LA2A build

[Nick6691]

Hi. I´m Nick and I´m new here.
I´m looking for info about an la2a build.
My first intension was to build the PTP version found on RecProAudio.
Then I saw the pcb version from Honeybadger Audio (there may be others aswell) that includes Lundahl Transformers
Anyone who has experience with pcb La2a projects?
What T4 should I go for? Transformers?

Would of course be the most interesting to do the PTP but I dont know if my electrical skills is enough.
I pretty ok at soldering and good at reading instructions but not able to fully understand scematics.
Maybe there is help in this group to solve thoughts and problems I can run into

Nick

 

[timtom]

Hi Nick,

I just ordered the honeybadger PCB and will start in the next weeks to build this one. I was also a bit overwhelmed with the PTP version.
I will use different transformers Edcor transformers for now as I already have them. For the T4 i will go for the IGS one or the ProReplicas one.

 

[Nick6691]

Interesting!
I heard good things about the IGS T4

 

[thomasdf]

If you can't read schematics, PTP and PCB is the same ... it's painting by numbers.
I personnally think PTP is the best way for such a simple circuit. If you are careful and proceed with method, it's pretty straight forward and every bit of info regarding the layout can be found online. Just find a big case, and try to use the room you have so you don't end up with every components above one another. You'll also be able to solder / desolder many times, do modifications etc... doing such things with a PCB can lead to cutting tracks, or messing them up with overheating.

Regarding transformers : it also depends what case you are using and how you plan to mount them. Lundahls have pins that need to be soldered to a PCB. Or you need to tinker and find a way to mount them, then wire them directly.
You can look at Igor's transformers, they are pretty good. I used them in a recent LA2A ptp build and I'm very happy, they are a great bang for the buck.

T4b: I went with Kenetek. Amazing. But they are alternatives, and good ones for sure.

Long story short : I think PTP is more DIY spirit, more rewarding Give it a shot ... if you feel like you're fucking it up it's always time to save your components and buy a PCB.

 

[living sounds]

I've got both the Kenetec (standard version) and the IGS T4B (in different KT LA2A Clones). Both are good, but I do think the Kenetec one is closer to the original and more versatile.

 

[Nick6691]

Long story short : I think PTP is more DIY spirit, more rewarding Give it a shot ... if you feel like you're fucking it up it's always time to save your components and buy a PCB.

Thanks thomasdf
Yes thats what I really want
Im thinking about the analog vibes chassis. Or do you have another chassis to suggest. Can the kenetec be bought in europe or is it just from usa

 

[Nick6691]

I've got both the Kenetec (standard version) and the IGS T4B (in different KT LA2A Clones). Both are good, but I do think the Kenetec one is closer to the original and more versatile.

Thanks
Can the kenetec be bought in europé.

 

[thomasdf]

The Kenetek can be found on eBay, have a look. I am located in Europe and bought it without problem.

The Analog Vibe chassis is nice for sure, but if it's your first build or first PTP build maybe you can buy a regular 3U enclosure... You'll have much more room to build the circuit. The vintage chassis calls for specific turret and parts, and is sometime a little bit narrow. And it's quite expensive and won't allow a PCB to be fitted if you change your mind regarding the building method.
You can still spend your money on a beautiful front panel, meter and knobs.

 

[Nick6691]

I’ll check ebay and looking for chassis alt.
Going to check the UTM transformers aswell

 

[dmp]

I and many others built the D-LA2A pcb by Silent-Arts
It's a very well done PCB. High quality.
I used a Jensen 1:1 line input and a Edcor WSM output ($23). I prefer the line input since I'm sending it line levels from the DAW, but the stock uses a 10:1 step up, which gives you way more gain. Some people use the high gain transformer and then cut the level.
Whatever you chose, you want a shielded input transformer to avoid oscillations with the high gain of a LA2A.
You could build it PTP but it is more work and takes more expertise - not a beginner project at all (honestly any high voltage tube gear is not a beginner project).
The layout is important in a LA2A due to the high gain and potential for oscillations, so trying to PTP would be particulalry challenging.
I built my own T4, but I'm not sure the parts can be found anymore

 

[Nick6691]

Thanks dmp for your thoughts. I shall take that to my conciderations. Im not really a beginner I’ve buillt an 1176 from kit a bounch of microphones both condenser and ribbons. Built my first studio in 1989 and been solderd ever since but never done a high voltage tube project
Hmm.

 

[beatnik]

The Recproaudio layout is well tested you can't go wrong with that. Or the Silent Arts PCB

I think the difficulty isn't really to build the thing, but potential troubleshooting.

The Analogvibes chassis is good quality but it's a bit too expensive, also the main Keystone turret board was discontinued everywhere last time I looked

You can also get a chassis from DIY racked https://www.diy-racked.com/product/la-2a-ptp-case/
This is not as neat as the Analogvibes but it's also a lot cheaper and many people including myself has used it with success.

 

[Nick6691]

Thanks beatnik for your input. Its alot to take in before deciding the way to go.
I found a turret board that I think will work

 

[thomasdf]

It will work for an LA2A build, for sure, but I am not sure it will fit in the Analogvibes chassis... It's approx 65mm deep but keep in mind that large current means risks of electrical arcs if your turrent are too close to the grounded chassis and not properly insulated.

 

[Toobme]

I put a rubber mat under my turret board and also raised up a 1/2” with some nylon standoffs.
That looks like the exact board I used for my first la2a build.
I found those a touch flimsy so found other alts at antique electronics’ site.
Like this one:

 

[Nick6691]

Found the turret board at digikey

 

[Nick6691]

Hi Nick,

I just ordered the honeybadger PCB and will start in the next weeks to build this one. I was also a bit overwhelmed with the PTP version.
I will use different transformers Edcor transformers for now as I already have them. For the T4 i will go for the IGS one or the ProReplicas one.

Have you started your build yet?
I decided to go honeybadger to and just got my PCB and some parts

 

[timtom]

Have you started your build yet?
I decided to go honeybadger to and just got my PCB and some parts

I started populating the pcb, power supply is done already now I need to get the remaining parts like tubes & t4 cell.

 

[Toobme]

This is my second DIR-Racked build. The case is black but turns out really nice, I think.
Calm before the wiring storm:

 

[Nick6691]

I started populating the pcb, power supply is done already now I need to get the remaining parts like tubes & t4 cell.

Have you decided about tubes and T4?