jsteiger

***ATTENTION!! The stepped VP25 & VP26 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!!***

As the title states, this is the official support thread for the VP2X, 500 series mic pre build that can be found at our capi-gear.com website. Per a private email request, I felt I should start this thread.

So, if you have any questions feel free to let them fly.

I will also post a few assembly pointers as I have no true "assembly guide". It is a super simple build. About as vintage API as you can get.

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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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Here are some general tips that I like to send out when guys are having trouble. It's a good place to start.

First, what DOA is it? A pre-built or a DIY? If it's a kit, swap the opamps and see if the problem follows. Also, have you seen the DOA install page DOA install I highly recommend never testing a new preamp build with a new opamp build. There are too many variables and you may never know what the issue is. If it's a pre-built opamp from me, chances are, it is not bad. Gary and Scott both run them in for many hours before sending them to me.

Have you completed the pre-start tests at the end of the old VP2x Assembly Guide? If you are building a VP312, the C to O DCR value will be about 8.5 ohms. Make sure all voltage readings are correct.

Double check all component values and make sure caps are facing the right way. Resistors cannot be measured once both ends are soldered to the PCB. You will get many odd readings. Either use the color codes to verify or one end must be desoldered to get an accurate DCR reading.

Double check the lead colors/pads for the output transformer. Take your time and be sure. Countless times I have heard back from folks who checked and checked and then a few days later realized that some of the leads were placed incorrectly.

Next, reflow the solder on the 3 pushbutton switches.

If it's the Grayhill stepped gain option, do you have 25k when measuring between the to outside pins of the switch? If not, check with a magnifying glass as there probably is a short between some solder pads. These can be checked end to end by probing between adjacent pins. You should get the resistance of each of the R's on the pdf as you work from one end to the other.

Scan the board and check all solder pads with a magnifying glass of some kind. The biggest issue, besides what I mentioned above are cold solder joints. Sometimes they can look fine but not be good.

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Cheers, Jeff
« Last Edit: September 21, 2015, 08:14:09 PM by jsteiger »
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Skylar

True, this is a simple build, and a very awesome project.

It's a snap to put together, the PCB is probably the easiest I've ever done.
Lot's of space [makes me not want to do another tiny DOA!]

Can't wait to hear how they sound!



...just waiting for input transformers...



Thanks for sharing this Jeff!



I'm going to put 4 of these in a 3U chassis with a +/-16V/48V power supply.
Here's the frontpanel layout I'm going for:





geoff004

Got both pres almost finished up last night
Here's what I'm wondering:
I opted to go without the output attenuator.  What do I wire to what for output?

Also, with the phantom power - does the switch get wired to points 1 and 2 (next to where it's labeled SW1)?
Thanks

jsteiger

Got both pres almost finished up last night
Here's what I'm wondering:
I opted to go without the output attenuator.  What do I wire to what for output?
Hi Geoff,
For the VP25 build with no attenuator, the Blue wire from the output x-fo goes to Pin #2 where the silk says "Opt-Blu" and the Orange wire goes to Pin #4 that is labeled "Opt-Ora". Directly left of the gold fingers.

Quote
Also, with the phantom power - does the switch get wired to points 1 and 2 (next to where it's labeled SW1)?
Thanks
I have them shown on schemo with a number inside a circle. You are correct though, to 1 and 2.
Cheers, Jeff
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3nity

Looks very nice.
To Jeff: why you have pushbuttons and a toggle switch? why dont you use another pushbutton? looks very nice tough..
thanks.
Life is a path, death the destination.

jsteiger

Looks very nice.
Thanks 3nity.  ;)
Quote
To Jeff: why you have pushbuttons and a toggle switch? why dont you use another pushbutton? looks very nice tough..
thanks.
A few reasons really. I wanted to separate the 48V from the other switches to help avoid an accidental ribbon problem. I also wanted a little different look than most of the 4 button 500 pres.

Lastly, which is a 2 part answer, I was happy with the boards layout this way. Gave me more freedom to not have another PB footprint crammed in there. I have another pre in the pipeline that has a very similar layout to this with a lot more components. I am able to use most of this layout and then just "add on", if that makes sense. It will make more sense when I get the other one out there.

Thanks, Jeff
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DIYnoob!

any idea how these sound? just like the 312 or better?
I touched two conductors today...the conductor with AC rattled my mouth, the one with DC kept it shut :)

3nity

@ Skylar.
You plan to hold the L bracket against the front panel by screwing the 2 pots?
looks nice! are those 990 modded to run on +/- 16V?

Thanks..
Life is a path, death the destination.

Skylar

3nity,

I think I will do a combination of small L-brackets on the big aluminum L-bracket to hold it to the bottom of the chassis as well as using anchoring the pots to the front panel.
I'm going to experiment and see what works best.

Correct, the 990s are mnats modded to run at +/-16V.

I'm going to try out some different DOAs in these pres...again, see what works best.



Jeff,
Got the input transformers on Monday!
Now, I'm just waiting for some PSU parts from Owel, and I can fire 'em up!

[silent:arts]

if you use 990 DOAs in a custom rack with a custom PSU I just would run them at +/- 24V
SSLtech: No bypass, I don't believe in it.
Gus: I think this build might have problems with DIY builders that don't know things like ohms law.


Skylar

Well, other DOAs I might try in there may require +/-16V, so I decided to stick with that.

But it's an adjustable power supply, so maybe I will un-mod the 990s back to +/-24V.

I guess that should increase headroom, correct?

jsteiger

any idea how these sound? just like the 312 or better?
They sound a little different than a vintage 312 card. They are similar for sure...from the same loins, if you will. To my ears, these pres are slightly tighter and a bit more focused in the mids and low mids. The 312 is a "c" hair brighter/more open in the top. Keep in mind though, the 312's we compared with, had the old Jensen 110K input transformers which are 1:8. I did not closely look at the rest of the card. It was an old BAE racked card.

On that note, these boards could quite easily be populated exactly like a 312 if one would want. Jumper over the coupling caps and series resistor. Next, leave out 2 decoupling caps and a post DOA load resistor. Oh, and use the 2503 version.

You plan to hold the L bracket against the front panel by screwing the 2 pots?...
This is how my face-plate mounts as well. Held by the pot nuts.

Hey Skylar, couple of questions.

I noticed you went flying leads on the 25K pot instead of PC mount. I'm guessing for versatility in your rack?? I think I mentioned an 1/8" temporary spacer between pot body and board. (See the [silent:arts] post a few down for a much better solution). I wanted the pots centered in the panel.

Speaking of your rack, how is that coming? Did you order it or are you manufacturing it? Solidworks is darned cool!

Cheers, Jeff

« Last Edit: May 30, 2009, 03:51:42 PM by jsteiger »
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Skylar

Jeff,

Yes, I didn't board mount the pots because I'm doing a custom front panel.
I just wanted to be absolutely certain that the shafts will line up with the holes on my front panel.
Leaving them free from the board gives me some wiggle-room.


I'm using a par-metal rack with a custom front panel.
I was hoping to have the front panel done by ddt, but I haven't heard from him in a while.
So, I may just have the holes cut by FPE and then have the 2-color silkscreen done locally.
Not totally sure how I want to have the front panel done yet...a lot of options.

DIYnoob!

sorry about getting of the subject...but has anyone heard how the VP25 or VP26 sound in comparison to API kike pre's?
I'm very interested in purchasing, and you guys seem like you're enjoying the pre's..

Thanks!
I touched two conductors today...the conductor with AC rattled my mouth, the one with DC kept it shut :)

[silent:arts]

went off earlier from work today to discuss my parcel out of the customers, took only 1 hour  :o  ;D

what a great project - went home, opened a beer, opened the parcel, fired the soldering iron up - and the pre was finished before this first beer was empty  :o :o :o
drinking now the second one to Jeff.

this is a really very fast and easy project.
now, when the knobs I want are in stock I will order a second one.



will do some measuring tomorrow if anybody is interested,
and I think I will do a little mod to have a phantom power LED (easy)

Jeff, thanks for bringing this to us  :) :-*

btw, if you don't have an 1/8" cardboard handy to solder the gain potentiometer (you won't in europe):
I did completely mounted everything with the unsoldered potentiometer.
the PCB brackets can be soldered from top  ;)
disassemble and solder the bottom.
SSLtech: No bypass, I don't believe in it.
Gus: I think this build might have problems with DIY builders that don't know things like ohms law.

jsteiger

went off earlier from work today to discuss my parcel out of the customers, took only 1 hour  :o  ;D

what a great project - went home, opened a beer, opened the parcel, fired the soldering iron up - and the pre was finished before this first beer was empty  :o :o :o
drinking now the second one to Jeff.
Nice Volker! Was the beer warm by the time you finished? Wait, I forgot, it was maybe warm when you started!  :)

Quote
this is a really very fast and easy project.
Yes, but there seems to be a lot of mud-slinging going on these days in regards to "paint by numbers". My kit falls into that category completely. Is that a problem? I don't think so. I would have killed for a kit like this 15-20 years ago!

Quote
...will do some measuring tomorrow if anybody is interested
I have to warn you, it won't look pretty. Phase shift and distortion for sure, but in a very pleasing way. The first time we AP'ed a mic input on my board, we thought channel 1 was f-ed up. Then we went to 2, then 3 and all were f-ed up looking in the same way! A big part of it is Ed's 2622. The best measurements that you can take on these pres, is taken with the ears.  8)

Quote
...Jeff, thanks for bringing this to us  :) :-*
No problem Volker. Been very much a pleasure. And :-* back at you with a little :P on the side.

Quote
btw, if you don't have an 1/8" cardboard handy to solder the gain potentiometer (you won't in europe):
I did completely mounted everything with the unsoldered potentiometer.
the PCB brackets can be soldered from top  ;)
disassemble and solder the bottom.
Now I feel like an idiot! That is a much easier, cleaner and more accurate way for sure! German ingenuity at it's finest!! The joys of plated thru-holes. BTW, did you like the massive solder pads?

Now, please report back when you've had the chance to A-B with you vintage BAE racked 312's. Curious on the input x-fo on yours. Is it AP2622 or JE 110K? The 110K will be a little "brighter" I believe.

Thanks and regards, Jeff
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[silent:arts]

Nice Volker! Was the beer warm by the time you finished? Wait, I forgot, it was maybe warm when you started!  :)
cold. up to the last sip.

... there seems to be a lot of mud-slinging going on these days in regards to "paint by numbers". My kit falls into that category completely. Is that a problem?
well I didn't bought a kit. but nearly. ;D
there are not too much parts in here, but since most parts are somehow special it makes sense buying it in kit form.
the capacitors have some special values, and some have a specific design / footprint. offering them for a perfect fit is great. the potentiometers aren't of the shelf too, and I hate metal work.

the "paint by numbers" - in my understanding - is more like people demanding this BOMs, Kits, what ever. I don't want to feel guilty if I don't offer this when selling just PCBs for a project.

for the measuring:
since there seams to be no interest here don't worry ;D
[and yes, the measuring doesn't say anything about sound - but is a part of my paying-job, and I'm curious]
anyhow, I will do comparable measuring against my BAE, which is with a Jensen input.
will mail you the results.

thanks again for the work you put in this.
you might have seen I try to sell another (very good sounding) API "clone" in the Black Market. they just don't fit the format I want to use in the future anymore ...
« Last Edit: May 30, 2009, 06:26:25 PM by [silent:arts] »
SSLtech: No bypass, I don't believe in it.
Gus: I think this build might have problems with DIY builders that don't know things like ohms law.

canidoit

I like how this is for the 500 series. I have a lunch box and I would like to know if you will be making an EQ kit in the future with the same way you are selling your pre-amp kits. It would be great if someone was doing the 550a or 550b thing.
iva dunit formerly known as canidoit

jsteiger

I like how this is for the 500 series. I have a lunch box and I would like to know if you will be making an EQ kit in the future with the same way you are selling your pre-amp kits. It would be great if someone was doing the 550a or 550b thing.
550a's and 550b's are no simple task. I have many other projects if front of me that I would like/need to do first.

However, thanks to the fine work of Peterc, you can find a kick-butt version of the API 553 in this thread. Now is the time to get in on this. I am.  8)
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jsteiger

...for the measuring:
since there seams to be no interest here don't worry ;D
[and yes, the measuring doesn't say anything about sound - but is a part of my paying-job, and I'm curious]
anyhow, I will do comparable measuring against my BAE, which is with a Jensen input.
will mail you the results...
Volker,

By all means, test away my friend. Direct comparisons will be interesting. And please, post the results here.

As a reminder (I know you are well aware), there should be a noticeable difference between the 2 preamps, especially in THD+N and of course Phase.

When will the "ear" tests take place? You may need more beer for that.  ;)  :D

Cheers, Jeff
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