D-LA2A Support Thread

[hugo]

Yep. I've been thinking of adding a fan to mine. It gets pretty warm in there, and my zero adjust goes whacky.

I fought a 40x40mm fan, 5v DC. Could somebody help me to find a good point to wire it?..
Thank you

 

[culteousness1]

Looking at the schematic, I would suggest to take the +5 V from the relay rails, i.e. terminal PL1.
But is there any current rating for your fan?

Cheers,
Carsten

 

[hugo]

Looking at the schematic, I would suggest to take the +5 V from the relay rails, i.e. terminal PL1.
But is there any current rating for your fan?

Cheers,
Carsten

I do not have any info on this...there is just a sticker with 5v wrote on it. I did not know if it was AC or DC, i connected at the heaters with resistor (to drop 1v). The fan was making a noise but no move because i think it needs DC current. Regarding your suggestion, will the fan work even in "bypass mode"  if i connect it to the PL1?

 

[culteousness1]

The +5 V power rail is not affected by any bypassing. So it should work as long as I don't miss anything obvious here  ;D

 

[desol]

With mine, I'm mostly worried about the effect of the heat with regards to the longevity of the components. Mainly, mine has original UREI opto's...which I've read do have a certain lifespan and are not affordable. I don't want to unnecessarily shorten the life of them because I didn't figure out if less heat is better. With the original layout, it wouldn't have been an issue(not that it is one with this layout). Also, there's noise. I wonder what amount of noise would be created by adding an internal 40mm fan? Maybe it's insignificant?

 

[hugo]

The +5 V power rail is not affected by any bypassing. So it should work as long as I don't miss anything obvious here  ;D

I finally decided to remove the fan, it was noisy like a computer. The case is vented, i did not notice any problem on my unit so it will stay like this...

 

[desol]

....I suppose I'll just drill a few more holes into the lid!

 

[hugo]

....I suppose I'll just drill a few more holes into the lid!

Mine is quiet, the vented case is enough i think. But if you use only nos components (carbon comp resistors), maybe you will have a drift. I also replace the neon with diodes, and do not see any drifting after 4h of using. I prefer to let one space between the bottom and an other unit, and i prefer to place the d-la2a at the top of the rack..

 

[desol]

I do have neons. The meter drifts like crazy...which isn't a huge deal. Zero adjust was first set...and then resistors specifically chosen for each T4 to properly reflect the correct amount of gain reduction, so adjusting the zero adjust really isn't an option if you want the correct representation of how much is going on. Even with the unit outside of the rack, it sits idle close to .5db GR(heated up). My major concern tho isn't the effect on meter drift, it's the effect on the longevity of the components inside.

I think the only option is to get a 1/4" drill bit and go nuts, in an orderly fashion.

 

[dmp]

Hugo,
I built mine in the same 2U  case as you did.
I did shielded wiring but I'm still getting oscillations at high gain settings. We were using it last week and a 16kHz oscillation was pretty noticeable.
Do you get any oscillations at high gain?

 

[hugo]

Hugo,
I built mine in the same 2U  case as you did.
I did shielded wiring but I'm still getting oscillations at high gain settings. We were using it last week and a 16kHz oscillation was pretty noticeable.
Do you get any oscillations at high gain?

Hi, i replaced the gain pots with 25k attenuators+75k resistors. The gain at maximum stay far from the oscillations point. Dead quiet also.

 

[dmp]

Hi, i replaced the gain pots with 25k attenuators+75k resistors. The gain at maximum stay far from the oscillations point. Dead quiet also.

Problem is that we want to gain. It was oscillating at a "normal" setting in the studio with high GR.

I did a line level input Tx so maybe that is why I am having a problem. I'm asking the circuit for much more gain.

 

[Barton]

Looking for advice on where I could be having an issue.  Sound passes fine, gain increase seems good, but I only get about 3 dB of compression with pen reduction maxed out.  Attached is a schematic showing voltage readings I've measured.  (Readings without an input or output signal).  Both channels are behaving the same way.

I also measured the following on the T4B pins when applying a 1k signal at 1.2 V.

Pin 3:  330 mV
Pin 5:  5 V
Pin 7:  -330 mV

Any thoughts on what the problem might be?

 

[[silent:arts]]

Make sure the stereo adjust trimmer is fully open. Try both extrem positions.

 

[rna]

HI everyone, I just built mine.  I got given the pcb and psu transformer from a friend for doing the turbo mod on his GSSL  so this project was a slow back burner for me.
I also had the oscillation problem with first positioning of transformers so I spread then out more.  I was getting an interaction with the XLR sockets where the connections are not shielded.
Don't judge me but I put red leds in the meter because the bulb was pulling 70ma. (its supposed to be run on 12v) wired so bypass has no illumination.
https://www.don-audio.com/Audio-Level-VU-Meter-WF1029X  A couple of leds and a resistor was 20ma so I will use this until I find a suitable 5v bulb.
This meter with no resistor measures 0VU = -13dbfs.  So I set both to this exactly using the trim on the front of the meter.  I would have preferred it to be -14dbfs but I do not record hot anyway so its not a real problem.  The proper meters are a bit big for 2U.

Q. I have soldered in a preset pot R25 so I could set the gain reduction exactly,  Is this OK?

I managed to get the stereo link working great.  When you adjust the stereo pot it affects both meters so keep an eye out.
As you turn the pot the 2 needles move in opposite directions.  At one moment they will read the same and you have reached stereo zen  ;D

I made the tb4's from scratch using parts from Curious Audio.  At this stage i have not noticed any major difference comparing these to the genetic one i bought as a control sample.  But I have not put it back in since the first tests as my ones worked great.

I am very pleased with how the unit sounds and behaves great job on the pcb's!! (and the documentation many thanks to all in the forum)

 

[rna]

front top view

 

[rna]

top view

 

[rna]

tb4's

 

[rna]

and the heater wiring hehe

 

[rna]

from the front