Neumann U67 Clone : D-U67 Tube Microphone Build Thread.

[poctop]

Hi All,  This is the Pad transformer relationship for the AMI transformer on the AMI mic pcb , if you have looked upon the datasheet i have just published there is an error on the specsheet from Oliver there is actually an inversion on the 2nd audio tap from  his datasheet i will get in touch with him today to ask him to correct that one the 2 black wire from the transformer will be grounded as those one are the core shield

the pad number on the mic pcb will used to wire the transformer accordingly.

Best,
Dan,

 

[mickdundee63]

The data sheet also lists two grey wires and one white whereas the transformer has one grey wire and two white.

 

[OPR]

I just wanted to thank you Dan For another awesome Project!! The 67 is heavenly!! 8)

 

[JessJackson]

The data sheet also lists two grey wires and one white whereas the transformer has one grey wire and two white.

i'll show you what i did to hook up the bv12. who knows.. we may have feedback backwards! lmao

 

[mickdundee63]

The data sheet also lists two grey wires and one white whereas the transformer has one grey wire and two white.

i'll show you what i did to hook up the bv12. who knows.. we may have feedback backwards! lmao

That just means your mic could get even better . I would appreciate your hookup info and hopefully all will be clarified with a corrected data sheet.

 

[Graph]

Hi, i have finished some months ago the D87 project, and i really love how it sounds

I was looking and make a tube mic, and decided for the D67. I wanted to know, which transformer is better? BV12 from AMI(the expensive option), from IOAudio(not so expensive) or T67 from AMI(the cheap one)?

And another question: D87 was pretty easy going project. Well.. i didnt run out in any several problem, it started worked with no issues. Is the D67 more difficult to build?

Thanks

 

[mickdundee63]

Hi, i have finished some months ago the D87 project, and i really love how it sounds

I was looking and make a tube mic, and decided for the D67. I wanted to know, which transformer is better? BV12 from AMI(the expensive option), from IOAudio(not so expensive) or T67 from AMI(the cheap one)?

And another question: D87 was pretty easy going project. Well.. i didnt run out in any several problem, it started worked with no issues. Is the D67 more difficult to build?

Thanks

There is actually two BV12 versions from AMI as well. One has NOS laminations and is more expensive. From memory the "Classic" model uses new lamination material and is around 300 - 350 USD whereas the authentic version with NOS lams is more like 500 USD. AFAIK no one has used the AMI BV12 in the D-U67 although Jessjackson used one in a P2P U67 build. As soon as I get my tubes in and the correct data sheet I will install one and do a comparison with a T67 D-U67. As for Iaudio v t67 I think the consensus is that neither is significantly better. They both give a slightly different flavour that is possibly less important to the final sound than your choice of tube and capsule.

The D67 is certainly more difficult but not significantly so. You also need to build a power supply so it's a lengthier build.

 

[Graph]

Thank you! No problem, i have already made several projects what really bothers me is the chance to make a simple mistake and connect the wires incorrectly so everything might blow up

But, is it possible to use the BV12(the 300-350, not with laminated NOS) in this build right? It fits correctly?

 

[wave]

Hi, i have finished some months ago the D87 project, and i really love how it sounds

I was looking and make a tube mic, and decided for the D67. I wanted to know, which transformer is better? BV12 from AMI(the expensive option), from IOAudio(not so expensive) or T67 from AMI(the cheap one)?

And another question: D87 was pretty easy going project. Well.. i didnt run out in any several problem, it started worked with no issues. Is the D67 more difficult to build?

Thanks

There is actually two BV12 versions from AMI as well. One has NOS laminations and is more expensive. From memory the "Classic" model uses new lamination material and is around 300 - 350 USD whereas the authentic version with NOS lams is more like 500 USD. AFAIK no one has used the AMI BV12 in the D-U67 although Jessjackson used one in a P2P U67 build. As soon as I get my tubes in and the correct data sheet I will install one and do a comparison with a T67 D-U67. As for Iaudio v t67 I think the consensus is that neither is significantly better. They both give a slightly different flavour that is possibly less important to the final sound than your choice of tube and capsule.

The D67 is certainly more difficult but not significantly so. You also need to build a power supply so it's a lengthier build.

According to AMI's website there is a BV12 with NOS lams and the T67.
The BV8 comes in modern lams and NOS lams...

http://www.tab-funkenwerk.com/id53.html

I built my DU67 with the T67 and I think it sounds great!

-Wave

 

[mickdundee63]

The other product is called the BV12 classic. It's not on their main price list page yet. You can see it in the photos above. It can be used in this build but it's not as straightforward as using the T67.

Shouldn't be too difficult once we have the corrected data sheet - any movement on that Dan?

 

[poctop]

The other product is called the BV12 classic. It's not on their main price list page yet. You can see it in the photos above. It can be used in this build but it's not as straightforward as using the T67.

Shouldn't be too difficult once we have the corrected data sheet - any movement on that Dan?

i would suggest using the AMI adaptor board and drill 2 holes for mouting the transformer on it
as per the error on the datasheet all it is is the inversion of the original referenced color from the neumann schematic on the second audio tap on the left side it should be white and green but his color are correct,

if you compare the datasheet above from oliver and this piture it will be clear,

SpecSheet for the New BV12 Classic Series From AMI https://cdn.groupbuilder.com/groupdiy/u/39511/58d02819942d5.pdf

let me know if it helps,
Best,
Dan,

 

[mickdundee63]

OK so it's only the original neumann colours in brackets that are wrong. So to be sure: the second audio tap blue wire on the AMI BV12 transformer has the polarity dot (green on the original schematic) and is 9 on the DU67 schematic?

My other problem is that the data sheet lists two grey wires and one white whereas the physical transformer has two whites and one grey. One of the white's has continuity with the green so I'm presuming this is the audio tap and the other white is the grey on the data sheet if that makes sense.

Also just to clarify - If I wire the AMI BV12 to the AMI t67 board i should still use the corrected wiring hookup (and NOT the original wiring hookup) as the error discovered was in the board not the t67 transformer, so the error will still be present with the BV12 if using the t67 board.

I realise I don't need to use the t67 pcb for wiring purposes but I think it will make it simpler for me.

Thanks for all your help looking forward to finishing soon!

 

[poctop]

OK so it's only the original neumann colours in brackets that are wrong. So to be sure: the second audio tap blue wire on the AMI BV12 transformer has the polarity dot (green on the original schematic) and is 9 on the DU67 schematic?

My other problem is that the data sheet lists two grey wires and one white whereas the physical transformer has two whites and one grey. One of the white's has continuity with the green so I'm presuming this is the audio tap and the other white is the grey on the data sheet if that makes sense.

Also just to clarify - If I wire the AMI BV12 to the AMI t67 board i should still use the corrected wiring hookup (and NOT the original wiring hookup) as the error discovered was in the board not the t67 transformer, so the error will still be present with the BV12 if using the t67 board.

I realise I don't need to use the t67 pcb for wiring purposes but I think it will make it simpler for me.

Thanks for all your help looking forward to finishing soon!

you should not be using the wiring pad on the aMI adaptor board then it will just create more confusion and extra labor,
as far as i can tell the error on Oliver datasheet was just in reference to original neumann color ,
i would suggest you wire it direct to the mic pcb using this as a guide,

the pad number on the mic pcb will used to wire the transformer accordingly.

as far as the 2 grey wire i bet Oliver could explain better , i would suggest you call directly or send an email ,
you could also use your DMM and inject a sine tone in the transformer to confirm what it is ,
maybe if you connect it the way you think it is it might just be correct as well ,
I tried contacting Oliver for this but he is extra busy lately


hope this helps,
Best,
Dan,

 

[mickdundee63]

Ok thanks Dan I will wire direct to the amplifier PCB, I'm sure it will be pretty straightforward once I have figured out the windings. I'm sure you have seen the very sad news that Oliver Archut has passed away. I will figure out the transformer by asking Jessjackson who has one wired in and by trial and error. Once I have it in and functioning I'll post the results here. Cheers.

 

[jeannot]

I'm very very interested by this project! do you think how long does it take to succeed?

 

[poctop]

I'm very very interested by this project! do you think how long does it take to succeed?

there is actually no good answer to this one , it really depends of your understanding and soldering skills and comprehension of basic electronics and the ability to follow instruction correctly

but as an advice it is always better to take your time and suceed the first shot rather than go fast and spend time in debbugging mode,

Best,
Dan,

 

[Barton]

I just finished my D-U67 and have a few questions.  The volume on the mic is extremely low.  To the point where I have to turn the gain on my  my mixer almost all the way up.  Below are the voltages I'm getting.  i removed the 56k resistor on the psu trim because I couldn't get any higher than about 194v  at B+ on the mic pcb.  The below measurements were measured after I removed the 56 k.

PSU Not loaded

B+ = 284v
H = -6.3v

PSU Loaded

B+ = 245v
H = -6.3v
a = 78.5V

Pin 1 = 330mV
Pin 2= 330mV
Pin 3= 1.7mV
Pin 4= -6.4 V
Pin 5 =  246V
Pin 6 =  -10.4mV
Pin 7 = -0.1 mV

FD = 0.933V
BD = 0.933V (Cardiod), 3.5V (Omni), 3.5V Fig. 8)
BCK = 7.9 V

XLR 1 = -0.2mV
XLR 2 = 347 mV
XLR 3 = 345 mV

Please heeellp.  This is driving me crazy.

 

[mickdundee63]

I have twice had mics passing audio but very low. Both times it has been a capsule wiring error. Once I had one of the capsule wires shorting to ground, the other time I hadn't bridged the backplates which were isolated.

 

[Barton]

Well given that this is the first I've ever heard of bridging isolated backplates, I'm going to venture to guess that is the problem.  My next question will clearly indicate how new I am to this.  How do you bridge the backplates?  The capsule I have is the HK67 from tskguy.

 

[mickdundee63]

Sorry that was probably misleading, you only need to bridge the backplates if they are isolated in the first place. For example, if you have Neumann's k87 capsule (built for the u87 which requires you to keep the backplates isolated) you can convert it for usage in a u67 by electrically connecting the backplates so they are no longer isolated. All this means is that you create an electrical connection between the two backplates, either with a short piece of wire between the wire terminals on the backplates of the capsule itself, or simply by connecting the wires that are attached to each backplate.

Given that tskguy produces both a 67 and an 87 capsule I'm presuming his hk67 doesn't have isolated backplates so this is unlikely to be the problem.  Hopefully someone else can confirm this.