D-LA2A Support Thread

[offthewallstudio]

I'm having a real tough time calibrating this thing. I see that people are changing R25 TBD? I do not have R 25 I have R 125 TBD.  And it is not a trim pot it is a 33k resistor i believe for drips cells. The good thing is that the unit passes audio. Pleeeeeeeaaaaaasssseeeee some one help me

 

[[silent:arts]]

R25 = R125 in the left channel, and R225 in the right channel.
This is the resistor which came matched with the T4Bs from Urei.

Btw, this is only for the meter and has nothing to do with the audio performance.
If you want to have it accurate Keith explains his procedure here:
http://groupdiy.com/index.php?topic=23253.msg276178#msg276178

 

[troubleous]

Hi again guys!

I've finally managed to wire the meter leds + pilot led succesfully and everything is working fine, EXCEPT one thing that I can't seem to figure out:

After replacing the neon bulbs with zeners, I still can't get the zero adjust calibrated the meters. I just can't reach zero on the meters (on GR mode), no matter how I adjust the trimpots (I have installed 100k trimpots on R125/225 position, but no help either). I have 3.6K resistors on my meters (NISSEI TN-73).

Anyone has a clue what the culprit could be?

Cheers,
Jarkko

 

[troubleous]

Aaand here is a pic of the unit in question

 

[[silent:arts]]

I have 3.6K resistors on my meters (NISSEI TN-73)

My google search comes to ebay.

Try without the 3.6K resistor.

 

[troubleous]

I have 3.6K resistors on my meters (NISSEI TN-73)

My google search comes to ebay.

Try without the 3.6K resistor.

That's the correct meter indeed! (Sorry, forgot to post the ebay link myself)

But, dang, I tried running one channel without resistor, but no change in the meter reading. I tried also running one channel without T4B, but no change with that either. Getting gray hair here (on top of the old ones).

When I turn on the unit, the needles rise below zero, but then slowly drop to pointing -1.

Anything else that could 'cause this?

Cheers!

 

[weiss]

Aaand here is a pic of the unit in question

wow. this unit looks awesome!

 

[offthewallstudio]

For calibration he said r25 i now know it is r124. Mentioned to replace the resistor with a trim pot i believe.  The resistor i have is 33k i think 1 watt. Not aure what trim pot to get. That is the only way to get the meter to zero?  Thanks

 

[offthewallstudio]

okay well I'm just about done with this thing. I have a few minor issues a little bit of noise left channel isn't compressing the right channel VU meter seems to be controlling the left channel VU meter. Defender light lamp is not installed. I have put a lot of time into this and a lot of money. I live in the Boston New Hampshire area and I need a pro to finish this properly for me. I'm going to travel to drop it off. maybe a school in the area would like to take this on as a project? I don't even know what to Google for help thank you

 

[troubleous]

Alrighty, after fiddling with my unit a bit more, It seems the culprit setting the meters to zero are the 6AQ5's.

As soon as they are in, I can't zero the meters - without them, no problem. I tried two batches of 6AQ5's and the same problem exists with both of them. I guess it's time to order some more of those and try to find proper ones.

When the 6AQ5's are in, the unit seems to work properly (compressing nicely, though the VU-meters are not calibrated).

Or could the problem be somewhere else than the tubes? I re-checked the heater wiring and re-flowed the joints just to be sure, but that didn't change anything.

Cheers,
Jarkko

 

[saxmonster]

Everything is in this thread to fix meters and what ever else might be going on.  The 33k resistor spot on both side has to be a trim pot in order to zero it out. I'll try to find the link.

 

[troubleous]

Everything is in this thread to fix meters and what ever else might be going on.  The 33k resistor spot on both side has to be a trim pot in order to zero it out. I'll try to find the link.

I've got the trimpot installed - but I can only zero the meters with the trimpots when the 6AQ5's are not in place. As soon as I replace the tubes, it's not possible to get the meters beyond -1. I've read people having problems with faulty tubes, so I'm starting to think it's my problem too.

Cheers,
Jarkko

 

[saxmonster]

can you get a larger trim pot so it swings further (down or up) away and see if you can get it to zero out and then compress and see if the meter is somewhat close to the actual compression on the signal out of your daw and back into your daw?

 

[troubleous]

can you get a larger trim pot so it swings further (down or up) away and see if you can get it to zero out and then compress and see if the meter is somewhat close to the actual compression on the signal out of your daw and back into your daw?

Will try and report back!

Cheers,
Jarkko

 

[chrisenglish]

Added Kingston's mod of shorting the 68K resistor after the input transformer in addition to the 2K7 comp/limit resistor to give it about 6-8db more gain when using it strictly as a tube amp. Was worried about sending the signal up to the front panel and back right after it comes off the input transformer, but it works great. This is the added "Preamp" selection along on the Comp/Limit switch.

I decided to go with the 12AY7 preamp mod (changed the R09 and R13 to 100k).

I have a DPST On/Off/On switch on the front panel

But I can’t figure out how to wire the preamp mod / limit / compressor switch, "shorting the 68k resistor"???

Thanks for any help!

 

[Nele]

Hi,

A while ago I've built this unit for someone else. It was working fine but the level readings we're off in outut mode. It turned out I forgot the 3K6 resistors, so I added them but the readings are still way off.
If I feed the unit a sine-wave of 1K at about -4db the output, the meter in output-mode is clipping to the right. I have to apply gain reduction the get it to read around 0db.
However if I check the signal coming from the d-la2a on my soundcard (Motu 16A) it reads -21db?? If I crank up the gain it will go to 0db but it sounds distorted.
The meters do track nicely in gain-reduction mode.

Any suggestions? It happens on both channels. They are matched and use matched T4B's.

 

[[silent:arts]]

You are confusing dBfs with dBu with VU.
With the 3K6 resistor the VU reads 0VU @ +4dBu.

The MoTu homepage states a 16As max. input level is +24dBu,
so +4dBu would read -20dBfs. This would match with your observation.
However, the MoTu has a trim range of 22dB, so it might vary.

 

[Nele]

Thanks!

 

[chrisenglish]

Added Kingston's mod of shorting the 68K resistor after the input transformer in addition to the 2K7 comp/limit resistor to give it about 6-8db more gain when using it strictly as a tube amp. Was worried about sending the signal up to the front panel and back right after it comes off the input transformer, but it works great. This is the added "Preamp" selection along on the Comp/Limit switch.

I decided to go with the 12AY7 preamp mod (changed the R09 and R13 to 100k).

I have a DPST On/Off/On switch on the front panel

But I can’t figure out how to wire the preamp mod / limit / compressor switch, "shorting the 68k resistor"???

Thanks for any help!

ok I still don't have this happening...I am really close but something in my wiring is wanky...

this is how i wired the preamp/ limit / comp / switch

the neons go out when I switch to GR ???
.....gain control works in Output /+4 not GR/VU

 

[elpapadelcrio]

Hi Everyone.

First time posting here.

Just finishing to populate the PCB and I need to confirm that the last component that I'm going to solder to it is the right one.  I'm planning to use a 0.1µF 63V Vikiin Polyester Film Box cap in C8 (C8 is not in Azone BOM) and since it is neighbor of  C6 (100µF 50V) leads me to believe it's voltage capacity will be enough, does anybody can shed light on this?

Thanks
Marco