Drips La2a Version 3 journey : )

Note, this is based from my experience building the Drips La2a Version 3 and other peoples experience may vary so take it with a grain of salt.

The lab. Working up to 6-10am these past few weeks trying to get these beasts completed. Garage is not the best place to do DIY I have realised. Frrrrreeeezing!  8)

Clear table is best to prevent scratching your case... eh.




Printed pics to reference from.


Preparing case for Drips pcb board. For setting PCB mount, best to drill a hole one at a time then re-align PCB, mark next hole then drill and so on.
eg.
Push bolt thru bottom case so that it portrudes and you can align your PCB board using that portruding bolt.


Place PCB on top of bolt and then mark the next hole while pushing the board flat since I had a slight warp on my board which straightens up once the PCB board is mounted properly.




Solder components


Interchangeable caps system for C1, C2, C3 so that I can change caps for different flavours. Using those NOS big chunky silver caps.


Implemented Output Transformer switching system as shown by braided cable portuding from the bottom of the PCB board.





Wiring used for the Output Transformer switching system

Wiring up


Remove rear panel of rack case to finalize wiring for rear panel section.
Wiring XLR cabling must be done by feeding cables thru and soldering XLR into place.


Drips ground lift system.


Rear panel ready.

Experimenting with the cable separation system to minimize possible hum coming from the Power Transformer.


Way too bulky and would probably cause fire. No good!


Ahh, finally. Strong enough to keep the cables apart a good distance.


Here we go  

So far this wiring works for me using 240 volts Mains Power. I used a 500mA slow blow fuse on my IEC socket that has an inbuilt fuse in it.




Note that when using this power transformer, the Hammond 369JX and Purusha's case, that you will struggle getting all the wires inside the hole on Purusha's rear panel. Sticky tape all the wires as one wire at the end and feed it thru the hole. The hole in Purusha's case is small and you may need to make it bigger since the cables from the transformer come from two sides of the transformer and the transformer does not have enough space underneath to run the cables well to the hole in Purusha's case. I couldn't be bothered. I hate altering a case that's meant to be pre-made and just used washers to raise the power transformer up slightly to allow space for all the cables to run underneath as it goes to the hole.

Seriously?  Get some balls already and turn the damn thing on, ya big poossy

ben

bdubya said:

Seriously?  Get some balls already and turn the damn thing on, ya big poossy

ben

Click to expand...

LOL, sure, and if it blows, you can pay for the $1,800.00 I have spent so far on this DIY 

canidoit said:

bdubya said:

Seriously?  Get some balls already and turn the damn thing on, ya big poossy

ben

Click to expand...

LOL, sure, and if it blows, you can pay for the $1,800.00 I have spent so far on this DIY 

Click to expand...

Drip has his own forum, you can check there.

http://www.dripelectronics.com/forum

Mark

Finalized inside wiring for the front panel


To finalize the rear panel, I left the rear panel disconnected so that I could have more room to solder cables to the board. Purusha's case has a very tight front and back spacing once the board is mounted. This is also a tricky area. I easily made the error on trying to make the cables short for better signal, but it did not leave me room to breath incase I made an error with soldering the cables to the PCB board. Luckily that did not occur and the length was just enough.


Rear Panel secured  


Front panel. Made an error here. Be careful with the Limit and compress switch. It may be upside down, which I did and had to turn it the other way around. You will notice when this switch is upside down, by putting peak reduction to almost max (3/4 CW) so that you can hear the compression/limit working well. You can tell when you are in limit mode because the sound will decrease in volume as compared to compress mode. Compress also has a more transparent compression than limit mode when you compare the two signal results.

Also the Meter switch I had wrong, so I had to swap the cables internally instead of turning the switch around.

The pots used in Drips BOM to this date will not match the legending on Purushas front panel. eg. the gain knob will turn past 100.

Top view finalized


Be careful when tightening the molex screw. I forgot that you turn the molex screw to a nice firm hold. I turned the molex screw to the point that it stopped turning like I am use to when tightening bolts but that is not the case with wiring and molex from my experience. You end up cutting the wire end or shortening the life span of that wire end that goes into the molex. I noticed it when I had to redo some of the molex wiring.  


Tested first without the Tubes or TB4 in.
From this experience, when testing the La2a without the tubes or TB4, when you turn the machine off, the VU lamp will remain slightly on or dim. You have to unplug the unit from the power for the lamp to turn fully off the lamp (This problem will disappear once you put the tubes in).

Tubes and TB4 in test.


Common mistakes I encountered.
The Limit Response and Stereo knob at the back does the following from what I know (correct me if I am wrong please):
Stereo - if this is not set on 0, the compression will not work on the unit.
Limit Response - is the threshold for when the compressor starts to act on a signal. From what I know, turning the limit response CW is to raise the threshold and CCW is to lower the threshold. I leave this at 0 so that the compression threshold starts at a lower level on the signal coming in.

I made a mistake with the wiring on this and it was in reverse and it gave me problems why the unit was not behaving properly. Maybe check these knobs when you are testing your unit and it is not behaving properly. Check for wiring and whether the knobs are set at 0.

Top panel secured  

I made a little hole for the VU meter little screw thing on Hairballs VU meter. As you can see right below the VU meter. I think it is useless though since there is a zero adjustment on the front panel.

Rear view, I have my DC reference switch below the IEC socket and also the Output Transformer link switch above the output XLR. Also the ground lift switches next to each XLR in and out.


I leave the DC ref switch on and I have not had a reason to use ground lift yet.

So far with the little time I have had to test this unit, it comes out pretty impressive!  ;D
It definitely has that tube familiarity sound about it and it definitely has the mojo when you can hear it compress! I am using RCA(12BH7A) and Telefunken(12ax7 #1) tubes. I will try this beast with Mullards but I am having second thoughts about using my interchangeable cap system incase the vintage NOS caps I have are faulty and it blows the unit  

One thing I noticed when calibrating for the first time. The internal neon light flickered slowly which caused the VU needle to pulse noticeably as well. Eventually the neon light came to a fast steady pulse that did not make the VU needle pulse anymore noticeably. Hopefully Drips can chime in on why this occurs. I wonder how long this neon light will last for since it is a light? I am thinking of replacing it with a zener like some people are doing.

I also thought this unit distorted easily at low levels when I first turned it on and put a signal thru but I think it is a matter of getting the wiring correctly and understanding how it works and adjusting the peak reduction, gain and limiter response knob to get it's optimum sound performance. I will know more once I get to use this unit more but it sounds excellent for the half an hour of testing I have done.  

nice job!