DIY CAPI VP26DI on Hairball Element platform

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dissonantdissident

Well-known member
Joined
Sep 7, 2014
Messages
78
Hey folks,

So, I recently got a CAPI VP26, and boy has it lived up to the hype.  I also have the VP25, but I'm really digging the sound from the smaller output transformer.  So, I've been kicking around the idea of getting a couple more, with stepped gain, so that I can make a stereo pair, this time trying the GAR1731.  The only hangup is that I really wish there was a kit with a DI, like the VP312. 

Well, then I see these new Hairball Element kits, and there's the Silver one, that you can customize.  This is a bit out of my league, but I emailed Hairball, and they confirmed that I could use a EA2623, and to wire it like the EA1166.  Well now, I can't help but think that this could be the answer to my prayers.  So I'm going to try and build a pair of these, and I figured I'd try to pregame the build as much as possible, before I start ordering all of the parts, as there are a good deal of components that are transformer and opamp specific, that you've gotta source, yourself.  So, the goal is to mount a EA 2622, EA 2623, and a GAR1731 onto the board, in an attempt to get as close as I can to what a theoretical VP26DI would sound like.

So to the top of the things you need to figure out yourself, and I'm going to go down the list, as in the silver assembly guide:
1. Power filtering- Don't see any reason to ignore the suggested values.
2. Input load and zobel:  Another thread says 150k for load, and 10k and 220pf for zobel)
3. Output load and zobel:  Not sure on these values for the EA2623
4. Feedback/gain network:  This seems to be opamp-dependent.  Will need to ask what a GAR1731 likes.
5. Don't see a reason not to follow suggested values, in this section.
6. not a problem
7. not a problem
8. Seems like suggested values make sense.
9. Suggested values.
10. 10ohm, seems to be right.

So, there are a few things I need to figure out, for my BOM. 

Alternately, could I buy the resistor and cap sets from CAPI, and simply find where each would go, in the hairball circuit?  The would definitely have the zobel, etc for the EA2623. That sounds way too simple, but sometimes it's best not to overthink things.

Whatcha think?
 
I would build another vp26 and get a couple DI boxes. Maybe DIYREC ferrites? Or some of the others floating around.

Use the Silver kits to build something unique  8)
 
This sounds crazy, and I didn't actually build it, but I own a VP26 with a DI. If you'd like I'll post a gut shot for you when I get to the studio
 
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