[BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread

[mulletchuck]

Ah ok.  I'll have to listen for it.  I might need to check my solder joints cuz it wasnt making any difference in sound.  Also the -10 switch had no audible effect, nor the lowpass switch.  But it was passing DI audio just fine, no weird sounds or noise. 

 

[jsteiger]

Chuck, the -10 and LPF are only active when in "Post 2622" DI mode.

The normal 20dB pad will work when in Pre 2622 DI mode. That will come in handy.

 

[mulletchuck]

Lol WHY DOESN'T THIS DIY STUFF COME WITH A MANUAL    ;D 

 

[jsteiger]

It's all described here Chuck. 

 

[mulletchuck]

Ok, so I can confirm that the relay tied to the cable insertion works.  But i can't seem to get the other relay to toggle, and upon inspection, all solder joints are clean, no bridging.  Any other test procedures?

addendum:  So, i did some probing with the DMM.  I put one probe on the negative side of C2, and the other probe on some of the resistors/diodes.  The Relay triggers depending on which component i probe.  So, somewhere on that relay board, I must have a short...

addendum #2:

Ok, so i figured out that the problem is with the DI itself.  When i used a TS cable, upon contact with the first connection in the DI, the transformer relay is triggered as expected.  When the tip contacts the 2nd connection in the DI, the other relay is triggered as expected.  When the tip touches the 3rd connection, the DI relay switches off and the little toggle switch has no effect.  TRS cables don't work. 

and now it seems to work fine.  Weird. 

edit #3:
and now I see the "DO NOT USE A STEREO CABLE FOR THE DI" lololol

Edit #4:

I've noticed that the LPF only works when the -10 is engaged.  Is that correct behavior?  Also, just verifying that the Pad switch stops working once you turn on 'Post 2622", and the -10 becomes the Pad switch.

 

[jsteiger]

.....edit #3:
and now I see the "DO NOT USE A STEREO CABLE FOR THE DI" lololol

Yes! Sorry if I did not make mention of this before! I use the ring-sleeve as a normal connection to ground so a TRS will not work.

Edit #4:
I've noticed that the LPF only works when the -10 is engaged.  Is that correct behavior?  Also, just verifying that the Pad switch stops working once you turn on 'Post 2622", and the -10 becomes the Pad switch.

Yes this is correct. From the website description: "The bottom or third ultra mini toggle is only active if the above two switches have been flipped to the right."

 

[mulletchuck]

ok cool.  Last Q, from a db-level point of view. 

Basically, to A/B the pre/post 2622 sound, i HAVE to have the -10 engaged otherwise the levels won't be the same and the test will not be accurate.  It appears to my ears that (Post2622switch & -10switch)db = pre 2622 level.  if I don't have the -10switch engaged, the DI input is, well, 10db hotter than the same gain/output settings out the post2622 being used. 

 

[jsteiger]

ok cool.  Last Q, from a db-level point of view. 

Basically, to A/B the pre/post 2622 sound, i HAVE to have the -10 engaged otherwise the levels won't be the same and the test will not be accurate.  It appears to my ears that (Post2622switch & -10switch)db = pre 2622 level.  if I don't have the -10switch engaged, the DI input is, well, 10db hotter than the same gain/output settings out the post2622 being used.

Could be Chuck. The post 2622 DI setting is Bo's standard version with no changes. Volker and I thought it'd be best to not make any gain changes to the HiZ circuits that we use. So, they will all be a little different. There a number of different ways you can adjust gain to compare. Just do what ever you feel best about.

 

[[silent:arts]]

ok cool.  Last Q, from a db-level point of view. 

Basically, to A/B the pre/post 2622 sound, i HAVE to have the -10 engaged otherwise the levels won't be the same and the test will not be accurate.  It appears to my ears that (Post2622switch & -10switch)db = pre 2622 level.  if I don't have the -10switch engaged, the DI input is, well, 10db hotter than the same gain/output settings out the post2622 being used.

I love dBs ;D
however, without any maths:
pre 2622 is with a step-up transformer following (= gain)
post 2622 is without without
if a 10dB pad is matching this Jeff is a lucky guy 8)
I'm sure this wasn't planed

 

[mulletchuck]

well, thank ya for inadvertently makin' it easy to A/B between Pre 2622 and Post 2622!!  lol

 

[Brolik]

Heyhey,

I screwed up real good. I was trying to modify one of my already-built-and-working vp312DIs with the Grayhill switch+pcb getup. In the process of attempting to desolder the bourns pot, I absolutely destroyed the 1, 2, 3 pads on the PCB (shiiiiiiiit.) I haven't done that since I was a newb.

I tried to work around my idiocy by running pad 3 on the grayhill pcb upstream to the small pad by cap C12 (which looks to be the same contact point) and running pad 1 on the grayhill pcb to ground on the mute switch, across from the contact that the phantom pcbs connected to. I thought I was very clever.

Now I get to the studio to plug it in and the grayhill switch is completely out of the circuit. The Pre works fine except that the gain switch doesn't do anything, it's like the contacts are shorted together and it's always at max gain.

Did I do the right kludging to solve my problem or is my theory itself screwed? I don't see any solder bridges, so I think my craft is fine. Is there a better way to go about it? Did I ruin one of my favorite pres? help!

 

[jsteiger]

Brolik, should be an easy fix. For the Rev B.1 boards, C12 is the phantom cap. You want the negative side of C13, the 330uF cap. As you have described, both 1 & 3 are just going to ground so the switch is out of the circuit. I would connect 1 to the same pin that the phantom LED is connected to.

 

[Brolik]

Thanks for the prompt reply Jeff.

Am I wrong or does the small pad near C12 connect to the negative side of C13? When I look at the bottom side of the PCB (Rev B.1 as you say) it looks like there is a channel going from the tiny extra pad to the negative terminal of C13. Are you saying I need to just hardwire pad 3 on the grayhill PCB to the negative side of the C13 cap?

 

[jsteiger]

That could be a via. I no longer have any Rev B.1 boards here. Beep it out with your DMM to check. If that is indeed a trace/via to R13, it is the other end of the "pot" or pad 1 then. Change that to the same lug as the LED.

If that does not solve it, desolder both leads from the main PCB. Then check the adapter "end to end" at each position to make sure the R measurements match the R string as shown on the VP-Gainswitch skiz.

 

[Brolik]

So, to summarize.

-disconnect and check the the adapter board for continuity and the right resistance values for each step

-Check to see if the pad in question does in fact go to the negative terminal C13
-If yes, then securely attach pad 3 from the adapter board
-if no, attach pad 3 from the adapter PCB directly to the negative side of cap C13

-Attach pad 1 from the adapter PCB to the same ground lug on the mute switch as the phantom LED

The End.

Correct?

I'll dive into this as soon as pesky work is over. Thanks again for all your help Jeff.

 

[jsteiger]

Brolik, I just opened the Rev B.1 ARES files. Slipped my mind to do so before.    That via does in fact connect to the neg side of C13 so you should be safe to use it. Also, both of the lowest pins (closest to the bank of resistors on the main PCB) on the Mute switch are direct connections to the ground plane. Either one of those will be fine for the pad #1 lead.

That being said, I would desolder and check the adapter board. Possible it is shorted to max gain somehow.

Keep use posted.

 

[Brolik]

hm. so I was barking up the right tree, huh? Guess I'm on the hunt for shorts. Thanks Jeff.

 

[Brolik]

Well, good news n' bad news. Good news first? right.

-My Grayhill switch and adapter board are working just fine! According to plan, perfect.

bad news.

-All three pads for the bourns pot are shorted together or perhaps shorted to the ground plane. There are no solder bridges in site, really the pads are totally gone. Is it possible that, in terribly mangling the desoldering process and totally destroying the solder pads, I managed to shunt all three pads to the ground plane? That would be great wouldn't it?

next: Solutions

-So, what if I cut the trace going from R15 pad to the little extra pad by c12, effectively taking pad 3 out of circuit (hopefully), then put the switch back as previously discussed? Sound like a plan?

 

[jsteiger]

Well, good news n' bad news. Good news first? right.

-My Grayhill switch and adapter board are working just fine! According to plan, perfect.

bad news.

-All three pads for the bourns pot are shorted together or perhaps shorted to the ground plane. There are no solder bridges in site, really the pads are totally gone. Is it possible that, in terribly mangling the desoldering process and totally destroying the solder pads, I managed to shunt all three pads to the ground plane? That would be great wouldn't it?

next: Solutions

-So, what if I cut the trace going from R15 pad to the little extra pad by c12, effectively taking pad 3 out of circuit (hopefully), then put the switch back as previously discussed? Sound like a plan?

Ah, OK. That makes sense now and only suck a little. Pads 1 & 2 are already connected to the ground plane so no worries there. For pad 3, you could either cut the trace between the via and pad 3 like you say or (next is what I would do) drill/cut the trace on the bottom of the PCB between C13 and the via. That way you are away from the ground plane and won't have another possible short between the cut trace and the ground plane. Anytime I do something like this I double check the resistance to make sure the trace is 100% cut.

Then just run your pad 3 jumper to the - of C13.

 

[Brolik]

Just a little update forya.

I took the lazy mans out and cut the top trace so I could use the pad by C12. Figured if it didn't work I could still resort to your method of cutting the cottom trace after. I cut the trace, checked for continuity, everything was fine so I connected the two leads and buttoned it up. Works like a charm. Victory!

Thanks for all your help Jeff, it's always good to have a friend when disaster strikes. Great kits too.

Now I just gotta see if I can do the same thing to my other VP312DI without the same difficulties...

Also, whats up with those eqs, hm?