D-LA2A Support Thread

[pH]

Thanks!

 

[tomcat]

And I found a pair of 12AX7s. this thing sounds awesome!!! Trying both the fast and slow drip cells, I can't decide, they are both great.

Both, make them switchable

 

[pablobolche]

Hi I am looking for the power transformer for my DLA2A. I have gone through the thread and can`t find the characteristics for this trafo, on the great azone us BOM it states only the primary specs 2x110v. Somebody please give me the rest.
thanks

 

[pacemaker]

Hi guys,
i am finishing a D-LA2A with sowter inputs and edcor wsm 10k/600 output,
i'm trying to calibrate the vu meter but when i send a 1V 0DBV from my generator,
and when i set the gain so as i get 0db on the vu meter, i got 2,80v output
is this the normal behaviour of the LA2A, ie can't get unity gain ?
or do i have a problem ?
if there's no problem, is there a way i can increase the meter resistor to get 0db in 0db out on the meter ?
regards,
Francois

 

[pacemaker]

bump

 

[[silent:arts]]

...
i'm trying to calibrate the vu meter but when i send a 1V 0DBV from my generator,
and when i set the gain so as i get 0db on the vu meter, i got 2,80v output
is this the normal behaviour of the LA2A, ie can't get unity gain ?
or do i have a problem ?
if there's no problem, is there a way i can increase the meter resistor to get 0db in 0db out on the meter ?

Francois, this is a standard VU meter. with a standard (external) 3k6 resistor it will read 0VU = 1,2277V(rms).
the D-LA2A can get set to unity gain:
feed it with +4dBu, set the gain to read 0VU at the meter, and you will get +4dBu at the output (with gain reduction set to zero for sure)

 

[pacemaker]

Hi Volker,
thanks for your answer,
i've just tried again, and with a 1.22V signal sent to pin 2 ( unbalanced )
with my generator  to the LA2A
if i adjust gain pot to get 1.22V output at pin 2
my meter, wich is an hairball audio, is reading -6VU,
is that a problem caused by the unbalance connection,
is it just a meter resistance adjustment,
or do i have a problem elsewhere and should investigate further ?
Thanks for your help,
Francois

 

[creal]

I have a stupid question. i' just started my DLA2A and i saw the PCB is printed from each side. I don't know if the component need to be soldering from each side??

When i soldering a component on a side,  i don't saw a solder everytime from the other side. Some hole stay white? it's normal or it need to sodering the side too?

Thx for your help

 

[[silent:arts]]

Francois,

this is transformer balanced, and the missing 6dB indicates one leg is missing
connect your unbalanced generator between pin 2 & 3, measure the output between pin 2 & 3, nothing shorted to GND (or pin 1)

 

[[silent:arts]]

When i soldering a component on a side,  i don't saw a solder everytime from the other side. Some hole stay white? it's normal or it need to sodering the side too?

soldering one side is fine (but with a good soldering technique the solder flows up to the other side )

 

[creal]

thx Volker, it's my first double side release

 

[pacemaker]

It works, amazing volker !
i love this forum,
you can learn everyday !!
thank you very much for your help
and for bringing us this awesome project
Best regards
Francois

 

[[silent:arts]]

Francois, now we want to see some pics ;D

 

[pacemaker]

Yeah !!
for now it's in use for a recording session,
but i will do that when it will be available,
( after cleaning the messy wiring ;-)
I would also like to put some TVA atom or mallory TC72 in place of the solen MKP,
and try to make a gain mod to get line level and mic level on a switch,
was thinking of using 25K pot and a switch to add a 75k resistor,
i have to calculate how much gain rannge i will have with only the 25k pot,
thanks for this project and all the others Volker !!
Regards,
Francois

 

[AMZ-FX]

Since the D-LA2A supplies 5V to the meter back-light (fairly low voltage) you may want wire the LED's in parallel so they can reach desired brightness. Since most LED's have ~2V forward voltage, two in series would be ~4V and the brightness would not be enough even with no series resistor.

No, the current through the LEDs determines brightness...  most LEDs can only handle 20ma max, so if we are using 5v power and put the two LEDs in series, a 62 ohms resistor would do the job, giving us around 17ma through the indicators.  You could go as low as 56 ohms for the current limiting resistor but any lower will shorten the life of the LEDs.

The backlight connection would be: +5v --> LED1 --> LED2 --> 62 ohm resistor --> Ground.

LED resistor calculator

regards, Jack

 

[ruckus328]

Hey guys, wondering if someone can help me here, having the same problem as pablobolche.  Some info on a power transformer would be much apppreciated, BOM doesn't really give anything useful.  Looks like something like this would kinda work:

http://www.antekinc.com/details.php?p=47

but doesn't get me the 5 volts for the relays.

Other thing I'm a little fuzzy on but think I've figured out ia the grounding scheme on this thing.  Looks like both of the 5V 2 pin headers on the L&R channels get jumped over to the 5V 2 pin header by the 5V regulator.  OK, good there.

Then there there's a set of 2 nonlabeled ground holes with a silkscreened line on them on the Left & Right channels in between the sowder 4383 connector and relay.  There's also a 3rd one over by the 3300uF cap by the 5V regulator.  I'm assuming each of these points wire to the star ground.  Why 2 ground holes in each one of these though?  Just want to make sure I'm not missing something here.

 

[pH]

Oops, sorry there Ruckus, forgot about those relays. I never use bypass relays so the Antek worked well for me.

-Paul

 

[kazper]

Hey guys, wondering if someone can help me here, having the same problem as pablobolche.  Some info on a power transformer would be much apppreciated, BOM doesn't really give anything useful.  Looks like something like this would kinda work:

http://www.antekinc.com/details.php?p=47

but doesn't get me the 5 volts for the relays.

Other thing I'm a little fuzzy on but think I've figured out ia the grounding scheme on this thing.  Looks like both of the 5V 2 pin headers on the L&R channels get jumped over to the 5V 2 pin header by the 5V regulator.  OK, good there.

Then there there's a set of 2 nonlabeled ground holes with a silkscreened line on them on the Left & Right channels in between the sowder 4383 connector and relay.  There's also a 3rd one over by the 3300uF cap by the 5V regulator.  I'm assuming each of these points wire to the star ground.  Why 2 ground holes in each one of these though?  Just want to make sure I'm not missing something here.

I'm sure that Antek will work, and you could use one of there smaller VA transformers to cover the 5V.
http://www.antekinc.com/details.php?p=7

As far as the grounds,  they were each made to use a spade type connector that exited towards the back. I think the design is that of a single PSU and 2x la2a circuits hence the 3 grounds as you discussed.If your flying leads use either.. but you probably know that...

 

[[silent:arts]]

grounding

 

[[silent:arts]]

My PSU transformer specs:

Prim: 2x115V 60VA
Sec1: 250V 0.05A
Sec2: 250V 0.05A
Sec3: 6.3V 2.00A
Sec4: 6.3V 2.00A
Sec5: 9V 1.00A
Screen: Cu Foil
Dimensions: 85mm x 39mm
Weight: 0.95 kg
ta 40/E 50/60Hz n. EN 61558

I have them in stock (EUR 36,60 + VAT if necessary),
but shipping costs to the US would be EUR 26,05