D-LA2A Support Thread
- Thread starter [silent:arts]
- Start date
Help Support GroupDIY Audio Forum:
Finally finished building my DLA2A, it passes audio but of course there is some osculation and little bit of noise. When using shielded wire for the pots I solder of course the shield to the actual pot itself and the other end of the shield goes to the ground wire going into the molex connector?
Thanks in advance,
Thanks in advance,
Paperweight
Member
From the back of the pot with lugs pointing up, you solder the shield wire to the left solder lug only. Grounding the shield to the back of the pot housing will create a ground loop and hum. If you start adding in other ground points around the chassis, you're gonna have a bad time tracking down where the overall noise is coming from. The shield should only be grounded at one end. The circuit board is grounded via the star ground which is connected to pin 1 on the Molex. This is where you want the other end of your shield connected. Once the Molex male connector is soldered to the board, it's hard to determine which is pin 1. Use a VOM to check for continuity between the individual pins and ground for that particular board section if you haven't grounded everything to the star ground already. Of course, the pin with the lowest resistance between itself to ground is pin 1 where your shield should be connected.
It might be a good idea to clean off any finish around the hole in the front panel, if applicable. That way, the housing of your pot is shielded already. I used to have the habit of using the back of the pots as a ground bus when I built tube guitar amps. Best practice is to have everything in the circuit grounded to a single solitary ground point. Merlin Blencowe has some really good pointers on grounding. http://www.valvewizard.co.uk/Grounding.pdf
It might be a good idea to clean off any finish around the hole in the front panel, if applicable. That way, the housing of your pot is shielded already. I used to have the habit of using the back of the pots as a ground bus when I built tube guitar amps. Best practice is to have everything in the circuit grounded to a single solitary ground point. Merlin Blencowe has some really good pointers on grounding. http://www.valvewizard.co.uk/Grounding.pdf
Paperweight
Member
hugo said:
I couldn't find a data sheet for that particular component. As long as the combined voltage is around 62 volts and each one is rated for at least 1.3 watts or higher, it should work.
Paperweight
Member
A question for {silent:arts}.
Several pages back, someone asked if their transformer primary wiring diagram was correct for 115-120 volt mains. You were insistent that they reverse the yellow and white wire connections for the live and neutral. Assuming the diagram wasn't altered after the fact, the two white wires should go to live and the two yellow wires get connected to neutral. Let me know if this is correct. Hardly any mention has been made of this. To add to the confusion, the US 120 volt wiring standard uses white as neutral. Not sure if this should be made an addendum to the front page.
Several pages back, someone asked if their transformer primary wiring diagram was correct for 115-120 volt mains. You were insistent that they reverse the yellow and white wire connections for the live and neutral. Assuming the diagram wasn't altered after the fact, the two white wires should go to live and the two yellow wires get connected to neutral. Let me know if this is correct. Hardly any mention has been made of this. To add to the confusion, the US 120 volt wiring standard uses white as neutral. Not sure if this should be made an addendum to the front page.
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Here are some voltages I'm getting from the listed components as follows:
NE1 = 60V
NE2=34.94V
Left channel TB4 I am getting 26V on pin 5 to GND
Right channel TB4 I am getting 7.16V on pin 5 to GND
Seems the Right channel is getting less volts on the listed components, everything on the heaters and sockets looks good.
Where should I start looking next?
NE1 = 60V
NE2=34.94V
Left channel TB4 I am getting 26V on pin 5 to GND
Right channel TB4 I am getting 7.16V on pin 5 to GND
Seems the Right channel is getting less volts on the listed components, everything on the heaters and sockets looks good.
Where should I start looking next?
![[silent:arts]](https://cdn.imagearchive.com/groupdiy/data/avatars/m/0/172.jpg?1620371656){kind=avatar}
[silent:arts]
Well-known member
Paperweight said:
A link would be fine.
Several pages back
I didn't talk about colors (The transformer doesn't care which color is L or N).
If you switch only one side it should be L, not N. Thus, in that specific drawing, the easiest way is changing L and N.
Since Germany doesn't have a polarized power connector we don't care much about L and N on IECs, but switch both sides.
Hope this helps.
ostudio
Member
Ahhh this kit looks very interesting! any possibility to purchase a complete kit?
[silent:arts]
Well-known member
No. I only sell the PCB and Power Transformer.ostudio said:
Paperweight
Member
ENS Audio said:
Check all solder connections of course. I'd go over each resistor to make sure the correct values were installed. If you have a VOM, it should be quick work.
Hello, I am double checking all the resistor values and noticed for R122 and R222 when the 33kohm resistors measure out at 33kohms when I measure them off the PCB but when the 33kohm resistors are seated I get 22kohms! What's up with that? So far everything I've been measuring so far with the resistors is correct. does it have to do with a short to ground on the actual PCB itself? 
[silent:arts]
Well-known member
Measuring in circuit ...
Look at the schematic: at least R111 + R110 is paralleled. Next to many other components.
Look at the schematic: at least R111 + R110 is paralleled. Next to many other components.
[silent:arts] said:
Doh, R122 has one leg going to ground which is why I got a weird reading when it was seated in the PCB. :-[
Anyways, I checked all my resistor values and everything looks great.
Now I powered up the unit with tubes and TB4 installed and it passes audio but of course there is lots of crackling when the gain pot is turned 3/4ths of the way up and when the gain pot is cranked 1/4th or all the way it cuts out. Plus when I switch from G.R. to Output I get lots of crackle, other than that the noise goes away in G.R. mode.
The V.U. meter shows a little bit of movement and that's only when it's in G.R. mode, in output the meter peaks all the way to the right. I haven't calibrated it yet so idk if that could be the reason why.
I might also mention that the voltage regulator is really hot, dunno if I need something more than the clipon heatsink I have on already or what to look for there.
That's all for now, guess I should order shielded cable and rewire the toggle switches while at it?
Thanks.
Paperweight
Member
The best thing to do is get one of the bolt on heatsinks and an isolation kit for mounting the regulator. You can use grease or a piece of thermal interface material to mount the heatsink to the chassis.
Paperweight said:
The best thing to do is get one of the bolt on heatsinks and an isolation kit for mounting the regulator. You can use grease or a piece of thermal interface material to mount the heatsink to the chassis.
I'll certainly do that but my biggest issue is with the damn gain pot, I can't turn it up all the way without it oscillating but if it's 3/4th's of the way turned up I get a pretty clear signal. This problem occurs whether the shield is tied to pin 1 or not.
Also my tb4's don't seem to be working, would you happen to know what voltages I should be getting from the tb4 pins?
I tried the trick where you open up the tb4 can to check with a flash light if it's lighting up and I don't see anything.
The meters seem to move a little bit and I can get the meter to move when I turn the zero adjust.
Other than that my main issues are with the gain pot and tb4, I can't really tell if it's compressing or not when I have my bass guitar plugged in. Right now the unit acts more like a very nice amplifier than a compressor/limiter. I don't know what to look for next.
bernbrue
Well-known member
Grounding issue. Take a line level instrument for testing the compressor.
Bernd
Bernd
bernbrue said:
I ran both of my bass guitars, one fretted and the other fretless which when the fretless is plugged in it starts clipping with horrible distortion whereas the other bass has only oscillations when the gain pot is turned up all the way.
I checked resistance from each ground test point to where my star ground is (next to the IEC) and I'm getting zero resistance.
It has to be something really stupid I'm overlooking. The only other concern is the TB4's don't seem to look like they are doing anything when I test them the way which was suggested by taking the TB4 cover off and shining a light on it in the dark.
Also I haven't calibrated the unit yet, not sure if I need to do that first. This noise and no compression issue is driving me nuts.
bernbrue
Well-known member
Hi,
I would do a rough calibration before spotting the other errors. You certainly downloaded the PDF file with the compiled information about grounding, wiring, calibration etc.?
Here it is!
http://groupdiy.com/index.php?action=dlattach;topic=32677.0;attach=7857
Bernd
I would do a rough calibration before spotting the other errors. You certainly downloaded the PDF file with the compiled information about grounding, wiring, calibration etc.?
Here it is!
http://groupdiy.com/index.php?action=dlattach;topic=32677.0;attach=7857
Bernd
