D-LA2A Support Thread

[justinheronmusic]

Close up of the PCB

 

[justinheronmusic]

Faceplate from Front Panel Express. My take on the classic LA2A faceplate, I know it's boring but I wanted it to feel real and familiar. I've always wanted an LA2A, as I use the plugin versions on my voice regularly. The color is the "Light Grey" setting on FPD, which still looks pretty white to me. Most of the font is .4mm engraver. I think I used a 1mm cutter for the lines on the left and right side, it's a little thicker than I would have liked, but this is my first Front Panel Designer made faceplate.

I went a 3RU case from Collective Cases. Their case is beautiful and well ventilated.

 

[Noisy1]

Nice looking faceplate! I like it. Your logo has a little Frank Lloyd Wright vibe to it. Fitting for your corner of the world.

 

[kosi]

Looks good !
What happened to the left side of the pcb ?
and, which Carnhill did you use ?

 

[PeteC]

Nearly finished my off board wiring , but one question regarding the dual/link switch wiring

Do I need to attach the black wire from each molex to the screen of the cable?

  Or is it simply that the two hot wires need to connect with each other via the single pole switch .
Thanks
Pete

 

[kosi]

  Or is it simply that the two hot wires need to connect with each other via the single pole switch .

correct, black is "only" for shielding

 

[justinheronmusic]

What happened to the left side of the pcb?

The left side of the PCB went to a friend who is interested in DIY. He wanted to practice his soldering skills on the board so he could prepare himself for an MNATS REV D build. My guess is that it's probably sitting on his workbench with some random components in it. Cutting the PCB was not the funnest project, as the line to cut is very thin and messing up would have been not cool! If I could do it again, I would have just populated one side of the board, and left the other side in tact.

Which Carnhill did you use?

The Carnhill is the VTB2291 Ungapped Output Transformer. I tied pins 2 & 4, and 6 & 7 together with some capacitor leads from a few capacitors I had mispurchased on eBay for a project a while back. That gave me 9600:600. I chose the Carnhill because the company has a reputation for having some "vibe"  or "weight" to their transformers. While it would have been nice to have Sowter on the input and output, the Sowter output was too expensive for me to justify. Then the idea was that I would use the Solen cap for the big 10uf (C5 is it?), which would be cleaner then a Mallory or a Sprague, so in order to "put back" some of the dirt I'd go with Carnhill over Jensen or Cinemag.

The Edcore has an amazing price, and was highly considered. The IGS ONE and the ONE LA both use the Edcore output transformer an Sowter on the input, which further enticed me. The ONE LA gets a lot of positive regards. I think I was just feeling the Carnhill more for whatever reason. Providing that things line up and I can build the D-AOC, I will probably go Cinemag, as they are made in the USA; shipping, resources, more economical, ect.

 

[PeteC]

Hi everyone

I will complete my offboard wiring today and will be ready to power up my DLA2A  ;D

Any recommendations on powering up and checks for the first time ?    - .i.e. TB4s out, tubes out , voltage checks in particular spots etc ?

Cheers
Pete

 

[justinheronmusic]

Hi everyone

I will complete my offboard wiring today and will be ready to power up my DLA2A  ;D

Any recommendations on powering up and checks for the first time ?    - .i.e. TB4s out, tubes out , voltage checks in particular spots etc ?

Cheers
Pete

It should pass signal in bypass; it should pass signal with tubes in in not bypass mode, and if everything sounds fine with tubes in and nothing is blowing up, put the T4B in and you've got yourself a DLA2A  8)

 

[PeteC]

One more question if I may.......

whats fuse rating is recommended for the Rondo mains TX ?  I am thinking of using 0.5A slo blo.  I am on 240v UK mains supply.

And is one fuse in the IEC side sufficient or should I fit a circuit fuse on the secondary side ?

( oh,  that's 2 questions ....)

Cheers
Pete

 

[PeteC]

happy to say my build works great on first fire up !
Mullards, GE and tesla tubes.
Edcors on the  in and out

Only issue is one of my budget nissei meters doesn't light up but that's easily fixed
Audio is superb !

Thanks to Silent Arts for this great project and pcb.

Pics to follow later.
Cheers
Pete

 

[hugo]

Hi all,

My D-la2a has got a strange issue :
When the output xlr is connected and the input is disconnected, i have a ground noise like a ground loop. When i plug the input, the noise stops (bzzzzz)  and i have self oscillation with an other noise (shhh)...
The noise is related to the gain, so it is before the preamp section... ? I do not know how to check this ...

Update : I tried to find the origin of the buzz, and when i removed the power ground (unit was on),  a big buzz started. I reconnected the power ground but the buzz does not leave...

 

[kosi]

And one more !

Here's mine, building was pretty quick, designing the faceplate took me over a year, but now, I learned to use Frontplattendesigner with the help of GDIY member Livingnote !

Input is Stancor WT-21, same as an UTC A11, see here:
https://groupdiy.com/index.php?topic=36416.0

Output Sowter 8940A

Left side old Ceramics and Sprague, right side Wimas and Solen.
Some small things missing, but works like a champ !

Thanks Volker and the rest of this cosy thread for all the help, I learned A LOT with this project.

 

[kosi]

inside

 

[hugo]

Hi all,
Stereo link is supposed to link the gain of both channels ?..because my stereo link affects only thepeak reduction. Is it normal ?
Thank you

 

[justinheronmusic]

inside

Nice! Have you noted any differences between the Electrolytic and the Solen channels?

 

[hugo]

Hi all,
Stereo link is supposed to link the gain of both channels ?..because my stereo link affects only thepeak reduction. Is it normal ?
Thank you

up...

 

[[silent:arts]]

Stereo link is supposed to link the gain of both channels ?..because my stereo link affects only the peak reduction. Is it normal ?

yes, this is normal.

 

[hugo]

yes, this is normal.

Ok so my unit is finished ! Thanks all.

 

[justinheronmusic]

Ok so my unit is finished ! Thanks all.

Did you already post photos?