[BUILD] STA LEVEL PCB OFFICIAL BUILD & HELP THREAD

[G-Sun]

What is the attack-time on these units?

 

[bernbrue]

Hi,
I haven´t really measured the attack time. In single and double mode it´s stock, in triple mode attack time is lowered drastically.

In single mode, the release C is 1 uF + 0.5 uF or 1.5 uF. The double mode hangs the 1 uF capacitor from a 10 Meg resistor. This provides a dual time constant where the .5 uF gives the fast attack/fast recovery and the 1 uF sets a variable gain-riding plateau. The triple mode uses double recovery and decreases the 56K attack R to 4.7K.

best
Bernd

 

[Bowie]

I also seem to have some trouble finding the 6AL5 rectifier tube. Can I use an alternative dual rectifier tube that's more commonly available?

Regards, Thomas

The 6AL5 diode is extremely common.  In EU you may find it easier looking for EB91, EAA91, or any of the designations in the link Bernbrue gave.
If your issue is the rectifier, then perhaps you meant the 5Y3?

 

[Bomper]

The 5Y3 was in the original PSU for STA Level. I'm making Bernbrue's design so this uses a solid state PSU. So, no need for the 5Y3. I'll continue my search...

Thx, Thomas

 

[kosi]

Hi, some help needed:

I bought the Sowter 9185 and 9062 transformers and I'm not sure, how to connect them.
I guess, the color codes on the pcb are taken from the originals ?

Output TX 9185
my guess for primary (first color is on pcb, 2nd Sowter TX)
Pink - Blu
Red - Orange
Brn - Violet

secondary; (in series for 600 ohm)
Grn - Grey
Blk - Blu
green and brown are connected

Input TX 0962
Primary
Blu - Pink
Brn - Grey
White unconnected ?

Secondary:
no clue: the 9062 has 2 pairs for 10k red/blue and violet/yellow
I don't know, wether to use only one pair (as the original is 600R:10K, 1:4) or put them parallel...

I attach the data sheets of both transformers.
thanks alot

 

[bernbrue]

Hi,
Almost right. Just a slight error.

To Output TX
Blue - pink
Red - orange
Brown - violett

From Output TX
As you mentioned

Input tx primary is fine as you mentioned, but the original is 1:8, so put the two secondaries in series.
Best
Bernd

 

[kosi]

Thank you very much !
See, I thought, the original uses 1:4, can't recall, where I found this info...

Everythings here and connected, I will do the first test-drive tonight

 

[bernbrue]

Did you buy the pcb from the second or later batch? If so, the input pot wiring is different than shown in the first thread. Wire deck 2 exactly like deck 1. You don't need to twist the wires.

In case the pcb is from the first run you just wire the pot as shown in the first thread.
Report back.
Bernd

 

[kosi]

I'm from the 2nd run and already discovered this !
Everything looks pretty good, B+ a tad high (320) and my 5Volts are a bit shy (4.4V) but I guess, it's not a biggy.
Using the  Don Audio toroid, btw

 

[bernbrue]

I will do the first test-drive tonight

Please report your first impressions.
Cheers
Bernd

 

[kosi]

First test is done,
audio passes, the unit compresses fine, input and output works, controlboard works, even my old Klangfilm meter works
and it's pretty quiet, lying here on my bench without a case.
Voltages are okay, compared to Bernds list
BUT
R3 is cooking, it got so hot, I could lift it off the pcb with my pliers. (1k 3W)
So I'm pretty sure, I wired something wrong.
I have one B- on the psu connector left empty. Is this correct ?
I connected every ground and the mass (on the Bias Mainboard) to one star ground.
Any ideas ?

 

[bernbrue]

Ok,
You need two wires from B+ and B- (main psu) to B+ in and B -  in (bias psu).  From their you need two wires going from BS and GND (bias psu) to BS and GND (bias main board ).  Additionally you need to provide the main board with B+ and B-. So take two wires leading from B+ and B- (main psu) to B+ and GND, marked as PS on mainboard.

Grounding: you can either make the grounding to star ground from the main psu or from the main board. In my build I just lead a single wire from the mainboard (it's the connector next to BS and GND) to a single point that connects chassis/mains ground. On the main psu I connected only the filament minus to star ground.  I made this connection switchable for the EL90  balancing procedure.

For HT TRIM on the main psu you should just use a wire bridge, no resistor at all. If nothing helps you might reduce R3 to 470R and use a 10W resistor that can be bolted to chassis.

Cheers
Bernd

 

[kosi]

thanks again, you are so quick and very helpful !
I drove down to BanzaiMusic and bought two 470R 25W resistors, put them in series and bolted them to my biggest heatsink, to be sure.
Now, they get about lukewarm, so everything should be fine, if I mount them on the chassis.
The unit is incredibly quiet, I nearly couldn't believe it.
Put some music and vocals thru it, wonderful, everything works as expected.

I wrote down some voltages for comparison:

BS is around 97V
Voltage @ R3is 411V

A 75
C 1.31
D 0.67
E 1.33
G 74
H 123
I 170
K 2.76
L 2.74
N 170
O 321
P 0.005
Q 0.036
R 320
S 217
T 19

I only have to order a case now...
and btw: I can easily use it as a mic preamp !

 

[bernbrue]

I´m glad you were sucessful. I wouldn´t run the unit too long without cooling the LM338 regulator. It´s getting hot as well. Concerning cases there are quite a lot options.
best
Bernd

 

[bernbrue]

Hi,
Although I completely understand your situation, I honestly have no info about the DRIP version of  this compressor and would recommend you to start a new thread.  I'm quite shure there will be people around that have successfully built the DRIP version. This thread is meant to support people who bought the version from Zayance and me.
Cheers
Bernd

 

[nielsk]

A few initial questions for my build:

Is there any problem/ changes required using 6v6 tubes on the output like the original one does instead of the EL90s?

Are the LEDs on the power supply boards just for power present indication, and can be left out (along with the current limiting resistors)?

I do not see R5 (B+ PS) on the BOM

Thanks!

 

[bernbrue]

Hi,
The 6V6 has a completely different tube socket and as far as I know the pin layout is different. Why not using the EL90/6AQ5 ? Technically speaking the 6V6 and EL90 are identical.

LEDs on psu can be left out.

R5 (psu) is 47K, 3 Watt

Cheers
Bernd

 

[nielsk]

I had been collecting 6v6s for this...
The local tube house has (for cheap!)6AQ5A and 6AQ5W, any preference?

 

[Bowie]

I had been collecting 6v6s for this...
The local tube house has (for cheap!)6AQ5A and 6AQ5W, any preference?

The designation at the end (W, WA, etc) is not as important as the brand.  6AQ5s are generally not as rugged as 6V6s but RCA, Sylvania/Phillips, and GE 6AQ5s are all good, fairly common, cheap, and should work great in this circuit. 

 

[prescott]

Hi!

I have 3,8v instead of 5. I cannot turn the trimmer any more
How can I solve this problem?