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

I would eliminate the rack slot and associated cabling next.

Hey Jeff,
They're eliminated.  Also switched to all the other slots in my 500 series rack and they all do the same thing.  I built another VP26 to see if swapping the VP26 would do it and the other one doesn't make the same noise.  I've now tried the problematic VP26 with 2 different Red Dots and one GAR2520 and I get the same issue with all of them.  It's currently very faint but definitely still there.  Any other ideas?

Thanks,
Drew

Hello Drew,

may I ask if you had anything connected to the input of your faulty VP26 when doing this test?
Also what was the gain setting at that moment,was it fully cw?
Might be a faulty cap discharging periodically,but I'm unsure,so therefore the questions.
Just curious.

Best regards,

Udo.

I had a SM57 attached, and then also a SM7B, just to eliminate the mic....   

Gain setting just turns the loudness of the clicking up or down, so I believe I could assume that since it's not the op amp, not the 500 series rack, and because the output attenuator quiets it down that it's gotta be on the VP26 itself? 

Could a poor solder joint cause something like this? 

Maybe I'm looking at this wrong, maybe this is a really cool effect and would be great with a back beat played to it.  But I'd like to know how to turn it off all the same.

Drew

drew571 said:

....Could a poor solder joint cause something like this?....

Click to expand...

Yes and most likely the problem since you have ruled out the other things. I would re-flow the entire board just to be sure.

Ok, I'll report back when I'm done.  Thanks.  Someone should design snap-in resistors/caps.  Just sayin.

Ok, I went back and heated up all the soldering points, then double checked for any soldering bridges.  Looks clean.  hooked it back up and the problem persists.  I changed the D plug on the back of my Tonelux V4 500 series lunchbox.  I ran a power cable to a different room in the house to plug in the 500 series rack.  changed out all the XLR cables once again.  Still there. 

Any other suggestions? 

Also, I just put together another VP26 this evening and it has the same problem. 

Maybe it's the internals of the Tonelux?  Should be under warranty yet.  Anyone near West Palm Beach, FL area that I could plug my modules into their 500 series rack so I can eliminate that?  I have now had 3 of these units that have all had the same problem.  Either I seriously suck at DIY or something else is going on. 

Drew

Hello Drew,

so summing this all up it says all three VP26 modules in that Tonelux rack seem to have the same issue,right?

My next questions are:

1.oes this pumping sound appear immediately after switching on or does it get worse when heated up,say for 20-30 minutes?

2.o the modules behave all the same in the same slot or does it get worse from outmost left to outmost right module slot?

3.oes the pumping sound get worse the more modules you plug in?

From what I feel by now is there is either a series build error on your modules (unlikely) or there is an issue with the power rails/psu inside the Tonelux box.

4.o you have a scope to check the voltage rails?

5.:And a last question for today (hahaha....),does the box have any jumpers or switches to change ground connections?

Let us know please,

Udo.

1. It does happen immediately.  Although, not every time.  I plugged them in tonight and it was still there, then I took the power and ran it to a UPS and it went away.  Then to confirm that it was just the fact that I hadn't been plugged into a UPS, I switched to the regular wall power.  It came back.  My joy was near.  I switched back over to the UPS in full hopes that i had solved it, and it was back on the UPS as well.  Suck.

2.  The clicking is DEFINITELY increasingly louder as the slots get closer to the power supply.  For example, the furthest slot out I can barely hear, have to have it cranked.  And the closest slot is very noticeable right away.

3.  No, loudness seems to stay the same, although I only have two modules to try this out with.

4.  I do not have a scope.

5.  I don't believe so. 

Does the above indicate that it is in fact the Tonelux?

That would actually be good news because it's under warranty I believe. 

drew

O.k. Drew,

thanks for answering these questions.

Especially answer #2 leads us to induced noise coming from the built-in psu.

So my guess is that the Tonelux Box is the issue,not the preamps,would say 95% sure.

Either the shielding of the psu isn't good enough or something is going wrong inside there.
Don't know if this psu is linear or a smps.
Anyway,to confirm (finally) might be best to check back in a different 500 series or 51x rack with an external psu.
Hopefully you can find someone in your area,I'm sure there are people there who can help you.

Best,

Udo.

Hey guys I made a really dumb mistake with a VP 312 DI.  I put the relay pcb in backwards for the DI section.  When I powered up nothing worked obviously.  That is when I discovered my mistake.  I've gotten the pcb out and turned around now and the DI works but the mic pre doesn't.  Did I fry the transistor on the board or something else while I had the pcb turned around?

Hello Guys!

So I recently purchased 2(x) vp26s w/ SLRedDot OpAMps and (2x) vp312s w/ the gar2520 opamps. So far I have two vp26s built. One of them works and sounds great! However the other one has some issues. First the Led light does not light up when phantom power is engaged (I think I might have to switch the leads. Hopefully when bending back the LED legs I don't break them off :/ ). I ran a sm57 and I get signal. I ran a condenser mic and if the phantom power is off and I crank the pre amp I get signal. Now, when I engage the phantom power it boosts the signal significantly. It's not the microphone or the lunch box because I tested it already with the other working vp26. I double checked all the resistors and made sure everything was where it's suppose to be, even re-soldered everything to insure proper connection. Any help would be greatly appreciated. Thanks

I think I responded to your email with some things to try. First flip the leads for the nonworking LED. Next see how that condenser mic works. You can measure DCV at the switch to make sure it's fully off. Depending on how long you waited, maybe there was still enough DC stored in the 120uF cap and that's why the condenser was working very low. The backwards LED will keep that cap from discharging quickly.

Hello everyone! 
This is my first post.  Thank you to everyone that has contributed to this tread.  I believe that I have read over a large portion of it and still not found what I was looking for.  I just recently built three vp26 and have run into the same problem with all three.  The preamps work great and all of the functions work correctly on all three except the phantom power which does not work on any of them.  There is something that I missed or got wrong on all three builds and I really am unsure of where to start in order to correct this.  But as I was saying as long as I am using a dynamic mic the preamps function and sound great but they do not work at all with a condenser.  Any help or suggestions would be awesome!  Thank you!!

JBHamby said:

Hello everyone! 
This is my first post.  Thank you to everyone that has contributed to this tread.  I believe that I have read over a large portion of it and still not found what I was looking for.  I just recently built three vp26 and have run into the same problem with all three.  The preamps work great and all of the functions work correctly on all three except the phantom power which does not work on any of them.  There is something that I missed or got wrong on all three builds and I really am unsure of where to start in order to correct this.  But as I was saying as long as I am using a dynamic mic the preamps function and sound great but they do not work at all with a condenser.  Any help or suggestions would be awesome!  Thank you!!

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I would say,  first measure your power supply/rack to make sure it is sending out 48v.  Could be a fuse in the power supply.  If you can confirm you have 48v, does the condenser work on a known working preamp?

Yes, the fact that none of the 3 builds have phantom working points to the PSU or maybe the return path from your mic cable(s).

Yeah I have several other preamps with phantom power and they work with them.  I also agree that it sounds like a power supply issue since it is affecting all 3 preamps.  My rack is a older API 6b lunchbox (non-dsub).  Does anyone have any advise about how to begin with it?  I have never really messed with it before, it was a recent purchase from ebay :-\

JBHamby said:

Yeah I have several other preamps with phantom power and they work with them.  I also agree that it sounds like a power supply issue since it is affecting all 3 preamps.  My rack is a older API 6b lunchbox (non-dsub).  Does anyone have any advise about how to begin with it?  I have never really messed with it before, it was a recent purchase from ebay :-\

Click to expand...

have you checked for +48 using your DMM. 
w/ your DMM,  put the + lead in pin 15,  - lead in pin 13 in the lunchbox card slots.  is your meter reading +48v?
if not perhaps there is a blown fuse in the lunchbox.

Nearly double posted with gunpoint recording.
I'd do this too.
I guess the +48 led is on?
If so then do as gunpoint suggests,measure pin 15 to pin 13.
If you have no reading try to measure pin 15 to pin 5.
There are two gnd points,maybe the ground reference is missing on pin 1 on the female xlr then.
If both measurements don't give you readings but the led is on then it could be that the lunchbox has been modified.I have read that pin 15 must be disabled when the lunchbox is used with a certain type of api eq.The mod is normaly done on the eq module by cutting a trace,but who knows,maybe the former owner wanted to go safe.Just a thought of course.

Tell us what your readings are,

best,

Udo.

P.S.:There's a cool chart in Jeff's floorbox assembly guide on page 8 for reference,look:
http://www.classicapi.com/catalog/images/FB-build/Floor-Box-Assembly-Aid-Rev_1.pdf

So I finally got a chance to work on the pre amp today and I switched the LED light's leads and the preamp lights up and works like it should. You're the man Jeff!

Quick Question: Is a burn in period required when assembly is finished? If so, what are the benefits and whats the proper way to go about it? THanks