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

[jsteiger]

Hi all. I've built two VP26s and two VP312s, all with no issues, but now after maybe 2 years of working well one of my VP26 pres is very quiet and a bit distorted. Sound does pass through, but it's really quiet. I tried swapping out the opamp (Rogue Five DOA 1.3), tried a different slot in my 500 series rack (Vintage King Rack 500), but no luck so far. Any advice? Attaching a picture in case it helps. Many thanks for any ideas...

Most likely a bad solder joint(s) somewhere on the build.

 

[malrooskee]

Hi there, just got my VP25 kits and while four of the five ceramic capacitors line up just fine with their identifiers, the C4 position one which should be an 82pF one has an identifier of 112J, whereas the build guide says it should be 82J. Like I was saying, the rest line up and this is the odd one out. Is this ok to install at C4?

 

[jsteiger]

Hi there, just got my VP25 kits and while four of the five ceramic capacitors line up just fine with their identifiers, the C4 position one which should be an 82pF one has an identifier of 112J, whereas the build guide says it should be 82J. Like I was saying, the rest line up and this is the odd one out. Is this ok to install at C4?

If you look close with good magnification you will see what you think is "11" is actually a not so great "8". That said, the supplied caps are indeed 82pF and not 1100pF.

 

[rockinrob86]

Hi all. I've built two VP26s and two VP312s, all with no issues, but now after maybe 2 years of working well one of my VP26 pres is very quiet and a bit distorted. Sound does pass through, but it's really quiet. I tried swapping out the opamp (Rogue Five DOA 1.3), tried a different slot in my 500 series rack (Vintage King Rack 500), but no luck so far. Any advice? Attaching a picture in case it helps. Many thanks for any ideas...

View attachment 92623

I fixed a few of these for a friend - his either had really low gain or were just cutting out. Some had dirty pads on the slot (scrubbed with toothbrush and alcohol) and the hardest one to get had a really dirty switch that shorted open. Finally got it situated and it was all good to go, has been working perfectly for a year or so now. They were a decade or so old and they smoked in the studio/car while carrying them in his lunchbox, so it happens.

 

[Frank00]

Hi guys,

I'm about to acquire a Capi VP25 (rev B pcb) from a friend. It's looks fine but I noticed a slighlty odd thing.
It seems like the orange and green wires are swapped on the 2503 transformer side. This doesn't really match up with the Ed Anderson datasheet, or any 2503 pic I've been able to find (new, clone or vintage).
Is it a problem? Does it make a difference?

I attached a pic for reference.

Please let me know.

Thanks

 

[Frank00]

It looks like he followed the color code on the pcb side btw.

 

[Ricardus]

Is this an older Rev of the board? I can't remember. But if there was some errata on that REV that required a build change perhaps Jeff can weigh in here.

 

[Frank00]

I think the current one is Rev C for both VP25 and VP26. This one (Rev B) has the old faceplate too.

But if there was some errata on that REV that required a build change perhaps Jeff can weigh in here.

Yes, that would be awesome.

 

[Frank00]

Hi guys,

I just got Jeff's response via email, here it is.

Hi Francesco

Every now and again the lead order might be different. Internally all is the same so nothing at all to worry about.

Best regards, Jeff Steiger
Classic Audio Products, Inc.

Thanks a lot to Jeff for the super quick response. I hope this may end up useful to someone else down the line.

Cheers

 

[Ricardus]

Hi guys,

I just got Jeff's response via email, here it is.



Thanks a lot to Jeff for the super quick response. I hope this may end up useful to someone else down the line.

Cheers

If it seems to be working right you should be fine. The only issue might be phase. Check to make sure input phase and output phase match.

 

[Frank00]

Yes, I was thinking about that too. I'll sure check when I pick it up.
Thanks

 

[biasvoltage]

I used one of my VP25s (that have been performing flawlessly since I built them 11 years ago) to test some GAR2520s I built. First GAR worked great, the second one caused the 47uf 16v electrolytic to blow up. Whoops! Is that capacitor in the audio circuit? I have some Audio Note 47uf 25v caps I bought for a different project but if this is a good place for a nice capacitor, I'll toss it in there instead.

 

[jsteiger]

I used one of my VP25s (that have been performing flawlessly since I built them 11 years ago) to test some GAR2520s I built. First GAR worked great, the second one caused the 47uf 16v electrolytic to blow up. Whoops! Is that capacitor in the audio circuit? I have some Audio Note 47uf 25v caps I bought for a different project but if this is a good place for a nice capacitor, I'll toss it in there instead.

The PSU decoupling caps are 47µF/25V. One on each PSU rail. I would replace with the same value or a higher voltage is fine. If you mean the 470µF axial cap then that is in the audio path and should be 470µF not 47µF.

 

[tristanrobertsaudio]

I have been trying to troubleshoot my capi vp26. The LED for the 48v was not operational so I swapped it with one laying around. LED now works. Preamp mute works and output appears to be operational. The preamp gain knob has audio signal (noisy audio signal) from 6 to 9 o clock but as soon as it passes that threshhold it becomes fluttery with no audio signal. I am uncertain of what the issue might be and have been touching on this one on and off for years. I built the op amp as well.

 

[jsteiger]

I have been trying to troubleshoot my capi vp26. The LED for the 48v was not operational so I swapped it with one laying around. LED now works. Preamp mute works and output appears to be operational. The preamp gain knob has audio signal (noisy audio signal) from 6 to 9 o clock but as soon as it passes that threshhold it becomes fluttery with no audio signal. I am uncertain of what the issue might be and have been touching on this one on and off for years. I built the op amp as well.

Its highly recommend to not try and debug a fresh module build with an unknown opamp. Could be the opamp is the problem. Could be the preamp is the problem. Could be there is a problem with both. We always recommend using a known good working opamp when testing out a new module build.

Could be the first LED was in backwards?

 

[tristanrobertsaudio]

Its highly recommend to not try and debug a fresh module build with an unknown opamp. Could be the opamp is the problem. Could be the preamp is the problem. Could be there is a problem with both. We always recommend using a known good working opamp when testing out a new module build.

Could be the first LED was in backwards?

It was a capi opamp build I just put it together. It is possible the LED was put in backward. I can pull the opamp from a working unit and put it in the other and then do the test since I know the other works. Probably a good start on troubleshooting. Thanks

 

[tristanrobertsaudio]

It was a capi opamp build I just put it together. It is possible the LED was put in backward. I can pull the opamp from a working unit and put it in the other and then do the test since I know the other works. Probably a good start on troubleshooting. Thanks

The opamp in that unit works just fine with my other vp26

 

[Mallman35]

Hey, I totally spaced out and turned on my VP26 without an discrete op amp inserted. Saw a little puff of smoke come out of my chassis. Did I totally screw myself? With my Gar2520 it sounds horribly distorted with a very low signal.

 

[jsteiger]

Hey, I totally spaced out and turned on my VP26 without an discrete op amp inserted. Saw a little puff of smoke come out of my chassis. Did I totally screw myself? With my Gar2520 it sounds horribly distorted with a very low signal.

If the smoke came from the VP26 without an opamp installed then I would assume you had one of the 47µF power rail decoupling caps installed backwards.

 

[Ricardus]

Hey, I totally spaced out and turned on my VP26 without an discrete op amp inserted. Saw a little puff of smoke come out of my chassis. Did I totally screw myself? With my Gar2520 it sounds horribly distorted with a very low signal.

The testing procedure Jeff wrote actually tells you to power it up without the DOA installed to do voltage checks ad what not.

Upload a high res pic of the component side of the board if you can't find where the magic smoke came from.