HellfireStudios

Re: Neumann U87 vintage circuit build thread
« Reply #100 on: March 26, 2012, 04:03:07 PM »
Boards just arrived. They look great. Thanks.

Does anyone know what SPDT (on-off-on) switch will fit on the new PCB (preferably in place of the connector at the bottom of board two) for the pattern selector?
The Mountain sub-miniature, right-angle, pc-mount switch (Mouser# 2MS3T2B2M6QE) might fit the bill, but I'm not sure whether the overall length of .79" might incur interference from the transformer housing. Mouser# 633-G13AP is a sure-fire fit, but it maxes out at .4 VA and 28VAC/DC. Would this work, or is it too underspec'd? Any suggestions would be greatly appreciated.

-James-
"Tommorrow is just yesterday in reverse. Just like friends are enemies in reverse." -Gary Busey


KasperNyhus

Re: Neumann U87 vintage circuit build thread
« Reply #101 on: March 26, 2012, 05:05:05 PM »
Hi guys

I can't figure out exactly how to calibrate R11.

I have a scope and use my soundcard as tone generator

I have tried to inject a 1k sine into the FC cap spot (without the capsule) but where do I put the ground leg from the soundcard - its a balanced signal but I only need the hot and the ground wire, right? Is the FC Bdy the spot for the ground wire?
And the test probe of course goes to the drain of the transistor but where to put the ground leg from the test probe?

Can someone please tell me - really slow - how to use a scope for calibrating these microphones

Sorry for being such a noob

/Kasper

Re: Neumann U87 vintage circuit build thread
« Reply #102 on: March 26, 2012, 05:08:46 PM »
Tuning Pointers. Hope this helps

with nothing connected to the  Front Capsule nor Rear Capsule ( important )For the sine Tone Method and THD Method : use the big RT and SW Pad on the board,  RT + ,SW -
feed it 0db (0.775VAC) at 1Khz and tweak the pot , if using your Daw as sine tone ,you should be able to hear what come from the mike with headphone or something you need to be able to ear separtely what come from the mike,  tweak the pot fully in 1 way and then fully the other way you should ear the sounds come louder and then get to almost dissapear, what you need to do is to tweak just after it becomes louder and there is no more Fizz in the sounds, you will clearly ear fizzing when the FET opens, just a bit past this point is the good approximative Bias, if you go too Far the Signal will becomes fizzy again but more subtile past this point.( easier to see on a scope) At this point the method is the same for using the Room capture demo software with the THD Meter you only use the THD Meter as an indicator , when the FET opens the Meter goes up at near 25-30% THD so you can clearly see what happening the more you tweak past the opening point the Less THD on the Meter until your reach about 0.4% thd that is fine. if you go too far the THD will slowly rise backup as the fizz in the sounds as the sine symmetry seen in a scope meter, doing it a couple of times is good pratice and you can actually verify your method with the ending drain Voltage if the ending voltage makes sense.

Hope this helps,
Dany,

Re: Neumann U87 vintage circuit build thread
« Reply #103 on: March 26, 2012, 05:12:55 PM »
Hi guys

I can't figure out exactly how to calibrate R11.

I have a scope and use my soundcard as tone generator

I have tried to inject a 1k sine into the FC cap spot (without the capsule) but where do I put the ground leg from the soundcard - its a balanced signal but I only need the hot and the ground wire, right? Is the FC Bdy the spot for the ground wire?
And the test probe of course goes to the drain of the transistor but where to put the ground leg from the test probe?

Can someone please tell me - really slow - how to use a scope for calibrating these microphones

Sorry for being such a noob

/Kasper

Relating My previous post you can set the scope,  the goals is to see the sine loosing its symetry on the top, happens when you hit the FET opening and then tweak until the lower portion of the sine wave looses it's symetry and then you back off the number of turn in the middle of that, so lets say 5 turn from loosing sym on top to loosing sym on bottom you would back off 2.5 turn from the bottom symetry shift.

please use the RT(+) and SW(gnd) pad for the sine tone calibration , you actally need to monitor the outup of the mic rather than the Drain Voltage, you will need your mic plugged in to a preamp also. and you can also use the Room cature program to Measure THD from the mic output wich i find more precise.

Dany,

KasperNyhus

Re: Neumann U87 vintage circuit build thread
« Reply #104 on: March 26, 2012, 05:24:02 PM »
Hi guys

I can't figure out exactly how to calibrate R11.

I have a scope and use my soundcard as tone generator

I have tried to inject a 1k sine into the FC cap spot (without the capsule) but where do I put the ground leg from the soundcard - its a balanced signal but I only need the hot and the ground wire, right? Is the FC Bdy the spot for the ground wire?
And the test probe of course goes to the drain of the transistor but where to put the ground leg from the test probe?

Can someone please tell me - really slow - how to use a scope for calibrating these microphones

Sorry for being such a noob

/Kasper

Relating My previous post you can set the scope,  the goals is to see the sine loosing its symetry on the top, happens when you hit the FET opening and then tweak until the lower portion of the sine wave looses it's symetry and then you back off the number of turn in the middle of that, so lets say 5 turn from loosing sym on top to loosing sym on bottom you would back off 2.5 turn from the bottom symetry shift.

please use the RT(+) and SW(gnd) pad for the sine tone calibration , you actally need to monitor the outup of the mic rather than the Drain Voltage, you will need your mic plugged in to a preamp also. and you can also use the Room cature program to Measure THD from the mic output wich i find more precise.

Dany,
Thanks Dany I'll try that

But if I need to monitor the mic output I guess I need the trafo? still waiting for my cinemag...

Re: Neumann U87 vintage circuit build thread
« Reply #105 on: March 26, 2012, 05:32:54 PM »
I do have to mention that the SW(gnd) and the RT pad are the bigger pad one on the PCB 1 , not to be confused with the traffo pad
D


Re: Neumann U87 vintage circuit build thread
« Reply #107 on: March 27, 2012, 02:02:22 AM »
Boards just arrived. They look great. Thanks.

Does anyone know what SPDT (on-off-on) switch will fit on the new PCB (preferably in place of the connector at the bottom of board two) for the pattern selector?
The Mountain sub-miniature, right-angle, pc-mount switch (Mouser# 2MS3T2B2M6QE) might fit the bill, but I'm not sure whether the overall length of .79" might incur interference from the transformer housing. Mouser# 633-G13AP is a sure-fire fit, but it maxes out at .4 VA and 28VAC/DC. Would this work, or is it too underspec'd? Any suggestions would be greatly appreciated.

-James-

would also like to know this. planning on modding the a460 body to use it as multi-pat.
Adam
only got here by owning a soldering iron and bad life decisions.

trancedental

Re: Neumann U87 Vintage Circuit Build Thread
« Reply #108 on: March 27, 2012, 08:25:44 AM »
Are there any suitable transformers & capsules made in or even available in Europe for this project? Shipping & customs / handling fees from the US / Canada is working out expensive >:(

Someone in Europe must still be able to manufacture these items nowadays?  8)

HellfireStudios

Re: Neumann U87 Vintage Circuit Build Thread
« Reply #109 on: March 27, 2012, 02:51:30 PM »
Are there any suitable transformers & capsules made in or even available in Europe for this project? Shipping & customs / handling fees from the US / Canada is working out expensive >:(

Someone in Europe must still be able to manufacture these items nowadays?  8)

Sowter might make a transformer (you should look for around a 10:1 ratio). I couldn't even venture a guess at capsules (other than the obvious and expensive Nueumann, AKG, and BLUE). Sorry I can't be of more help.
"Tommorrow is just yesterday in reverse. Just like friends are enemies in reverse." -Gary Busey


HellfireStudios

Re: Neumann U87 Vintage Circuit Build Thread
« Reply #110 on: March 27, 2012, 03:03:55 PM »
berkleystudios, the Apex 460 is a killer platform for mic modding, mainly C12-style designs, but the head basket is too far off for the U-87 sound. The head basket on the U-87, much like the U-47, is integral to the sound of the mic. The options listed elsewhere for this mod are much more suited to the task at hand. I'm using a Carvin CM87S (comes with case, shock, power supply, cable- $130) and the only thing I dislike is the lack of a pattern switch on the outside of the mic. There are plenty of other options that may fit you a little better, but they will all work better that the 460.
"Tommorrow is just yesterday in reverse. Just like friends are enemies in reverse." -Gary Busey

Re: Neumann U87 Vintage Circuit Build Thread
« Reply #111 on: March 27, 2012, 06:53:04 PM »
berkleystudios, the Apex 460 is a killer platform for mic modding, mainly C12-style designs, but the head basket is too far off for the U-87 sound. The head basket on the U-87, much like the U-47, is integral to the sound of the mic. The options listed elsewhere for this mod are much more suited to the task at hand. I'm using a Carvin CM87S (comes with case, shock, power supply, cable- $130) and the only thing I dislike is the lack of a pattern switch on the outside of the mic. There are plenty of other options that may fit you a little better, but they will all work better that the 460.
oh no not an apex 460, an a460. u87 style diy mike kit.
http://www.diymic.com/

i have build one, just ordered a second since im building 2. would like it to be multi pattern though.... would it be as simple as drilling a whole and installing a switch to the board at the proper points?
Adam
only got here by owning a soldering iron and bad life decisions.

HellfireStudios

Re: Neumann U87 Vintage Circuit Build Thread
« Reply #112 on: March 27, 2012, 08:14:57 PM »
Sort of...

On a lot of other mics, the switch would have to be mounted internally (on a PCB or subframe). As for the outside switch access, the easiest place to accomodate a switch is where two outer parts come together. Like the headbasket and body sleeve.
The problem with this mic style is that there is a plastic disc directly under the headbasket baseplate (with inconviently placed screws as well). This makes "just add a switch" difficult.
I intend to use a 7-pin mic cable and required jacks to allow relay-based switching at the dedicated phantom power supply that came with my mic.
If your mic doesn't come with a power supply, you could build a dedicated polar pattern/7-pin to 3-pin XLR conversion box with a transformer sized for the relay(s) you choose (usually 5-24 volts).
"Tommorrow is just yesterday in reverse. Just like friends are enemies in reverse." -Gary Busey

stanz

Re: Neumann U87 Vintage Circuit Build Thread
« Reply #113 on: March 27, 2012, 09:39:39 PM »
***delete***
« Last Edit: March 28, 2012, 03:29:01 PM by stanz »

Re: Neumann U87 Vintage Circuit Build Thread
« Reply #114 on: March 28, 2012, 02:49:23 AM »
Hi everybody,
I just finished my first U87. I builded it with the Peluso K87i cap and the Cinemag CM2480 ytransformer.
I tried it yersteday on a vocal session at the studio. And it sound great! I tried it with a DIY SSL preamp, a DIY API preamp, and a UA LA610. Really really great with the Universal Audio.
I build it on a Behringer B2-Pro body, the pcb don't screw on the body at the exact place so I had to fix it like I could. But no problem.
Here are photos of the mic with the painting.
I have to give one thousant thanks to Dany (ploctop) for his help on my building, all the answers he gave to my questions, and his project!
Hope all of you will have as pleasure as I have with this mic and with the building step.
Sorry if I made english mistakes, this is not my native language.
Have a good day.

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Re: Neumann U87 Vintage Circuit Build Thread
« Reply #115 on: March 28, 2012, 02:50:31 AM »
Sorry for the links!

Re: Neumann U87 Vintage Circuit Build Thread
« Reply #116 on: March 28, 2012, 02:51:39 AM »

kante1603

Re: Neumann U87 Vintage Circuit Build Thread
« Reply #117 on: March 28, 2012, 04:56:00 PM »
Hi,

any inside pics please?
I'm especially interested in how you mounted the transformer as well as how you did the switch arrangement (have bought the B2 too but not opened yet,just curious about it).

Thank you,

Udo. :)
« Last Edit: March 28, 2012, 05:39:25 PM by kante1603 »

mrcase

Re: Neumann U87 Vintage Circuit Build Thread
« Reply #118 on: March 29, 2012, 02:39:27 AM »
loog great! how did you get rid of the stupid behringer engraving? or did you just paint it and its still there?

Re: Neumann U87 Vintage Circuit Build Thread
« Reply #119 on: March 29, 2012, 03:18:26 AM »
Hi,

for kante,
 I will try to take other photos of the inside. The pcb is just in place with a little cord, I have to make new holes in the pcb to fix it. The transformer just sit between the pcb and the XLR connector, it isn't fixed but don't move at all.
For the switch, if you take a look at the B2 head of the mic, you will see that there are 6 pins wich connect the head to the body. You will use 4 of them for the capsule, so the 2 others can be use for the low cut or the pad. For the other one and the polarity switch, you have to put cables. I don't connected them to the switch and prefer open the mic for changing the polarity of the mic (I use cardioide 90% of the time)  If you find another solution, I'm open to it!

for mrcase,
 for the Behringer engraving, I used a metalic mastic, a dough (excuse me if I don't find the fine word) for obstruct it.
If you don't understand, in France this mastic could be named "sintofer" (it is the brand name I think), and it is used for stripe on car's body. So you put it on the engraving (it dry really fast), you sand it with very small sand paper, perhaps you will have to make those two steps a second time, and finally just have to paint it (with a spray for me).

Hope this help you.

Have a good day.

Adrien


 

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