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

[Seditionary]

yes -- jeff's build guide on the vp28 is awesome !  very, very helpful.  and these channels sound incredible. 

i finished 2 of these with op amps that worked on first fire up.  the only thing i had a bit of a problem with is one of the LEDs... in the build guide jeff recommends bending the amber LEDs at 45 degrees... i'd recommend not bending those quite so much... maybe 30 degrees or so... as they lay pretty flat on the board... if they are bent at too much of an angle and you push them in slightly at an angle, SNAP... you'll lose an LED in the faceplate... (which i did)... so i recommend only slightly bending these to fit into the hole. 

the vp28 sounds amazing with all the op amps i've tried! !  but the op amps AND THEIR CONFIGURATION definitely change the tone.

i've tried the vp28 with gar2520's and a mix of gar2520 and gar1731... i think i prefer the mix of gar2520 and gar1731... but even their position makes a difference !  i originally chose the 1731 in the position near the input transformer as it was a fatter signal when i was testing vocals through it after i had completed the build... but i just did a test running mixes through with both op amp configurations. although they both sound great... there really is quite a difference ! the 1731 closer to the input transformer really warms things up... but kind of smears the highs a lot like hitting tape... trying the test again with the 2520 closer to the input transformer (which is how dr. bill has his op amps configured (thanks dr. bill!)), it still has the tape like saturation vibe, but without smearing the highs so much! so setting it up that way -- 1731 near the output transformers, gar2520 near the input transformer is brighter and clearer, which i think is better for mix buss. not as muddy, but still technicolor saturated. it sounds incredible! !

thanks so much to jeff who is such an amazing dude. besides offering these amazing sounding circuits, he is a teacher. he almost always responds immediately, which is mind blowing and super human... and he gives you just enough guidance in order for you to learn and figure out more on your own. jeff steiger is a diy guru teacher electronic rock star.

 

[chunger]

Hey guys,

The photo build tutorial is now complete in broad strokes.  Please check for errors.  The preamp shown in the photos works right out of the gate, so I assume the build was at least mostly correct.  But, if any errors are spotted, please let me know immediately.

 

[OOF]

Jeff, the VP28s sound wonderful.  Great design. And I must applaud both you and Chunger for the tremendous amount of work it took to put together the build process to help us.  With all of the components packed so clearly and Chunger's crazy-thorough video, it's a breeze to build these.  thanks very much-- loving them.
david

 

[Stone]

Hey Jeff.  Just building 2xVP28s.  It is my first ever build and I'm a lot of fun doing it too! 

I have a quick question for anyone that may be able to help.  I'm having problems identifying the Ceramic Capacitors C3, C4, C6, C10/C11 (my multimeter isn't reading the correct values.)  Could anyone help me identify them?

102J/5A = As there are 2 of these I'm assuming this is C10/C11.  Is this correct?
82J/5A =
27J/5A=
221J/5A =

Thanks in advance for any help...it is greatly appreciated!

Stone

 

[jsteiger]

102J/5A = 1000pF/50V
82J/5A = 82pF/50V
27J/5A= 27pF/50V
221J/5A = 220pF/50V

 

[Stone]

Thanks Jeff!

 

[Stone]

@Jeff.  Newbie question here!  Almost finished building both VP28's but accidentally cut one of Output Transformer wires too short.  Is it OK to solder the wire to make up the length and then protect it with either electrical tape or heat wrap?

Thanks!

 

[jsteiger]

Yeah, just extend it with a cutoff piece and make sure the solder joint is good and solid. Then use a piece of heatshrink on it.

 

[Stone]

@Jeff.  Thanks!

 

[Cgaines]

Hey Jeff, I've had my vp28 built for awhile now and love it! I do have a question though. Is the vintage style gear noisier than new gear? I just built a u87 clone and it requires a lot more gain than my other mics. Since I had to turn up te gain I noticed a low level him I hadn't noticed before. Is that normal or should I check something?

 

[jsteiger]

The pre should be very quiet. What you are describing doesn't sound normal to me. It sounds like maybe a grounding issue of some sort. Maybe something rack or cable related? Maybe mic related? If the pre is built correctly then it will not be from it. Is it like this with all mics? I have had guys use the VP26 with ribbons and gain wide open. They have commented on how surprisingly quiet the pre is a full gain. The VP28 will preform in a similar way with the fader set at 0dB. Increasing the fader level will of course increase whatever noise and/or hum may be in your signal already.

Dunno if this helps or not.  :-\

 

[Cgaines]

Well after doing some more tests I've decided it has to be the mic... I only have the problem with that combination though. Any of my other mics plugged into your pre are extremely quiet with the input gain wide open. But my mic on other pres doesn't make any noise. Just a weird thing I guess. I'll go back and ground my mic every possible way I can and see if that rids me of my problem.

 

[Stone]

I just finished building 2xVP28's with a gar2520 closest to the input transformer and 1731 closest to output transformers.  This was my first ever DIY project, let alone first ever time near a soldering iron(!) and I couldn't be happier with the results. 

After completing the build I plugged them in and was blown away!  Not only did they work straight out of the gate but they sound absolutely glorious!  It's hard to describe in words but they make you feel like you are right in the room with the music, and not listening on speakers. 

Jeff I cannot thank you enough for designing and making available such a fantastic piece of gear.  I can't believe I lived without it for so long!  I also wanted to thank Chunger for his photo's and comments.  They were invaluable and I honestly don't think I could have completed this build without them.  Thanks for putting so much thought and time into them.

Anyway...just wanted to share my excitement!  I'm looking forward to testing some different op amp configurations but am loving the combination of 2520's and 1731's at the moment. 

Thanks again Jeff and Chunger!

 

[jsteiger]

Excellent news and congrats on a successful build!!

 

[rCHESS]

Really diggin the vp28's.  Just completed my second one and all I can say is they sound GREAT!!!  Thought I would add a photo of my Classic API stuff so far.  Thanks Jeff, Chunger,  and the list could really keep going (there is a lot of great info around here).  I have have learned a lot from this forum and am having a blast with the builds! 

 

[New Soul Rebel]

Yahoo! About to build my first VP28's. Here goes... toward anarchy and oblivion!!!  : ;D

 

[freestylemovement]

Hi,
i'm a first time VP28 builder, i have signal, 48v etc.  sounds beautiful except a couple things.

in Mic mode the signal is very very very low.

in Line mode (when patching another pre or line level signal) the level is more acceptable and sounds very nice.

but still both gain pots are at maximum level which doesn't seem right.

but in either case the HP Filter needs to be in for signal to work.

i know it's a shot in the dark, but has anyone encountered this issue  before?

 

[jsteiger]

The HP filter needing to be engaged sounds like maybe some cold solder joints on the HPF switches and/or 5-pin header. The signal is routed onto that small board and thru the switches even if not engaged. This could possibly be the cause of all your troubles.

As with any build like this, are both opamps known to be good, solid and working? Who built them? Did you follow the DOA install page on my site?

 

[jmcnul]

Hey all,

Just got finished with a 28 and I'm getting a crazy hot signal, like I need a pad on any source when mic is engaged. Is this normal? 

 

[kante1603]

Hey all,

Just got finished with a 28 and I'm getting a crazy hot signal, like I need a pad on any source when mic is engaged. Is this normal?

Hello and welcome to the forum,

can you explain your signal chain a bit more in detail?
What microphone do you use and what sigmal are you picking up?
What is connected after the mic pre,can you monitor it at this point?
At least we should know about what level we're talking when you say it's a "hot" signal.
Also interesting if the gain switch shows a normal action concerning the steps,maybe you've swapped gain resistors?

Best regards,hope to have helped,

Udo.