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

looks great jeff!

i'll have a read when i get a chance & let you know if i spot any typos  

1st Class Jeff.

Very Nice  

Just about any beginning DIY guitar cord solder guy with this manual
should be able to build a VP2x with GREAT success.  Lots of good
tips for us old timers too!!  No one should be afraid to try
this assembly as the manual is bullet proof. Looking forward to building mine.

GARY

what a great guide. don't want to know how many time you put in this.
I'm sure even my wife, no - even my daughter could finish one without my help.
unsure of the pets since they don't speak english.

great work Jeff !!!

The guide looks great. I wish I had waited a few weeks until it was available before I built my first two. But the good news is I got my second pre working today. Thanks to Jeff and haima for their help with troubleshooting techniques. Your instructions were great and introduced me to some new circuit troubleshooting concepts. That is one of the great things about his site, the way you guys offer your support. Now I want to build a pair with different transformers and DOAs for another flavor in the Lunchbox.

Thanks to Jeff for a great design and to Gary for an awesome DOA. What else you guys got up your sleeves?

surfkat said:

The guide looks great. I wish I had waited a few weeks until it was available before I built my first two. But the good news is I got my second pre working today. Thanks to Jeff and haima for their help with troubleshooting techniques. Your instructions were great and introduced me to some new circuit troubleshooting concepts. That is one of the great things about his site, the way you guys offer your support. Now I want to build a pair with different transformers and DOAs for another flavor in the Lunchbox.

Click to expand...

Hey very good news surfkat! I am curious to hear what the problem was, if you don't mind. It may help someone else in the future.

What else you guys got up your sleeves?

Click to expand...

Well...to take a play from Peter Purpose's playbook, "a bunch of hair and some flabby skin!".

Cheers, Jeff

It appears that one leg of my Pad switch was a cold solder joint. I had originally suspected this and I finally confirmed this with Jeff's method of troubleshooting. Not sure why I did not find it sooner but it was all part of my DIY lesson and now I am a tiny bit smarter. I plan to record some guitar tracks today with these pres and see how they sound. Thanks Jeff!

surfkat said:

It appears that one leg of my Pad switch was a cold solder joint. I had originally suspected this and I finally confirmed this with Jeff's method of troubleshooting. Not sure why I did not find it sooner but it was all part of my DIY lesson and now I am a tiny bit smarter. I plan to record some guitar tracks today with these pres and see how they sound. Thanks Jeff!

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Cool deal surfkat. Let us know what you think after some tracking time.

Best, Jeff

surfkat said:

It appears that one leg of my Pad switch was a cold solder joint. I had originally suspected this and I finally confirmed this with Jeff's method of troubleshooting. Not sure why I did not find it sooner but it was all part of my DIY lesson and now I am a tiny bit smarter. I plan to record some guitar tracks today with these pres and see how they sound. Thanks Jeff!

Click to expand...

[EDITED after I realized my problem was with in the Phase Switch and not the PAD switch]

The Phase switch is in the middle of the 2 other pads, so after um place them , you cannot solder it from the top of the board.

Jeff, maybe you should add in your guide and advise so that people, place the Phase switch on the board before the other 2 switches.
Solder it's pins  from top and bottom of the board, and only place the other switches after hand.

what do you think?

it isn't really necessary to solder from top,
it is just comfortable.

I soldered from the bottom (only).
except the gain Pot at the beginning

i agree - i generally always solder only from the bottom, unless there's a particular reason to do the top of a component...

not that it hurts to solder both sides, but i wouldn't sweat it.

i usually heat the pad only first for a half a second before touching the iron to the component leg - tends to make the solder flow INTO the via, rather than staying at the top.

[quote author=haima]
i usually heat the pad only first for a half a second before touching the iron to the component leg - tends to make the solder flow INTO the via, rather than staying at the top.
[/quote]

This is a great tip. Thanks.

I am wondering if anyone has built this pre with other transformers that fit this layout and if so which models. I am thinking of doing that and I am open to suggestions. While I love this vintage API sound with Ed's trannies I might like to find something different for a contrast. Anyone tried Cinemag or Jensen on these?

I haven't tried Cinemag or Jensen, but I made one with a Carnhill 9045 input, and I like it alot.  You have to get creative with mounting it, mind you, as well as changing other components in the circuit, which makes it a bit more involved than the straight-up VP25, but the end result is potent, IMHO.  I had a Purple KDJ4 in for the op-amp at first, but I have PPA's 2055 in there at the moment and I like it alot.  Not that the Purple was bad in any way at all; it kicks ass.  The upper midrange and highs were different with the 2055, though, in a way that I like.  The output was the 2503.  Its more or less the same circuit as an Eisen "neveish" that I built a while back with the tables on their site, but with EA-2503 instead of the Profile 4804 that I had in the neveish, and, ultimately, the 2055 instead of the KDJ4.  Oh and I left out the attenuator, mostly cuz I'm cheap, and I was concerned about there being enough space for the 9045 with it in there,  and I knew the output would be more tame than the VP25.  BUT I think I'll put one in eventually because it WILL fit and its a nice feature.  Thanks, Jeff 



ben

bdubya - I would be curious to see how you mounted those transformers. Maybe you can post a pic or two.

surfkat said:

bdubya - I would be curious to see how you mounted those transformers. Maybe you can post a pic or two.

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Hey surfkat.  Will do as soon as my wife hands over the camera.  She's the visual, I'm the audio.  I located it more or less where the 2622 would go, but moved resistors to the underside of the PCB as needed to free up more topside space.  I then used permanent double-sided tape tabs, 4 of them, placed on the pcb surface, but not over any traces, as I'm uncertain if the tape will interact with the pcb over time (the package says its good for plastics, but better safe) to hold the transformer snugly in place.  I thought about using little L-brackets with the existing mounting screws of the 9045, but didn't really want to drill up the PCB that much.  The tape, while a bit domestic, worked nicely for me.  I really will post some pics in the next couple hours/days. 




ben

Jeff I am wiring up the VP26  in and out xlrs.
Is it input (high to pin 2) and (low to pin3), audio grd. to pin1?

Thanks PJ

pjdiy said:

Jeff I am wiring up the VP26  in and out xlrs.
Is it input (high to pin 2) and (low to pin3), audio grd. to pin1?

Thanks PJ

Click to expand...

http://51xaudio.com/alliance/pinout.html

Denyle Guitars said:

pjdiy said:

Jeff I am wiring up the VP26  in and out xlrs.
Is it input (high to pin 2) and (low to pin3), audio grd. to pin1?

Thanks PJ

Click to expand...

http://51xaudio.com/alliance/pinout.html

Click to expand...

Hey PJ, Denyle beat me to it!!!

Connect your shield to pin 5. Use the pin-out info on that 51x link for the rest of the connections.

If I'm adding a vu meter to a vp25 I would add it off the extra winding of the 2503, right?  (I can't remember what the lead colors are offhand).  Of course with the meter's proper external resistor.

I tried doing that, but I think something is funny because the meter shows more level when the tpad attenuator is all the way down then when it is all the way up with the same input signal.  
Is this normal?
Any insight would be mucho appreciated!
Thanks!

Edit:  Nevermind...made an absurdly stupid mistake!!!!  Insert pic of guy banging his head on a wall!!!!

Hi guys, I just recently came to read more often around here and stumbled upon the VP2x when sneaking how the 51x alliance is doing in the meantime...
I have to say I am pretty impressed by the build manual you did, Jeff!
This is a great job done right.
I remember when I first tried to do a fabio board with all those options and bar/non documentation really, assuming everybody who starts building a 312 copy is able to figure all out in DIY style or discussing it in looong build threads. (No offense against fabios boards, they were really cool.)
Your VP's are a different beast really and I hope many will do them, pushing the idea of 51x diy lunchboxes forward.
I think they are a great opportunity for beginners to start sincere diy, because everything is well-thought and build guide is exceptionally well made.

Phew...had to be said.

Now I have a general question about output transformers in 500/51x style that I stumbled upon reading the build guide.
I remember the API style out trannies are not really lightwights, so to speak. Due to 500/51x card concept, the out trannies are mounted on-board. Since launchboxes might be moved from time to time (to live events or other studios), how is mechanical stability taken into account? I have seen (rackmount-style) units where trannies broke the pcb due to fast 'tour-style' movements of the case. Did anyone experience something similar with lunchbox modules? Or, is there a possibility e.g. in the 51x cases to mount heavy transformers off-board in the case? (I know, this may be a tradeoff against fast swapping of modules.....)

Kind regards,
Martin

no 200kOhm reading on the V= lug of the op amp section. readsing are 200-500Kohms for every other lug test. The lug tests for V+ are not coming up