D-LA2A Support Thread

[Studio Mollan]

Yes, R37 is the high-pass filter. Has rather extreme effect on sound so like I said, put it on the front panel.

R11 is the global feedback resistor. LA2A make up gain amp is absolutely swimming in negative feedback with that 68k. It's a very linear amp, complete devoid of any recognizable tube distortion. You won't know it's tubes until someone tells you because the excess feedback removes all distortion.

R11 as a pot is basically an extra gain control. Try 50k in series with a 470k pot maybe. It will give you a lot of extra gain (and control), and you will be able make those 12AX7's sound distorted by removing feedback. But 12AX7 distortion sounds like crap and now you have a stupid amount of gain, so you probably don't want that. Harmonic distortion, yes, but not nice.

Solution: replace 12AX7 with 12AY7. You will lose some gain, but will be able to take it back by removing some of the excess feedback. Now the distortion sounds much better.

and NOW you have a tube amp!

Hi!
I'm going to try this on my la2a clone. The pot instead of the fixed 68k resistor. What taper should the pot have?
Thanks!
/
Emil

 

[kml23956]

Does anyone have a copy of the US BOM? The link on the first page is dead?

 

[firfe]

Mr. Firfe, did you cross check the tubes from left to right?

hello
thank for help.
yes i've try to cross check the tube...and i've change all the tube by new one...same probl.

it's looks like the T4B don't work.
but i don't know how to test them.
i'v found some answer in the web but not clear for moment.
i have some freetime again to check my compressor this week .
best
jf

 

[desol]

BOM  is back up?  ;D

 

[frazzman]

Sorry to ask this question again... But I just wanted to check on the wiring of the primaries on the RONDO transformer...

With dual primaries - (2x White & 2 x Yellow) - For 230V operation - do I wire one yellow primary to the IEC connector & one white primary to the other side of the IEC connector and then join remaning yellow and white primaries together?

This is the first time i've had a toroid with twin primaries...

 

[desol]

High voltage operation should be in series...low voltage in parallel. So yes, yellow and white to mains, yellow and white joined together.

ie:

 

[frazzman]

High voltage operation should be in series...low voltage in parallel. So yes, yellow and white to mains, yellow and white joined together.

ie:

Thanks for confirming
I browsed through so many peoples build photos but couldn't really make out this detail to confirm my understanding of the 230v wiring, maybe lots of 115v builds
I'm just about ready to put this all together. If I need to crimp one more molex connector I will be insane

 

[desol]

Molex's can be a pain... 

- Obviously (just wanted to add) , on that 230v wiring, make sure that the joined yellow and white are from each one of the primaries. Just sayin...

 

[frazzman]

Molex's can be a pain... 

- Obviously (just wanted to add) , on that 230v wiring, make sure that the joined yellow and white are from each one of the primaries. Just sayin...

Oh yeah, of course.. You mean because there's a white and yellow/green wire in the secondaries ? The primaries have the black Heatshrink around then which makes them easy to identify. I've built about 4 pultecs in the past but I always find these high voltage circuits nerve-racking on first power up even though I know everything's as it should be, something about a 630v cap that is (and should) keep you on your toes

 

[desol]

Molex's can be a pain... 

- Obviously (just wanted to add) , on that 230v wiring, make sure that the joined yellow and white are from each one of the primaries. Just sayin...

Oh yeah, of course.. You mean because there's a white and yellow/green wire in the secondaries ?

No, just that somebody not in the know might tie one primary together (mistakenly) and put 230v across a single primary... 

 

[frazzman]

Molex's can be a pain... 

- Obviously (just wanted to add) , on that 230v wiring, make sure that the joined yellow and white are from each one of the primaries. Just sayin...

Oh yeah, of course.. You mean because there's a white and yellow/green wire in the secondaries ?

No, just that somebody not in the know might tie one primary together (mistakenly) and put 230v across a single primary... 

You mean my mistakenly joining yellow to yellow or white to white ?

 

[desol]

;D Yes... I suppose so.

I can't really remember if one is just yellows and one is white's...or if there's a yellow and white on each.. or...
We understand each other...that's the important part.

 

[frazzman]

;D Yes... I suppose so.

I can't really remember if one is just yellows and one is white's...or if there's a yellow and white on each.. or...
We understand each other...that's the important part.

Good good, I just wanted to make sure! There's two pairs of yellow, two pairs of white, each pair has Heatshrink around them. In the builds I've seen, I noticed a lot of people wiring them in parallel but I'm down under so it's 230v all the way. Thanks for your help

 

[finbase]

Helo folks!

I've been trying to find the answer quite eagerly, but couldn't... My apologizes if this is already thoroughly covered.

I'm just wondering that in which la2a revision and production year this Volker's D-la2a/project schematic is based on? My la2a experiences are more or less based on UAD plug-ins, but as far as they're concerned I've found that the Greyface is sonically THE la2a for me. If I've understood it right, UAD's Greyface is emulated after the very first production batch and revision. So that's something I'd like to build also...

So my questions (one already asked..)
-In which revision this Volker's d-la2a is based on?
-If not based on the Greyface (revision 1), is this project easy to "modify" so that the result would be sonically equivalent?

Although I'm still a complete n00b as far as electronics are concerned, and I have a few more beginner-friendly projects on my to-do list first, the thought of building a D-la2a unit is darn obsessing... So why not start studying the topic already!

Thanks,
finbase

 

[frazzman]

Helo folks!

I've been trying to find the answer quite eagerly, but couldn't... My apologizes if this is already thoroughly covered.

I'm just wondering that in which la2a revision and production year this Volker's D-la2a/project schematic is based on? My la2a experiences are more or less based on UAD plug-ins, but as far as they're concerned I've found that the Greyface is sonically THE la2a for me. If I've understood it right, UAD's Greyface is emulated after the very first production batch and revision. So that's something I'd like to build also...

So my questions (one already asked..)
-In which revision this Volker's d-la2a is based on?
-If not based on the Greyface (revision 1), is this project easy to "modify" so that the result would be sonically equivalent?

Although I'm still a complete n00b as far as electronics are concerned, and I have a few more beginner-friendly projects on my to-do list first, the thought of building a D-la2a unit is darn obsessing... So why not start studying the topic already!

Thanks,
finbase

Hi finbase... it sounds like maybe you're looking at this the wrong way... trying to make hardware that models that sound of the software you like...I don't know what revision LA2A volker's design is from but I'd be willing to tip it sounds more faithful to the original than the UAD plugins do

 

[finbase]

Yes, I know that my question isn't too relevant...

Unfortunately a hobbyist like me don't have the access to all the fantastic hardware. I am a professional musician, but my sound engineering is more or less only a passionate and enjoyable hobby, like this DIYing is starting to be. Nevertheless, I know quite well "tonewise" what I like and what I don't.

So let's put it in other words: what are the main parts on the la2a circuit that affects the unit's "timbre"? Input and output transformers and tubes, of course, but I assume that some particular capacitors in the signal path too? If I want to emphasis the "low mid body" (200-400Hz), what kind of options do I have?

Hopefully my quesiton makes sense to someone. My intention is not to make the others tired with my daydreams...

 

[finbase]

Yes, I know that my question isn't too relevant...

Unfortunately a hobbyist like me don't have the access to all the fantastic hardware. I am a professional musician, but my sound engineering is more or less only a passionate and enjoyable hobby, like this DIYing is starting to be. Nevertheless, I know quite well "tonewise" what I like and what I don't.

So let's put it in other words: what are the main parts on the la2a circuit that affects the unit's "timbre"? Input and output transformers and tubes, of course, but I assume that some particular capacitors in the signal path too? If I want to emphasis the "low mid body" (200-400Hz), what kind of options do I have?

Hopefully my quesiton makes sense to someone. My intention is not to make the others tired with my daydreams...

Ok, I've been thinking about my questions more thoroughly...

Just forget my previous my messages. The answer to my question is quite obvious: "call it EQ, baby!"

 

[melomane]

crazy stuff! I will order soon a kit

 

[[silent:arts]]

we do not have kits for this ;-)
just PCBs and PSU transformers.
with all the other parts, it is DIY  ;D

 

[frazzman]

I'm preparing for tonights grand unveiling... first power on. I think everything looks good, does this toroid wiring look correct?

PSU is Wired in series for 230v operation. The picture shows it all, but in case its not clear... There are 2 pairs of primaries, i've got the white of one pair tied to the yellow of the other pair. Then of the remaining 2 primary leads - white to IEC (L) and yellow to IEC (N)

IEC Earth tied to chassis as usual, and toroid earth wire tied to chassis as well.

One other thing I noticed, in silent-arts original picture of the toroid wiring, his picture shows a "brown" and a "brown/red" wire. On my transformer, there are only 2 pairs of brown wires. I take it these can be used interchangably?

Thanks a lot