[BUILD] CAPI VP28~500 Series~2-Stage Preamp~Official Support Thread

jsteiger

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***ATTENTION!! The VP28 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!!***

Since the kits have started shipping, it's time for the support thread!  :)

**This is a somewhat complicated build. Harder than a VP312DI but easier than a Love Child. I recommend reading completely thru the Assembly Aid before starting on anything. There are some points made in the doc that can save you much time and prevent crucial errors during the build.

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September 21st, 2015 Update:
All support docs for this project can be found on the recently added
Support Docs page at www.capi-gear.com
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--------------------------------------------------------------------------------------------------------
March 18th, 2016 Update:
Rev B boards are now shipping for the VP28. To easily identify, the Rev B boards are green and they have the CAPI® label affixed. To find out what has been changed, please read the
Rev B Addendum. Like with all projects, it is crucially imperative that you follow the BOM that matches the revision of the PCB that you are building.
--------------------------------------------------------------------------------------------------------


Some details can be found here http://capi-gear.com/catalog/product_info.php?products_id=318

temp-VP28.jpg


Cheers, Jeff
 

jsteiger

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Sorry for the low quality of the following pics. I know 'Chung's work will make me want to take these down but until he gets them done, these will have to do.

Just click the thumbs to enlarge!!  :)

Finger tight hardware on the 553F-Sub-HPF PCB, top view.


Finger tight hardware on the 553F-Sub-HPF PCB, bottom view.


553F-Sub-HPF PCB, lightly snugged into position on the main PCB.


The important thing in this crappy pic, is to note the outside tooth lock-washer placed between the VP28 L-bracket and the small Keystone bracket.


The 4-40 x 1/8" undercut flat head screw tightened thru the front of the VP 28 L-bracket.


After final adjustments and a tightening of the HPF board's fasteners, it's time to solder the 5-pin header thru the access slot in the L-bracket.


Recommended bending and installation of the four LED's on the main PCB.


Recommended bending and installation of the signal present LED onto the long 2-pin header.
 

chunger

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OK. . . as is customary in the Chinese Labor Camp, I waited a few weeks after receiving this package from jsteiger. . . you know.  To keep people guessing about delivery time-frames.  But, at some point, you need to begin cryptic communications in broken english allegedly for technical clarifications. . . then, of course, ignore those clarifications and do what you were going do anyways. . . ok.  It may be a bit too late in the evening to be typing so I'll just start posting pictures  :eek:

Let's see what's in the box, shall we?

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Another fine kit from Classic Audio Products of IL.  In keeping with the new no-nonsense anodized black look, this kit looks well laid out and intuitive to assemble.

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This build will feature the stepped grayhill gain switch option, so we begin by sorting the resistors for the gain switch and fader.

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Carefully bend the leads and install resistors to their designated positions.

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Bend the leads to hold resistors in place, flip the board over onto a nice, flat surface and solder from the back side of the PCB.

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. . . and trim the leads when finished.

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My aim with heat settings on my temperature-regulated iron is to limit the time the iron is actually on the component/PCB. I also try to  apply just the right amount of solder  to flow a smooth bead  that carries through a little bit to the top side of the PCB. . . all in the shortest amount of time practical so as not to damage the components.

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Next, sort the remainder of the resistors for the main PCB as well as the transistor and diodes.

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It's worth noting even though all of the small diodes on this PCB are the same that the tiny markings on the 1N914 diodes read:

91
4B

It doesn't hurt to confirm.
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Populate the resistors,

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and install diodes.  Orientation is important on the diodes.  Make sure the side marked with a solid stripe corresponds to the arrow screen-printed on the PCB.

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Diodes are populated.  Double check to confirm orientation is correct on all of these.

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Install Q1 transistor next.

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Next, locate the bag that contains hardware.

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And locate the Millmax sockets for the 2 DOA's.  Watch out.  They like to roll on the floor.

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Insert these from the back side of the PCB.

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Set soldering iron temp a bit on the hotter side and solder.  We want a little bit of solder to bleed over to the front side

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but not quite as much this. . . oops.  It's still ok. . . just not as pretty as it should be for an instruction set.

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Next, sort the capacitors for the main PCB.

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and watch out for the markings on this little bugger.  68pF.

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And populate the capacitors.  I start from the short ones and work my way up to the tall ones, but it doesn't really matter what order.

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Before I got to the larger electrolytics, I pulled the IC socket.

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Next, install the electrolytic capacitors.  Polarity is important on these. The solid line indicates the "-" side of the capacitor.

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on the radial caps, the longer of the legs is the "+" side.  Also, the solid line indicates the "-" side.

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Caps installed.

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chunger

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Location
Northern California
Next, pull these switches.

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And install onto the PCB

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Solder one pin and then check alignment with the screen printing on the front side of the PCB.  Make sure the switches are sitting flush to the PCB and are aligned as straight as possible.

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Solder in the rest of the pins after verifying alignment and making adjustments.

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repeat for the other 3 switches.

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Next, pull this toggle switch.

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SW2 fits on the back side of the PCB.

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IMPORTANT!  Before soldering in these pins, clip the leads close to the PCB.  The high pass filter board that goes directly above this switch will interfere otherwise.

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Solder after trimming the leads close.

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Next, pull the 2 grayhill switches.

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And install.

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Solder 1 pin only and confirm that the switch is positioned tight to the PCB and properly aligned.

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Install the 2nd grayhill switch and do the same.  Solder 1 pin and adjust for perfect alignment.

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When satisfied with the alignment, solder in the rest of the pins.  Be careful not to use too much solder and bridge the contacts.  If necessary, verify with a magnifying glass that the solder joints are clean.

Next, pull the stop pins and retaining stickers.  Be careful, if these pins fall on the floor, they may very well never be recovered.
The Grayhill switches now have factory set stops. There is no need for the stickers or pins.

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Install stop pins at the 12:00 position.
The Grayhill switches now have factory set stops. There is no need for the stickers or pins.

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And install stickers to retain the pins.
The Grayhill switches now have factory set stops. There is no need for the stickers or pins.

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Next, pull the EA2622 input transformer.

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Note the dot on the sticker on the transformer.  This indicates pin one.  Align pin 1 with the dot silk-screened on the PCB.

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Install a piece of double-stick foam tape.

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And install the transformer.

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Next, pull the hardware to install the 2 output transformers.

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And pull the output transformers.

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put a flat washer on 2 of the long screws.

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Install screws on the transformer.

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flip the transformer over and install another flat washer which will sit between the PCB and the transformer.

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And place the transformer on the PCB.

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Install lock washers.

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And then nuts.

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Tighten from the top side with a phillips head screwdriver.

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And repeat for the 2nd output transformer.

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Align both transformers with the screen printed boxes on the PCB and tighten them down.

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Carefully trim the leads to length, strip and tin the tips, and organize with some short strips of shrink tubing.

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And begin installing the transformer leads to their corresponding labelled terminals on the PCB.

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and repeat on the other transformer.

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iron is installed.  IMagine how many kits Jeff could sell if there could just stay in stock  ;D

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Next, locate this long header.

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And install onto the PCB.

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Solder 1 pin and align tight to the PCB and perpendicular.  After everything looks aligned, solder the other pin.

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Next, sort the components for the HPF PCB.

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Install the L-header first.

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I used a clamp to secure the header while leaving one pin exposed on the side.

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And solder that exposed pin first.

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Then, shift the clamp to the other side and solder the opposite pin.

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With the header tightly secured, solder the remaining pins.  OK. . . the method may be over-complicated, but it gets the job done.

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Pull push-button switches for the HPF board.

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And place onto the PCB.

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Solder 1 pin on each switch.

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And verify alignment on the front.  Adjust as necessary before soldering in the rest of the pins.

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Next, populate the electronic components.

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Pull mounting hardware for the HPF PCB.

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And install the brackets finger-tight only at this point.

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Lock washer goes on this side.

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Followed by the nut.

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Repeat on the other side.

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And the HPF PCB is assembled.

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chunger

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Next locate the caps for the pushbutton switches.

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The pair of black ones go on the high pass filter PCB that was just assembled.

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And the rest go on the main PCB.  Red (48v phantom power), gray, white gray in that order.

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Next, pull hardware to mount the main PCB onto the L-bracket.

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Start by inserting the screws from the bottom of the L-bracket.

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Tighten the rear standoffs all the way and install the front 2 half way only so the PCB can slide over and into position.

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Pull Hardware to set the high pass filter PCB onto the main PCB.

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Install the lock washer onto the screw.

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Set the HPF PCB onto the main PCB.

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And attach from the bottom with the screw/lock washer.  Finger tight will do right now.

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Carefully slide the main PCB assembly onto the L-bracket.

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Pull hardware to set the main PCB.

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Align the front of the PCB snug and square to the L-bracket and install rear star lock-washers and nuts.

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With the PCB in position, we can now tighten down the front standoffs.

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And install the small lock washers and nuts onto the front screws.

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Verify that the main PCB is square to to the L-bracket and tighten all 4 nuts.

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Pull hardware to mount the front of the HPF PCB onto the L-bracket.

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Insert the star lock washer between the L-bracket and the HPF PCB assembly like this.

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And insert small screw from the front and tighten down.

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Locate the front panel and install.

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Align the front panel to the 4 main PCB pushbuttons and to the L-bracket.  Then, install the 2 grayhill switch nuts (discard the Grayhill switch lock washers).

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Next, adjust the HPF PCB so the pushbuttons are aligned with the front panel.  The screws holding this in should only be finger-tight at this point so the board can move.  When happy with the alignment, tighten down these 3 screws to lock the HPF PCB into position.

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From the cutout on the back side of the L-bracket, solder the HPF PCB header to the main PCB.

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Next, pull the 5 LED's.

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Cut and bend the leads like this.  I chose to retain one short pin and one long pin when I cut the LED just for personal reference.

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Carefully position one red and 3 yellow LED's onto the main PCB from the bottom of the L-bracket.

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Notice the short leg of the LED's correspond to the silk-screened arrow mark.

Once happy with the LED positioning, solder the leads to the main PCB pads.

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Pull the 2 clear sections of heat-shrink tubing.

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cut these to reveal about 1/8" and slide them over the tall jumper near the front panel.

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Next, connect the green LED to this jumper.  Some bending will be involved.  Please excuse my mis-matched shrink tubing.  Shortly after taking the previous photo, I must have accidentally flung the supplied tubing piece across the room when putting the camera down and I could not find it, so I had to use another one from my kit which was not the same diameter.

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The LED will end up looking something like this.

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Make sure the short end of the LED corresponds to the silk-screened arrow mark on the PCB for this LED just like the others.

Carefully position the green LED and make any final tweaks necessary for a tidy fit.

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And solder into position.

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Next, I used some water on a Q-tip to clean off some of the residue left on the faceplate from installation.

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Pull knobs and shaft adapter.

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Use pliers to position both knobs in the 12:00 position (pointing straight up), and position the shaft adapter so the gap is facing down.

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Press the adapter onto the Grayhill switch shaft until somewhat flush with the top of the post.

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Install knobs.

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Next, pull the 2 colored stickers that go on top of the knobs.

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Peel off the paper backing and install.

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For this build, we will need 2 opamps.  I chose to use Gary Barnett's GAR2520 op amp kits for this build.  These are fast becoming my go-to op-amps for API-type builds and sound phenomenal.

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Pull the pins from the kits.

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and insert into the opamp sockets of the main PCB.  This positions the pins perfectly for soldering and also loosens up the sockets that can be extremely stiff the first time an opamp is inserted.  It is much easier to insert the pins one at a time like this.

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Place the GAR2520 PCB's onto the pins and solder in place.

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Pins are perfectly aligned and the op-amps are ready to be populated.  The documentation provided with the GAR2520's is VERY thorough and walks you step-by-step through the process.  A steady hand and an eye toward detail are required.  I will populate a pair to the best of my current ability.

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and opamps complete.

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Next, pull the IC that drives the green signal LED.

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and carefully insert into the socket on the main PCB making sure to align the dot with the notch on the socket.  Do not press the IC into position until you are absolutely sure all of the delicate pins are properly positioned in the socket.

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Note the IC's orientation.

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Next, install the 2 GAR2520 opamps or the +, -16V opamps of your choosing on the main PCB.

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The VP28 is now complete.  Humans win. . . again.  If all went well, it should run right out of the gate.

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I sincerely hope you've enjoyed this installment of "Build Jeff's Stuff' as much as I have and find this photo documentary helpful  ;D
 

bigevil

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Jul 24, 2011
Messages
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park place & boardwalk...

this comment box is now for sale.

Thanks for looking...






to the mods, this is only a joke.
 

jsteiger

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Messages
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Location
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bigevil said:
park place & boardwalk...

this comment box is now for sale.

Thanks for looking...






to the mods, this is only a joke.
Ouchy ouch!! Man that was Big....and Evil

So how much you want for it?

Haha, also a joke  ;) ;D
 

michal_k

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Nov 12, 2008
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France
wow, love the metalwork, especially the undercut screw hidden behind the front panel. impressive.
 

J Adams

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Feb 29, 2012
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Got my first one built.  Took around 4 hours but I think I can do my other one faster.  I built the 4 opamps while I was waiting on the 28s to get in stock so that helped.  Anyhow, just tested everything on it, and everything works, first try!  Won't try it out on some tracking till probably next week though  :(  I think the hardest part for me was getting the LEDs in there right, but even that wasn't bad.  Might just be bc its 5 in the morning and I need to go to bed.
 

jsteiger

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J Adams said:
...Anyhow, just tested everything on it, and everything works, first try!
Excellent news! Congrats!  8)

...I think the hardest part for me was getting the LEDs in there right, but even that wasn't bad...
They can be a little tricky the first time. After building a few dozen, I fly thru them in no time.  ;)
 

J Adams

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Feb 29, 2012
Messages
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I hit  2 very minor snags building the second one (my own fault), but still got it done in about 3.5 hours.  Again, everything works on it, first try.  Great design on the boards Jeff, can't wait to see how these fair in my sessions next week.  Even though they take a lot longer than the 25s and 312s I built, I think it was more fun as well.

Oh, and the reason I have both big knobs on one is because I don't have a small enough allen wrench for the small knobs but I wanted to at least test them both out.
 

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jsteiger

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Looking good man!  8)

What were the snags? Maybe it could help someone in the future not fall in the same rabbit hole.
 

jsteiger

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gevermil said:
When is the Entire Bundle avalible
They were available late last week but I was cleaned out of 2623-1's in a about a day. I have another batch being shipped out this Thursday so I should have them in hand Friday. That will put the VP28's "in stock".
 

J Adams

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Feb 29, 2012
Messages
4
I really don't remember, other than thinking some things were taking me longer than they should have bc I was tired.

What size allen wrench does the top knob use?  I have a ton of allen wrenches here but none small enough.  Stopped by WalMart after work tonight (only place open at 1AM) and they did't have anything smaller than what I have. 

These preamps (and gar2520s) are the only thing I have ever built or soldered.  I am glad I started with the 25s/312s before attempting the 28, and I thought even though the assembly guide was not as thorough as the other one you did, between that and the BOM I was perfectly fine and felt very comfortable with everything. 
 

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toby-e

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J Adams said:
What size allen wrench does the top knob use?  I have a ton of allen wrenches here but none small enough.  Stopped by WalMart after work tonight (only place open at 1AM) and they did't have anything smaller than what I have. 

Most set screws on knobs are 1/16" – it was a bitch for me to find one of those in Europe since it's right between 1.5mm and 2mm, and none of them will work  :mad:

Nice set of preamps you have there :) Can you describe the sonic differences?

-toby
 

jsteiger

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J Adams said:
...What size allen wrench does the top knob use?...
The small 3/8" blue pointer requires a .05" Allen wrench. The larger 1/2" clear pointer is 1/16". You will probably need to visit an Ace Hardware or something more "specialized" than Wal-Mart.  ;)

I am surprised that Imperial sizes are not readily available in the UK. I can go to any hardware store here and buy Imperial or Metric anything. Bastards.  :mad:

BTW, nice lunchbox!  8)
 

GregNey

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Newton, MA
Both of mine worked on the first try too. If you read the manual first and take your time it's very straight forward. The only "mistake" I made was using the wrong type of washer on some screws. Cheers Jeff- Thank you for your hard work!
 

tronax

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Jun 30, 2011
Messages
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Great job on this one, Jeff!  Successful build, took a few evenings of an hour here and there.
(only 1 leftover washer, and couldn't seem to find two lock washers, but I probably shouldn't build these things late at night!!)

In the studio now, comparing it to my other pre's... Enjoying it so far.
Thank you thank you thank you for the signal indicator LED!!!

-Chris

EDIT:  *love* it on guitar. driving the preamp gain hard results in some happiness. :)
 

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