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

[[silent:arts]]

for sure I will do the measuring

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

doesn't depend on beer ;D
my guess for a real ear test is end of october at some test concerts.
next project
(they have been the cause for me to DIY - always in the need of something never existed before).

 

[jsteiger]

...next project
(they have been the cause for me to DIY - always in the need of something never existed before).

Now that's some pretty cool stuff. I need to brush up on my Deutsch though I think. Did you notice, one of their web-shops looks like a heavily modified osc store?

Anyhow, keep an eye out for a little package. 8) I dropped a few love nuggets or goodies as Peter says for your AP extravaganza. I sent you one of Scott's SL-2520 red dots, a gar2520 and a Huntington 2520 from my personal stock. So, test away my friend. This will be interesting! 

Cheers, Jeff

 

[[silent:arts]]

... Did you notice, one of their web-shops looks like a heavily modified osc store?

haven't ever visited the shop until you mentioned it. yes. cool
some more guys I can ask for support  ;D ;D ;D

Anyhow, keep an eye out for a little package. 8) I dropped a few love nuggets or goodies as Peter says for your AP extravaganza. I sent you one of Scott's SL-2520 red dots, a gar2520 and a Huntington 2520 from my personal stock. So, test away my friend. This will be interesting! 

8) 8) 8) 8) 8) 8)
with my stock of different DOAs we will have more than 10 to test.
this will get very interesting. all test will be done according to the German broadcast norm called "Pflichtenheft".

 

[jsteiger]

Some t-pad advice...

Hey yall,

After a couple of help email-conversations behind the scenes, I have created a little PDF document that should make the t-pad wiring for my pre's a snap. I will also include this doc in the provided zip file for the future.

Anyhow, here's the pdf:


Have fun!

Cheers, Jeff

 

[[silent:arts]]

8) 8) 8)
cool, this exactly how I did it  ;D ;D ;D

 

[jsteiger]

*Attention* to all who have purchased the first run of these boards...

Thanks to Volker, [silent:arts], an error has been discovered in regards to the polarity being inverted at the input. It is a silly mistake that is at least easily rectified. I guess I will blame it on Murphy and his damned law as I have no other logical explanation!  

This is in reference to "Classic VP25 Rev A" and "Classic VP26 Rev A.1" only.

The schemo's are correct(mostly). C1 and C2 are reversed but that is of no real consequence at all. Basically, the mic input signal at pins #8 and #10 should be reversed.

The end result of this polarity reversal, can be done a few ways.

Option #1 is how the next revision of boards will be. It is theoretically the most correct way. Here is how I am handling the fix on my boards. Cut 2 traces and add 2 small jumpers.


Option #2 is much simpler as will give the same end result. All you have to do is reverse the 2 primary leads on the output transformer. The colors are different depending upon which version you have.


And that will handle it. Sorry about the error. I guess it's not the first time these things happen and it probably won't be the last. Still doesn't make me feel good but they sure as hell do sound good!  

Thanks and best regards, Jeff

 

[[silent:arts]]

Jeff,

thanks for offering the fix. no problem here with it.

have some time next week, where I will do the output fix first.
than do some measuring.
after that I will reverse it, and do the input fix.
than do some measuring.
I doubt there will be a difference ;D

and since there is a polarity switch and the sound engineers decide by ear no problem.
I'm just a measuring guy  ;D ;D ;D

 

[jsteiger]

...I doubt there will be a difference ;D ...I'm just a measuring guy  ;D ;D ;D

I also doubt there will be a difference. Will be interesting to see for fun.

In glancing down this page of this thread...I started to wonder if we should just have this conversation in private. Kind of like that anyhow...tap, tap, tap, check one two...is this damned thing on ? ?  :

Did you have the time to record any of your DOA tests? I am curious to see how they compare under scrutiny. I saw the pile of them on your bench in the "show me your workbench" thread. Cool! ;D

Cheers!
Jeff

 

[[silent:arts]]

Jeff - one thing to learn, my friend:
10 sold PCBs, one build  ;D
sometimes it looks like 100:1 

the DOA tests are done, and all DIY units are spot on !!!
just need some time to put the results in some form.

but to tease:
the gar2520 is very close to your vintage huntington.
only misbehavior: 1 dB less noise.

 

[jsteiger]

...the DOA tests are done, and all DIY units are spot on !!!
just need some time to put the results in some form.

but to tease:
the gar2520 is very close to your vintage huntington.
only misbehavior: 1 dB less noise.

Ahh Volker! !    That is some good info and a nice tease!

To the ears, which cannot be trusted, they are also very close.

I will have to speak with Gary to see if he can increase the noise a tad  ;D ;D

Take your time compiling the results. We will wait patently with baited breathe. 

best, Jeff

 

[jsteiger]

Hey guys,

Volker sent me a few links to some of the AP tests he has been running. He said to feel free and post them so I am.

Most are of the VP26 pre with various DOA's.

The first one is a vintage BAE racked 312.

**All of the AP graphs and test results have been temporarily deleted by [silent:arts]. Scott Liebers had noticed a difference in results to the tests he has ran. This prompted Volker to reevaluate his test procedure and criteria. I'm sure he will have this info back up soon. See his post a few down from here.**

Quite interesting I think. Plus, this gives us all a little taste of what Volker will be putting into the 51x website!

Very cool Volker! ! !  ;D ;D Thanks much for providing this info!  

Best, Jeff

 

[Skylar]

Volker...wow!

You've obviously put a considerable amount of work into this.

Thank you, and...thank you!
What an excellent source of information on DOAs!

I've got my VP25 channels up and running with Pier's APP2050s.
They sound great, but I'm waiting for the front panel to be engraved before I can put the whole thing together and rock.
I have a couple of DIY 990s that I tried swapping in there, but I think I feel the same way as Jeff...not my thing.
The APP2050s sounded great however.

I'll post some pics as soon as the front panel is here and the whole unit is put together.

 

[gar381]

but to tease:
the gar2520 is very close to your vintage huntington.
only misbehavior: 1 dB less noise.

  WOW !!!
Thanks for the nice review Volker !!!

(I'll have to work on increasing the noise ;D)

GARY

 

[[silent:arts]]

sorry guys, I deleted all measuring since some manufactures complained about it  

no, this is not the reason  

actually Scott Liebers SL-2520 curves he made are different to mine, and rechecking with other measuring equipment / set up tells me he is right. :-[

since I don't know if I have mixed up the curves, the AP at work is broken, the measuring routines of my colleague are faulty, I took all the files down. we don't want to mess with may be faulty measuring.
another thing I just realized while playing with Scotts SL-2520: there is a huge different if the DOA is just powered on or measured 20 minutes later.

anyway, I will check the AP, will write my own test routines and will re-check every DOA at home with an A2.
this will take some time, but we want real & proven results.

in the meantime I might buy some more DOAs for testing ...
thanks Scott for doubting the results, you have been right.
on the A2 I see even a peak at 20 KHz (after ten minutes on)

I feel very sorry for this (but you should always trust your ears anyway)
end of next week we should be ready again ...

 

[Tubemooley]

Volker..... Don't worry. Take your time. I would much rather wait for reliable test results. The fact that you pulled down the results because you're questioning your test procedure and your test equipment shows that you are honest and scientific. And two guys on two different continents (you and Scott L.) are working independently but collaborating on one inquiry. This is fabulous. Take all the time you need. And by the way...... I believe the "heat up" time phenomenon is real. I have no direct evidence of this. But the junctions have to heat up and stabilize for the best performance. Even at 25C room temperature, those junctions are going to be up over 50C I believe after running for 30 minutes. Possibly higher. Einstein had to wait three or four years for his theory of General Relativity to be independently confirmed experimentally. DW.

 

[ultra-alex]

finished two 26´ today. this is indeed a very relaxing build. perfect for a weekend afternoon. thanks for the tipp with the beer, volker! now i just wait for my frontpanels, some nice knobs and of course the 11 slot rack...  ;D
thanks jeff!
cheers, alex

 

[haima]

hey guys,

just about to mount my profile 4804 (aka 2503) output transformers on my VP25 boards - it seems that the mounting holes are plated and therefore appear to be connected to the ground plane... (sorry, i don't have a multimeter with me right now to check for sure).

so do i need to insulate the transformer core using washers or anything? the schematic doesn't show any connection to the output transformer core...

cheers,
Haima

 

[[silent:arts]]

yes, the output transformer core is grounded

 

[3nity]

nop dont insulate them!

 

[jsteiger]

As I packaged up a kit with a raw face-plate yesterday, I got to wondering how you guys who have the raw plates have finished them.

I would quite enjoy some pics if you have any.

BTW, Pan60 over at GS has an assembled VP26 with 4 different DOA's from members here at the Forum. He got it last week. We are just starting a little interview process that will include Ed, Gary, Scott, Pier and myself. Pan60 is of course completing a full product review in the way only he can! Should be quite fun and interesting not to mention some good "kudos" to our great forum here. 

Best, Jeff