GroupDIY

Project Specific Discussions => Preamplifiers => Topic started by: jsteiger on September 05, 2010, 02:00:12 PM

Title: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on September 05, 2010, 02:00:12 PM
***ATTENTION!! The stepped VP312DI kits are now shipping with Grayhill switches that have factory set stops. This means there will be no stop-pins or stickers shipped or required. A quick glance at the switch should give this away as there are no holes to put the stop-pins in!!***

Hi everyone,

Since I don’t plan on an official assembly guide, this thread is to support my VP312DI project. Kits can be found here at capi-gear.com (http://capi-gear.com/catalog/index.php?cPath=22_117_55_92). This is a very unique preamp with the most versatile Direct Inject on the DIY or pro market, AFAIK. Many thanks to my friend Volker Mayer, [silent:arts], for the collaboration on the cool and fun HiZ Plug-In part of this project. We both hope to see the open format being used in other projects soon.

The VP312DI is pretty easy over all. It is a little more complicated than my other VP2x or VP312 builds. If you have built one of those, this should be no problem.

--------------------------------------------------------------------------------------------------------
September 21st, 2015 Update:
All support docs for this project can be found on the recently added Support Docs (http://capi-gear.com/catalog/support_docs.php) page at www.capi-gear.com
--------------------------------------------------------------------------------------------------------


--------------------------------------------------------------------------------------------------------
February 2nd, 2016 Update:
Rev D boards are now shipping for the VP312DI. To easily identify, the Rev D boards are green. The circuit is 100% identical although a few part labels and designations have changed. Like with all projects, it is crucially imperative that you follow the BOM that matches the revision of the PCB that you are building. I still have a good amount of the Sub DI boards left in black. Once those are gone, the reorder will be green and have the CAPI® affixed  :D
--------------------------------------------------------------------------------------------------------


MAKE SURE YOU INSTALL ALL 12 MILL-MAX DOA SOCKETS FROM THE BOTTOM, LIKE I SHOW IN THE VP2x GUIDE. This is very important for the HiZ Plug-In, especially if you plan to use the Jensen tranny Plug-In.

-------------------------------------------------
1. Start With The T-Pad
(Rev B.1 only)
-------------------------------------------------
I start with the t-pad on the VP312DI build. I do this so I can use 2 of the small PCB’s as spacers between the body of the t-pad and the board. Other parts on the PCB at this time can get in the way. The desired space is 1/16”.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/1_t-pad/1_t-pad.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/1_t-pad/1_t-pad.jpg)
I have chosen to continue using the solder-lug version so Hairball Mike and I can combine our orders to help keep the prices down.

Solder only the 2 middle lugs at this time making sure that the t-pad is parallel to the PCB. This will allow for adjustment if needed.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/1_t-pad/2_t-pad.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/1_t-pad/2_t-pad.jpg)

Temporarily assembly the PCB to the L-Bracket. After securing the nuts, make sure the t-pad’s bushing and lug is centered in their respective openings.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/1_t-pad/3_t-pad.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/1_t-pad/3_t-pad.jpg)

Disassemble the PCB. Make any adjustments if necessary. When soldering the rest of the lugs, try not to over-heat the pot. A good, solid solder joint can be completed without filling the thru holes with solder.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/1_t-pad/4_t-pad.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/1_t-pad/4_t-pad.jpg)

-------------------------------------------------
2. The Bourns 25K potentiometer is next
(Any Rev)
-------------------------------------------------
Install the Bourns pot following the same general steps that can be found in the VP2x Assembly Guide. This will help to make sure the faceplate is aligned properly for the next few steps.

As a tip, you can temporarily attached the faceplate to the bracket with a Quick-Grip clamp. Make sure you center it over the bracket holes and keep it nice and even.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI/RevC/1_Bourns-t-pad.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI/RevC/1_Bourns-t-pad.jpg)

(http://www.capi-gear.com/catalog/images/gallery/VP312DI/RevC/2_Bourns-t-pad.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI/RevC/2_Bourns-t-pad.jpg)
I mention the caps in that last pic as I change up my steps a little and combine some of the steps. I have built so many of these that I do little things to save time.

-------------------------------------------------
3. The Sub-DI.1 PCB Is Next
(Any Rev)
-------------------------------------------------
The next step is to fully populate the Sub-DI.1 board, with the exception of the 3 sub-mini switches.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/2_Sub-DI.1/1_Sub-DI.1.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/2_Sub-DI.1/1_Sub-DI.1.jpg)

Fit the Sub-DI.1 PCB on top of the main PCB, lining up the appropriate thru holes. I start with the 3 corner holes. For these 3, I use cut off leads from the Elna cap. They are the largest diameter leads in the kit. Slightly bend them and drop all 3 into the corner holes. This will lock the small board in and allow very little if any, movement.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/2_Sub-DI.1/2_Sub-DI.1.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/2_Sub-DI.1/2_Sub-DI.1.jpg)

Before soldering these 3 leads, I carefully clamp the 2 boards together.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/2_Sub-DI.1/3_Sub-DI.1.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/2_Sub-DI.1/3_Sub-DI.1.jpg)

It is very important that the 2 PCB’s are tight to each other. I check this before and after soldering the 3 leads from the top and the bottom.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/2_Sub-DI.1/4_Sub-DI.1.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/2_Sub-DI.1/4_Sub-DI.1.jpg)

I use cut off leads from the 1N4004 diodes for the remaining 5 holes. Again, a slight bend is all that is needed to keep them from falling thru.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/2_Sub-DI.1/5_Sub-DI.1.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/2_Sub-DI.1/5_Sub-DI.1.jpg)

-------------------------------------------------
4. The NKK Sub-Miniature Switches
(Any Rev)
-------------------------------------------------
Next we will fit all 3 of the NKK sub-mini switches to the bottom of the Sub-DI.1 PCB. Hold the switch bodies flat and tight to the board soldering only 1 of their bracket pins at this time.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/3_NKK/1_NKK.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/3_NKK/1_NKK.jpg)

Temporarily assembly the PCB, L-bracket and faceplate. Thumb tighten the 2 pot nuts making sure the faceplate alignment is nice and parallel to the L-bracket. The 3 mini toggles should fit nicely in their respective holes.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/3_NKK/2_NKK.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/3_NKK/2_NKK.jpg)

Turn the assembly over. You will have access to switch pins.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/3_NKK/3_NKK.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/3_NKK/3_NKK.jpg)

Carefully solder at least 2 additional pins for each of the switches. Try not to burn or melt any of the components!
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/3_NKK/4_NKK.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/3_NKK/4_NKK.jpg)

Disassemble the PCB from the metal and finish soldering the switches.

***Clip the 3 pins for SW1. This needs to be done to make sure that they don’t later interfere with the Sub-DI.2 PCB.

-------------------------------------------------
5. Onto The Sub-DI.2 PCB
(Any Rev)
-------------------------------------------------
Fit the 4-pin 90° header to the Sub-DI.2 PCB. I like to clamp it to the board and solder from the bottom.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/4_Sub-DI.2/1_Sub-DI.2.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/4_Sub-DI.2/1_Sub-DI.2.jpg)

Next, fit the 1/4" Neutrik jack onto the PCB. It will snugly snap into place. Before soldering, you need to make sure that the edge of the jack housing sits slightly beyond the edge of the PCB. If the PCB is flush or proud of the jack housing, you should file or sand this edge of the Sub-DI.2 PCB.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/4_Sub-DI.2/2_Sub-DI.2.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/4_Sub-DI.2/2_Sub-DI.2.jpg)
I have randomly check a dozen or so of the boards and so far, have not found any that stick past. Making sure will just let the jack pull the PCB perpendicular to the faceplate for a neater looking assembly.

When you have confirmed the proper fit, solder the jack to the PCB.

Insert the 4-pin 90° header pins into the Sub-DI.1 PCB. DO NOT SOLDER at this time! Again, we will temporarily assemble the metalwork to the PCB assembly. Center the Neutrik jack in its faceplate hole. Put on the plastic washer and hand-snug the knurled nut.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/4_Sub-DI.2/3_Sub-DI.2.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/4_Sub-DI.2/3_Sub-DI.2.jpg)

After flipping the entire assembly over, you will have just enough access to solder all 4 pins of the 90° header.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/4_Sub-DI.2/4_Sub-DI.2.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/4_Sub-DI.2/4_Sub-DI.2.jpg)

-------------------------------------------------

Next you can take the assembly apart and complete the rest of the build as normal.

The remainder is pretty straight forward.

-------------------------------------------------
6a. Phantom LED
(Rev C.1 only)
-------------------------------------------------
The LED installation has changed a little for Rev C.1. A lot of the info in 6b is still pertinent so definitely go thru it. The end result should look more like this pic though.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI/RevC/3_LED.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI/RevC/3_LED.jpg)

-------------------------------------------------
6b. Phantom LED
(Rev B.1 only)
-------------------------------------------------
For me, the last step before the knob and bullet cap dressing is the phantom LED. I solder 2 small transformer lead cut-offs to the pads labeled 1 and 2. Those will be routed to the C&K toggle as shown.

I prep the LED by cutting a piece of shrink tubing a little less than 1”. Slip it onto the shorter or cathode lead. I bend about a 1/16” L onto the end of this lead.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/5_LED/1_LED.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/5_LED/1_LED.jpg)

Insert the LED into the hole in the faceplate keeping the longer anode lead to the left and the shorter cathode lead to the right. Slightly bend the cathode lead down and solder it to the last lug on the Mute switch.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/5_LED/2_LED.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/5_LED/2_LED.jpg)

Next, insert 1 lead from a 10K resistor and the lead from solder pad 2 into the middle lug of the C&K toggle switch. I adjust the anode lead of the LED and the other lead of the 10K R so they touch. Solder and trim the leads back.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/5_LED/3_LED.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/5_LED/3_LED.jpg)

There are probably a number of different ways to do this so modify as you see fit.

BTW, the drop over the 10K R is about .21 watts. I have not had any problems with a 10K 1/4 watt resistor here. If you want the LED brighter and change the R to anything less than 10K, I would recommend using a 1/2 watt R.

Here’s another angle. Note that if you thread the nut on the C&K toggle first, then the lock washer, then into the metal, the larger trim nut will fit nicely on the front side.
(http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/5_LED/4_LED.gif) (http://www.capi-gear.com/catalog/images/gallery/VP312DI-build/5_LED/4_LED.jpg)

Have fun!!  :)

Cheers, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: horvitz on September 06, 2010, 11:16:21 AM
Anybody else working on one of these?  Just got mine up and running this morning.  Really fantastic!!  I'm super excited to really put it to use.  Outstanding work again, Jeff.

The lower-left of the board is a bit of a fun puzzle, but Jeff's notes above cover everything you could need to get it together correctly.  No problems at all on this end.

  Brian
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: dandeurloo on September 06, 2010, 01:27:25 PM
looks amazing!
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: [silent:arts] on September 11, 2010, 04:52:06 PM
Huha, I completely missed this thread :o
Jeff, again too much building information for a DIY forum ;D

btw, I need two of those beauties.
best modern but classic API 312 adaption so far, all features in I would like for myself ;D
[rev02 with a stepped grayhill switch for gain as an option would be nice for stereo applications]

nice work, my friend
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on September 13, 2010, 07:44:13 PM
Thanks Volker. I had to quote your last post so I could see how you gave me tinny, text crap about the stepped Grayhill. I will never live that down.  :'(  FWIW, with careful work, you could mount a 71 or 56 series in there with a little daughter board pins pointing up, flying lead wired! Do it. Do it.

For those who asked, I updated my first post with a few pics of how I handle the LED. There are probably a dozen different ways to do this, most better than mine! But it will get the job done and stay for many years.

Cheers, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: [silent:arts] on September 15, 2010, 04:12:17 AM
Thanks Volker. I had to quote your last post so I could see how you gave me tinny, text crap about the stepped Grayhill. I will never live that down.  :'(  FWIW, with careful work, you could mount a 71 or 56 series in there with a little daughter board pins pointing up, flying lead wired! Do it. Do it.

great idea, at the moment I'm unsure if it fits, but I will give it a try ;D
(http://www.silentarts.de/DIY/temp/VP312DI-Grayhill-1.png)

could you mail me the distance from the Bourns pin2 to the mounting screw?
(or a dxf file from that area)

this will become my "all features I ever wanted" 312.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on September 15, 2010, 10:06:57 AM
...great idea, at the moment I'm unsure if it fits...
Volker, I think it will fit just fine. Couple of flying leads and you are in business.

Keep in mind that the Bourns pot has an 1/8" shaft. This should be no problem. Digi keeps some 71 series in stock with an 1/8" shaft.

Hows this?
(http://i276.photobucket.com/albums/kk12/jsteiger1965/VP312DI-Rev-B.gif) (http://i276.photobucket.com/albums/kk12/jsteiger1965/VP312DI-Rev-B-1.jpg)

I suppose if I was smart, I would have the board set up for either the Bourns or the Grayhill 71. Damn.  ???

Oh well.

Best, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: [silent:arts] on September 16, 2010, 03:37:40 AM
cool Jeff, thanks 8)

I suppose if I was smart, I would have the board set up for either the Bourns or the Grayhill 71. Damn.  ???
mhm, isn't this a DIY forum ???  :o :D ;)
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: [silent:arts] on September 16, 2010, 05:19:52 AM
ok, what do ya think:

(http://www.silentarts.de/DIY/temp/VP-GAINSWITCH-3D-01.gif)
(http://www.silentarts.de/DIY/temp/VP-GAINSWITCH-3D-02.gif)
(http://www.silentarts.de/DIY/temp/VP-GAINSWITCH-3D-03.gif)
(http://www.silentarts.de/DIY/temp/VP-GAINSWITCH-3D-04.gif)

I will do a small run - anybody else interested in this ?
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: j_fraser on September 16, 2010, 07:40:37 AM
Relatively new to this forum, but loving the Group DIY 51x Rack and PSU builds, and now looking forward to getting my hands on a couple of Jeff's VP312DI's, just for starters! 

I'd be very interested in a few of these Volker, say approximately eight, if you could put my name down?

Many Thanks

Justin
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on September 16, 2010, 09:20:20 AM
ok, what do ya think:
I think you do great work my friend!  8)

Quote
I will do a small run - anybody else interested in this ?
Yes, for sure. I think I will make these an "add-on" to all my preamp kits. If someone selects "Stepped Switch and PCB", it will just be the small difference between the 71+PCB and the Bourns pot. Should be a small increase I think.

Again, nice thought and great work! ;) ;D

Cheers, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: [silent:arts] on September 17, 2010, 06:13:23 AM
I think I will make these an "add-on" to all my preamp kits. If someone selects "Stepped Switch and PCB", it will just be the small difference between the 71+PCB and the Bourns pot. Should be a small increase I think.
In this case it might be the best to mail the Gerbers to you?
and some dxf to double-check the dimensions?
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on September 17, 2010, 07:54:37 AM
In this case it might be the best to mail the Gerbers to you?
and some dxf to double-check the dimensions?
That's fine with me Volker, but up to you.

I do have other files to order over the next few weeks. I can just give you whatever you want.

I finally built the DK HiZ Plug-In proto but have not had the chance to power it up yet.

Cheers, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: [silent:arts] on September 17, 2010, 09:45:05 AM
well, it makes more sense if you sell them ;D

dimensions:
(http://www.silentarts.de/DIY/temp/VP-GAINSWITCH-Dimensions.png)

you have the gerber files in your mail.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on September 17, 2010, 11:09:36 AM
well, it makes more sense if you sell them ;D

you have the gerber files in your mail.
Nice work Volker. I will give things a double check for good measure. I see the email.

Hey, I even have an attachment this time!  ;D :P
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: dandeurloo on September 17, 2010, 09:00:02 PM
You guys are on to some smart stuff!  I can think of a number of uses for little stepped switches like that!

Good work as usual.

Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: [silent:arts] on September 18, 2010, 03:22:35 AM
I can think of a number of uses for little stepped switches like that!

but keep in mind this version can't replace any standard potentiometer (it only has two pins).
I did this for too reasons:
- you can easily step down the steps (from 12 to 11 or 10) without doing any solder bridges
- accuracy - each gain step has its own single resistor. makes it easy to find the exactly dB steps you want, and stereo matching easiest.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Winetree on September 23, 2010, 05:20:39 PM
Build two units now.
Question: on the Plugin Relay board it shows CR1 = IN749 4.3V zener.
How do you tell the difference from the other diodes?
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on September 23, 2010, 06:46:27 PM
...Question: on the Plugin Relay board it shows CR1 = IN749 4.3V zener...
Robert, the best way I know is a little lighted magnifier. Look for "4V3" printed on the side in absolutely minuscule text. I just have a little cheapo from Walgreens that does the trick.

On the same subject, it is imperative that the zeners on the main boards be properly located and placed or things will not work right!

I'm sure there is another way that maybe one of the smarter cats around here will share.  ;D

Cheers, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Winetree on September 24, 2010, 03:01:56 AM
I'm running the passive Hi-Z
Do I still install the 16-24V Hi-Z  Switch?
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: spacecho on September 24, 2010, 05:24:18 AM
Hello Guys,

so i have just put one of these together - with melcor 1731 , fet DI and Cinemag I/O iron.

it all looks good but when doing the resistance test (before powerup) all of the test points gave resistance into the megaohm range straight away(all good) except when probing the V+ to C conection.... it starts with a lower resistance 80k and slowly rises - it got to about 300k but really slowly - has any one had a similar experience when testing?

just thought i'd check before powering up....
cheers

spacecho
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on September 24, 2010, 06:38:46 AM
I'm running the passive Hi-Z
Do I still install the 16-24V Hi-Z  Switch?
No, it is not necessary for the passive circuits. You can install it if you ever find the desire for an active alternative. If you are 100% sure you will also use the passive versions, by all means you don't need it.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Winetree on September 24, 2010, 01:43:58 PM
Is there a parts layout for the Sub D.I. Board.
I didn't realize the diodes would be such a problem.
Only found 2 of the 4V3's. Checked values found 2 groups
one around 610 and the other 750. 4V3 in the 750 range.
what goes where?

Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on September 24, 2010, 02:36:11 PM
Each relay PCB gets (1) 4.3V zener and (2) 914's.

I have a stuffing guide on the product page.

Here it is. This will clear things up for you.
(http://www.classicapi.com/catalog/images/gallery/relays/P-I-Relay.1/Plug-In-Relay.1-layout.gif) (http://www.classicapi.com/catalog/images/gallery/relays/P-I-Relay.1/Plug-In-Relay.1-layout.pdf)

Hello Guys,

so i have just put one of these together - with melcor 1731 , fet DI and Cinemag I/O iron.

it all looks good but when doing the resistance test (before powerup) all of the test points gave resistance into the megaohm range straight away(all good) except when probing the V+ to C conection.... it starts with a lower resistance 80k and slowly rises - it got to about 300k but really slowly - has any one had a similar experience when testing?

just thought i'd check before powering up....
cheers

spacecho
This should be fine. You are really just checking for a low resistance or a direct short.

Cheers, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Winetree on September 26, 2010, 10:33:22 PM
Great got the relay boards.
Where's the info for the SUB-D.I. board. Cap & diode value and layout.
Could make some out with the pictures but not everything.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Winetree on September 26, 2010, 10:54:24 PM
found the Classic VP312DI Sub-DI.1 BOM in the DOC's you sent.
Great job, thanks.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on September 26, 2010, 10:56:54 PM
found the Classic VP312DI Sub-DI.1 BOM in the DOC's you sent.
Great job, thanks.
Haha. I just sent them again. Thought maybe I forgot.  :)
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: geoff004 on November 28, 2010, 07:43:55 PM
sorry if I missed it -
does the fet DI work at 24V?
thanks
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on November 28, 2010, 08:11:40 PM
sorry if I missed it -
does the fet DI work at 24V?
thanks
Yes it will and that can be independent of the DOA operating voltage.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: geoff004 on November 28, 2010, 08:57:44 PM
thanks for the reply-
got them both done but haven't yet powered them up.
Stuffed with Gar1731s until something else comes in.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: ethervalve on December 28, 2010, 07:21:13 PM
Hi,
Before I attempt to power mine up I just wanted to verify a couple things about the standard 500-series version:
A) Should I just leave sw1; sw2; C2; C3; CR3; and CR4 unpopulated or are there any jumps that need to be installed?

and

B) I just wondering if someone could explain how the J1-1 (DC Block/Cap coupled output|Output cap bypass) three pin header works?

Thanks in advance.

Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on December 28, 2010, 08:01:08 PM
Besides cutting the card edge connector, you will need to do some jumpering if you are building a VPR version.

(http://www.classicapi.com/catalog/images/gallery/VP312DI/500-VPR-mod.jpg)

You must jumper the opamp V select which is SW2.

You will also need to jumper the V select for the HiZ Plug-In which is SW1 on the DI PCB. The jumper for this goes from the center hole to the right hole (or the 16V hole).

C2 and C3 should not be installed.

CR3 and CR4 should not be installed.

For the J1 description:
The safest place for the shunt is in the DC Block position. This will put the coupling caps in the circuit so any DC offset from the opamp will not get to the 2503 output tranny. When in "straight into the 2520" DI mode, some opamps have significant DC offset which can damage the output tranny. I put the bypass position for those who will not use the "straight into the 2520" mode if they want to have the same circuit as a vintage 312 card.

Cheers, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: ethervalve on December 29, 2010, 03:18:56 PM
Thanks Jeff! Everything worked perfectly.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on December 29, 2010, 03:33:57 PM
Thanks Jeff! Everything worked perfectly.
:) Excellent! :)
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bruce0 on January 07, 2011, 01:28:10 AM
Somebody nice gave me a VP312DI kit for christmas!...

I read that I am supposed to stuff the Sub-DI Rev A sub pcb first (posted elsewhere on this board).  However I don't have access to a schematic, parts list or stuffing guide for the VP312DI.  For that matter, there is R14, which doesn't exist on the VP26, but is marked on my circuit board for the VP312DI.

I see above that one poster refers to "Docs" re stuffing the Sub-DI board... Does anyone know where they are?

Maybe Santa needs to write a note to Jeff...

The kit looks great though... nice fit and finish, lovely little attenuator....


Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bruce0 on January 07, 2011, 07:26:03 PM
Got the BOM, thanks Jeff!

I have another question.  Does anybody know what values resistors R9 and R10 are supposed to be?  The BOM says 750 Ohms, the kit contained 750K.

Actually, never mind.  The Chunger post to the rescue.  His perfect pictures of the boards show that the value on his kit was a 750 Ohm.

Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 07, 2011, 07:59:58 PM
Got the BOM, thanks Jeff!

I have another question.  Does anybody know what values resistors R9 and R10 are supposed to be?  The BOM says 750 Ohms, the kit contained 750K.

Actually, never mind.  The Chunger post to the rescue.  His perfect pictures of the boards show that the value on his kit was a 750 Ohm.


Yes indeed they are 750R. I still have a few "bad" kits out there that were shipped with 750K. If someone finds this, please send me a note so I can replace them for you.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 08, 2011, 05:20:40 PM
Bruce,

I get a very high reading no matter which position the switch is in. Do you have a HiZ Plug-In installed? If so, try without it. Any chance of a pic of the rear section of the board from the DOA to the gold fingers area?

Best, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bruce0 on January 08, 2011, 05:53:19 PM
Jeff:
I updated my previous post with the picture you requested.

Note that when I connect the positive lead to common I get 21K, and when I connect the negative lead to common I get 40K

Also, I went to the back and tested VC to ground on both of the relay cards.  one of them shows resistance, the other is shorted, is that normal?

Note in the picture the HiZ switch is in the 24 position, but it doesnt matter, the switch that makes the difference is the DOA switch.  24v position everything looks fine, 16 V position and I get the higher resistance.


bb

I should also say that when it shows these resistances (V+ to C) they don't show right away, they slowly rise, like there is a capacitor charging somewhere.  But they stop for over a minute at 40K.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 09, 2011, 08:57:17 AM
...Also, I went to the back and tested VC to ground on both of the relay cards.  one of them shows resistance, the other is shorted, is that normal?...
Yes. There is a normaled connection in the 1/4" jack that connects VC to Gnd. When a jack is inserted it opens.

Your build looks fine in the pics. The only thing I can think is there may be something on one of the relay boards. Do you have a desoldering tool to easily remove them and investigate?

Best, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 10, 2011, 10:25:51 AM
Bruce,

This (http://www.groupdiy.com/index.php?topic=38094.msg471424#msg471424) is basically the circuit I use on the relay board.

Is it possible that you swapped the 4V3 zener and one of the 914's? Probably not but thought I would ask.

I can send you a few parts if you need them.

I won't be able to check my build until later today.

Cheers, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bruce0 on January 10, 2011, 01:13:29 PM
When testing V+ to C after the build, I got 40K resistance, and the appropriate resistance is higher according to the VP2x Docs.  It turns out that if I set the DMM on the 20M range or the 2M range, it showed high resistance.  On 200K however it showed 40k.

This only happens when the OP-AMP switch is turned to 16V.  On 24 V it is fine.  This is because the relay card is in the 16V circuit only.  And Notice that the same is true of the relay card itself.  There should be high resistance between V+ and VC (which is normally grounded on the board when there is no DI plugged in). I was getting 40K ish there too.

This whole problem can be attributed to a strange Meter, or interaction between the meter and the capacitors in the circuit.  

I went and bought a new meter, and everything reads fine (high resistance).

Just in case someone else had the problem.

bb
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bruce0 on January 15, 2011, 12:14:27 AM
Now that I got the problem sorted out (turned out there was no problem), I got a chance to try it out today.  Tried various guitar and bass through it.  Really liked some of the bass sounds, the attenuator gives a lot of control, which is fun.


One problem.  When the Post2622 switch is flipped left, I get no audio signal from the DI.  TO the right it works fine.  The same is true with 2 different HiZ cards.



So maybe I do have some problem.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 15, 2011, 10:17:15 AM
Switching the "Post 2622" right will give you the "straight into the 2520" Bo circuit.

Switching that left will run your signal thru the HiZ Plug-In module. Did you get a passive version of the plug-in? If so, checking with that could eliminate your HiZ Plug-In as the cause.

Make sure you have voltage on the +V socket of the HiZ Plug-In.

Can you power the module with it flat on your bench? You will need to. With no HiZ Plug-In, voltage applied to the module, insert a mono 1/4" jack into the socket. Keep the "Post 2622" switch to the left. Probe with your DMM to make sure you have continuity between the 1/4" jack tip and the HiZ In socket of the HiZ Plug-In.

If you do not have continuity...the issue will probably be on the relay card just behind the 1/4" jack socket.

If you do have continuity...the issue is with the HiZ Plug-In.

Let us know.
Best, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bruce0 on January 16, 2011, 04:51:32 PM
Jeff:

Thanks so much.

Yes I can power the unit open on the bench.

I presume from your description that the relay card behind the 1/4" socket is the one that is activated by the Post 2622 switch, and the one in the center of the board is activated by insertion of the 1/4 Jack. Is that correct?  So the one that goes to Bo Mode, is the one near the jack?

I have tried the unit with a Passive (DIY - Old Altec Mic Pre Transformer reversed), and with an active.  I do have 2 different actives, and after I make your tests I can try that ( I was reluctant to Fry 2 if there was some problem).

I will make the tests, but based upon the fact that the Passive didn't work either, it sounds like it is the relay card near the Jack.  Is that consistent?

(Luckily... and thanks to your suggestion, I have a Hakko 808...  And as you said, it does just want to make me de-solder something... it works so well (I have been harvesting old mic-pre transformers)).

I will return with more data.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 16, 2011, 05:11:25 PM
...I presume from your description that the relay card behind the 1/4" socket is the one that is activated by the Post 2622 switch, and the one in the center of the board is activated by insertion of the 1/4 Jack. Is that correct?  So the one that goes to Bo Mode, is the one near the jack?
Yes, correct Bruce.

Quote
I will make the tests, but based upon the fact that the Passive didn't work either, it sounds like it is the relay card near the Jack.  Is that consistent?
Yes I would agree. With a 1/4" jack inserted, you should hear that relay clicking/activating when you flip the "Post 2622" switch back and forth. Without a 1/4" jack inserted, the "Post 2622" switch does nothing since it needs the ring-sleeve-ground connection made by the jack body itself.

Which reminds me, DO NOT USE A STEREO PLUG FOR A GUITAR CABLE HERE!!!

Quote
(Luckily... and thanks to your suggestion, I have a Hakko 808...  And as you said, it does just want to make me de-solder something... it works so well (I have been harvesting old mic-pre transformers)).
;D ;D 8) 8) :D :D They are not super cheap but well worth the money.

Keep us posted.
Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bruce0 on March 03, 2011, 01:00:05 AM
I pulled the relay cards out, which is possible with the hakko desolderer amazingly, and traced one. 


I figured out that the Zener was in the wrong place all the time (switched with one of the 914b's exactly the same on both cards).   Ooops.
 I had checked it against the BOM but somehow missed it.  I think you may have asked this first... and I did check.

In any case, thanks for your help.  Pre is tested and working fine.


(... the way I found this was I traced the card, wrote up a schematic, looked at it, and realized it wouldn't work. )

Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on March 12, 2011, 10:36:25 AM
Hey all,

I have published a long-over-due pic with some notes on how to complete a proper & permanent VPR 500 series mod to the VP312DI PCB.

Here is a thumb:
(http://www.classicapi.com/catalog/images/gallery/VP312DI/500-VPR-mod.gif) (http://www.classicapi.com/catalog/images/gallery/VP312DI/500-VPR-mod.jpg)

I have also updated the first post of this thread with this info.

Happy Saturday!  :)

Cheers, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: rob61 on March 31, 2011, 10:31:17 PM
I'm interested in adding a pair of these to my new 51X rack.

1. What difference in sound is there between the FET and the IC version of the active DI circuits?

2. Has anyone tried the new 24V APP2050E DOA? I've been using the gar2520 and Red Dots in my other +16 CAPI pres. How would this compare in sound?
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: chunger on April 01, 2011, 12:29:56 AM
I'm interested in adding a pair of these to my new 51X rack.

1. What difference in sound is there between the FET and the IC version of the active DI circuits?

2. Has anyone tried the new 24V APP2050E DOA? I've been using the gar2520 and Red Dots in my other +16 CAPI pres. How would this compare in sound?

I find the FET IC to be bity and aggressive perhaps in the upper mids?  Very forward to my ear. . . the IC version runs very hot gainwise.  Bass response is very smooth on that one in fact, I find it pretty neutral and smooth. .. perhaps due to the larger cap?  This is primarily playing with it on bass guitar and primarily on the APP2050E.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: rob61 on April 01, 2011, 02:02:58 AM
Thanks Chunger... have you also used gar2520 or Red Dots? If so, how does the APP2050E compare? I'm finishing up wiring my 51X...

Anyone else compare these? Any input appreciated.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: chunger on April 01, 2011, 03:39:45 AM
don't have red dots, but have the 2 gar2520 and the gar melcor clones.  Haven't played with them in the VP312DI though.  Only on the VP26's.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: NoBass on July 12, 2011, 06:11:43 AM
Help !!

My VP312DI killed one of my DOA  :'(

It worked very well for a few weeks, with AWESOME results on both kick and drum ambience, but all of a sudden, between two takes, it stopped making sound. At first I thought it was my old API2520 that had gone wrong, but I put a red dot inside and it didn't make a sound. The DI however, is still working. I switched it off, and afetr only 2 minutes of testing, I could feel the red dot burning hot.

What's wrong ?

(BTW I tried my old API2520 in a VP26, it just doesn't work anymore  :'( )

NoBass
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on July 12, 2011, 08:11:11 AM
Believe it or not, this is a first, IIRC. What rack are you using? Is the VP312DI built VPR style or 51x style? My first thought is to check the voltages at the DOA sockets. Are you 100% sure that CR1 and CR2 are 1N914'a and not the zener's from the Sub-DI board? Also, if you are using the DI circuit set to post 2622 a lot, the shunt jumper should be set to DC Block/Cap Coupled Output. I have heard of guys smoking there PPA amps this way because of the higher DC offset. The DC offset from API2520 is typically pretty low, unless the opamp was on it's way down anyhow.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: NoBass on July 12, 2011, 09:28:02 AM
I'm using a 51x rack ; the VP312 is 51x-style. The voltages are the first thing I checked after the DOA died, and they're just about right (+- 0,5V). I ran the DOA at 16V (of course). I never used the DI, I just checked it, and yes the jumper is set at "coupled output"...
I can't really check CR1 & CR2 because their name is toward the pcb but I remember checking them...

About the opamp, I know nothing about its history, so I may have been "on its way down".

But as I said, even with another op-amp, it does not produce any sound and I'm not comfortable letting the opamp get this hot...
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on July 12, 2011, 09:45:51 AM
If it's not passing a mic signal and the DOA is known to be good, I would first check the PK2 relay to make sure that with no 1/4" jack inserted, pins 8 and 10 get coupled to the input transformers primaries. With a ground signal present at PK2's VC pin, the rear mic in will be couple to the 2622. When a 1/4' jack is inserted, the normal of the sleeve's contact is broken/opened which disconnects the ground from PK2's VC pin and switches the relay to the HiZ Plug-In as the source for the 2622's input.

If all of that is good, you will have to look at the output section. That is very short and sweet really but I would make sure it is not a solder joint on either the Mute or Polarity C&K switches.

Did you get the skiz I sent out a few weeks ago?

Cheers, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on July 12, 2011, 10:29:16 AM
Hey guys

To help keep things simple and easy, I put a link to the most current version of the VP312DI schematic near the beginning of the first post of this thread.

The most current one has today's date of 7-12-2011. I found a small error and corrected it. The VC labels for the PK relay's were flipped the wrong way around.

Cheers, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 12, 2011, 05:06:31 PM
Hi all

Since the Rev C.1 version of this project has been officially released and started shipping, I had to update a number of the support docs and details.

--The new schematic can be found near the top of the first post of this thread. The older Rev B.1 is still there for history sake.

--I also added the VP-Gainswitch install guide PDF to the first post. Both the Bourns and Grayhill 71 gain options are now found on the PCB.

--I added a few pics to aid in installation of the new Bourns t-pad, since the footprint is on the main PCB.

--I added a pic of the new LED layout as that has changed slightly.

I think that's it. Ask away if anyone has any questions.

Cheers, Jeff
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: mulletchuck on October 23, 2011, 04:19:20 AM
finished my build!  Fired up perfect first time!   couple q's, tho:

Should I hear the relay's switching on/off when i flip some of the toggle switches in the front?   cuz I only hear them switch when i turn on the 51x power supply or turn the power supply off.

Everything worked, tho.  DI was nice and clean, Mic sounded just like the VP26.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 23, 2011, 09:15:21 AM
Chuck, when you insert a 1/4" plug, it will open the normalled contacts on the Neutrik 1/4" jack, which will activate the relay that's behind the input transformer. Once a plug is inserted (and only with plug inserted) flipping "Post 2622" will activate the relay just behind the Neutrik jack.

This pre will sound a little different than a VP26 once you start comparing them side by side.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: mulletchuck on October 23, 2011, 09:31:06 AM
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. 
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 23, 2011, 09:34:48 AM
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.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: mulletchuck on October 23, 2011, 11:53:47 AM
Lol WHY DOESN'T THIS DIY STUFF COME WITH A MANUAL  :o  ;D  :P
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 23, 2011, 11:59:33 AM
It's all described here (http://classicapi.com/catalog/product_info.php?cPath=22_117_55_92_94&products_id=159) Chuck.  ;)
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: mulletchuck on October 24, 2011, 12:07:02 AM
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.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 24, 2011, 08:35:25 AM
.....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.

Quote
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."
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: mulletchuck on October 24, 2011, 12:21:12 PM
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. 
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 24, 2011, 12:26:19 PM
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.
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: [silent:arts] on October 24, 2011, 03:11:35 PM
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 :-)
Title: Re: VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: mulletchuck on October 24, 2011, 07:50:11 PM
well, thank ya for inadvertently makin' it easy to A/B between Pre 2622 and Post 2622!!  lol
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Brolik on January 04, 2012, 11:44:23 AM
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!
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 04, 2012, 12:07:05 PM
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.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Brolik on January 04, 2012, 12:29:32 PM
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?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 04, 2012, 12:51:59 PM
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.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Brolik on January 04, 2012, 01:43:41 PM
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.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 04, 2012, 02:12:24 PM
Brolik, I just opened the Rev B.1 ARES files. Slipped my mind to do so before.  :o  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.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Brolik on January 04, 2012, 03:39:57 PM
hm. so I was barking up the right tree, huh? Guess I'm on the hunt for shorts. Thanks Jeff.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Brolik on January 04, 2012, 07:30:53 PM
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?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 04, 2012, 07:44:14 PM
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.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Brolik on January 05, 2012, 11:28:08 AM
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?  ;)
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 05, 2012, 11:32:16 AM
Good news, congrats and thanks for the update.

Lotta work trying to do 3 new modules at once and still move forward on the console stuff. Unfortunately, everything suffers, especially the console stuff.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Brolik on January 05, 2012, 03:46:01 PM
good. go nice and slow on the console so that I have enough modules to fill one before it comes. start with those eqs!
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: New Soul Rebel on February 01, 2012, 01:07:36 PM
A day of woes! on my VP312DI biuld

I soldered the wrong TPAD, I did not realise I had more than one type in teh package. f**k! desoldered and resoldered the right one.

I also now have led working fine on the phantom power switch.

Still no sound the. The OPAMP is getting very HOT quickly.

I am not sure whether the rear relay is working. Would this cause the circuit to 'back up' and get hot?

the jack inserted, hear click no problem, switch 2622 hear click no problem.

But no sound still.

I have checked and rechecked all my solders. Does this sound like a the dreaded relay problem again?

I want more VP312DI's because they are superb on synths. I want another pair, but f**k, ever time I build one I get problems.

any ideas guys?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on February 01, 2012, 02:08:41 PM
Well, like I said, there will probably be no magic bullet or smoking gun fix. When having trouble like this the "pot shot" approach to finding and fixing will most times never work. The only way to find and solve is systematic and methodical.

First, common sense things with the opamp. Is it a known good solidly built opamp? Who built it? Has it been verified good in another working device? Is the voltage switch set incorrectly for the opamp installed? I never test a freshly built preamp with a freshly built opamp. Too many variables.

From there, you will need to follow the schematic like a road map. You can follow signal from the input up to the opamp with no opamp installed. When in mic mode, does injected signal get to the first relay board? Does it get past it? Keep following all the way to the opamp.

When inserting a 1/4" jack, the rear relay will switch to DI mode. Follow the signal throughout the DI signal path as well.

This may seem like a frustrating time, but the rewards when you can systematically follow signal thru an entire device and find the culprit will be very rewarding. It will only make you a better builder as well.

Best of luck and keep us posted.

Cheers, Jeff
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on February 25, 2012, 01:13:10 PM
Matt

So what was the finding on swapping the opamp? You need to first do this to rule out DOA issues. If you have done this and the problem stays with the preamp, then we know to look elsewhere on the pre.

All of the things I am about to post can be deciphered by looking at, reading or following the schematic. This will become a necessity with the amount of kits you build if it's not already. Good troubleshooting skills will out weight good build skills any day. No matter how good a builder one may be, there will always come a time when you need to sort out an issue.

So, think it may be the t-pad? Easy. Let's bypass it and see what happens. By looking at the skiz we can see that the t-pad follows the 2503 output transformer. Desolder the Blue and Orange leads from the 2503. Temporarily solder them to an XLR or whatever means you need to monitor the output. Again from the skiz, Blue will be + and Orange will be -.

What are the results? Same issues? No sound and opamp heating up? I think we have ruled out the t-pad.

In a general studying of the 312 schematic, what would happen if the 2503 is bad? What if the primaries are shorted within the x-fo? Very rare but sh*t does happen. Again, in following the skiz, the DOA's output would be directly shorted to ground. Not good. Would probably cause a very fast over heating of the opamp. Maybe next you should desolder all the leads from the 2503 and measure DCR to see.

What is DCR between the following: (again, that damn schematic is the key!)
Red to brown?
Blue to green?
Yellow to orange?
Violet to gray?

Make sure your DMM is set to properly measure resistance under 100 ohms. Let us know what you find.

Last thing to mention, before I would have gotten to the above, I would have injected signal and followed it all the way thru the preamp. Where it stops would be the area to look. If the above holds true, things would be fine up to the DOA's input. Would be a great help to yourself if you could verify this. You will be thanking me for it one day down the road.

Best, Jeff
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: New Soul Rebel on April 09, 2012, 08:08:07 AM
Jeff...

I soldered a NEW 2503 into my VP312DI and it worked straight off the bat!

Here are the readings of what the 2503 I took out.

Red to Brown 8.3
Blue to Green 8.3
Yellow to Orange 8.3
Violet to Gray 8.3

Which would seem to imply there is nothing wrong with the 2503 right?

If this is so, then I will test this 2503 in one of my new vp312s now. If it works, then I can only say it must have been a cold solder joint.

Would be unusual for me, but I guess it happens. I'll get back to you.

Matt
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on April 09, 2012, 09:00:08 AM
Matt

Those readings are normal and correct.

The other thing you should look for is a direct short. Start with one color, and measure against all the others. These should all have no reading on your DMM, except the sets above.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: New Soul Rebel on April 09, 2012, 01:21:20 PM
 :D

Its in the other VP312 without any bother Jeff.

I must have cold soldered. Sorry to waste everyone's time.

Still, learned a little about the 2503 in the process

Matt
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: grant on April 10, 2012, 06:03:19 PM
Problem:  I'm getting 8.2k ohms resistance between V+ and C on the DOA sockets.  (All other tests between other op amp sockets have resistance greater than 200k ohms).  This is without any DI boards installed.  With a DI board installed the resistance falls to 4.87k Ohms.  It's still 8.2k Ohms without a DI board installed.

Extra info:

•Slightly burned the "body" of C2 on Sub-DI.1
•I did install all of the "optional" resistors and capacitors.  I wasn't even sure of pros and cons of this.
•This is a 500-VPR mod version.
•Previously I was 100% on these builds--four VP26s and six op amps built correctly the first time.
•I don't have "any" electronics knowledge or troubleshooting skills.
•I don't have desoldering equipment.
•To my eye, everything looks good.  I don't see any solder bridges.


Any ideas?  I would sincerely appreciate any help.  If there is nothing new (that already hasn't been stated on this board), would someone recommend a book or website that will teach me how to troubleshoot and repair electronics?

Thanks,
Grant
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on April 10, 2012, 06:23:47 PM
Grant, this is normal for a VP312DI board. It is due to the relay PCB's and holdup resistors. So, continue on.

If you mean the 150k R, that is a load R that will slightly decrease the input Z when in mic mode. Leaving it out will tend to give a slightly more "open" sound, typically.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: grant on April 10, 2012, 06:45:04 PM
WHAT A RELIEF!! THANK YOU!!

Yes, I did mean the 150k R but also C10 and C11--everything labeled with one asterisk on the BOM. 

By "open," do you mean that it will have more high frequencies?  If so, I might just remove it (after a good listen).

Thanks again for your prompt reply.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: twitme on May 23, 2012, 11:01:35 PM
I just unpacked my vp312DI kit [Rev C.1, VPR 500 series version] and have two questions.

A)  It did not include resistor R19 [10R .5W 5% CF].  The BOM does not list it as optional, but I do see on the schematic that it lies in between the LED and the ground.  Is the intention to simply short those pads instead of putting a low-ohmage resistor there?  Or should I get ahold of one of those resistors?

B) When cutting the wire-lengths for the output transformer, is it crucial for the sound quality that they are cut as short as possible?  Or is the purpose of cutting them tightly so that they are nice and snug?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on May 23, 2012, 11:14:43 PM
I just unpacked my vp312DI kit [Rev C.1, VPR 500 series version] and have two questions.

A)  It did not include resistor R19 [10R .5W 5% CF].  The BOM does not list it as optional, but I do see on the schematic that it lies in between the LED and the ground.  Is the intention to simply short those pads instead of putting a low-ohmage resistor there?  Or should I get ahold of one of those resistors?
That is the larger brown bodied resistor. I pack the kits in groups. I just checked the others I have here and they all have that R in them. My guess is, it is in your kit to. If not, I will gladly drop one in an envelope for you. I do not recommend a hard jumper as it will throw the star ground and isolation between CHA and GND in your rack out the window.

Quote
B) When cutting the wire-lengths for the output transformer, is it crucial for the sound quality that they are cut as short as possible?  Or is the purpose of cutting them tightly so that they are nice and snug?
Just try to keep them short for neatness as much as anything. Many inches long is not a good idea but an extra 1/2 inch will not hurt anything.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: twitme on June 22, 2012, 02:12:50 PM
I've just finished building and testing my vp26 and vp312di preamps (one of each).  Mostly things are working.  However the DI on the 312di is giving me a super high-output low frequency oscillation not related to the instrument when I plug an instrument into it.  (sounds like "wub wub wub", and I'm not a fan of dubstep.)  Everything else is functioning perfectly.  The DI I've built is the HiZ-IC1-rev01.  I do not have another DI module or DI pre to test with at the moment.

Although everything else is functional, doing the opamp socket tests found in the vp2* assembly guide I did end up with some weird results.  I'll post those below for both the vp312DI and the vp26.

unpowered DOA socket test:
vp312di:

-V / +V = no reading
-V / C = no reading
C / +V = 9.6 kOhm
C / O = 375 kOhm
+V / O = 386 kOhm
-V / O = no reading

powered DOA socket test:
vp312di:

+V / C = no reading
-V / C = .32 volts


And for the vp26:

-V / +V = shows 300 kOhm and continuously rising as I hold the test terminals on
-V / C = no reading
C / +V = no reading
C / O = no reading
+V / O = no reading
-V / O = no reading

powered DOA socket test:
vp26:

+V / C = .25 volts
-V / C = .26 volts

Things sound great though.  *shrug*.  Bad DMM?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: twitme on June 22, 2012, 03:18:07 PM
Sorry to waste your time Jeff.  I reseated the DI plugin and the op amp in the 312DI and it's working perfectly now.  Also the low voltage readings were a result of my sh*tty test-jig that I put together.  I tried using the preamp with mic and DI using the test jig into my backplane and I got no sound at all.  Remove the test jig and all works perfectly.

I'm still slightly concerned about the 9.6kOhm reading in the above unpowered test, but otherwise things are working great! 
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on June 22, 2012, 07:50:58 PM
....I'm still slightly concerned about the 9.6kOhm reading in the above unpowered test, but otherwise things are working great!
This is perfectly normal and exactly as expected for a VP312DI. It's due to the hold up resistors for the relay boards.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on June 24, 2012, 07:02:26 PM
Well, i finished my VP312DI (stepped). It's my first project ever so i was expecting a problem, which happened :D. The module powers, nothing funny, phantom engages on and off (tho the led slowly fades away when i turn it off, it takes some seconds). When i plug a microphone i get nothing, i got barely something through the pre to a console, but nothing from the pre to a speaker, just noise (a lot of it when i crank the gain). DI seems to work better, i get an acceptable guitar tone, but it distorts fast at low gain, which i dont think is normal either.


=(

pics here, hope its something obvious and visible :D


  (http://img159.imagevenue.com/loc143/th_620084243_IMG_0150_122_143lo.JPG) (http://img159.imagevenue.com/img.php?image=620084243_IMG_0150_122_143lo.JPG) (http://img288.imagevenue.com/loc588/th_620121169_IMG_0155_122_588lo.JPG) (http://img288.imagevenue.com/img.php?image=620121169_IMG_0155_122_588lo.JPG) (http://img156.imagevenue.com/loc577/th_620155113_IMG_0156_122_577lo.JPG) (http://img156.imagevenue.com/img.php?image=620155113_IMG_0156_122_577lo.JPG)
(http://img153.imagevenue.com/loc81/th_620191778_IMG_0157_122_81lo.JPG) (http://img153.imagevenue.com/img.php?image=620191778_IMG_0157_122_81lo.JPG) (http://img107.imagevenue.com/loc497/th_620232821_IMG_0158_122_497lo.JPG) (http://img107.imagevenue.com/img.php?image=620232821_IMG_0158_122_497lo.JPG) (http://img268.imagevenue.com/loc455/th_620259384_IMG_0159_122_455lo.JPG) (http://img268.imagevenue.com/img.php?image=620259384_IMG_0159_122_455lo.JPG)
(http://img244.imagevenue.com/loc481/th_062030869_IMG_0160_122_481lo.JPG) (http://img244.imagevenue.com/img.php?image=062030869_IMG_0160_122_481lo.JPG) (http://img107.imagevenue.com/loc136/th_620349303_IMG_0161_122_136lo.JPG) (http://img107.imagevenue.com/img.php?image=620349303_IMG_0161_122_136lo.JPG) (http://img133.imagevenue.com/loc405/th_620396373_IMG_0162_122_405lo.JPG) (http://img133.imagevenue.com/img.php?image=620396373_IMG_0162_122_405lo.JPG)
(http://img170.imagevenue.com/loc336/th_620437722_IMG_0164_122_336lo.JPG) (http://img170.imagevenue.com/img.php?image=620437722_IMG_0164_122_336lo.JPG) (http://img152.imagevenue.com/loc239/th_620464127_IMG_0166_122_239lo.JPG) (http://img152.imagevenue.com/img.php?image=620464127_IMG_0166_122_239lo.JPG) (http://img234.imagevenue.com/loc65/th_620522911_IMG_0167_122_65lo.JPG) (http://img234.imagevenue.com/img.php?image=620522911_IMG_0167_122_65lo.JPG)
(http://img28.imagevenue.com/loc44/th_620560470_IMG_0169_122_44lo.JPG) (http://img28.imagevenue.com/img.php?image=620560470_IMG_0169_122_44lo.JPG) (http://img106.imagevenue.com/loc592/th_620602463_IMG_0170_122_592lo.JPG) (http://img106.imagevenue.com/img.php?image=620602463_IMG_0170_122_592lo.JPG) (http://img147.imagevenue.com/loc47/th_062064170_IMG_0171_122_47lo.JPG) (http://img147.imagevenue.com/img.php?image=062064170_IMG_0171_122_47lo.JPG)
(http://img168.imagevenue.com/loc891/th_620665500_IMG_0172_122_891lo.JPG) (http://img168.imagevenue.com/img.php?image=620665500_IMG_0172_122_891lo.JPG) (http://img292.imagevenue.com/loc30/th_620688883_IMG_0174_122_30lo.JPG) (http://img292.imagevenue.com/img.php?image=620688883_IMG_0174_122_30lo.JPG) (http://img230.imagevenue.com/loc214/th_620711761_IMG_0175_122_214lo.JPG) (http://img230.imagevenue.com/img.php?image=620711761_IMG_0175_122_214lo.JPG)
(http://img103.imagevenue.com/loc1096/th_620740699_IMG_0178_122_1096lo.JPG) (http://img103.imagevenue.com/img.php?image=620740699_IMG_0178_122_1096lo.JPG)
     
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on June 25, 2012, 10:34:41 AM
The biggest trouble folks have with this build is the small relay PCB's. If the zener diode gets put in the wrong place, the circuit will never function properly. I can only see the side of the PK2 board but in the pics, it sure looks like there is a 1N914 where the zener should be.

I also notice the 3-pin option jumper is not installed. Without it, the coupling caps between the opamp and 2503 are always in the circuit. This is the safest way to have the module set up so you can surely leave it as is with no worries. Just wanted to point that out. You are good just like you have it......missing.  ;)

Check out those relay boards.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on June 25, 2012, 01:03:35 PM
hard to photograph those little buddies... Its gonna be a ***** if i need to desolder... i only have wick and a solder-sucker
  (http://img150.imagevenue.com/loc500/th_639285623_IMG_0179_122_500lo.JPG) (http://img150.imagevenue.com/img.php?image=639285623_IMG_0179_122_500lo.JPG) (http://img139.imagevenue.com/loc562/th_639321579_IMG_0182_122_562lo.JPG) (http://img139.imagevenue.com/img.php?image=639321579_IMG_0182_122_562lo.JPG) (http://img216.imagevenue.com/loc561/th_639351316_IMG_0183_122_561lo.JPG) (http://img216.imagevenue.com/img.php?image=639351316_IMG_0183_122_561lo.JPG)
(http://img235.imagevenue.com/loc121/th_639385794_IMG_0184_122_121lo.JPG) (http://img235.imagevenue.com/img.php?image=639385794_IMG_0184_122_121lo.JPG)
     
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on June 25, 2012, 01:35:03 PM
Well, I guess I was also asking you if you for sure identified the 4V3 zener diodes and made positive they went in the right location. If you say no, then you have a 33.33% chance they are right.  :-\

I am pretty certain PK2 is done wrong. I can't really see the part label for CR2 in the pics. The angle is not good. Maybe you can figure this out. Go back and verify what the label should be by viewing 'Chunger's build thread. Your pics are clear enough when I zoom in but the angle is not the best.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on June 25, 2012, 04:13:18 PM
Well, I guess I was also asking you if you for sure identified the 4V3 zener diodes and made positive they went in the right location. If you say no, then you have a 33.33% chance they are right.  :-\

I am pretty certain PK2 is done wrong. I can't really see the part label for CR2 in the pics. The angle is not good. Maybe you can figure this out. Go back and verify what the label should be by viewing 'Chunger's build thread. Your pics are clear enough when I zoom in but the angle is not the best.

Yeah, it was wrong and i corrected it, its weird, now the DI sounds more natural and without distortion, but when i connect a mic nothing happens... i thought it was the stepped attenuator but despite some knob issues, it does what it's supposed to when i connect a di guitar... could it be i didnt use tape between the 2622's and the pcb? :O
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on June 25, 2012, 10:43:50 PM
... could it be i didnt use tape between the 2622's and the pcb? :O
No that won't be it. Did you still have a 1/4" plug in the 1/4" jack when trying the mic? The 1/4" jack controls the PK2 relay so when a plug is inserted, it switches to DI mode. With no plug it is in mic mode.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on June 26, 2012, 02:21:46 AM
... could it be i didnt use tape between the 2622's and the pcb? :O
No that won't be it. Did you still have a 1/4" plug in the 1/4" jack when trying the mic? The 1/4" jack controls the PK2 relay so when a plug is inserted, it switches to DI mode. With no plug it is in mic mode.

Yeah i just noticed it cause i assembled my 2nd VP312DI and im proud to say everything seems to be working fine (minus the re led, i dont know wth is up with it hehe)... Tho i only get DI guitar tone when i engage the post2622 switch... that isnt normal is it? :(

still was a triumph hehe...
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on June 26, 2012, 09:57:44 AM
.....everything seems to be working fine (minus the re led, i dont know wth is up with it hehe)... Tho i only get DI guitar tone when i engage the post2622 switch... that isnt normal is it? :(
If the phantom LED doesn't work, it is most likely backwards. Forgot to mention before that it is normal for the LED to fade over a few seconds when turning off the phantom. That is just the draining of the 120uF cap.

If the "pre 2622" setting does not work, that will probably be the HiZ Plug-In circuit. Swap in a different Plug-In and see if it helps. I don't recall if you have any of the Pikatron passive versions but they are easiest to test with since build errors with them are virtually nonexistent.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on June 26, 2012, 02:17:05 PM
.....everything seems to be working fine (minus the re led, i dont know wth is up with it hehe)... Tho i only get DI guitar tone when i engage the post2622 switch... that isnt normal is it? :(
If the phantom LED doesn't work, it is most likely backwards. Forgot to mention before that it is normal for the LED to fade over a few seconds when turning off the phantom. That is just the draining of the 120uF cap.

If the "pre 2622" setting does not work, that will probably be the HiZ Plug-In circuit. Swap in a different Plug-In and see if it helps. I don't recall if you have any of the Pikatron passive versions but they are easiest to test with since build errors with them are virtually nonexistent.

It was backwards... And you were right about the HiZ, there was some sloppy soldering apparently, i re-flowed and now everything's working, i got my first 100% working VP312DI (tho the front-plate assembly is mediocre, hope this doesnt brake it in the long run)

Now im off to find the mistake in my first vp312di, mic signal isnt there...
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on June 26, 2012, 03:47:02 PM
I would look at the 4V3 zener diode on PK2.

Glad you are up an running with at least one!  :)
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on June 26, 2012, 05:13:56 PM
I would look at the 4V3 zener diode on PK2.

Glad you are up an running with at least one!  :)

im pretty sure the zeners are ok now, i did correct one that was wrong... i've been reflowing some questionable joints but still no mic signal through... i did notice some things that i hope can help the diagnosis... DI works just fine... when i unplugged the guitar and went for mic signal, i notice i get a lot of noise in when i activate the DI's -10db pad, and also noticed a lot of noise when i turned the lunchbox off... The crappy thing is a have a good DMM but i dont know where to probe or what the obtained results would mean =P
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on June 26, 2012, 06:19:03 PM
Do you have a way to power your modules without being in a rack? A bench supply of sorts?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on June 26, 2012, 08:26:47 PM
Do you have a way to power your modules without being in a rack? A bench supply of sorts?

nope, that would be cool, i already am into that, but apart from the blue 30 pin card edge connector i dont know what else is needed  hehe
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on July 04, 2012, 04:24:41 PM
well, since i already assembled the other 9 modules, ive been checking the malfunctioning VP312DI... i had a couple diodes of the rilays mixed up, and i mixed up C12 and C13 too... Its all been fixed but i still cant get mic signal, could i have harmed something with stuff in the wrong position? DI still works fine (and did with the diodes and c12/c13 mixup)
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on July 04, 2012, 09:39:05 PM
You need to see if that PK2 relay is functioning right. The relay should flip when you insert a 1/4" plug in the DI jack. If it is not being activated, I would most likely think it is something on the PK2 board.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on July 05, 2012, 10:49:27 AM
You need to see if that PK2 relay is functioning right. The relay should flip when you insert a 1/4" plug in the DI jack. If it is not being activated, I would most likely think it is something on the PK2 board.

Flip would mean "emmit a small contact noise"? ... Is there a way to check if the PK2 relay is functioning right with a DMM? I have a Fluke 115
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on July 05, 2012, 11:47:03 AM
You can beep for continuity between the A+ pin and the O+ pin (mic mode). Next would be the B+ pin to the O+ pin (DI mode). This info is on the skiz. There is just enough room where the 90 degree header comes out of the relay PCB to get your probe tips in. If this relay is not flipping with the plug going in/out of the DI jack, it's either a problem on the PK2 relay build or the control signal which can also be followed on the schematic. You must have DC applied to the main board for this to work.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on July 24, 2012, 01:47:30 AM
You can beep for continuity between the A+ pin and the O+ pin (mic mode). Next would be the B+ pin to the O+ pin (DI mode). This info is on the skiz. There is just enough room where the 90 degree header comes out of the relay PCB to get your probe tips in. If this relay is not flipping with the plug going in/out of the DI jack, it's either a problem on the PK2 relay build or the control signal which can also be followed on the schematic. You must have DC applied to the main board for this to work.

I just tested that and everything beeps exept B+ to O+ (di mode) in the relay that's next to the neutrik connector. It was impossible to get there so i "assembled" the module just with the faceplate (no L bracket) and tested from the back in my empty lunchbox. Any ideas?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on July 24, 2012, 10:16:33 AM
The relay in question that selects what input goes to the 2622 (mic or HiZ Plug-In) is PK2 that is situated more in the center of the PCB just behind the input transformer.

PK1 routes the DI input signal to the HiZ Plug-in or to the post 2622 position. You need to flip the mini toggle on the front to get this relay to active/deactivate. This can only happen with a plug in the DI jack.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on July 24, 2012, 05:55:16 PM
The relay in question that selects what input goes to the 2622 (mic or HiZ Plug-In) is PK2 that is situated more in the center of the PCB just behind the input transformer.

PK1 routes the DI input signal to the HiZ Plug-in or to the post 2622 position. You need to flip the mini toggle on the front to get this relay to active/deactivate. This can only happen with a plug in the DI jack.

Ok, so the relay in question is working... But still no mic signal, any other idea Jeff? I bought a hakko desoldering station recently, i think we're approaching the point where i buy another pcb and some parts and redo it...
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on July 24, 2012, 06:58:15 PM
Do you get a DI signal thru the HiZ Plug-In?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on July 24, 2012, 09:16:42 PM
Do you get a DI signal thru the HiZ Plug-In?

yes i do
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on July 24, 2012, 10:39:20 PM
Well, I can't think of any reason why the mic in won't work then. If the relay PK2 board is fine, then the only difference between the output of that relay card from DI mode to mic mode, are a few inches of PCB traces and the gold fingers #8 and #10. Is this maybe an issue that lies between the card and the mic? Meaning rack or outside cabling?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Pliplo on July 26, 2012, 12:50:17 AM
What i just noticed is that the POST 2622 switch doesnt appear to do anything, just a minor noise when i flip it but no change in sound. And the -10 pad next to it engages regardless of the post2622 switch's position. the LPF doesnt seem to be doing anything either.

Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on July 26, 2012, 09:06:58 AM
Well, many things are not making sense here. My suggestion is to pull both relay boards and make sure they are working right. I test them on a breadboard. 98% of all problems on a VP312DI build are related to those little relay boards.

If Pre 2622 DI mode works, mic mode should also work.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: qmp audio on September 24, 2012, 06:32:10 PM
Im curious about replacing the EA2622 with a JT-115K-EPC + 990c.   The pinout isn't quite the same size,  but its only 0.05" difference so it could probably be extended to fit.  Anyone done any mods to this to make the impedance work w/ a 990c better?  I also read the feedback values should be modified.

Thoughts?
Thanks,  trying to see if this is something worth exploring or not.

http://jensen-transformers.com/datashts/115kepc.pdf

http://www.classicapi.com/catalog/images/gallery/2622/2622-specs.pdf
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: New Soul Rebel on October 28, 2012, 09:33:51 AM
same problem
« Sent to: New Soul Rebel on: October 27, 2012, 05:47:56 AM »
« You have forwarded or responded to this message. » ReplyQuoteDelete
Hello,

I have a vp312di , and i have th same problem (I.e. HOT OPAMP) . The doa is very hot and dont sounds.

How do you solve the problem please?

Thanks
Nacho



Hi Guys, I got this PM from Nacho. I resoldered the output transformer and it solved the problem

Just thought i'd share it here.

Matt
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Piscolabis on October 28, 2012, 12:53:05 PM
Hi,

 Please Help!!! :o



In the past I have a bad solder in the gar2520 that made it very hot but I fixed it. Does its posible that it was damaged?

The DI goes perfectly with and without post transformer. sounds perfect.

I hear the sound of the relays.

If I disconect the mic the noise disapears.
I checked the impedance between 2 and 3 pins in mic input and is 28 ohms.
Its normal?

I have tested the mic and it woks fine in other preamps.

I am checkiing without chasis, with the 38 pin connector directly to the xlrs and PSU, how should this be connected?
Should I make a starpoint for grounds. I dont use ground between the transformer and the main connection
I follow the attached 51x schematic only with +-16v.
Its posible that is was a ground noise?
Cause I dont know how to conect the grounds from psu to module.

Sorry for my english and I will apreciate any help
Nacho





Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 28, 2012, 01:05:37 PM
You must connect all the ground pins to earth or there will be no return path. If you are only working with a card edge connector on the module, I would run one ground wire from pin 1(Chassis) to the star ground point of your psu. Next connect pins 5 and 13 with another wire to your star ground point.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Piscolabis on October 28, 2012, 01:37:59 PM
You must connect all the ground pins to earth or there will be no return path. If you are only working with a card edge connector on the module, I would run one ground wire from pin 1(Chassis) to the star ground point of your psu. Next connect pins 5 and 13 with another wire to your star ground point.

How I should connect the xlrs pinout 1 pins? to the pin 1 of connector or starpoint?
Thanks
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 28, 2012, 02:13:36 PM
Pin 1 of the input xlr should go to chassis ground. This will provide the necessary return path for phantom. The output pin 1 can float and connect to nothing. The trafo balanced output is not referenced to ground.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Piscolabis on October 28, 2012, 03:00:06 PM
Pin 1 of the input xlr should go to chassis ground. This will provide the necessary return path for phantom. The output pin 1 can float and connect to nothing. The trafo balanced output is not referenced to ground.

I just tried several combinations:
Disconect 48v to discard that this is a problem.
Connect the grounds to psu starground, with the pin 1 of mic to it and also to chasis.
I check that in the pcb are conected 5 and 13. I have to conect also externally?

I don´t know what more can I do.

Thanks for your fast answer
Nacho


Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 28, 2012, 03:14:57 PM
You must connect either 5 and/or 13 to the PSU star ground. Yes they are connected together thru the preamp's ground plane but this ground plane cannot be left floating. You must connect it to the PSU's star ground. These are all connections that are made with the rack so you must duplicate all of them.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Piscolabis on October 29, 2012, 07:36:30 AM
Thanks for your help Jeff

The noise its still there.
Ive follow your instructions with the ground.
I have checked all the soldering points.
I used all the original components except resistors.
In the Zero resistor i put a bridge.
Could it be the 2622 placement?, I dont use a stick in the bottom but dont touch the pcb.


Any idea?




Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 29, 2012, 10:31:32 AM
If all the card edge connctions are made, I would think its maybe the opamp or maybe the mic or mic cable. What opamp is it and who built it? It could also be the solder joints on the relay/relay PCB just behind the 2622.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Piscolabis on October 29, 2012, 01:14:33 PM
I have checked te mic ( sm57) and cable in other preamps and dont have noise.
I have a gar2520 of yours.
Before I desolder the relay pcb to check I whould like to check with other op amp.
But I dont have any doa.

Its posible to use some IC to dOA adaptor to check with a standard IC?
I can build a pcb to check.
Or to check the gar2520 in other way?

Thanks ;)
Nacho

Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 29, 2012, 01:24:42 PM
I would definitely recommend another opamp to test the pre. An IC opamp will work fine if it has larger output transistors to drive a transformer. Was the gar2520 a prebuilt or a kit? Gary burns his in and tests before shipping to me so if it's a prebuilt, chances are 99.99% it is a solid opamp.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Piscolabis on October 29, 2012, 01:56:56 PM
Its not a prebuild, its a kit. I build it  :)
I will try with other Op amp and I will inform you.
I have some TL072, TL071, TL062, NE5532.
Which one you recomend me to try?

thanks a lot
If you come to Spain I will invite you to a Paella sure..  ;D
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: mulletchuck on November 01, 2012, 04:21:13 AM
Are there any dudes in California near Agora Hills who have these?   My buddy is interested in comparing them to his 512C. 
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: dandeurloo on November 01, 2012, 05:07:51 PM
tell your buddy to just sell his API's and buy twice as many of these!

Maybe he is close to Dr Bill on GS?  I know he has some.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: mulletchuck on November 02, 2012, 03:05:54 AM
lol sadly, my buddy is ignorant about these things, and refuses to believe that DIY stuff sounds better than name-brand stuff.   
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on November 02, 2012, 09:46:06 AM
lol sadly, my buddy is ignorant about these things, and refuses to believe that DIY stuff sounds better than name-brand stuff.
Haha.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: mulletchuck on December 05, 2012, 06:49:31 PM
are the gain settings between the VP Gainswitch kit (http://classicapi.com/catalog/product_info.php?cPath=51_133&products_id=237) and the Rev C kit identical?   I picked up a broken rev B version and got it working again, but it is a Variable Gain version, and i want match my Rev C Stepped Gain that I built last year.   
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on December 05, 2012, 07:05:48 PM
Yes they will match.

Congrats on the repair BTW!  ;)
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 07, 2013, 07:30:32 PM
The 12V shunt supply for the relays is always connected to the +16V rail. It is before the switch for DOA voltage, not after. The assumption is that this module will be in a 51x rack where there will be +/-16V as well as +/-24V all day, all the time.

Maybe elaborate on what is working and what is not, and on what voltages and so on.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: qmp audio on January 19, 2013, 10:33:44 PM
2 modules... 2 different issues im trying to resolve:

1:  Had a vpr modded vp312 di  working great for almost 2 years now.   now the relay on the DI doesn't seem to be switching off.   no mic signal only DI.   everything looks good, and its been working,  so im assuming its a failed part somewhere.   was going to start w/ the neutrik, but curious if anyone has an idea of where to look first,  or if there's been anything similar.

2:  just finished a 51x version.   threw a 990c in there as its the only 24v opamp i have around.   everything works great except noticed 2 things.
•  the post xfr switch results in a loud pop.   but works otherwise.
•  the 10db pad on the di gets very noisy,  but the noise goes away when the low pass is engaged.
Could these issues be related to the 990c opamp?  or could the be some other issue?  The 990c is new and functional.
Thanks much for any insight.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on January 19, 2013, 10:49:17 PM
1. Could be a solder joint as well. Very hard to say. If you have a good desoldering tool, you could try a different relay PCB to see of the trouble follows the relay PCB or not.

2. I would try with a 2520 and see if the issues go away. You can also measure for DC offset not only after but before the opamp. My guess is the 990 is not a happy camper in this circuit. Typically, the 990 is not a good match for a 2622.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: qmp audio on January 29, 2013, 02:32:59 PM
1. Could be a solder joint as well. Very hard to say. If you have a good desoldering tool, you could try a different relay PCB to see of the trouble follows the relay PCB or not.

2. I would try with a 2520 and see if the issues go away. You can also measure for DC offset not only after but before the opamp. My guess is the 990 is not a happy camper in this circuit. Typically, the 990 is not a good match for a 2622.

Thanks much.   DI was in fact a solder joint on the neutrik.   a reflow solved that issue.

Will report back on the other module when i finally swap the amps out and test DC offset.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: mhuss on April 13, 2013, 12:15:39 AM
I just finished up my 51x VP312 DI build, and it worked the first time.  :D ;D :D However, I noticed one problem -- when I'm in Post2622 mode, and I engage the -10db switch, it attenuates the signal as expected, but there's a *very* noticeable hiss added as well. The preamp is dead quiet in all other configurations, Hi-Z and normal.  (God forbid I should have to disassemble that Sub-DI section...  :-\) Is it possibly just Johnson noise from the series 2M2 resistor?

I'm using the discrete FET1 Plug-In, 51X +/-24v, and a 24v 990 DOA from Hairball .

--mark
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: qmp audio on April 13, 2013, 02:38:51 AM
I'm using the discrete FET1 Plug-In, 51X +/-24v, and a 24v 990 DOA from Hairball .
--mark

Try switching to 16V and throw a 2520 in there.   see if the issue persists.   I have the same issues when i put a 990c in the circuit.  I understand that the 990c really wants a different impedance than the 2622 provides.

I do have a 312 setup in 24V w/ a 990c in the circuit.   I primarily use that module as a bass DI with the post xfmr in.  However... the pad does introduce noise w/ my JH 990c for me.  I also get some popping artifacts w/ the 990c when flippin switches ( i always mute when changing things) .    i think it sounds great as a DI w/ only the post xfmr switch engaged.   That's my primary use for that module w/ the 990c.   I've been using it as my tom mic pre w/ the 990c and really like the sound w/ my 421s.

do some searches for 312 and 990c and theres some good info ( some from john hardy ) about how the 990c interacts w/ the 312 circuit.
Jeff also has commented about 990c interactions in the 312 circuit... earlier in the thread i believe
 

If you want to use 24v w/ the 312,   look into the jlm 2520s.   there are others but that one seems to work really well in the vp312.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: entresolmusic on April 19, 2013, 02:24:50 PM
Hello!

I am a happy Vp312 Di kit owner. I have the stepped version and i have a question. I am in the middle of soldering the first resistors for the gainswitch.

 It says that i am suppose to get 25 k. Well i do get 25k from : left of R11 and at the bottom left of R1?.

It says that it is suppose to be from the wiper pad. Is that to the left of between R2-R3? when i probe from there nothing happens. but i do get 25 k the other way.

Any help would be appreciated.

Thanks!


Edi
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on April 19, 2013, 02:47:28 PM
I need to correct those directions. It should be from one end of the switch pins to the other, not the wiper.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: mhuss on May 17, 2013, 03:20:17 PM
If you want to use 24v w/ the 312,   look into the jlm 2520s.   there are others but that one seems to work really well in the vp312.
I do -- I'm filling up my 51X rack with 16v modules.  ;)

I got a 2520 from JLM, and I like it a lot. Thanks for the pointer.

--mark
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: tgs on August 01, 2013, 05:05:52 AM
Two VP312DI 51x modules built; one working perfectly, the other needs some love and care!

I tried the DOA in a different module and it's working; also tried the module in a different slot. So I've ruled out those things. Relays are "clicking" as they should, too.

The problem: I'm getting very weak signal and it's only treble. Same thing with DI, or I can't even hear the signal. Strangely, when I switched the DOA, I was getting no signal, until I really pushed the input and the signal jumped out, now with full frequency range. But after some silence it's dead again. Changed back to the first DOA, weak, treble-y signal again. I can turn the input gain all the way up and I can hear the signal distorting. So, something wrong with the output?

Where should I start looking?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on August 01, 2013, 10:22:13 AM
Are the the opamps fully seated? http://classicapi.com/catalog/DOA_Install.php (http://classicapi.com/catalog/DOA_Install.php)

I think you will have to inject signal and follow the signal thru the circuit using a probe to see where things go south.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: tgs on August 01, 2013, 10:33:33 AM
Are the the opamps fully seated? http://classicapi.com/catalog/DOA_Install.php (http://classicapi.com/catalog/DOA_Install.php)

I think you will have to inject signal and follow the signal thru the circuit using a probe to see where things go south.

I think so but I will have a closer look tomorrow. Bit odd that I get the same problem with both the DI and mic input though.

I can send a test tone through the pre when I'm back in the studio tomorrow. But will I need an oscilloscope? I don't have one yet. Even if I did, I would feel a bit lost on where to measure too.  :-[
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on August 01, 2013, 10:44:14 AM
There are many posts here about signal tracing probes. I don't do it this way myself but you can use a powered speaker so you can actually listen for extreme changes. You can also use a DMM set to ACV.

Doe the problem happen with DI set to both post and pre 2622?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: tgs on August 01, 2013, 12:28:40 PM
I'm ALMOST certain it does but I'll have to double check. I'll report back tomorrow.

EDIT: I should probably also mention that this is the board where I managed to run a gar2520 with the NPN and PNP mixed up AND ran 24V through it... So maybe I damaged something else in the process as well?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: tgs on August 03, 2013, 01:06:50 PM
I checked now and I get the same behavior with Post 2622 activated. The behavior is the same as the other one, i.e. the level drops when I activate Post 2622, but the output is still VERY weak and only top-end. I am quite sure that the DOAs are properly seated as well, they seem to go all the way down like on my other modules and they sit flush with the board.

See edit in my previous post for some additional cause for concern though.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on August 03, 2013, 01:28:04 PM
Well, I would assume from the pre/post 2622 when in DI mode symptoms that the 2622 is not the cause. It's time to inject and trace signal. There is no magic bullet cure except figuring out where things go bad.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: kante1603 on August 03, 2013, 01:36:50 PM
Hi,

if you have a working module lay them side by side and compare them,try signal tracing as Jeff suggested.
Despite of that when you say the signal lacking of bass and being weak  often indicates something like "one leg lifted" on the output or swapped or badly connected transformer wires.
Might be a godd idea to check them and also look for cold solder joints.

Just an idea,

Udo.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: tgs on August 04, 2013, 02:40:36 AM
Took the board out, cleaned it a bit, went over some solder points. Gray cable from the transformer looked a bit funny so I fixed that (does that actually go anywhere though? Trying to learn how to read schematics properly.). Red and brown looked like they may have been bridged so I cleaned off the solder and applied new.

Long story short: it's working!! Thanks for the help, guys!
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: kante1603 on August 04, 2013, 04:34:27 AM
Congrats :)

Udo.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: entresolmusic on November 19, 2013, 10:03:31 PM
Hello,

I have an  issue on my VP312Di that I didn't had before, it used to run very good.

When I run sound through it (mic or a DI) it sounds very thin, low, like a crackling low pass filter. The switches for post 2622 seems to work, the -10 too, and I don't know about the JLPF. The PAD doesn't work, the MUTE does. Phantom too and both gain and fader works too.

I really don't know where to start since it was fine before. maybe something came loose or moved.


Let me know if there is any test I can start with or if you guys need more info.



thanks!



Eddie
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on November 20, 2013, 09:37:48 AM
Eddie

As mentioned in the email, I would look at the nonworking Pad switch. Try reflowing the solder to that switch. That fact that it is not working is a big clue!
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: entresolmusic on November 20, 2013, 12:33:57 PM
I will try that tonight Jeff, yesterday I didn't had time.


Thanks for the quick answer.


Eddie
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: dipfrik on December 06, 2013, 08:41:44 PM
Hey,

i finished my 1st VP312DI but no sound at all. 48V works fine with a mic including the LED.
I started with with the quick Startup Testing Procedure and the problems are there ;)

Here my readings with no opamp and not connected to a power source:

-V and +V = 0
-V and C = 0
C and +V  = 4.7k
C and O = 6.2M
V+ and O = 6M
-V and O = 0

Everything should be way over 200k or?

OMG ;)

Thanks for any help, Sven
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on December 06, 2013, 09:01:33 PM
These look OK for a VP312DI.

Eliminate any possible, rack, cable, mic, converter etc problems first....then DOA's.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: dipfrik on December 06, 2013, 09:18:42 PM
Everything external is fine here. I can switch to my JLM or OV560 with the same setup and they are running as expected.
What are the next steps? Measuring the +/-V and C sockets with connected power and they are +/-16V as expected.

Can i test with JLM99V op amp to see if the problem is there? I don't think so or, because they are working from 24-34V or?

btw. permanent VPR mode added.

Thanks, Sven

Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: dipfrik on December 06, 2013, 09:24:14 PM
i'am building on the Rev C.1 PCB
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on December 06, 2013, 09:37:56 PM
You can test with those opamps. Scroll thru this thread. Almost every conceivable issue has been discussed here previously.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: dipfrik on December 06, 2013, 10:38:14 PM
OK the Zener Diode on PK2 was wrong positioned.
Now i hear the PK2 relay switching when i put a jack into the HiZ Jack. Still nothing comes out.
Should the Mic audiopath with a "good" PK2 working or can the whole audiopath with a wrong Zener in PK1 still be a problem?

Thanks, Sven
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: dipfrik on December 06, 2013, 11:00:45 PM
When should i hear the PK1 relay clicking?
Actually when i'am on 48V and put a jack into the HiZ, the 48V are away and if i'am remove the jack from the HiZ the 48V are coming back.

Again no audio at all.

Thanks, Sven
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on December 07, 2013, 10:16:07 AM
Check both relay builds. They are usually the problem with most folks.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: dipfrik on December 07, 2013, 03:21:29 PM
Yes, i will definitely do that!

Thanks, Sven
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: technoteo on March 17, 2014, 04:00:53 AM
Here is a couple of vp312 just finished.

(http://i827.photobucket.com/albums/zz193/technoteo/vp312_zps77539ef0.jpg)

it just took me 6 hours to finish both units and GAR2520!!

ah...BTW they sound fantastic!!
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Matt D on May 27, 2014, 11:21:13 PM
My VP312 has been doing nicely for a couple of months now.  Then about a week ago the DI stopped working. The pre was at my band practice space so I haven't had a chance to look at it until today.  When I opened it up I noticed right off the bat that C12 has exploded.  It looks like it's in correctly polarity wise to me but perhaps I messed it up.  My first question is: Are the exploded cap and non-functional DI possibly related, or am I dealing with two separate problems?  The pre passes signal with the blown-up cap.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Matt D on May 27, 2014, 11:47:30 PM
Here is the cap.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Matt D on May 27, 2014, 11:55:58 PM
Did I miss anything hard wiring the SW2 connections?  What else could douse that cap to blow up other than a reversed polarity?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Matt D on May 27, 2014, 11:58:18 PM
Also, in the meantime can I run the pre in "output cap bypass mode" to bypass C10?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Matt D on May 28, 2014, 12:27:40 AM
As you can see in the pictures, I had the blocking cap in/out connector on incorrectly.  Running in cap bypass mode.  The DI works fine.  Still wonder what it was that made the cap blow up....
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on May 28, 2014, 06:32:03 PM
Typically, if that cap sees a voltage near or above it's rating it will blow. It almost looks like a bad leaky cap, not one that exploded but who knows. I would not run the pre in cap bypass mode without measuring the DC offset. Do you have a way of doing that? The pre will need to be on the bench flat in front of you while under power to check the DC offset.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Matt D on May 29, 2014, 11:24:30 AM
Thanks for the reply.  I have one of your ribbon cable/extender card units so setting it out flat on the bench is no problem.  Where should I take the measurements?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on May 29, 2014, 11:47:58 AM
Set your DMM to read DC voltage. Red probe to the top of R9 and the black probe to a good ground reference point like where the phantom LED is connected tot he top of the pushbutton switch.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Matt D on May 29, 2014, 12:10:25 PM
I'm reading .03v DC between R9 and the cathode of the LED.  This is in cap-bypass mode.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on May 29, 2014, 12:43:10 PM
That is normal for red dot so no problem there. Just send me an email thru the store and I'll send you a new cap. I would suggest NOT using the DI on post 2622 mode unless the output is cap coupled.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: technoteo on June 25, 2014, 08:32:42 AM
Hallo everybody, I need some help

Yesterday one of my CAPI 312 almost went on fire!!!  :'( :'( I had 2 VP28 in the first slots, two 312 and a LC53 in the fifth slot. I had this pres up and running since march, so three months of great work. Suddenly, after one hour of work smoke start getting out one of the 312...as you can see in the pictures the GAR 2520 is gone  :( ........ the output transformer was really hot. I checked if something else was black or broken, but I can't see anything damaged or hot on the main board.

The 312 was cabled in a patch bay but I wasn't using it, I was using the VP28s and everything was ok. I turned off the PSU, get the damaged module out and then tested all the other ones. Everything was working as usual. The fuse on the PSU didn't blow. My question is : what the hell happened since I used it for three months and didn't move or changed anything?
Can anyone suggest me what to check before puttin' in another 2520 ....

(http://i827.photobucket.com/albums/zz193/technoteo/Gar2520%20Blown/img1_zps77de69ee.jpg)

here are the other pictures:
http://s827.photobucket.com/user/technoteo/library/Gar2520%20Blown

Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on June 25, 2014, 09:23:22 AM
Was the opamp fully seated? http://classicapi.com/catalog/DOA_Install.php

I would post on the gar2520 build thread or better yet start a new thread. I would assume the issue is opamp related not necessarily a module problem.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: technoteo on June 25, 2014, 09:40:38 AM
Thanks Jeff for the fast reply.
Yes the opamp was fully seated....
Do you think the output trafo could be damaged?
I will open a new thread in gar2520.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: technoteo on June 27, 2014, 05:49:34 PM
Just discovered that gar2520 cannot be mounted on the 312 with 24V rail  :o :o
What am I supposed to use instead of Gary's DOA? red/blue dots?

Teo
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: qmp audio on June 27, 2014, 06:15:43 PM
Just discovered that gar2520 cannot be mounted on the 312 with 24V rail  :o :o
What am I supposed to use instead of Gary's DOA? red/blue dots?
SL2520's require +-16V

Can just use +-16v selection in the vp312?  should be switchable, no?

If interested in 24v opamps,   check out
JLM http://www.jlmaudio.com/shop/index.php?_a=viewCat&catId=17
JH990  http://www.johnhardyco.com/990OpAmpDetails.html
hairball 990 http://www.hairballaudio.com/shop/product_info.php?cPath=37&products_id=132
APP http://groupdiy.com/index.php?topic=33576.0

However,  i suggest doing some research on the impedance of the 312/2622 xfmr and the 990c,  I have used 990c's in 24v w/ the vp312s and some weird things happen w/ the DI options,  but otherwise sound pretty great to me.  Been my tom mic pre setup for a while w/ GREAT results.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: technoteo on June 27, 2014, 06:19:22 PM
SL2520's require +-16V

Can just use +-16v selection in the vp312?  should be switchable, no?

If interested in 24v opamps,   check out
JLM http://www.jlmaudio.com/shop/index.php?_a=viewCat&catId=17
JH990  http://www.johnhardyco.com/990OpAmpDetails.html
hairball 990 http://www.hairballaudio.com/shop/product_info.php?cPath=37&products_id=132
APP http://groupdiy.com/index.php?topic=33576.0

However,  i suggest doing some research on the impedance of the 312/2622 xfmr and the 990c,  I have used 990c's in 24v w/ the vp312s and some weird things happen w/ the DI options,  but otherwise sound pretty great to me.  Been my tom mic pre setup for a while w/ GREAT results.

wow
thank you very much !
 ;)
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: taliska on June 28, 2014, 11:09:45 AM
Just discovered that gar2520 cannot be mounted on the 312 with 24V rail  :o :o
What am I supposed to use instead of Gary's DOA? red/blue dots?
SL2520's require +-16V

Can just use +-16v selection in the vp312?  should be switchable, no?

If interested in 24v opamps,   check out
JLM http://www.jlmaudio.com/shop/index.php?_a=viewCat&catId=17
JH990  http://www.johnhardyco.com/990OpAmpDetails.html
hairball 990 http://www.hairballaudio.com/shop/product_info.php?cPath=37&products_id=132
APP http://groupdiy.com/index.php?topic=33576.0

However,  i suggest doing some research on the impedance of the 312/2622 xfmr and the 990c,  I have used 990c's in 24v w/ the vp312s and some weird things happen w/ the DI options,  but otherwise sound pretty great to me.  Been my tom mic pre setup for a while w/ GREAT results.

Don't have vp312s myself, but I think this DOA might work at 24v too (well it says it will with three resistor swaps):

http://www.whistlerockaudio.com/cart/index.php?main_page=product_info&cPath=35_39&products_id=106

Don't know much about the jensen 918s, but I'm loving the DIY990s in my Lola, so I figured I'd try the "older brother" in my vp26s and if I prefer them to the gar2520 then I'm going to mod them to work at 24v and build some vp312s to put them in... (Trying to fill more 24v slots in my 51x racks!)...if they're not my thing, then I'll probably look at the JLM instead...
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on June 28, 2014, 11:52:09 AM
The 2622 is a 1:7 input transformer. Not that a 990 won't work with it but it is not ideal to plug a 990 into a typical API style preamp. John explains his reasoning behind using a 1:2 with the 990 in his preamps here https://www.youtube.com/watch?v=4si5gljy6AA (https://www.youtube.com/watch?v=4si5gljy6AA)

As always, YMMV  8)
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: taliska on June 28, 2014, 04:26:44 PM
The 2622 is a 1:7 input transformer. Not that a 990 won't work with it but it is not ideal to plug a 990 into a typical API style preamp. John explains his reasoning behind using a 1:2 with the 990 in his preamps here https://www.youtube.com/watch?v=4si5gljy6AA (https://www.youtube.com/watch?v=4si5gljy6AA)

As always, YMMV  8)

Ok, watched the video and understand his comments about bandwidth, though I'm not technically knowledgable enough to know how that interacts with 990 style op amps, so I'll defer to your greater knowledge! ;)

I'll continue looking around for other DOAs that can run at 24v. I've already got a JLM LA500, so I've already got a 99v I can test at some point (which has already been mentioned as a good match in this thread, but surely is a 990-style op amp also?), but I'd like to see if there's anything else about... (it's not really an immediate problem...I'm looking to switch to vp312s at some point so I can free up the 16v my vp26s are using...)

Did some googling and found this page which is quite useful:

http://www.eisenaudio.com/diy500/tables/opamps/

and clicked through some links arbitrarily and noticed that there are two 2520 style DOAs that expect high impedance and work at 24v (there are probably more, these are just the first couple I checked because I recognised their names!):

http://www.soundskulptor.com/uk/sk25.html
http://www.seventhcircleaudio.com/OpAmps/sc25_about.htm

It's good to have options... ;)
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: duantro on August 24, 2014, 11:10:43 PM
I'm wanting to install Cinemag input trannies and thought i'd drill 2 holes for zip ties, around the 51x text area. See photo for location. It appears that along the left edge portion in the photo is the ground plane. Any one see a problem with this?
edit: the photo got flipped sideways, so I edited description to make sense.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bruce0 on August 26, 2014, 02:53:08 PM
I have done similar things on other projects, but I usually take a piece of perfboard, and put a few pins in it, and mount the trafo to the perfboard (zip ties and hot glue) and then mount it like the regular trafo using the pins.  Usually you can make this work.

I mostly use DB25 male connector pins (loose ones) but you could use a diode led or any solid wire really.

That way you don't damage the main board, and you can keep the leads short.

You do have to watch "total height" to make sure you stay within the 500 series module dimensions.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: duantro on September 06, 2014, 02:55:26 PM
I finished my pair a few days ago and these things are really sweet and very big! Almost have a natural compression to them. Thanks so much Jeff!
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Patrick from Davis on September 14, 2014, 07:47:20 PM
Whelp, I got a problem.  I get the mic signal through fine and clean.  I get a bass through the DI and it sounds great.  But...  The 48V fuse on my 51X power supply went.  I don't know when, but I am assuming immediately.  I checked between the 48V and ground on the card edge and of course continuity.  Grrr.  The build was an odd one.  During the build the retina in my left eye detached, so there was a bit of a pause in the middle.  Everything is going a good as expected for me, back to the build.  I also had soldered the small sub board with the DI switches on the wrong side.  I used my Hakko to unsolder it and put it on the correct side.  I am hoping that there is not a short between the two boards that would cause this.  Any ideas for how to track this down would be greatly appreciated.

Also, I got the gain switched version and the switch goes one more step beyond what the face plate shows.  It is Rev C.1 and the switch did not have holes to put pins in.  Thanks in advance.
Patrick

Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on September 14, 2014, 09:53:04 PM
There are 12 gain steps with Grayhill option. You can have either a "hidden" step at the full CW or full CCW, whatever you prefer.

Check the chemo for the board to board pads that get the small leads soldered to them. It sounds like you make have a short there for the 48V.

Sorry to hear about your eye. That sounds crazy scary! I hope things are OK for you now.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Patrick from Davis on September 15, 2014, 12:21:19 AM
I'm doing well with the eye, but there is still a gas bubble in it, part of recovery.  It kind of makes it like having a goggle on that is half full of water.  But, you get used to it.  And it definitely could be worse.  Oddly enough the black solder mask makes things hard to see, but I'll find it.  Does the small board (with the 14" jack assembly) attached to the main board have the 48V going to it?  I get continuity between the two anchoring holes that are closest to the relay board and the outside edge.  I removed the solder and pins with the Hakko and it still gives continuity.  If that is by design, then I'll keep hunting.  Currently I have not come across anything, but I'm getting the iso propyl out to start cleaning.
Patrick

Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: galaxis5757 on September 15, 2014, 09:32:51 AM
Hi there,

First: Sorry for my terrible English. But I will try. ;-)

A few years ago I did built two VP312DI Rev. C.1 for a friend.
Now I have them back, and one has a problem.

It doesn't matter in which position the preamp gain switch is set. (Stepped gain)
Signal stays the same.

I looked at the soldering of the resistors and the switch but they all seems to be okay.

Does anyone have an idea where to look to find this error?

Greatings from Holland.

Huub.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Patrick from Davis on September 16, 2014, 11:00:47 PM
Well I got the Sub DI.1 Rev A board off of the main board, and the short is gone.  However the BB8 pad is toast on the Sub DI board.  Any suggestions for adding a jumper so that the 48V passes properly?  I have to clean the board up a bit and then try to figure out if there is a short on the board,  or if it was the attachment.
Patrick

Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on September 17, 2014, 09:26:10 AM
The 48V track just passes across the Sub board so locate the proper BB pads for it and solder a jumper wire.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Patrick from Davis on September 17, 2014, 10:49:27 AM
That's what the file describing the circuit on that board looked like, but I can convince myself that it just can't be that easy.
Patrick

Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Patrick from Davis on September 21, 2014, 01:11:38 AM
Despite my best attempts to try and break this thing in every possible way, and some I believe were considered impossible until recently, everything works.  I just had to take the Sub DI board with the 1/4" jack off and reattach it, add a jumper so the 48 V would work, and viola, everything is functioning as it should.  I am very happy with the FET module on it for bass sounds, it is very nice.  Now to get some decent stuff down with a mic through this pre, other than, "La la la, this thing on?"  Thanks again Jeff for providing such wonderful toys.
Patrick

Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on September 30, 2014, 01:51:37 PM
Jeff, finished the VP312DI. The preamp gain pot makes a lot of loud noises when turned. It's not the stepped gain. This is when I try it with a phantom powered microphone. The Output attenuator does not make noise,  but increases/decreases a hum. What should I look for in troubleshooting?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on September 30, 2014, 04:02:55 PM
As always, rule out the opamp. Next go thru and touch up any bad or iffy looking solder joints. The biggest trouble folks have with this preamp build are the relay boards.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on September 30, 2014, 09:40:05 PM
Jeff, Ok. Thanks. I got a little confused since I'm not completely sure about some electronics stuff. To make sure, the diode's stripe goes in the direction of the arrow. Correct?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on September 30, 2014, 10:32:24 PM
Jeff, Ok. After knocking around on my main pcb with my multi-meter, I found that the diode at CR6 is not giving me any reading. Whether this is the problem or not, it's obviously wrong - correct? The other similar diode CR5 is giving me a reading.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on September 30, 2014, 11:46:08 PM
OK. I'm getting a reading from the CR6 diode now. However, hum is still there. No audio. Bad noise when turning the Preamp  Gain and pressing the mute and phase reverse buttons. No noise when pressing the pad button. Luckily, I bought an extra op-amp. I'll try building another one. I can't imagine being more careful than I was on the first op-amp, but I'll try. Thanks for you help.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on October 01, 2014, 01:28:14 PM
I hooked up the 312DI with the test jig.  The hum was the same. Have not built the new op-amp. However, after a few minutes, the Cap C10 blew. Pop! I was hoping that I installed backwards or something and that would be my problem, but I installed C10 correctly. I think it's something with the Input Gain pot. It's super noisy. Anyway, I'll get a new cap for C10 from Mouser and try to build the new op-amp. Should I just buy an op-amp that I know has been tested?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 01, 2014, 01:39:27 PM
The only way that cap will blow is if there is DC offset from the opamp. There is a major problem with the opamp. Is it seated properly? http://classicapi.com/catalog/DOA_Install.php

Trying to test a fresh preamp build with only a fresh opamp build can be a tail-chasing experience. I never recommend it.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Patrick from Davis on October 01, 2014, 01:59:32 PM
As sort of an off shoot of what Jeff recommends, I'd get a hybrid op amp (or two) to have around for testing.  They are much easier to build than the discreet ones.  Once you confirm that they work, you can use them for your builds to hold as many constants as possible when debugging.  They are also pretty cheap at less than $10 a piece unassembled.  I bought two for exactly this purpose, and they really have been quite helpful in narrowing down my errors.
Patrick

Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on October 01, 2014, 02:12:09 PM
I had read that about fresh pre amp builds needing a solid op-amp. I'm really, really careful, but I still make mistakes. I'm going to buy a working, tested op-amp right now. I'm obsessed with getting this thing going.
Patrick, thanks for the advice. Much, much appreciated....I'll look into that too.
Jeff, on another note, your test jig kit is genius. I did however, have a lot of problems with the Omron female receptacle - it's really cheap plastic and very easy to break when applying enough pressure to puncture the ribbon cable. I broke one, ordered one that seemed a little stonger, then broke the other one but somehow made that work. Is there another option?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on October 03, 2014, 04:13:06 AM
I built the other GAR 2520, VERY carefully.  I used a magnifying headset and triple checked my work. I got the new C10 cap in. Pluged in the VP 312DI.  It's making the same loud clicking noise as it did before, so I turned off the power as quickly as I could. I tried it with the test jig....same thing.
There's not a lot of info about the DC Block/Cap coupled output. I installed it like in Chungers thread, but I think that he was building a 51X....not sure. Anyway, I need help.  I really don't think it's the op-amp. What else could it be? I made the relay boards as carefully as possible.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 03, 2014, 10:46:17 AM
There is info on the purpose of the coupling cap earlier in this thread as well as on the PCB page at my site. With an API preamp, in mic mode, you will see typically around 80mV max of DC offset around the opamp. With the VP312DI (or any DI that uses the post 2622 method) you will see 1V or more of DC offset. This can be a little less or a lot more depending on the opamp. This is true for the 51x or VPR version of this build. That is enough DC to damage the 2503 output transformer. So we have the 470uF blocking cap. That cap is rated at 16V so 1 or 2 V will be no problem. Slamming it with significant DC from a bad or improperly installed opamp and the cap goes boom. If this cap explodes, it is a sign that something major is wrong with the opamp.

No offense Reverend but "I really don't think it's the op-amp" is not the same thing as "I have tested this opamp in another known working circuit and it is fine". Maybe a red dot would be a good choice at this point? Scott tests them all before shipping so the likelihood of getting a bad one from the start is basically null.

Also, folks have had weird problems getting these going most always related to the relay boards. I would also suggest reading thru this thread from the beginning.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on October 03, 2014, 02:51:25 PM
There is info on the purpose of the coupling cap earlier in this thread as well as on the PCB page at my site. With an API preamp, in mic mode, you will see typically around 80mV max of DC offset around the opamp. With the VP312DI (or any DI that uses the post 2622 method) you will see 1V or more of DC offset. This can be a little less or a lot more depending on the opamp. This is true for the 51x or VPR version of this build. That is enough DC to damage the 2503 output transformer. So we have the 470uF blocking cap. That cap is rated at 16V so 1 or 2 V will be no problem. Slamming it with significant DC from a bad or improperly installed opamp and the cap goes boom. If this cap explodes, it is a sign that something major is wrong with the opamp.

No offense Reverend but "I really don't think it's the op-amp" is not the same thing as "I have tested this opamp in another known working circuit and it is fine". Maybe a red dot would be a good choice at this point? Scott tests them all before shipping so the likelihood of getting a bad one from the start is basically null.

Also, folks have had weird problems getting these going most always related to the relay boards. I would also suggest reading thru this thread from the beginning.
I've ordered a pre-built and tested op-amp from someone else. I wanted to purchase one from CAPI, but I couldn't find them on the website. I'll just wait until the pre-built and tested one gets here and see what happens. Thanks.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on October 04, 2014, 12:32:38 AM
The diode at CR6 is giving me a reading. The diode at CR5 isn't.  Is that normal?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on October 04, 2014, 12:41:31 AM
The diode at CR6 is giving me a reading. The diode at CR5 isn't.  Is that normal?
This is backwards from what it read the other day.  I was wondered if one of them was dead (I know, not likely).  So I pulled CR6 and re-soldered (I know it's not a good idea).  After I reinstalled it, it was giving me a reading, but then, CR5 now isn't giving me a reading.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on October 04, 2014, 02:47:44 AM
Here's an issue I had. In the file I was emailed, in the pdf of the Relay layout, the layout is not like the relay that I received. The pdf has R1 in the top left corner. The relay I received has Q1 in the top left corner. Where the diodes go in the relay, there are not circles to show polarity, there is the diode symbol. I guess that I could have made a mistake on the relay since I've never really seen the layout for my relays. Both are the same for PK1 and PK2....each says  P-1 Rev. A 2. It may be hard to check the relays without the right layout.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 04, 2014, 11:01:36 AM
I updated the layout for the relay board quite a while ago when I changed board houses. All of the part #'s and values remain the same for each and every part. I changed the diode silkscreen to match what I have been using on some of my other small footprint boards. The silkscreen arrow points to the pad that the black band (cathode) goes to. Its pretty standard fare.

Besides wrong facing diodes, the main problem on the relay boards is folks not identifying the 4V3 zener and just thinking all the diodes are the same. They are NOT the same.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on October 05, 2014, 04:51:40 PM
I updated the layout for the relay board quite a while ago when I changed board houses. All of the part #'s and values remain the same for each and every part. I changed the diode silkscreen to match what I have been using on some of my other small footprint boards. The silkscreen arrow points to the pad that the black band (cathode) goes to. Its pretty standard fare.

Besides wrong facing diodes, the main problem on the relay boards is folks not identifying the 4V3 zener and just thinking all the diodes are the same. They are NOT the same.
Ok. Thanks Jeff. However, in the zip file I was sent, the old relay board layout was sent with R1 in the top left corner. I didn't get a layout that had Q1 in the top left like my newer version. Sorry.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 05, 2014, 04:57:36 PM
Ok. Thanks Jeff. However, in the zip file I was sent, the old relay board layout was sent with R1 in the top left corner. I didn't get a layout that had Q1 in the top left like my newer version. Sorry.
No matter as the part values and numbers are the same for both versions of the PCB. The circuit did not change.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on October 05, 2014, 10:28:07 PM
Ok. Thanks Jeff. However, in the zip file I was sent, the old relay board layout was sent with R1 in the top left corner. I didn't get a layout that had Q1 in the top left like my newer version. Sorry.
No matter as the part values and numbers are the same for both versions of the PCB. The circuit did not change.
Jeff, Sorry to be such a bother. Don't kill me - you were right. Good news. I've found something wrong with the relay. I had the caps swapped. 18uF where 10uF should have been. I tried to pull them out and swap them back, but now, since it was so hard getting this relay out, I'm sure it's best to just get a new relay. Just to make sure....(I'm building the VP312DI 500 series version NOT the 51x version. So I need the 12V version of the relay - correct?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 05, 2014, 11:26:47 PM
Yes. The 12V relay kit is used for either VPR or 51x. There must be something more than the caps. It would still work with those 2 caps swapped. Check to make sure the 4V3 zener is in the correct way and position.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on October 09, 2014, 01:24:21 AM
Yes. The 12V relay kit is used for either VPR or 51x. There must be something more than the caps. It would still work with those 2 caps swapped. Check to make sure the 4V3 zener is in the correct way and position.
Ok. I got the new relay and built it really, really slowly and meticulously. I bought a new JJ1731 op amp (I would have bought a GAR2520 from you, but I don't think you've got them right now). I built a BB2521 very, very slowly.
I've still got the same thing, the output attenuator brings up hiss and the preamp gain does the same thing except there's a little bit of fuzz oscillation when I twist that knob.
I keep turning the power off, unplugging the power and switching the op-amps between the tested 1731 and the BB2521 and its all the same. New relay in the main PCB position (the caps and all are right in the relay next to the DI section of the pcb.
I'm going to send a couple of pictures and make another post. Thanks for walking me through this. Please be on the lookout for the pictures.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on October 09, 2014, 05:26:40 AM
Is J1-1 in right?
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 09, 2014, 11:51:42 AM
Is J1-1 in right?
Yes you want the output coupling caps in the circuit to protect the 2503 from DC.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on October 09, 2014, 02:05:31 PM
I've ruled out the op-amp, the relay, J1-1, and checked the whole pcb upside and down. I've got a test jig so I can test it on the bench, but I don't know how to do it/where to start. Can someone help me figure this out? Thanks.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on October 09, 2014, 04:56:54 PM
You will need to inject a test tone sine wave and follow the signal thru the pre using the schematic as a "road map". There are a number of helpful post around the site here describing the process.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on November 22, 2014, 12:03:28 PM
Jeff, You were right. It was a relay board. It was the one near the DI stage. I found two solder joints that were touching while inspecting with a magnifying headband.  I got the headband AFTER I soldered the relay boards, and I feel certain that I wouldn't have made the mistake if I had them through the whole project. I think it would sure help other newbies like me to work with the headband magnifier.
Anyway, I got it working and the use of the extension jig came in really handy and is great for testing my other 500 series units.
The 312DI sounds awesome and thick. I can't wait to use it on my next project which is going to be cranking up very soon.
Thanks so much for putting up with me. Now I've got to decide what the next project is.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on November 22, 2014, 12:25:15 PM
No worries Reverend, I am glad you found it! Congrats  :)
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: prh on November 22, 2014, 05:50:52 PM
Just a suggestion (which works for me)...

Working with the schematic, a continuity tester can be really helpful in finding solder bridges. 
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: Reverend on November 25, 2014, 05:12:07 PM
Just a suggestion (which works for me)...

Working with the schematic, a continuity tester can be really helpful in finding solder bridges.

PRH, I found the solder bridge looking through the magnifying headband, but I had the schematic out with a test tone and my DMM, but I'm such a newbie, I really didn't know how to do it. Can you recommend a YouTube or website that may help me learn how to use the tester with the schematic? Thanks. Hope that this isn't too off topic.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: rainton on January 14, 2015, 06:31:56 PM
I tried to find some info here on this already but had no luck and also sent a message through the capi website but
had no reply so far.

I want to build two of the VP 312DI in 1U rack with my own front panels

What is the best way to add a LED-Peakmeter like this one here :
http://sound.westhost.com/project60.htm

to the circuit to monitor the input stage?

Or maybe a clipping LED circuit that features a multi-color LED that gives me SIGNAL (green) and CLIPPING (red)

Thanks for any advice!


Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bugbrand on July 28, 2015, 06:58:20 AM
Sorry for the bump, but I wondered if anyone could quickly answer::::

Are Classic API kits (in particular the VP312DI which I just received) RoHS / Lead-free compliant?
I ask because I could use leaded solder, but do 99.9% of my work lead-free.

Sorry if I missed this info anywhere...

Thanks! Tom
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on July 28, 2015, 12:47:13 PM
Sorry for the bump, but I wondered if anyone could quickly answer::::

Are Classic API kits (in particular the VP312DI which I just received) RoHS / Lead-free compliant?
I ask because I could use leaded solder, but do 99.9% of my work lead-free.

Sorry if I missed this info anywhere...

Thanks! Tom
The majority of the items are RoHS compliant but not everything. You can solder them however you want.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bugbrand on July 28, 2015, 01:11:52 PM
Thanks Jeff - it is not that I need to comply with RoHS, more that I'd prefer to use my regular lead-free approach.

So, let's change the focus to lead-free rather than RoHS -- Leaded solder is OK on lead-free, but lead-free is not good on leaded parts. So, I'd like to try to be as sure as possible before beginning the build.

Of course, I thought some more and presumed most parts would be lead-free - checked some Mouser parts etc and of course the PCBs/DOA-pins/etc. are gold finish. Most parts these days are RoHS, anyways..

Well, I'll see how it goes - will check with BOMs and part codes.

Thanks, Tom
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on July 28, 2015, 01:17:16 PM
Thanks Jeff - it is not that I need to comply with RoHS, more that I'd prefer to use my regular lead-free approach.

So, let's change the focus to lead-free rather than RoHS -- Leaded solder is OK on lead-free, but lead-free is not good on leaded parts. So, I'd like to try to be as sure as possible before beginning the build.

Of course, I thought some more and presumed most parts would be lead-free - checked some Mouser parts etc and of course the PCBs/DOA-pins/etc. are gold finish. Most parts these days are RoHS, anyways..

Well, I'll see how it goes - will check with BOMs and part codes.

Thanks, Tom
Let us know how you do Tom. Since I am not shipping assembled modules, I don't worry as much about it.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bugbrand on July 28, 2015, 01:47:49 PM
Well, quick run through the VP312DI rev.c.1 Main BOM - all parts come back as RoHS except 3 unsearchables - the 2 EA transformers and the Bourns TPad (though the other Bourns is RoHS).
It'd be interesting to know on the transformers, but otherwise it sure is looking likely that all is fine lead-free.
Thanks Jeff!
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bugbrand on July 29, 2015, 05:30:37 PM
Fine going on the main unit - nice kit, for sure!

But, on to the DOAs [got a GAR1731 & a GAR2520 kit] - these have PCBs without AU surface finish, so.. Jeff, I presume you get these made yourself? Can you tell me what surface finish you use for these? [HASL or HASL RoHS - I always presume 'regular' HASL would be tin/lead]. Anyway, going to stop work now until I'm back at the workshop tomorrow [where I can make them with leaded solder..]


One minor notice - CAP C10 was provided as 6.3V rather than spec'd 16V [from the BOM] - 6.3V seems perhaps low?

Also, haven't yet found a detail mention on optional R3 [sorry, didn't get through the 2nd half of this thread *yet*] - marked optional on BOM, and I see it on the schem.. . Hmm..


Thanks!
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: jsteiger on July 29, 2015, 05:46:37 PM
Fine going on the main unit - nice kit, for sure!

But, on to the DOAs [got a GAR1731 & a GAR2520 kit] - these have PCBs without AU surface finish, so.. Jeff, I presume you get these made yourself? Can you tell me what surface finish you use for these? [HASL or HASL RoHS - I always presume 'regular' HASL would be tin/lead]. Anyway, going to stop work now until I'm back at the workshop tomorrow [where I can make them with leaded solder..]


One minor notice - CAP C10 was provided as 6.3V rather than spec'd 16V [from the BOM] - 6.3V seems perhaps low?

Also, haven't yet found a detail mention on optional R3 [sorry, didn't get through the 2nd half of this thread *yet*] - marked optional on BOM, and I see it on the schem.. . Hmm..


Thanks!
Gary supplies me with the gar1731 and gar2520 kits so I can't answer that question. Maybe post on their respective build threads?

That 470µF cap should never see more than 1V DC on it and that is only if the pre is in post 2622 DI mode. Under typical conditions it will be more like 100mV or a little less. If it is more than that, there is a series problem somewhere else!

R3 is the 150k load R. This will slightly lower the  input Z of the preamp. Leaving it out tends to yield a slightly more "open" sound. I usually build 312's without it.
Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bugbrand on July 29, 2015, 05:50:13 PM
Thanks for replying so quickly Jeff. That clears up the 2 points nicely then - thanks.

Started busting through the rest of the thread & saw about the GAR build threads so, yes, will ask there.

Title: Re: [BUILD] VP312DI, 500/51x Mic Pre + Direct Inject Build Support Thread
Post by: bugbrand on July 30, 2015, 02:38:48 PM
Hmm - well, the unit is working nicely apart from the HIz Plugin (IC version) which is currently confusing me somewhat - though I do wonder if I'm doing anything dumb (not very up on preamps etc yet)

Running into the HiZ input, with PRE 2622 mode - if I turn up the Preamp Gain too much I start getting a nasty 10Hz oscillation - with the Pad switch in, this is up near the top of the preamp gain setting, and much lower on the dial with the pad out.

Working fine in POST 2622 mode. [which I believe bypasses the HiZ plugin card?]

Hooking up the scope (and running the module on one of your test jigs) - firstly, I see roughly 1VDC offset on both output pins (no offset on the input pin).
At high gain, out+ wobbles at 300mV PtoP, while out- is more like 2V PtoP! [10Hz jaggedy waveform]

Interestingly, with the stock OPA2604, once it has gone into this oscillation, I bring the gain back down but there's then a MHz oscillation still on the Out- pin [not present on the out+ pin] - the audio output is fine again, though that oscillation can't be all that good..
I chucked in a TL072 and that doesn't suffer the MHz oscillation, but behaves the same with the preamp gain 10Hz oscillations.

Any thoughts?!
Thanks! Tom
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: ENS Audio on December 01, 2015, 01:36:47 AM
Just finished my 312DI and started measuring resistance between DOA sockets as instructed by the assembly guide.  Everything measured out @ 200k + Ohms between the DOA sockets EXCEPT between V+ and C sockets where I get less than 10k Ohms. 

Went ahead and resoldered a few cold solder joints and I still get the same problem with resistance below 200k Ohms between V+ and C   DOA sockets.


Thanks.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: ENS Audio on December 01, 2015, 01:41:15 AM
Also I tested voltages between the DOA sockets and everything is around 16 vdc.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on December 01, 2015, 11:16:30 AM
.....between V+ and C sockets where I get less than 10k Ohms. 
This is correct on the VP312DI. The measurements shown in the VP2x Assembly Guide are specific to the VP25 and VP26.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: ENS Audio on December 01, 2015, 04:12:38 PM
.....between V+ and C sockets where I get less than 10k Ohms. 
This is correct on the VP312DI. The measurements shown in the VP2x Assembly Guide are specific to the VP25 and VP26.

Ok then now I need to find out why the 2520 transistors are overheating (DOA voltage selection switch is selected at 16v btw)  even though all the measurements on the DOA sockets are correct. 

Also there is no output sound except for some low noise which cancels out when I hit the mute switch.  I've resoldered the few cold solder joints that were found as well.

Other than the DOA socket resistances I've checked, everything on the gain switch reads the correct measurements of 25k ohms.

Not sure which part of the circuit to start investigating next, this is driving me nuts lol.


By the way, I must commend you on the quality of these boards and everything I've purchased over at CAPI.   Especially the floor box PSU, love how the sides of the chasis are two great big heatsinks, great stuff.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: ENS Audio on December 01, 2015, 07:23:51 PM
After looking around at the PCB I've noticed that I soldered one of the relay boards backwards like a total dumbass!   :-[  So I had to snip away all the header pins and desolder the relay board in order to remove it from the main PCB.

 I'm going to solder some diode leads as a substitute and put the relay board in the correct orientation.  We'll see what happens after that.

Other than that everything else looks good, can't believe I soldered that thing backwards, must be dyslexic.  :P
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: ENS Audio on December 02, 2015, 12:19:31 AM
Went ahead and soldered the relay board in the correct orientation, now I get sound only through 48v phantom power with a condenser plugged in.  No sound when I plug one of my guitars into the DI input and the DOA transistors gradually start heating up after 10 mins or so with the unit running.  Guess it's safe to say I'll need a new relay board with components.

Is there anything else I should measure/test in the meantime til I replace that particular relay board?


Thanks,
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on December 02, 2015, 12:40:07 AM
Is the opamp a fresh build? Maybe there is trouble on that board?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: ENS Audio on December 02, 2015, 12:48:02 AM
The DOA was already assembled when I received it, it's the version with the smd resistors.  I see something written on the board with the date 05 15 if that helps any.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on December 02, 2015, 10:15:52 AM
The DOA was already assembled when I received it, it's the version with the smd resistors.  I see something written on the board with the date 05 15 if that helps any.
That's a red dot so it won't be that then. Just wanted to make sure the opamp wasn't a kit build. The output transistors to get nice and warm.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: ENS Audio on December 02, 2015, 05:47:10 PM
The DOA was already assembled when I received it, it's the version with the smd resistors.  I see something written on the board with the date 05 15 if that helps any.
That's a red dot so it won't be that then. Just wanted to make sure the opamp wasn't a kit build. The output transistors to get nice and warm.

Until I get another relay board is there any other parts of the preamp I should check to see that I have proper measurements {volts/amps/resistance/ on such as the input and output transformers ?  Or am I going to have to go through checking values through each and every component?

Thanks,
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on December 02, 2015, 08:04:53 PM
Which relay board was the problem? You can view the schematic to see if it was the one that switches to DI mode. Sounds like you are OK in mic mode?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: ENS Audio on December 03, 2015, 01:37:27 AM
IT'S FINALLY WORKING!   ;D  Looks like the 9v for my fretless bass needed to be changed, wow this sounds incredible and I don't even have it running through my bass amp yet.  I can only imagine how much better it will sound going through an LA2A and API Eq  ;)

The only problem I've noticed very little hiss once it's turned all the way up and when the phase button is engaged it's a little crackly.

Would you happen to have a link to where I can get the calibration test results as far as noise levels, etc (if that makes any sense, still a noob at this)

Thanks for all your help and providing such awesome kits of the real deal,  all you guys at the white market have made it possible to finally own the stuff of legends few of us could ever afford.  8)



Now time to order some other Hi-Z plugins and other DOAs to try!
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on December 03, 2015, 08:51:43 PM
The only problem I've noticed very little hiss once it's turned all the way up and when the phase button is engaged it's a little crackly.
Is this 2 separate concerns?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: ENS Audio on December 07, 2015, 01:09:20 AM
The only problem I've noticed very little hiss once it's turned all the way up and when the phase button is engaged it's a little crackly.
Is this 2 separate concerns?

There's some distortion when I have the gain 3/4th's or the output attn 3/4th's up.   I'm running the 312 through my focusrite saffire pro 14 and the gain is only turned up 1/4th of the way on the audio interface.

Do you want me to post a screen shot of the levels in visual analyzer?


Thanks.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on December 07, 2015, 09:53:07 AM
Do you have the opamp fully seated? http://capi-gear.com/catalog/DOA_Install.php
If its correct, these other issues indicate you have something placed wrong or possible bad solder joints on the build.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: ENS Audio on December 07, 2015, 04:15:48 PM
Do you have the opamp fully seated? http://capi-gear.com/catalog/DOA_Install.php
If its correct, these other issues indicate you have something placed wrong or possible bad solder joints on the build.


I'll check that as well, I suspect maybe some of the components were damaged on the relay board when I was desoldering it in order to resolder the board in the correct orientation.

Also, I tried looking for some information on calibrating the 312DI, wanted to know at what Hz should I set my signal generator when tracing out the board.  I am using visual analyzer and using the Focusrite Saffire Pro14 as my audio interface, unless you recommend I fire up my old tektronix 2225 50 Mhz scope.

Thanks.


Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: ENS Audio on December 08, 2015, 12:50:46 AM
UPDATE:  Well it looks like I've made some progress here, turns out the tantalum cap on the Hi Z plugin was soldered backwards ('+' mark on the cap inserted to the '+' on the PCB layout DOH!)  Plus one of the wires I used to jumper the relay I desoldered wasn't soldered in the main board.

It sounds so awesome when I'm directly monitoring the output when my bass guitar is plugged in, I can turn the gain up full blast and can set the output atten to '0' BUT when I run the output from the preamp to the input of my focusrite saffire it appears the audio interface cannot handle all that gain and it clips terribly causing me to set the output atten more than halfway.

Is this because my audio interface only has so much headroom or do I need to further troubleshoot the mic pre for more problems?


Thanks.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on December 08, 2015, 09:31:52 AM
I am no DAW guy so I can't say about interfaces and such. You can easily measure the preamp for max gain though. With the output full up at 0 and the preamp gain cranked, the pre will amplify the input signal by appx 60dB.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: the19thbear on December 22, 2015, 03:55:28 PM
Hi. I just took over another guys project here. He couldnt get it working.

He had turned C6 and C5 diodes the wrong way around (the ones that are right after the +/-16 volt inputs) and a wire to the transformer had broken off. And the LED was turned the wrong way. He had it powered up this way, and im surpriced it didnt blow anything up.. (well maybe not).
After i fixed these very visible error i actually got the unit kind of working. Phantom power is on(led is on) and everything seems to work except that all the low freq from the mic input/di input are cut off. Its like a constant low cut at around 400hz or so (just listened through cheap headphones).
The mute/pad button work. I havent been able to test the phase button yet.

I can read i schematic and follow very basic signal flow, but is there something obvious that could have been damaged by the earlier person powering it on with C5/C6 turned the wrong way around?
Or is there a built in low cut filter where he might have put in a wrong resistor value?
I know this is a shot in the dark since you guys and gals dont have the actual unit in front of you, but any help would be appreciated! Maybe a way i can test each area on the PCB by tracing the sound?

Thanks:)
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: the19thbear on December 25, 2015, 04:30:02 PM
Ok. So i just went through the schematic.
All caps on the main board seem to be the rigth ones. (dont know about the 3 small extra boards yet - the PK1 and PK2 and then i have one more board on it, i think its the 2520 blue dot).

I found a really weird problem though.
Whenever i engage the phase it turns the phase AND makes the signal a lot louder?!? What the heck?
Looking at the schematic i dont really see how that could be done?
Any suggestions?
Mute/Pad works.
I still have very poor bass repsonse on both DI and MIC input. There is some serious low cut going on.
Since it is happening on both DI and mic, my logic tells me that the low cut problem is some where after PK2, right?
Are there some measuring points later in the circuit where i could probe with a headphone amp and see where the problem arises?

So in a nutshell:
-Why the added volume when phase reverse?
-Between what points in the signal path would you say the low cut error is happening?
-CR6 and 5 were reversed by mistake and the unit powered up. What needs to be replaced?

Schematic link:http://www.capi-gear.com/catalog/images/gallery/VP312DI/RevC/VP312DI-Rev-C.1-schematic.pdf

Thanks:)



Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: the19thbear on December 26, 2015, 04:26:49 AM
So another post:

I go out of my 500 rack with crocodile clips connected to the xlr out pins on the 500 rack into my soundcard via line in
By mistake i hooked up the clips on xlr output pins 2 and 3 (hot and cold) and not 1 and 3 (ground and cold).
But the weird thing is that when hooking it up via pins 2 and 3 (hot and cold) it works perfectly! If i plug in the clips correctly i still get low cut and the big volume jump with phase pressed in. But connected to pin 2 and 3 the low freq seem perfect and the phase switch only switches the phase.

What could be wrong here?

Its his 500 rack as well (lindell audio).. Could it be damaged?
Thanks again!
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: the19thbear on December 26, 2015, 06:05:42 AM
Hmm.. seems it could all be narrowed down to bad cabling (for now).
 I found my proper XLR to jack converter cables, and once everything was plugged in to/from the soundcard/500 rack all seemed to work fine!
I have to test it with balanced/xlr connections later though:)
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on February 02, 2016, 11:28:22 PM
--------------------------------------------------------------------------------------------------------
February 2nd, 2016 Update:
Rev D boards are now shipping for the VP312DI. To easily identify, the Rev D boards are green. The circuit is 100% identical although a few part labels and designations have changed. Like with all projects, it is crucially imperative that you follow the BOM that matches the revision of the PCB that you are building. I still have a good amount of the Sub DI boards left in black. Once those are gone, the reorder will be green and have the CAPI® affixed  :D
--------------------------------------------------------------------------------------------------------
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: Kevinkmny on March 24, 2016, 10:46:12 AM
Ok gents, time to get over my fear of troubleshooting....

I checked for resistance without op amp installed. All seemed to check out.

Powered up the module without the op amp and I started to get smoke....which looked like it was coming from C12, which appears to be installed correctly...

Any suggestions as to next steps greatly and humbly appreciated!

K
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on March 24, 2016, 12:33:42 PM
C12 is the storage cap on the 48V rail. That would most likely not be the cause of smoke. If it were in backwards it would probably have exploded, quickly. I don't think it would be from C12. Typically, letting the smoke out would be an opamp thing.....
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: Kevinkmny on March 24, 2016, 04:04:27 PM
I didn't have the opamp in the socket though...

Any suggestion as to next steps?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on March 24, 2016, 04:13:18 PM
I would dbl and triple check all parts and orientation. If there is smoke, you have something wrong somewhere. Tracing it down can be hard without know what/where to look. There is always the option of letting whatever the problem is go up in smoke so you know for sure. I am not exactly recommending that though. Sometimes, there is only so much I can do from here.....
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: Maddin89 on April 26, 2016, 09:06:24 AM
Hello,
I finished my first VP321DI yesterday. On Mic and DI input I have a distorted signal. The distortion stays the same on all gain settings and all switch positions. Except for the mute switch ;)
I read the thread but can't find a similar problem. I recorded a short example; maybe someone had a similar problem.
I checked all orientations and diodes; everything looks good to my eyes.
What voltages should I check first?
Thanks
Recorded through the VP321DI:
https://www.dropbox.com/s/z03uhf2mwjx7s8p/error.wav?dl=0
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on April 26, 2016, 10:09:00 AM
The first piece of data that should be disclosed when posting a fresh build problem is, what opamp is installed and who built it?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: Maddin89 on April 26, 2016, 11:45:13 AM
The first piece of data that should be disclosed when posting a fresh build problem is, what opamp is installed and who built it?

Sorry  I forgot to wrote that. It's a SL-2520 Red Dot, Assembled. The build is VPR 16V.
500 Rack is a Fredenstein Bento 10
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: blackartmixing on September 14, 2016, 10:01:07 AM
ok a few issues with my CAPI VP312DI.  DOA prebuild red dot SL-2520, Hi-Z Pikatron UP3096M kit, VPR Floor Box PSU (tested and working)

Sounds like its a bit of a mess.  one thing to note, i had the PK1 soldered in the wrong way when i first powered on.  i realised today and thought this must solve my issues but everything is still the same when i changed to the correct orientation. 
I've checked my diodes on the relays and all seems good there.  CR1 is different to CR2 and CR3. 
reflowed solder to both relays, DI jack and transformer wires. 
any idea where i should start to troubleshoot this?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on September 14, 2016, 10:18:38 AM
The biggest error folks make on these are on the relay PCB's. Its usually swapped around or wrong facing diodes. I have also seen people have the relay rotated the wrong way.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: blackartmixing on September 14, 2016, 11:03:05 AM
Yeah i've read through the whole thread so i'm aware of that so i did really try and check all that stuff before i posted.  i've attached a photo.  maybe you can quickly check and see if there is anything obvious.

more photos
http://blackartaudio.net/wordpress/wp-content/uploads/2016/09/DSC02386_resize-1.jpg

http://blackartaudio.net/wordpress/wp-content/uploads/2016/09/DSC02385_resize.jpg
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: blackartmixing on September 16, 2016, 05:42:19 AM
i fixed it.  all working perfectly now.  i hadn't realised that the connections between the Sub-DI.1 PCB board and the main board were actually part of the circuit and i hadn't solder in one.  i just added that and now everything works. 
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: TheLavaBed on October 07, 2016, 12:16:24 PM
Hi Jeff (and everyone else who is smarter than me).

I'm wrapping up a build on 2 VP312DI's (VPR Rev C.1 Versions), and am getting nothing when plugging into my 11 space rack that has had no issues for years.  I chose against the DC Block / Cap coupled output (just from a purist standpoint).  This is my 3rd CAPI build (2x VP26, 2x VP28), and the only one that I have had any issues with.  Phantom power lights are turning on, but I'm getting no signal with an sm58 plugged in. 

I'm at my 3rd "walk away" moment, where I just need to take a break for clarity.  I have read this thread front to back at least 3x over the last four days, and I know that there are readings I can take that will help assessing the possible issue (which I will do after the weekend). 

Before I do so though, here's the question:  I forgot to buy a HiZ plugin kit when purchasing the preamp.  If this is not plugged into the circuit, will the microphone side of the preamp work?  I don't seem to be getting any output at all.  Even when I plug and unplug cables from my patchbay, I am seeing no small jumps in Pro Tools when I move cables before the preamp, but am clearly seeing meter jumps when I pull the cable on the output side.

Thanks!!

-Mike   :)
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on October 11, 2016, 06:31:13 PM
Hey Mike

With no HiZ Plug-In installed, the VP312DI will work fine in mic mode. It will only work for DI when in "Post 2622" mode. The most common error with these builds are wrong locations/orientation for the diodes on the relay PCB.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: TheLavaBed on October 25, 2016, 02:25:44 PM
Thanks Jeff!  I'll be diving back into this later in the week.  I'm almost positive that the diode orientations are correct, but will look over the PCB's closely.  I'll go back through this thread and take the same readings that others have taken and report back my results.  Hopefully that will lead me somewhere.

-Mike
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: bartbusch on December 22, 2016, 09:19:50 AM
I just finished the Rev D VPR version of the VP312Di with stepped gain. While it wasn't necessarily a difficult build, thanks to Chunger and Jeff's build guides, there were a few things that I got hung up on at the end. R16 is now where you put the 10k vertical resistor and the LED for the phantom power (not R17).  I got hung up on trying to figure out how to mount two components in one position on the PCB. Jeff's build does show this but I couldn't tell what I was looking at so I just wanted to point it out that the long leg of the LED is connected to the resistor that is mounted vertically. The short leg goes into what is labeled LED on the board. Then those two are soldered together to make one component in a sense. Hopefully this pic will help.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: bartbusch on December 22, 2016, 09:26:40 AM
The other thing that neither build guide made mention of is that there HAS TO BE a jumper or switch installed in SW1 and SW2 in order for this thing to work. I had no switches and didn't know if it was somehow being connected inside the PCB.  Long story short, save yourself a little extra wire and install jumpers where it indicates "for VPR". 
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: bartbusch on December 22, 2016, 09:28:44 AM
I eventually stumbled upon this picture on the product page for the VPR jumpers and here's what that looks like.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: bartbusch on December 22, 2016, 09:30:56 AM
Here's what the final build of the Rev D version with stepped gain looks like.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: bartbusch on December 22, 2016, 09:35:55 AM
Here's another view
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: TheLavaBed on December 30, 2016, 05:22:59 PM
Hey Mike

With no HiZ Plug-In installed, the VP312DI will work fine in mic mode. It will only work for DI when in "Post 2622" mode. The most common error with these builds are wrong locations/orientation for the diodes on the relay PCB.

Hi Jeff (and everyone smarter than me)...

So, I built two VP312DI's - one is (mostly) working, and the other is not working at all.  I built them at the exact same time (put components on one board, and then the other).  I've inspected visually, and can not see anything wrong.  I'm more than happy to take measurements, but I have no idea where to measure in a way that would be helpful.  I saw this on a previous post, but I don't know where to take these measurements (I'm assuming on the card end pins):

-V and +V = xxxx
-V and C = xxxx
C and +V  = xxxx
C and O = xxxx
V+ and O = xxxx
-V and O = xxxx

My rack is a 16V rack.  Opamp is a GAR that I purchased assembled from CAPI.

Anyway, here are the issues:

Preamp 1:  Microphone side seems to be working completely.  Input pot, Output Attenuation, Phantom, etc.  However, when I plug in a bass into the DI section, it works for a minute.  All switches seem to do something.  Then, after about 15-30 seconds, it gets distorted sounding, and begins to fizzle out, eventually making no sound at all.

Preamp 2:  Totally dead, no audio passes.  Phantom power light turns on.  When plugging and unplugging patch cables on the front side of the preamp, nothing shows up in Pro Tools.  When unplugging cables on the output side (after the pre) pops are seen on Pro Tools.

Any help would be appreciated.  I love CAPI Pres (thanks Jeff!!).  These are the 7th and 8th CAPI's I have built, but the ones I'm having the most difficulty with... I'm losing it as I get older.  I had to buy magnifying glasses this time to read the diodes... Never had to do that before  :o

Thanks,
Mike
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on December 30, 2016, 07:19:53 PM
Mike, it sounds potentially like bad solder joint(s). The biggest error folks make on these builds is misplace diodes on the small relay boards.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: TheLavaBed on December 31, 2016, 12:26:00 PM
Mike, it sounds potentially like bad solder joint(s). The biggest error folks make on these builds is misplace diodes on the small relay boards.

Thanks Jeff - I'll look into it and let you know what I find.  I've read your posts about the relay boards, and tried to take a close look at those.  I'll go through the main board of each first and see if it helps.  If not, I'll remove the relay boards, and see if touching up those solder joints helps.

Thanks for the support of your products Jeff!!

-Mike
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: Hynek on January 26, 2017, 10:08:40 AM
Here's what the final build of the Rev D version with stepped gain looks like.

bartbusch - your photos were a lot of help, sped up my build quite a bit, thank you!
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: DrywOwens on March 21, 2017, 06:14:28 PM
Hi all,
I just finished a VP312DI Rev D build using vintage API components. As I perform the test, I seem to be getting 10.1 ohms resistance between V+ and C on the DOA sockets. I currently do not have a DI board installed. Is this normal?? All other tests result in a reading well above 200K.
Thanks in advance!
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on March 21, 2017, 11:20:24 PM
Hi all,
I just finished a VP312DI Rev D build using vintage API components. As I perform the test, I seem to be getting 10.1 ohms resistance between V+ and C on the DOA sockets. I currently do not have a DI board installed. Is this normal?? All other tests result in a reading well above 200K.
Thanks in advance!
This is totally normal and expected for a VP312DI or VP312.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: Kevinkmny on April 03, 2017, 01:01:14 PM
I'm getting 4.0K ohms on that same measurement....is that ok too?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on April 03, 2017, 01:23:13 PM
I'm getting 4.0K ohms on that same measurement....is that ok too?
It is dependent on where the shunt jumper for the DC cap coupled output is at. It should be fine though.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: Kevinkmny on April 03, 2017, 06:42:41 PM
Hmmm,

In apply power with the op amp not installed I'm getting 16 volts (or -16V?) between -V and C but nothing between +V and C...

Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on April 03, 2017, 08:29:40 PM
Hmmm,

In apply power with the op amp not installed I'm getting 16 volts (or -16V?) between -V and C but nothing between +V and C...
Did you jumper over the voltage select switch as shown on the VPR mod?

(http://www.capi-gear.com/catalog/images/gallery/VP312DI/500-VPR-mod.jpg)
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: mdmitch2 on May 29, 2017, 10:33:52 PM
I built one of these recently, and everything is working fine except I'm not sure about the IC1 hi-z plug in. It's insanely hot. The only way I can use it with a bass is to use the 20db pad, and input gain at zero or one. I also have a pikatron, and it works fine, and the level is actually lower than when using post 2622 mode. 

So is it normal to need the pad when using the IC1? I verified that it's assembled correctly... it would be pretty hard to screw up.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on June 01, 2017, 11:16:51 PM
I built one of these recently, and everything is working fine except I'm not sure about the IC1 hi-z plug in. It's insanely hot. The only way I can use it with a bass is to use the 20db pad, and input gain at zero or one. I also have a pikatron, and it works fine, and the level is actually lower than when using post 2622 mode. 

So is it normal to need the pad when using the IC1? I verified that it's assembled correctly... it would be pretty hard to screw up.
Well, it goes like this. The Hi-Z Plug-In output is coupled to the 2622 input transformer so there is gain from that as well as the rest of the preamp. The IC1 is a balanced output and runs about 6.5dB hotter than the FET1 which is about 15dB louder than the Post 2622 mode. The FET1 is basically a unity gain impedance convertor. Technically speaking, the Post 2622 mode is down about 17dB since there is no gain from the 2622.

You can try adding a u-pad to the output of the IC1 board. Replace the two 100Ω series output R's with 820Ω R's and then solder a 160Ω shunt across them at the output side. This will drop the output to pretty well the same level as the Post 2622 setting. Of course simply engaging the mic pre pad will do almost the same thing.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: mdmitch2 on June 02, 2017, 02:43:42 PM
Thanks Jeff -- I'll just use it with the mic pad -- no biggie.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: rwrwrw on September 30, 2017, 07:26:11 PM
Hi,

I'm currently building a couple of these vp312DI preamps and I wanted to know how leaving the optional capacitors C10 470 uf 6V3 & C11 .01uf 100V out effects this preamp?

I know that leaving the R2 150k resistor out gives a more open sound. Curious if these capacitors do something similar.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on October 01, 2017, 01:45:58 AM
Hi,

I'm currently building a couple of these vp312DI preamps and I wanted to know how leaving the optional capacitors C10 470 uf 6V3 & C11 .01uf 100V out effects this preamp?

I know that leaving the R2 150k resistor out gives a more open sound. Curious if these capacitors do something similar.
They are there to block DC from possibly damaging the output transformer when the DI is used in Post 2622 mode. If you ever plan to use the DI in Post 2622 mode then make sure the caps are installed and the shunt jumper is set to leave them in the circuit.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: rwrwrw on October 01, 2017, 10:29:40 AM
Ok good to know!

I'm guessing that means the shunt jumper should be on "DC Block/Cap Coupled Output" ?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on October 01, 2017, 12:00:54 PM
I'm guessing that means the shunt jumper should be on "DC Block/Cap Coupled Output" ?
Yes, exactly  ;)
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on January 07, 2018, 06:27:22 PM
I just added a new FET HiZ Plug-In module to the store for use in the VP312DI preamp. It replaces the old FET1.

Details are on the product page here http://capi-gear.com/catalog/product_info.php?products_id=571

(http://www.capi-gear.com/catalog/images/gallery/HiZ-Plug-In/active/FET-ZCON1-parts.jpg)
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: pkordel on January 30, 2018, 01:14:15 AM
Hi guys, I love these kits and am about to start on my second 312DI. In a way, it seems like these builds go from pretty easy to hard and then pretty easy again.
I'm talking about hitting snags and troubleshooting. My first project was a VP26 and it went great until I somehow misaligned it when inserting it into a 51x 511 rack and the power resistor next to the OT caught fire when I powered up, oops!

Anyway, that's for another thread. My first 312DI build went great and seemed to work just fine initially but now when I switch on phantom power I hear a hissing and crackling, static like sound that comes and goes. Dynamic mics and the DI (IC) work fine. I reflowed the pushbutton switches but no improvement as yet. It does point to a cold solder joint somewhere just looking for suggestions where to start looking. Another symptom: when I push the pad switch, there is slight static and a pop, possibly DC leakage somewhere?

The rack is verified good as is the slot. Measuring 48V where it should be on the PCB.

I guess you could say I'm on a DIY uphill slope right now with: a VP26 with fried power resistor; a VP312DI with phantom power noise; a VP28 with a wonky output fader; a GAR1073 missing an 18K resistor; a GAR2520 where Q3 snapped off when I tried to nudge it to install Q2.

Waiting for a desoldering station and replacement parts from mouser to arrive to undo, undo haha. Good time for deep breathing...

Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on January 30, 2018, 10:28:02 AM
...My first 312DI build went great and seemed to work just fine initially but now when I switch on phantom power I hear a hissing and crackling, static like sound that comes and goes. Dynamic mics and the DI (IC) work fine. I reflowed the pushbutton switches but no improvement as yet. It does point to a cold solder joint somewhere just looking for suggestions where to start looking.
I do publish the schematic for this build. If you take a quick look you will see less than a handful of components involved in the phantom power circuit. I would look for a cold solder joint on one of those parts firstly the 120µF cap.

Quote
Another symptom: when I push the pad switch, there is slight static and a pop, possibly DC leakage somewhere?
The polarity switch is disrupting the signal between the opamp and transformer so it will never be 100% silent. It will indeed "pop" more if DC is present. I do recommend that you set the shunt jumper to "DC Block/Cap Coupled Output" especially if you ever use the pre in Post 2622 mode. If you want to verify the amount of DCV present, just probe between ground and one end of the 1Ω R. Again, use the schematic to locate the position. It won't be "DC leakage somewhere" it be DC getting to the polarity switch.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: pkordel on January 30, 2018, 09:48:56 PM
I do publish the schematic for this build. If you take a quick look you will see less than a handful of components involved in the phantom power circuit. I would look for a cold solder joint on one of those parts firstly the 120µF cap.
The polarity switch is disrupting the signal between the opamp and transformer so it will never be 100% silent. It will indeed "pop" more if DC is present. I do recommend that you set the shunt jumper to "DC Block/Cap Coupled Output" especially if you ever use the pre in Post 2622 mode. If you want to verify the amount of DCV present, just probe between ground and one end of the 1Ω R. Again, use the schematic to locate the position. It won't be "DC leakage somewhere" it be DC getting to the polarity switch.

Thanks Jeff, I'll try your suggestions later today. I do have the shunt jumper set to DC Block.

Cheers
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: seanweaverguitar on May 09, 2018, 03:32:10 PM
I've been looking at the schemo for about the past two months now studying every part before working up the nerve to order/do this build....

How does VC of the PK1 relay connect to GND via BB3? Looks like that goes to the ring of the TRS jack when the Post 2622 switch is flipped,  but on the jack diagram itself, I don't see the ring connected to GND?  What am I missing here?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on May 09, 2018, 04:01:06 PM
I've been looking at the schemo for about the past two months now studying every part before working up the nerve to order/do this build....

How does VC of the PK1 relay connect to GND via BB3? Looks like that goes to the ring of the TRS jack when the Post 2622 switch is flipped,  but on the jack diagram itself, I don't see the ring connected to GND?  What am I missing here?
The function will only work when a mono 1/4 plug is inserted into the stereo jack. The jack is connecting ring to sleeve thru the plug itself.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: seanweaverguitar on May 14, 2018, 04:17:46 PM
The function will only work when a mono 1/4 plug is inserted into the stereo jack. The jack is connecting ring to sleeve thru the plug itself.

Ah yes, I'm slow checking back in here but that makes perfect sense now. Thank you very much for taking the time. I'm finishing up a blues guitar project and allotting funds for more projects once I get paid so I think a 312DI is in my future once I'm certain I'm not going to screw it up or at least have a full enough understanding to know how to troubleshoot the circuit if I run into problems (the Hairball builds were successful last winter but they were my first and I wanna make sure I really understand the schematics, have read through entire build threads, have the right equipment (got the Hekko, no desoldering station though; Fluke 179, but no oscilloscope or high powered magnification yet)  and am fully prepared to take on a project like this without a build rescue service....I think I'm close).

At this point the only thing still making me scratch my head is the -10dB pad in post 2622 mode. I'm probably reading the schematic wrong but working on it. Still not seeing how the pad circuit is completed with SW2 in either position. Really trying for weeks on end too.  Looks like in either position it's going through R1 & C2 on the Sub DI board but I'm not sure how or where it completes depending on which way the switch is flipped. If it's still not making sense in a couple more weeks I'll give up and post back here again.

(I'm doing the work, I'm baby-stepping. I really am hungry to learn this stuff)

Thanks for the clarification Jeff. I really do appreciate it
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: Jroq82 on May 22, 2018, 02:53:49 AM
Hey guys,

I’m building  this mic pre, and I’ve ran into a problem, and there doesn’t seem to be a resolution through out the thread. Upon placing the sub DI 1 and placing it as described in the thread, on top of the main PCB, the switches for post 2622, -10, and J lpf, do not line up with the holes on the face plate. What it seems like is the sub DI PCB, looks like it should be on the bottom of the main PCB. Would this correct this issue?  I have already soldered the 5 leads to hold the sub DI PCB in place on top of the main PCB. So that makes it very hard to remove. But wanted to check here to see if anyone has had this issue? Attached is a picture of what it looks like with the face plate. Thank you.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on May 22, 2018, 10:12:39 AM
Hey guys,

I’m building  this mic pre, and I’ve ran into a problem, and there doesn’t seem to be a resolution through out the thread. Upon placing the sub DI 1 and placing it as described in the thread, on top of the main PCB, the switches for post 2622, -10, and J lpf, do not line up with the holes on the face plate. What it seems like is the sub DI PCB, looks like it should be on the bottom of the main PCB. Would this correct this issue?  I have already soldered the 5 leads to hold the sub DI PCB in place on top of the main PCB. So that makes it very hard to remove. But wanted to check here to see if anyone has had this issue? Attached is a picture of what it looks like with the face plate. Thank you.
I am guessing that you soldered the NKK switches onto the top of the PCB when they should be on the bottom? Please see step #4 on the very first post of this thread.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: Jroq82 on May 22, 2018, 01:54:23 PM
Hi Jeff,
 As always thank you for your quick response.  I have in fact soldered them to the bottom,  As step 4 indicates. All the other knobs and push buttons fit nicely. Please See photo attached, to confirm switches are in correct. Hopefully you see something incorrect. Thank you.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on May 22, 2018, 02:40:34 PM
Hi Jeff,
 As always thank you for your quick response.  I have in fact soldered them to the bottom,  As step 4 indicates. All the other knobs and push buttons fit nicely. Please See photo attached, to confirm switches are in correct. Hopefully you see something incorrect. Thank you.
Ah, OK now I see it. The t-pad was incorrectly soldered directly to the PCB which is throwing off the entire module's alignment.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: Jroq82 on May 22, 2018, 02:55:36 PM
Ah, OK now I see it. The t-pad was incorrectly soldered directly to the PCB which is throwing off the entire module's alignment.

So should I space it like it says for revision B, even though I have revision D? That would make sense, as it is slightly off.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on May 22, 2018, 02:58:17 PM
So should I space it like it says for revision B, even though I have revision D? That would make sense, as it is slightly off.
No, the steps for that start with #2 in the first post of this thread. The steps are fairly detailed out.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: Jroq82 on May 23, 2018, 03:04:38 AM
Thank you for the insight. I corrected the issue, I now have a working 312!
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on May 23, 2018, 09:51:57 AM
Thank you for the insight. I corrected the issue, I now have a working 312!
Excellent, congrats!
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: seanweaverguitar on May 24, 2018, 01:32:05 AM
Alright I figured out the schematic (the DI pad part that was the last part I wasn't yet able to make sense of a few days earlier when I last posted). As funds come in I'll have one of these on my to-do list for sure. Still a little nervous to take on a project without a build rescue service not yet having an oscilloscope or other test equipment past the Fluke 179 (one step at a time) after a couple Hairball builds (both of which were successful) but think I can do this and very much look forward to before long. Thanks again for answering my question about how the PK1 relay connects to GND through the ring. That really helped and now I more or less understand the schematic. I'm on a mission to keep learning and build more gear in the process & this is one high on my list so you'll definitely be hearing from me. Thanks again Jeff   
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: shogami on July 15, 2018, 05:36:27 AM
I just finished building my second VP312. Everything seems to be working fine, except phantom power is not powering up, or LED is lighting up.
I doubled checked and went through possible, suspicious soldering spots, but doesn't seem like helping.
What would be the instant places I should be checking for this issue? Any help would be greatly appreciated!
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on July 15, 2018, 10:01:24 AM
I just finished building my second VP312. Everything seems to be working fine, except phantom power is not powering up, or LED is lighting up.
I doubled checked and went through possible, suspicious soldering spots, but doesn't seem like helping.
What would be the instant places I should be checking for this issue? Any help would be greatly appreciated!
Its hard to tell in the pic but it appears that the LED leads are shorted against each other? Might be an optical illusion. The schematic is published for this build so you can see where to measure for 48V if you check the skiz.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: shogami on July 18, 2018, 03:10:35 PM
Its hard to tell in the pic but it appears that the LED leads are shorted against each other? Might be an optical illusion. The schematic is published for this build so you can see where to measure for 48V if you check the skiz.

Hi Jeff,

Thank for your guidance. I've checked out the schematics, tested out the unit for few days.
Did some continuity test with DMM, especially around BB1, BB8 and BB4 pin, seems to be making a healthy connections. LED wasn't shorted.
There was a healthy continuity from J2-15 to SW6.
At this point I'm not really sure what is causing phantom to not work...LED is still not turning on, nor the 48V.  :'(
Everything else functions perfectly,  from all the mute, phase etc, to DI functions.

Uploaded few more photos...

https://www.dropbox.com/sh/zcn80x714q87roh/AACcsugg293kMOAxLvbU8XG3a?dl=0

Sorry for taking your time, but again, any help will be greatly appreciated!

Sho
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: TillM on July 18, 2018, 07:25:42 PM
First of all.
Which kind of lunchbox do you use ? I had some trouble with a Bento2 with the phantom power. The power board had some problems and the regulator fired up two times.

Second:
You had some solder joints who look really bad.
You should definitely resolder some points (there are lot of joints where you can see the gold solder pads)
95% of problems are poor solder joints.
Also use some isopropyl to clean the pcb.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: shogami on July 19, 2018, 12:45:04 AM
First of all.
Which kind of lunchbox do you use ? I had some trouble with a Bento2 with the phantom power. The power board had some problems and the regulator fired up two times.

Second:
You had some solder joints who look really bad.
You should definitely resolder some points (there are lot of joints where you can see the gold solder pads)
95% of problems are poor solder joints.
Also use some isopropyl to clean the pcb.

Hi TillM

I use Radial Six Pack. I have another VP312DI (Rev. C PCB), VP28's and they all power up fine, so I doubt if it's a lunchbox chassis issue.
And thanks for pointing out. I assumed if I tested continuity with DMM, it'd be a good enough connection, but I will definitely look over again and try re-soldering some points.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: mhbunch on October 26, 2018, 04:49:59 PM
OK! long story involving my wurlitzer 120 and sustain pedal/grounding ,but!

Accidentally shot mains voltage into the DI of my 312. now its about 20db quieter than my other 312. (just the DI, mic input works the same).

What did I fry? nothing looks burnt up.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on October 26, 2018, 07:25:16 PM
OK! long story involving my wurlitzer 120 and sustain pedal/grounding ,but!

Accidentally shot mains voltage into the DI of my 312. now its about 20db quieter than my other 312. (just the DI, mic input works the same).

What did I fry? nothing looks burnt up.
Not sure but could be a few things. Which way was the pre/post switch set at the time?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: mhbunch on October 26, 2018, 07:38:18 PM
Not sure but could be a few things. Which way was the pre/post switch set at the time?

I think it was post. Volume is affected both ways tho.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on October 26, 2018, 09:04:54 PM
I think it was post. Volume is affected both ways tho.
Post would go straight into the 2520. Maybe the opamp is damaged? Do you have another you could test it with?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: poserp on December 05, 2018, 02:14:00 AM
Hi! I'm just finishing a build of 2 312DIs + gar1731 opamps. I fired up the first one (haven't done the second yet...) and smoked resistors r14 and r15 on the opamp after applying power. Is this probably due to a fault in my op-amp build or did I do something wrong on the main PCB? If it's an op-amp issue, then I'm probably not the best op-amp builder and will purchase some pre-built op-amps.

Thanks!
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: TillM on December 05, 2018, 03:55:15 AM
Op amp is faulty.
Check the directions of the diodes and if you put the BD140 and BD139 in the right direction. Also check solder bridges.
Fire up the 312 without OP amps and check the voltages at the mill max pins where you stack the op amps in.
Where a you live ?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: poserp on December 05, 2018, 02:08:09 PM
Op amp is faulty.
Check the directions of the diodes and if you put the BD140 and BD139 in the right direction. Also check solder bridges.
Fire up the 312 without OP amps and check the voltages at the mill max pins where you stack the op amps in.
Where a you live ?

Thanks! Will do -- I presume that voltages and such should match those in the older 2x assembly guide on the CAPI site.  There's not smoke or anything without an opamp installed (the LED for phantom doesn't light, but I'm certain now that I have the LED wired backwards -- I connected the short pin on the LED to r16), so at least nothing else is frying (yet). Once I have #1 working, I'll finish out the build for #2 (basically done, broke the phantom switch and scratched the front-panel because I suck at assembly. Good thing, I think, that I'm waiting to get one fully-functional first though...).
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: poserp on December 06, 2018, 02:38:31 AM
O.k., so I tested resistance across the pins according to the VP2x assembly guide. All resistances were over 200k except for V+ and C -- that measured 9.6k ohms. Is that wrong? It measures that way on both of my boards, so if it's wrong then I have a component misplaced (I put together part layout sheets for my builds, and triple-checked to ensure they were the same and matched the BOM (building Rev D) and such. That being said, perhaps I misidentified a resistor -- I used my ipod camera to zoom in and take pictures so I could work out the color bands, I did a similar thing with the diodes. Perhaps I have a diode in the wrong place?

Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on December 06, 2018, 10:45:09 AM
O.k., so I tested resistance across the pins according to the VP2x assembly guide. All resistances were over 200k except for V+ and C -- that measured 9.6k ohms. Is that wrong? It measures that way on both of my boards, so if it's wrong then I have a component misplaced (I put together part layout sheets for my builds, and triple-checked to ensure they were the same and matched the BOM (building Rev D) and such. That being said, perhaps I misidentified a resistor -- I used my ipod camera to zoom in and take pictures so I could work out the color bands, I did a similar thing with the diodes. Perhaps I have a diode in the wrong place?
That resistance is correct for this build.

The resistance measurements posted in the VP2x guide are specific to a VP25 or VP26. The VP28 and both VP312 versions are slightly different.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: poserp on December 06, 2018, 02:01:19 PM
That resistance is correct for this build.

The resistance measurements posted in the VP2x guide are specific to a VP25 or VP26. The VP28 and both VP312 versions are slightly different.

O.k., good, thanks! I tried my best to lay out the parts correctly, I really did... I'll check voltages later today to make sure they're correct.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: glasscock777 on December 09, 2018, 02:10:35 PM
Hi everyone, just finished putting together a vp312di 51x version and i'm having some problems. i hooked it up to my rack ( capi 11 space and psu ) and upon powering it on +24 and -24 fuses popped... decided to flip the switches on the preamp to 16v and +16 and -16 fuses popped as well... any ideas whats causing this? ( please bear with me, i'm a hardcore noob with this stuff  ;D )
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on December 09, 2018, 02:13:26 PM
Hi everyone, just finished putting together a vp312di 51x version and i'm having some problems. i hooked it up to my rack ( capi 11 space and psu ) and upon powering it on +24 and -24 fuses popped... decided to flip the switches on the preamp to 16v and +16 and -16 fuses popped as well... any ideas whats causing this? ( please bear with me, i'm a hardcore noob with this stuff  ;D )
Likely a direct short somewhere on your build. Did you try without an opamp and without a Hi Z Plug-In inserted?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: glasscock777 on December 11, 2018, 08:47:36 PM
Likely a direct short somewhere on your build. Did you try without an opamp and without a Hi Z Plug-In inserted?

Just got more fuses in the mail, tested without opamp and hi Z plugged in and no fuses blown... didn't do one at a time though, just with both unplugged. sounds like i messed something up with one of them?
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: jsteiger on December 11, 2018, 11:47:11 PM
Just got more fuses in the mail, tested without opamp and hi Z plugged in and no fuses blown... didn't do one at a time though, just with both unplugged. sounds like i messed something up with one of them?
Yes.
Title: Re: [BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread
Post by: poserp on December 12, 2018, 03:41:08 PM
That resistance is correct for this build.

The resistance measurements posted in the VP2x guide are specific to a VP25 or VP26. The VP28 and both VP312 versions are slightly different.

O.k., got some op-amps assembled by pros and, sure enough, pre #1 had no smoke/fire or any other issues when I fired it up. I'll finish off #2 this week and double-check the audio (didn't have time to listen, only did smoke tests thus far).