[BUILD] CAPI VP2X~500 Series~Preamp Kit~Official Support Thread

[jbjoubaud]

Guys,
I just want to make sure.
When you do the tests in section 12, which probe do you put in first ?
For instance :
12.1.d Probe between the “C” and “O”(Output) sockets for the DOA. Your reading should be a high resistance, over 200K Ω.
Is black probe on the "C" then red probe on the "O" or red probe on the "C" then black probe on the "O" ?

Either way, for 12.1.d I have the value fluctuate slowly beetween 75k and over 200K (slowly goes up, then slowly goes down, etc...)

Thanks for your help !


edit : I redid the test and if put the red prob on "O" and black on "C", I get around 6.4M ohm. If I have the black probe on "O" then I get the fluctuating thing.

 

[jsteiger]

When measuring DCR it won't much matter. These results seem fine.

 

[jbjoubaud]

Thanks Jeff.
Just did the last test and all is working fine, I'm stoked ! Can't wait to put this baby to use.

 

[ccstudios]

i havent been using my vp26s since my posts earlier. i used them this past session and noticed a few things. i was tracking guitar and within 5 or 6 hours of my session, one of my vp26s started sounding real thin and the output was reduced by 5-10db. i pushed in and out the switches, turned on and off my lunchbox, and checked my signal path, but still it was having that same problem. as much as i love them when theyre working, im almost fed up with these and want to sell them  do you think its a transformer problem?

 

[jsteiger]

Sounds like a cold solder joint somewhere or maybe something opamp related.

 

[ccstudios]

i changed the opamps to my diy990's from hairball audio and i still get the same problem. also, i dont know if you remember, but the signal "spikes" and clips my converter on harder transients even though i have the output level real low.

 

[laddie.music]

Does chunger have a VP26 build thread of pictures yet?

 

[jsteiger]

Yes, he did one a few years ago. Just search "newbie builds" and you will find it. I have a link to it in the support docs email that gets sent out.

 

[RemcoJVG]

Hi Jeff and other diy dudes,

a quenstion.
iN de rev b BOM there are 14 resistors listed, in the pakkage there are only 11 resistors
confused.

 

[jsteiger]

a quenstion.
iN de rev b BOM there are 14 resistors listed, in the pakkage there are only 11 resistors
confused.

My guess is you are looking at the wrong parts bag. The resistor bag for a VP25 or VP26 will have 14 R's, 1 red LED and 2 4004 diodes in it. The bag with 11 R's will have a label that says VP-Gainswitch. Those are the R's for just behind the Grayhill switch, if you ordered the stepped gain kit.

 

[RemcoJVG]

a quenstion.
iN de rev b BOM there are 14 resistors listed, in the pakkage there are only 11 resistors
confused.

My guess is you are looking at the wrong parts bag. The resistor bag for a VP25 or VP26 will have 14 R's, 1 red LED and 2 4004 diodes in it. The bag with 11 R's will have a label that says VP-Gainswitch. Those are the R's for just behind the Grayhill switch, if you ordered the stepped gain kit.

Yea duh... lol

OK one finished and seems to work.
i noticed that it sounds a bit lowpassed, even a slightly bright
I also noticed that i got a high reading when probing on r14 (both vp26's)
I get 14 in stead of 10. does it matter?
I now start assembling the 2nd one. see if i get simmular results

Remco

 

[jsteiger]

You cannot accurately measure the DCR of a resistor while both ends are soldered to the PCB. Measure them carefully first. If you find the need to measure them after soldering, one end should be desoldered and lifted free from the PCB.

 

[RemcoJVG]

You cannot accurately measure the DCR of a resistor while both ends are soldered to the PCB. Measure them carefully first. If you find the need to measure them after soldering, one end should be desoldered and lifted free from the PCB.

jeff,

tnx for the quik response

i did me measure them before soldering. i assume it was ok sinds it was for both pre's.
anyway i'm almost done with the second pre. i'll let you know

Remco

 

[RemcoJVG]

Ok, did some quik recordings...
I tried several instruments acc guitar, vox bas direct via dibox ect. and it sounds great!!!!! i am surprised how open it sounds. a bit of level balancing and panning and it sound already halfway like a record.
One thing that concerns me is (could be operation error) that on el. guitar it starts to clip very quikly.(it is not sateration)
I mean that in the DAW the incoming signal is something like -6 and the waveform is showing clearly chopped of transient.
It is realy a nastly crackling sound.

Remco

 

[jsteiger]

On both of them or just one? This is not normal. Could it be some converter setting or something other than the pre(s)? This type of outside issue seems to happen a lot and folks always think it's the pre. Not saying it's not, but for sure rule out any and all outside possibilities.

 

[RemcoJVG]

On both of them or just one? This is not normal. Could it be some converter setting or something other than the pre(s)? This type of outside issue seems to happen a lot and folks always think it's the pre. Not saying it's not, but for sure rule out any and all outside possibilities.

both pre's, and yeah good chance something else is wrong. I checked on the converter(rme 3296) and in/output is set to +4, that should be correct.
i'll check it with an other pre later. see what happens

 

[pitol678]

Hi, so I've gotten a vp26 (and 28) going within the last month or so and they are fantastic sounding. However I can get neither of them to provide phantom power for a condenser, no other issues. I'm using a radial workhorse 3-slot unit so is there a way to test the unit specifically to see if it's the rack? Otherwise I'm at a loss, and even if I did get a test jig from CAPI, I'm not sure I am capable of diagnosing the issue. Any help would be much appreciated!

 

[orenradio]

Pitol,

If you have the Cube, be sure to flip the 48v phantom power switch on the back.

 

[pitol678]

Oh...my...goodness...

Um yeah that was it. Im not sure if I am relieved or embarassed  On the bright side I put together the units correctly, on the other hand, its like saying saying "my car wont start" and someone asking "did you put gas in?" Then Im like "are you kidding me, of course I...oh wait" As a disclaimer, this is my first 500 rack  :-[

Well thanks!

 

[pittsburgh]

Jeff, Can you post the instructions for testing these pres with an injected sine wave signal? Your posts say that it's available on the first few pages, and I've looked, but it's a bit of a goose chase on here.

Thanks,

-Pittsburgh