D-LA2A Support Thread

[FarisElek]

My meters are 1db off from each other when in +4db mode. Does anyone have any clues to what may cause that?

Ryan

 

[wlinart]

Since the 12ax7 are getting more expensive, i'm looking at the 6n2p tubes as alternatives maybe. But the pinout is different. I found this picture. Am i right in thinking that for the D-la2a i'd have to:
- cut the trace between pin 4 and 5
- rewire the heaters to pin 4 and 5, and connect pin 4 with the other tubes' pin 4, and pin 5 with the other pin 5 and pin 9 of the 12bh7 and 6AQ5
- rewire 9 to ground
I'm not sure of the last step, is it necessary? And where can i easily connect to ground? I was thinking maybe at the ground pins from c171/172/173/174, because those are closeby. Any advice?

 

[shoetique]

I've put together a video that showcases my [silent:arts] D-LA2A build. The video covers LA-2As in general, my build notes, various upgrades and the calibration procedure. There are even some clips of the unit in action!

Thanks so much to everyone in this thread. Your insights and knowledge have been invaluable.

 

[ryanthomas1323]

Hello, I'm Ryan, new member here - first post.

I just purchased the PCB for this project and Volker has alerted me that he is no longer selling the Rondo PSU transformers. Has anyone used an alternative? Or does anyone know of an alternative?

Thanks for any help,
-Ryan

 

[shoetique]

Hello, I'm Ryan, new member here - first post.

I just purchased the PCB for this project and Volker has alerted me that he is no longer selling the Rondo PSU transformers. Has anyone used an alternative? Or does anyone know of an alternative?

Thanks for any help,
-Ryan

Any chance you could order the one Volker used directly from Mueller Rondo? If not I can try to help you spec out an alternative one.

https://www.mueller-rondo.com/eng/products/winding-technology/toroidal-transformers/

 

[ryanthomas1323]

Sorry Shoetique I missed your reply, I did email Mueller Rondo (including part# and specs etc) to see if they would send me one. That was about two weeks ago now and I still haven't heard back from them. I suppose I should look for a source in the USA for this, anyone know of a good place to start?

 

[shoetique]

Hey Ryan - I just reached out to the following to see if they have a suitable replacement:

Mouser
DigiKey
Toroid.com
MPJA.com

I also sent a request to mueller-rondo. I'll let you know if I can find anything.

 

[beatnik]

I know a company here in Italy making custom toroids as well as EI and C core Transformers. I'm not sure they have English speaking customer service but I'm happy to help you. They are A.E.I. Onori
Usually no problems with one offs

 

[ryanthomas1323]

Shoetique/beatnik, thank you for the help! I suppose it makes sense to see if there is a reply from USA source, and if not I would love if you could help me with Italian manufacturer.

 

[shoetique]

@ryanthomas1323 I actually heard back from Mueller-Rondo! You can still buy this from them for 67 EUR shipped. Not sure if that shipping price is to the UK or USA. It might be more for USA. I used the contact forum on this page to request a quote: https://www.mueller-rondo.com/eng/contact/

Make sure you request the specific part number for the Toroid: R2-0060-0011

Let me know how it goes!

 

[ryanthomas1323]

Right when I saw your message it occurred to me to check my spam folder, and there it was from March 27th. Thanks for your help.

 

[The_Nimaj]

This is great news. I'm parting out this build and was just about to get into the weeds of finding a suitable replacement.

 

[The_Nimaj]

@ryanthomas1323 I actually heard back from Mueller-Rondo! You can still buy this from them for 67 EUR shipped. Not sure if that shipping price is to the UK or USA. It might be more for USA. I used the contact forum on this page to request a quote: https://www.mueller-rondo.com/eng/contact/

Make sure you request the specific part number for the Toroid: R2-0060-0011

Let me know how it goes!

I heard back from them as well and was quoted 56 EUR + 51.30 EUR shipping to US. It may not make sense at that price, so I'll have a go at rigging a replacement. Not ruling out putting two power trafos in there...

 

[Raato]

On a last mile with my build. It has been a great journey - Lots of learning, but no problems so far. But now little help seems to be required.

Everything else seems to be working correctly - Except for the VU meter

When "Gain Reduction" mode selected meter shows amount of gain reduction correctly, but when I switch meter to show output level it is not functioning properly. When I feed the normal calibration signal in needle barely moves. Meter is getting some signal, but not showing what it should.

When I raise the Gain level or push it with hotter signal meter needle starts to bounce wildly.
It looks almost like it is trying to move to wrong direction.

Same problem is on both channels - Otherwise compression and signal seems to be working and going through as it should.
I've double checked the wiring and molex connections to be working.

I am getting around 60V from Zener

Has anyone experienced the same? Or have idea where I should look?

 

[andow]

On a last mile with my build. It has been a great journey - Lots of learning, but no problems so far. But now little help seems to be required.

Everything else seems to be working correctly - Except for the VU meter

When "Gain Reduction" mode selected meter shows amount of gain reduction correctly, but when I switch meter to show output level it is not functioning properly. When I feed the normal calibration signal in needle barely moves. Meter is getting some signal, but not showing what it should.

When I raise the Gain level or push it with hotter signal meter needle starts to bounce wildly.
It looks almost like it is trying to move to wrong direction.

Same problem is on both channels - Otherwise compression and signal seems to be working and going through as it should.
I've double checked the wiring and molex connections to be working.

I am getting around 60V from Zener

Has anyone experienced the same? Or have idea where I should look?

Which meter are you using?

 

[Raato]

Which meter are you using?

Thanks for piping in Andow!
Oh right - Could've mentioned that straight away.

I have Nissei TN-73-HS
with 3,6k resistor from switch to positive terminal on a meter

 

[Raato]

This is the exact one. 500uA 520Ohms

https://a.aliexpress.com/_EuiSGQX

There is spec sheet in Description

 

[andow]

I would suspect it's not a real VU meter and the rectifier is missing. Which would explain why it works for gain reduction where a DC signal is present.

 

[Raato]

Thanks a million Andow!
You were right on the money. I thought I had ordered correct meters, but clearly no.

I added Bridge Rectifier made with 1N5818s and needed to up the resistor to 4.7k in order to get it to show correct output level.
And voila!

So at this point it seems that everything is working as it should.
Just need to fix some wires and it should be ready for upcoming vocal recordings.

What a glorious day!

 

[The_Nimaj]

I heard back from them as well and was quoted 56 EUR + 51.30 EUR shipping to US. It may not make sense at that price, so I'll have a go at rigging a replacement. Not ruling out putting two power trafos in there...

Just to follow up on this, I ended up using an Antek AS-05TC250 . I cut the lead of the 5v on the transformer and jumpered the second 6.3v to the 5v Relay rail at the terminal blocks ( The 5v tap would've been a little too close for comfort to the drop out voltage on the regulator I used). This works well and is inexpensive (currently $32 + 8.5 shipping) for US buyers.