[BUILD] CAPI VP28~500 Series~2-Stage Preamp~Official Support Thread

[Axelerator]

..just received some germanium opamps from Pier, and want to try them in the first stage. as they have an output offset, i have to install a 220-470u cap
after the amp.my question is if there is already a cap in the out ?
and will there be some space on pcb for this as it is already crammed a lot ?

axel

 

[jsteiger]

..just received some germanium opamps from Pier, and want to try them in the first stage. as they have an output offset, i have to install a 220-470u cap
after the amp.my question is if there is already a cap in the out ?
and will there be some space on pcb for this as it is already crammed a lot ?

axel

Hey Axel, yes the PCB layout for the VP28 is fairly dense but I already have a 470uF coupling cap after each DOA so you should be fine.

 

[Axelerator]

8) that was fast !

 

[tonycamp]

1 down, 3 to go. This is a really well engineered kit ??? very impressive, nice job Jeff

 

[tonycamp]

then there was 4

 

[Axelerator]

..most nice boards i have ever seen, pure beauty..
but i have maybe done a little mistake, i have put in the opamp sockets from above and soldered them, so they are working but coming 2-3 mm hgher now
i dont think that will be a problem with the height later but if so, please somebody warn me !

axel

 

[kante1603]

Hi Axel,

shouldn´t be a problem.
I´m re-arranging my racks at the moment,so I had them in my hands an hour ago.
Took a pic from both side by side with a ruler on the frontpanels,there´s roughly 9 to 10mm space (I have gar2520s in).
Hope that helps.

Have fun,

Udo

 

[Axelerator]

very nice, thanks , udo !
so happy soldering..
greets
axel

 

[Axelerator]

uups, next one.. i skipped a picture of chunger while installing the output transformers...i now have mounted both 2623 facing downwards the pcb...
so as everything else is build now, the unit is complete finished ...just wanted to try her out..
is there crazy interference with the both trannys magnetical fields, maybe cancellation somehow or is it just to keep the leads shorter what would be no issue i think because maybe now the wires are 1 cm longer than other way round.
so please somebody chime in (again.. )

btw, it seems that the screws of the blank aluminium knobs are a little bit bigger than my 1.5 mm inbuss srewdriver and smaller than my 2 mm inbuss one.
i havent found  a unit between them yet and would like to know which one i have to order, for example if it is some inch-scaled driver

thank you a lot

axel

 

[mulletchuck]

TX orientation shouldn't matter.  it just affects wire length.

 

[jsteiger]

In this situation with the transformers, you will be fine Axel.

The small 3/8" pointer knobs require a .05" allen key.

 

[Axelerator]

great news
love this forum !

axel

 

[voidar]

Very nice kit jsteiger and very helpfull tutorial chrunger!

I just finished the kits I got a week ago. Some observations.

1. Instead of the double-sided tape chunger uses under the input I had to improvise with cutting up some foam from the kit.

2. The fader knob is of a different design and fits around the shaft from the start, which brings me to something that has me confused:

I am sure I installed the Grayhill switches correctly and you would think one of the nuts of the knob is supposed to rest against the flat cut-out of the shaft.
But the only way I could have the knobs face the right value is to have the nuts bite into the shaft of the switches. I am a bit worried if this will hold up and that I will have to reset the knobs all the time. Are they supposed to be like that?

3. The tip of the small LEDs break off easily. I had to super glue two of them. Thankfully the glue didn't dim them.

Also, another question.

Which of the op-amps is the fader/output amp?

 

[tonycamp]

Very nice kit jsteiger and very helpfull tutorial chrunger!

I just finished the kits I got a week ago. Some observations.

1. Instead of the double-sided tape chunger uses under the input I had to improvise with cutting up some foam from the kit.

2. The fader knob is of a different design and fits around the shaft from the start, which brings me to something that has me confused:

I am sure I installed the Grayhill switches correctly and you would think one of the nuts of the knob is supposed to rest against the flat cut-out of the shaft.
But the only way I could have the knobs face the right value is to have the nuts bite into the shaft of the switches. I am a bit worried if this will hold up and that I will have to reset the knobs all the time. Are they supposed to be like that?

3. The tip of the small LEDs break off easily. I had to super glue two of them. Thankfully the glue didn't dim them.

Also, another question.

Which of the op-amps is the fader/output amp?

Strange on the Leds, i just built 4 with no problems at all. A good idea on the gray hill switches (for the stone hands type ;D), if your worried about stripping the hex to shaft contact, is to position the knob where you want it, pull 1 hex completely out, take a pencil and mark the bottom of the hex with plenty of "lead", screw it back in tight, loosen both hexes up, pull the knob off, it should leave a pencil mark on the gray hill shaft. Take your dremel and carefully flat spot the shaft, repeat for the 2nd hex. Ive done this on drill bits, works great, but for the vp28, i would just lighten your grip monkey fist! ;D

my guess is the bottom opamp is channel fader, BUT DONT TAKE THAT TO THE BANK!!!

 

[kante1603]

3. The tip of the small LEDs break off easily. I had to super glue two of them. Thankfully the glue didn't dim them.

Wow,how did you manage that?Have never heard someone breaking an led before.....did you use a hammer? ;D

Cheers,

Udo

 

[voidar]

Well, the poiny plastic "nose" which is inserted into the holes are quiet tiny. I don't know how I managed  , but it's an annoying complication at the end of the build. I almost cried  :'(.

 

[tonycamp]

i've been running my 1972 jazz bass through the vp and into my ampeg svt,...DAMN !!! I will use it my next bass gig for sure! Rear pickup only, fingers at the bridge, ladies and gentlemen, please welcome... Jaco Pastorius!, slower and fatter!,... yes,..no,....Its...welcome,... Jacob Pastorius! ??? Good enough for the girls i date!!! ;D

 

[jsteiger]

The A1 DOA closest to the 2622 is for the preamp. A3 is the post fader booster.

I started stocking the knobs with the 1/8" hole for the fader switch to simplify things a bit. The set screws are not supposed to sit on the flat. It would be nice but impossible with the way each is made. BTW, I did get a quote from GH on a solid shaft. The price increase was insane so we have to deal with the flat. Tony's method is a good one if you can't get them correct without a flat. I have built many and not had trouble. The preamp gain is the same and so are all 6 switches on a LC53A build.

Ginger with those LED's!!

 

[tonycamp]

The A1 DOA closest to the 2622 is for the preamp. A3 is the post fader booster,

I had a feeling if i suggest either, it would be or? : I hope you didn't go to the bank with that :-\

 

[desun]

Ordered one of these yesterday, looking forward to building it!