumps back to on. I measure 4 v on the bypass board, is this too low for the 5v relays ?

2. Output too hot. I don't understand, where i can mount all the attenuator pads, that Bernd mentioned earlier. Do you build them on breadboard or solder a spiderweb hanging around in the unit ?  Has anybody done this and can upload a picture ?

In the moment, I favor the T Pad solution, where I use a U-Pad followed by a T-Pad attenuator
http://groupdiy.com/index.php?topic=56485.msg720958#msg720958

what a nice compressor
will upload a few pics in the next days

 

[bernbrue]

Hi,
Im happy that you like it. 
Well, yesterday I tried to tame the real hot output of my sta level as well and just soldered one of the H pads shown above together.  Even with this attenuation output is still too hot.  I have to try another solution. I used the output screw terminal to fix the resistors. You could either solder the resistors directly to the XLR out or change the values of the already existing output pad. I have to admit that I haven't found the ideal solution for that. 
The low output of the 5V rail and the hanging relay is really strange. I have to talk with Tony about that.
Bernd

 

[bernbrue]

Hi,
Well, the relays should work even with 4V. In case you installed the control led for the 5V rail you could try to take it out in order to reduce current consumption.  Check, if you powered the relays in series or in parallel, not both at the same time!
Bernd

 

[kosi]

How do I power them in series ?
Here's how I connected the relays

 

[bernbrue]

Bridge the two solderpads marked "S" (series) and make the + 5V switchable.
Bernd

 

[Monoklang]

I will soon populate my PCB's, should I wait until this "hot output / output pad" problem is solved?

Or is that something that not everyone got?

John

 

[bernbrue]

Well, all the parts in the bom are basicly stock values. The output stage is similar to a 10W guitar amp. So yes, the output is hot. We decided to stick to the values in the schematic, since we can't know, which input/output transformers people will use, whether they use the input/output pad or not.  It seems reasonable to build this compressor with stock values and adapt things to your personal needs. You can always modify it later or add another pad in addition to the already built in pad. So I would stuff the boards right now, test it in your studio environment and modify it accordingly.

@ Kosi: Would you draw your pad solution on a piece of paper?
Bernd

 

[Monoklang]

Ok. Am I right here regarding the input and output:

Increasing input gives more compression but not a higher output.

And the output is just a 6dB attenuator.

So the design itself got a hot output?
Wouldn't a -20dBfs uncompressed signal (with input at its minimum) come out as a -20dBfs signal?

John

 

[kosi]

I installed the U-pad followed by a T-pad attenuator from CAPI and the first tests are perfect.
The output works like a "normal" compressor, e.g. I have Input and Output at 12 o'clock and the volume is about the same bypassed and compressor engaged.
I used 1/2 W resistors and the CAPI T Pad Adapter, I attach a picture.


Regarding my relay problem: I connected my relay as you said, but the problem remains....

 

[bernbrue]

Hi,
Thanks for the nice drawing. I posted a link to a balanced t pad calculator. See first post.  Input/output impedance is 600 ohm. You can set the amount of attenuation you need/want and the values for the resistors are calculated. Can anyone who has already finished his unit chime in and test it? I'm quite busy at the moment and won't have time to do intensive test. Moreover my mixer has got +6db broadcast level and although the output of my sta level is hot it is still operating in the headroom of my mixer.

@ Kosi: is it possible that you bought relays for 12 or 24 volt? I found a detailed datasheet of the relays. Please check your mouser shopping list and the datasheet
http://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Specification+Or+Standard%7F108-98007%7FL%7Fpdf%7FEnglish%7FENG_SS_108-98007_L.pdf%7F1-1393793-2

Bernd

 

[kosi]

Just to make sure, I meant a variable T-pad attenuator, not a simple T-Pad.

relay: these are definitely the 5V versions. I changed the switch, but no solution. I can hear the relay clicking, btw.

 

[bernbrue]

Well, then one of the relays seems to be defective.
Bernd

 

[kosi]

Bingo !
I removed the V+ Led and the resistor like you suggested. Now I have 4.5V and it works like a charm.
Should have tried earlier, but I was too lazy to lift the psu board again...

Thank you

All I have to do now, is think about a proper way to mount my U Pad. in the moment, it's free floating

 

[bernbrue]

Pictures, pictures!!  ;D  

 

[kosi]

here it is !
As you see: no proper knobs, but the rest is finished

 

[kosi]

my very diy U pad holder...

 

[kosi]

inner goods

 

[bernbrue]

Congratulations,  that's a very nice build.  You've found an elegant solution for the bypass switch. I would love to hear the Sowter transformers. I've built mine with Jensen input and Edcor output and honestly it's my best sounding vari mu compressor . I hope you like yours as well.
Cheers
Bernd