[BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread

[jsteiger]

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.

 

[qmp audio]

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

 

[New Soul Rebel]

same problem
« Sent to: New Soul Rebel on: October 27, 2012, 05:47:56 AM »
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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

 

[Piscolabis]

Hi,

Please Help!!!



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

 

[jsteiger]

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.

 

[Piscolabis]

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

 

[jsteiger]

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.

 

[Piscolabis]

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

 

[jsteiger]

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.

 

[Piscolabis]

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?

 

[jsteiger]

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.

 

[Piscolabis]

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

 

[jsteiger]

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.

 

[Piscolabis]

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

 

[mulletchuck]

Are there any dudes in California near Agora Hills who have these?  My buddy is interested in comparing them to his 512C. 

 

[dandeurloo]

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.

 

[mulletchuck]

lol sadly, my buddy is ignorant about these things, and refuses to believe that DIY stuff sounds better than name-brand stuff. 

 

[jsteiger]

lol sadly, my buddy is ignorant about these things, and refuses to believe that DIY stuff sounds better than name-brand stuff.

Haha.

 

[mulletchuck]

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. 

 

[jsteiger]

Yes they will match.

Congrats on the repair BTW!