Neumann Vintage U87 Clone : Build Thread.

[poctop]

did you clean arround the (G pad) on the board where is the capsule connection, check you gate solder point,  chack the cleaniliness of the board underneath also,have you been using the telfon standoff for the FET connection the gate pin is lifted.
Dan,

 

[HellfireStudios]

What is the best way to put new ends on the capsule wires,  they are very thin.  Too thin for strippers.

Thanks
-Scott

Some have suggested using the tip of their soldering iron to burn it off does the trick. I think it might be messy at best, and detrimental to the iron at worst. I suggest, with the capsule protected, using a lighter or other small flame source to heat the wire sleeve to a just-barely-melted state, and quickly pull off the desired amount with your fingerrnails. A small set of scissors or needle nosed pliers have done stand-in work for my fingernails on occasions when the sleeving was too hot to touch. Hope this helps.

-James-

 

[saxmonster]

Capsule pads are clean so is the G area.  Don't know what it could be, could I have damaged it by inserting to loud of a signal during biasing.  Cause it took me a while to figure out how to do it properly.  maybe a component is going bad.  Can I test anything with me dmm?

 

[poctop]

Capsule pads are clean so is the G area.  Don't know what it could be, could I have damaged it by inserting to loud of a signal during biasing.  Cause it took me a while to figure out how to do it properly.  maybe a component is going bad.  Can I test anything with me dmm?

I Guess what you could do is try a new FET in and Rebias,  FET transistor are very fragile entity so it is possible you may have damaged it
Been there done that with FET and Zener also,

Dan,

 

[poctop]

Here is a pointer on Really good solder any ongoing future project    it is no clean solder type with virtually no flux 0.81mm it is smooth as butter and leave virtually no residue , this is the best stuff i had a chance to try and i have been using it for years now,

Dan,

 

[saxmonster]

I put a new fet in and its doing the same thing, so I put the old one back in, hahahaha.  I just don't remember hearing the sound before so I don't think it was always there.  And this was the first I used the mic since i baised it two weeks ago.  What supplys the phantom power to the mic.  Becasue of the non consistent noise maybe its releated to that?

I hope this can be fix, getting nervous, I am sure it can be

 

[kante1603]

I put a new fet in and its doing the same thing, so I put the old one back in, hahahaha.  I just don't remember hearing the sound before so I don't think it was always there.  And this was the first I used the mic since i baised it two weeks ago.  What supplys the phantom power to the mic.  Becasue of the non consistent noise maybe its releated to that?

I hope this can be fix, getting nervous, I am sure it can be

Hi,
Please let us know a bit more of the surrounding conditions.
As this seems to be non-consistant the causes can be the outside of the mic as well as the inside.
Easy check is to shoot out the outside.Just plug the mic to another channel,swap the xlr cable.
After this you'll know a lot more.
When it is the mic itself we must know a little bit more to help you.
What's the gain on your preamp or channel input set to and how exactly do you monitor this?
We need as much as possible info!Sometimes it's not the issue you're looking at (the mic ) but something completely different-maybe just a broken headphone amp or a section on the monitor controller etc.So let's shoot these possibilities out first.Maybe you have never noticed it because any signal will cover these plops.
O.K.,up to here.
Next step is investigating the mic.The plops don't sound like a loose wire,more like a part is charging and discharging randomly.Can be a faulty cap.
A very important question is then in which mode this happens?
If it is in cardioid check the plops again,listen to them and switch the mics hpf in and out.If the sound of the plops change then I bet it's the capsule itself.If not it must be after it in the circuit,I would still think then it is in the high impedance part.

So first make clear all surrounding stuff and the listening situation.

Let us know,good luck,

Udo.

 

[saxmonster]

This is what I did so far.

I know it's not the preamp or headphones or cable.  I plugged in a different mic that needed phantom power and it's not there.  I reattached the capsule pads and transformer pads and cleaned along them before and after I reattached.  With alcohol. I replaced the fet and swapped c6 with a wima cap.  I also replaced the pot with resistors that added up to it.  Still snapping crackeling and popping granite  It is soft.  Just shouldn't be there.  Could it be a cap or what. How About the capsule wire over heating from attaching on and off many time,  errr I just want it to be fix, hahhahahah.

 

[HellfireStudios]

My Peluso BV11P test results are in. After mutiple rounds of testing. I finallly came up with a way to get the results I know I heard. This is the signal path:

I ran the output of a cable tester's signal generator to the secondary of both the Cinemag and the Peluso transformers (I'm using them in reverse for step-up operation). Their primary sides were sent to two sides of a very handy A/B box. The box's output was then routed to a small Marshall Guitar amp. A KRK reference omni was pointed directly at the center of the speaker (like it matters in omni). An iPad2 and Alesis I/O Dock were set up to provide preamp, phantom power, and register SPL through the SignalScopePro app (not cheap) from the KRK mic. Canare quad core cable with Neutrik XLR's were used for the mic signal.

My, hopefully scientific enough, results are:

The Cinemag CM-2480 was measured at 91dB. With no changes to mic placement or wiring, the Peluso BV11P was switched in place of the Cinemag via the aforementioned A/B box. It measured 87.9dB. That's a tad over 3dB. If memory serves, when a signal is doubled (like when duplicating a track in your DAW) it's output increases by 3dB. This alone indicates to me that the Peluso is only stepping up the voltage by 1/2 the amount the Cinemag is. In this reversed-from-normal operation, their outputs should have been similar. If the Peluso is over spec'd, as John claimed it might be, It's output should have been slightly higher not 3dB lower. As far as I'm concerned the information at hand proves what the voltage tests told me days ago. This Peluso BV11P is a 5:1.

If anyone, with more knowledge than I, could find fault in my testing method or outcome. Please speak up. I don't want to be right, but I'm afraid I might be.

-James-

 

[poctop]

My Peluso BV11P test results are in. After mutiple rounds of testing. I finallly came up with a way to get the results I know I heard. This is the signal path:

I ran the output of a cable tester's signal generator to the secondary of both the Cinemag and the Peluso transformers (I'm using them in reverse for step-up operation). Their primary sides were sent to two sides of a very handy A/B box. The box's output was then routed to a small Marshall Guitar amp. A KRK reference omni was pointed directly at the center of the speaker (like it matters in omni). An iPad2 and Alesis I/O Dock were set up to provide preamp, phantom power, and register SPL through the SignalScopePro app (not cheap) from the KRK mic. Canare quad core cable with Neutrik XLR's were used for the mic signal.

My, hopefully scientific enough, results are:

The Cinemag CM-2480 was measured at 91dB. With no changes to mic placement or wiring, the Peluso BV11P was switched in place of the Cinemag via the aforementioned A/B box. It measured 87.9dB. That's a tad over 3dB. If memory serves, when a signal is doubled (like when duplicating a track in your DAW) it's output increases by 3dB. This alone indicates to me that the Peluso is only stepping up the voltage by 1/2 the amount the Cinemag is. In this reversed-from-normal operation, their outputs should have been similar. If the Peluso is over spec'd, as John claimed it might be, It's output should have been slightly higher not 3dB lower. As far as I'm concerned the information at hand proves what the voltage tests told me days ago. This Peluso BV11P is a 5:1.

If anyone, with more knowledge than I, could find fault in my testing method or outcome. Please speak up. I don't want to be right, but I'm afraid I might be.

-James-

  since i dont own any more bv11p i would strongly suggest that you give a call to John yourslef and explain your findings to him,
i think that would be important to this stage . he always answer the phone when he is in is workshop, he is quitly available and ressourfull when you talk to him.
Hope this will help figuring out this ordeal of Bv11,
Dan,

 

[kante1603]

This is what I did so far.

I know it's not the preamp or headphones or cable.  I plugged in a different mic that needed phantom power and it's not there.  I reattached the capsule pads and transformer pads and cleaned along them before and after I reattached.  With alcohol. I replaced the fet and swapped c6 with a wima cap.  I also replaced the pot with resistors that added up to it.  Still snapping crackeling and popping granite  It is soft.  Just shouldn't be there.  Could it be a cap or what. How About the capsule wire over heating from attaching on and off many time,  errr I just want it to be fix, hahhahahah.

O.K.,
seems to be the mic.
But for the further checks:You have only repeated what you have already written in your previous posts but did not answer my questions.Again,this is really important.If we don't have enough information we can not help you.Especially the hpf check as mentioned would be interesting now.

Udo.

P.S.:In what invironment did you record the sound sample,was that kind of a dead room?What was the gain setting on the pre?

 

[kante1603]

@James

Hi,
duplicating a track in a daw will result in +6 dB,not 3.Don't swap dB calcs ( that's a different story).
Actually there's a nice discussion about how to identify tech. specs of transformers here:

http://www.groupdiy.com/index.php?topic=48544.0

Maybe you can get better info on yours with one of the described methods there....

Hope to have helped,

Udo.

 

[HellfireStudios]

Even a three decibel output difference is far too much. Especially for transformers said to have the same ratio. Voltages don't lie (most of the time). The difference in output was corresponding with what my ears heard and what the SPL meter read.
In proper orientation for this circuit, I would likely see a 3dB increase in volume. While that sounds good in theory, wouldn't Neumann have put a cheaper-to-manufacture and louder-output-to-boot transformer in their mics in the first place? Unless, of course, the impedance would be off, and the tonal shift from preamp to preamp would be unlike the original we are trying so hard to copy.
I'll be giving John a call very soon. He was pleasant the last time I spoke with him. I wouldn't think he would knowingly sell a 5:1 as a 10:1. I'll see if I can get this resolved quickly, and get back with some answers probably only I need...

 

[wave]

Just got home from a gig. Somebody was nice enough to drop a little box with donor mics in it 

Tomorrow we shall have some audio samples of the RK-87.

First up vintage flavor...

Dave

 

[kante1603]

Just got home from a gig. Somebody was nice enough to drop a little box with donor mics in it 

Tomorrow we shall have some audio samples of the RK-87.

First up vintage flavor...

Dave

Very nice Dave,
I'm really curious how this works out.

Have fun,

Udo.

 

[kante1603]

Even a three decibel output difference is far too much. Especially for transformers said to have the same ratio.

Agreed.

Voltages don't lie (most of the time).

Wrong,it depends on the measuring method (e.g. the loads) and-if done with a dmm-if it is capable to really read a voltage at say 1kHz etc.

I'll be giving John a call very soon. He was pleasant the last time I spoke with him. I wouldn't think he would knowingly sell a 5:1 as a 10:1. I'll see if I can get this resolved quickly, and get back with some answers probably only I need...

I can´t imagine that either.Please keep us posted even if it´s just "only" your problem,it might help others in the future.

Btw:Matador was kind enough to write something for a possible work-around in your case.Have you replied?Just curious,I guess I know what he´s refering to.

Good luck,

Udo

 

[DUDE GUY]

Hello all,

I hope your builds are going well. Mine seems to have hit a wall. First, some
perspective:

Source V: 48.0V
L1 & L2: 46.6V
Zener: 22.88V
R18: 46.6V
R19: 46.1V
Top of R17: 22.89V
FET Drain: 10.53V
FET Source: 2.62V
R12: 10.54V
R13: 43.4V
R14: 20.73V
R8: 39.7V

Issues:

1. The mic will not output the 1k sine tone. I see it on the scope, but cannot
see any signal coming back into my daw (I've checked my signal chain going to my
daw and all is good). Thoughts?

2. I attempted the bias procedure, but the only symmetrical distortion I can
achieve looks like the attached picture and I assume this is bad. My scope is
pretty old, maybe it's the problem?

Your help is very much appreciated, thanks everyone.

- DUDE GUY

 

[DUDE GUY]

Here's another shot of my scope with the 1k sine tone at a higher output.

 

[MagnetoSound]

Hey there, Dude ...

1. The mic will not output the 1k sine tone. I see it on the scope, but cannot
see any signal coming back into my daw (I've checked my signal chain going to my
daw and all is good). Thoughts?

2. I attempted the bias procedure, but the only symmetrical distortion I can
achieve looks like the attached picture and I assume this is bad. My scope is
pretty old, maybe it's the problem?

Where are you scoping that signal? At the drain or coupling cap? If so, that distortion, and the fact that there is no output from the mic, suggest a short at the secondary.

The scope is not the problem.

 

[HellfireStudios]

Voltages don't lie (most of the time).

Wrong,it depends on the measuring method (e.g. the loads) and-if done with a dmm-if it is capable to really read a voltage at say 1kHz etc..

Btw:Matador was kind enough to write something for a possible work-around in your case.Have you replied?Just curious,I guess I know what he´s refering to.

[/quote]

I apologize about the misunderstanding. In my other thread about possible uses for a 5:1, I mentioned doing a voltage test with a 10.6VAC supply and read the stepped down voltages at the ends of both transformers. This test indicates the same thing as the listening/SPL test did. Check out the "There's no UNDO button" post for and my findings.

Udo, where is the Matador write up on a work around?