LA2A pcb project

Hi guys

Some of you might already knew, I am working on a LA2A pcb. The board is done and I'm currently stuffing it. Here is the board design:



The psu is separated from the main board and since the actual size of the main board allow it, we can put 2 of them side by side with and make a stereo unit. It has the footprint to allow Cinemag or sowter input Iron, output is install on the chassis and hardwired. I plan making a full build manual with all usefull informations, mouser BOM, etc. There will be some minor modifications and changes on the board by the way.

Anyway, let me know what do you think guys

here is the layout in picture

Interesting project, this pcb would be a good companion for a Tube Mic Preamp to form a nice channel strip.

Yup, with the proper size mic pre board and a proper psu The advantage is that their is some room to make proper rc filter combination and get the right value in case you make a stereo unit or a kinda channel strip

Great idea, been wanting this forever (just to busy / lazy to do it myself!)
Suggestion, a dual footprint on the tube sockets so one can use individual MilMax type sockets, like commonly used on a 2520. This allows it to be much more likely to fit in a 2 space enclosure,  as the tubes will sit much closer to the PCB

That's a good idea. I'm making the small mods to the board before releasing it so i'll definetly incorporate your idea. Do you have some mil-max part number?

Nice, looking forward. As a person who`s never worked with "high" voltage & tubes, I am looking forward to the documentation  8)

Try Mill-Max 0316-0-15-01-34-27-10-0 / 0322-0-15-01-34-27-10-0
I prefer the 0316-0-15-01-34-27-10-0, but go ahead and make the hole at least 0.89 to fit both as 0.87 is very tight

Nice looking project Deepdark  Would this layout be somehow adaptable to 51x format?

Best,
Iwan

DjaiTeam said:

Nice looking project Deepdark  Would this layout be somehow adaptable to 51x format?

Best,
Iwan

Click to expand...

Thanks I really don't know if it would be possible to make it 51x format. We would have to convert some 24V to 275vdc and run a heater section, too. Probably not impossible, but I've never designed anything for the 500/51x format.

Hi all

Things go well and I'm planning finishing the unit probably for Christmas, or in the holidays. The input transformer will not be the CMLI 10/600, but the CM-2570 (not on their site). It has larger lamination than the UTC A-10, and reported to give more signal level. I'll simply draw it's footprint on the board, for those who would like the pc pin version (a little more expensive because of the square shape of the can for the pc pin version). Output will be CM-2840 instead of the 2810.

Also, would you like me to add a little board / or footprint to accomodate the use of a Vactrol (VTL5C4/2) with resistors and diode, so one can use the vactrol instead of getting the T4B module?

I'll let you know about the developement, and post some pictures soon.

Hi deepdark, any chance to add Haufe transformer footprint to your pcb? I got lots of them and member silent arts sells them pretty cheap, too. I know its a lot of work, but there is no cinemag distributer in europe afaik and Sowter iron is pretty expensive.

I would love to buy some of your pcbs when available  8)
I think  the T4b cell is important for the sound of a LA2A, but I have never compared it to a Vactrol solution.
An additional board could be a good idea!

I could speak with Silent Art then, to know exactly what he has in stock and what would fit an LA2A (I never worked with these Transformers).

For the T4B, in fact, is there to control the compression, attack, release. Replacing it with Vactrol of about the same attack /releasing spec would act the same as a T4B, correct me if I'm wrong. It's a valuable replacement So I'll add a little board with Vactrol footprint as am option of the T4B.

Let's see what he has in stock.  Maybe a RK310  would make sense as input transformer. Its a 1:1 type. Thats not a bad thing, because it makes it easier to integrate the LA2A  in modern DAW enviroment for bus and master duties. For the output position a Lundahl 5402 or a its Edcor equivalent comes to mind.

Its always nice to have different options for the transformers. On the other hand its a lot of extra work, no doubt!  Thats just wishful thinking...

No matter how you do it in the end, thanks for your effort and the good work!

Lundhal would be a good option for the european guys I could try to make the footprint for Lundhal and I'll also make a 4pins molex connector to use chassis mounted transformer. I plan using the Cinemag CM*2570 for input and it's pc pin version's too big and it's squarish shape, so I'll simply use the standard version and hard wire it to the molex connectors. What I can do, is making a list of known working transformers and integrated it into the build manual. So we will have the option to mount on the board the Cinemag CMLI 10/600 (an other one that work, with lower ratio), the sowter 1009 and if possible, the lundhal as well as having molex connector to ease the use of external board transformers and make a clean wiring job that is easy to remove for troobleshooting duties, or to try some other transformers. Sounds like a deal?

My vote is for lundhal, cinemag, and edcor as an economic choice.  Look at some of the smaller trafos too, size of mic inputs, there are 1:1, 1:2, 1:4, etc that could also be used reversed for 2:1 or 4:1, etc, if one wishes.  Maybe a small "perfboard-style" section for the input trafo, that way people could use whatever they wanted with a couple of jumpers? With some mounting holes for stud-mounted trafos??

Also, I like the Vactrol idea.  I was going to use some 8-pin dummy plugs for this, but having them on-board is nice too. Maybe with a jumper so you could pick one or the other? Didn't drip do something like this with switchable T4Bs?

mitsos said:

My vote is for lundhal, cinemag, and edcor as an economic choice.  Look at some of the smaller trafos too, size of mic inputs, there are 1:1, 1:2, 1:4, etc that could also be used reversed for 2:1 or 4:1, etc, if one wishes.  Maybe a small "perfboard-style" section for the input trafo, that way people could use whatever they wanted with a couple of jumpers? With some mounting holes for stud-mounted trafos??

Also, I like the Vactrol idea.  I was going to use some 8-pin dummy plugs for this, but having them on-board is nice too. Maybe with a jumper so you could pick one or the other? Didn't drip do something like this with switchable T4Bs?

Click to expand...

Drip did a switchable version with fast and slow t4b, with a simple dpdt switch. I'll make a secondary little board to mount a vactrol with diode and resistors. With some little dip socket, we could simply remove and try some other vactrol (faster one), test how it sounds, etc. The goal is to let people choose what they prefer, and keep the board small enought to be able to put 2 in one case and make a stereo unit.  8)

Great project Deepdark!

And I agree with guys about more option for audio transformers(maybe you can add OEPs)!

And Vactrol will be great option!

Little update:

I've just finished stuffing the board. I only found 3 little mistakes that will be corrected in the revision board. The front panel is drilled, power tranny is mounted on the back panel. Now I'll start wiring it all. I sould say that I'm a little stressed right now haha. Hope everything will just go fine and there will be no trouble such as oscillation or stuff like that

Power supply installed and works good.