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

[jsteiger]

Could it be an outside the module issue? Have you tried a different rack slot, cabling, mic etc?

 

[ninopelo29]

The sound happens without a mic or mic cable connected.  The only cable I have connected is the output 1/4" which makes no noise when connected to the second module.

I've tried every slot in my Radial Workhorse and the good module makes no noise in any slot and the bad one makes noise in every slot.

The noise only happens when the phantom power is on. When I initially powered the cards up, there was no noise, tho. It started making a slight crackle after about 10 minutes and then got full blown crazy after 15 minutes and hasn't stopped since.  It makes me feel like a part went bad...I'm gonna replace the phantom components and eliminate that as a possibility.

Can I order the components in the phantom power circuit from you?

...and thanks again for all your help Jeff! You rock, sir!

 

[jsteiger]

The sound happens without a mic or mic cable connected.  The only cable I have connected is the output 1/4" which makes no noise when connected to the second module.

I've tried every slot in my Radial Workhorse and the good module makes no noise in any slot and the bad one makes noise in every slot.

The noise only happens when the phantom power is on. When I initially powered the cards up, there was no noise, tho. It started making a slight crackle after about 10 minutes and then got full blown crazy after 15 minutes and hasn't stopped since.  It makes me feel like a part went bad...I'm gonna replace the phantom components and eliminate that as a possibility.

Can I order the components in the phantom power circuit from you?

...and thanks again for all your help Jeff! You rock, sir!

For kicks, just try removing the 120µF cap ands see if that does it. If so I can send you a replacement.

 

[ninopelo29]

Hey Jeff (and All),

I'm stumped. I removed the 120uF cap and the noise is still there.

I resoldered all the components again and tested for continuity point-to-point across the whole pcb. Everything checked out ok, but the noise persists.

Here is a sample of the noise (I had to record it with my phone, so please turn down your speaker):
https://soundcloud.com/ninopelo29/api-noise-sample

Any other recommendations?

Thanks again for all your help, Jeff

 

[jeroberts]

Hi all --

I am about to start my first VP-26 build and was wondering what the best kind of lab power supply is for testing them. 

I was looking at the one below, but I'm a newbie to DIY and I'm not sure if it could deliver enough voltage.

http://www.amazon.com/gp/product/B000CSQK5E?psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s00

 

[okgb]

Having strange problem where polarity switch , seems ........... to either dim the signal or full waveform on one side of output ?
it's a pretty straight ahead circuit and I've built plenty before so this must be something stupid simple,  all resisters are correct
I'll pull the switch and check it out of circuit ,

Does this ring any bells with anyone ?

 

[jeroberts]

Hi All,

I am working on my first VP-26 build.  I finished my build and plugged the unit into my 500 series rack.  Everything was working perfectly for a few minutes, then there was a pop and the VP-26 started producing smoke.  Now it isn't working at all.  After a quick inspection, it looks like the one of the connections on the gain knob is the thing that blew.  Has anyone had this happen to them?  If so, what can I do to fix it?

Josh

 

[jsteiger]

Hi All,

I am working on my first VP-26 build.  I finished my build and plugged the unit into my 500 series rack.  Everything was working perfectly for a few minutes, then there was a pop and the VP-26 started producing smoke.  Now it isn't working at all.  After a quick inspection, it looks like the one of the connections on the gain knob is the thing that blew.  Has anyone had this happen to them?  If so, what can I do to fix it?

Josh

I myself have never heard of such a thing. Are you sure it was on the gain pot? I'm not imagining a way this could happen.

 

[jeroberts]

Hi Jeff,

I'm not 100% sure, but to me it looked like some of the plastic on the PCB was burnt around the gain pot.  Also, the smoke was coming out from that area.  I will take another look at it tonight and let you know if I find anything else.

 

[jsteiger]

It was most likely the opamp.

 

[jeroberts]

It was most likely the opamp.

Ok.  How could I check to make sure it's the opamp?  Also, would that entail getting a new opamp or do you think I could fix it?

 

[jsteiger]

It was most likely the opamp.

Ok.  How could I check to make sure it's the opamp?  Also, would that entail getting a new opamp or do you think I could fix it?

If you smoked something it should be kinda easy to spot. My age old rule of thumb, never start with a fresh preamp kit and a fresh opamp build. Too many variables to trouble shoot. You need to have one or the other in known to be good working condition. If its the opamp, its best to post in the respective opamp build thread.

 

[jeroberts]

Thanks, Jeff.  That's good advice to follow.  I'll take a look at the op amp to see if it blew.  I'm actually using the SL Red Dot op amp though, so is it possible that soldering it into the PCB the wrong way could result in smoke?  I messed up soldering the op amp standoffs and wound up resoldering them a few times.  There was some solder stuck in the bottom of one of the standoffs so the op amp actually wasn't going down all the way and I soldered a few of it's legs to the standoffs to keep it in place.

 

[jeroberts]

Quick update: I cleaned up the connections on the op amp and everything is working now.

 

[phanlon]

Hi there,
Looking for some help. I just built a pair of vp-26s. Fired them up and one works perfectly. The other seems to be working but the volume is very, very low. With the gain cranked all the way talking into a 58 hits -38 in pro tools. Switched cables and its definitely the pre.

Want to know where I should start to look. I should add that the gain pot on the quiet pre doesn't feel smooth when it's turned.

Thanks

 

[jsteiger]

Rule out the opamps first. Are they fully seated? http://capi-gear.com/catalog/DOA_Install.php

 

[phanlon]

Swapped them between units. The quiet pre is still quiet. I have also double checked all of the resistor values. They are all as they should be. Not sure where to check next.

 

[jsteiger]

At this point, you will have to inject a -40dBu sine wine and see where the signal stops. You will need to use the schemo as a road map. You should use the good working unit as your benchmark.

 

[phanlon]

Got it. Just ordered the test Jig from your site today.

 

[bulley]

Hi,

I'm having an issue with a VP26 that I built about 6 months ago. It's been working fine but the sound now distorts at low levels. If I bang a loud signal through it the sound briefly becomes undistorted again before the distortion fades back in. There's obviously a dodgy connection somewhere but I've re-soldered everything and haven't got anywhere. Any ideas what might be causing it?

Edit: I've also found now that with this module in the +16V light is blinking when I power up my lunchbox (Lindell 506). I think this is some kind of protection so there's something bad happening somewhere. It powers on properly after about 10 seconds.

Edit: SOLVED! One of the capacitors was shorting. Why it's taken 6 months to decide it's a problem I don't know but everyone relax, you can all stand down.

Thanks,