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

JessJackson said:

kaguenpituak said:

I have do the complete mod. (5-12,1-4,7-10) and no sound change...I have compared with another no mod. Tomorrow I will try only 5-12

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Now thats weird, this would suggest that the feedback circuit IS symmetrical!!... We shouldn't have to be here testing and guessing polarities and windings of Oliver's transformers. I think he needs to explain exactly the windings on his T67.

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according with the hand drawing I have from him with polarity , with the correction applied everthing is correct now ,  it has been tested by DMP and Dandeurloo, and another member and proof on sample. Maybe Oliver could chime in on this ,


Best,
dan,

I've been so busy writing and producing I haven't had a moment to do the mod myself but I think today will be the day.

JessJackson said:

I've been so busy writing and producing I haven't had a moment to do the mod myself but I think today will be the day.

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that would be awesome to have your confirmation as well,
Thanks Jess,
I guess we need that day,  i am trying so hard to make sure i do my part ,
Best,
dAN,

according with the hand drawing I have from him with polarity , with the correction applied everthing is correct now ,  it has been tested by DMP and Dandeurloo

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I have NOT tested this out. I only have Max's transformers, I haven't had a AMI to try. As I've posted a few times, I would expect reversing all three windings to make no difference in the circuit. Transformer windings do not have absolute polarity, only with respect to each other. (to flip phase / to not flip phase)

dmp said:

according with the hand drawing I have from him with polarity , with the correction applied everthing is correct now ,  it has been tested by DMP and Dandeurloo

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I have NOT tested this out. I only have Max's transformers, I haven't had a AMI to try. As I've posted a few times, I would expect reversing all three windings to make no difference in the circuit. Transformer windings do not have absolute polarity, only with respect to each other. (to flip phase / to not flip phase)

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Sorry i must Have made a typo,  but here it is again ,

here is some sample before and after the complete fix. Thanks To Dan for the samples.

Errata Feedback winding polarity  http://groupdiy.com/index.php?topic=50021.800 reply # 814

AMI T67 Corrected Wiring to main microphone pcb

From transformer board to mic PCB

Pad 5 ----->  mic pcb pad T1212
Pad 12 -------> mic pcb pad T55
Pad 1 --------> mic pcb pad T44
Pad 4 --------> mic pcb pad T11
Pad 7 --------> mic pcb pad T1010
Pad 10 ------> mic pcb Pad T77

with wiring error
https://dl.dropboxusercontent.com/u/43869772/U67/Feedback%20winding%20Correction/Orginal.wav

With wiring correction  WoW
https://cdn.groupbuilder.com/groupdiy/u/39511/58d02819941ac.wav

here is some sample before and after the complete fix. Thanks To Dan for the samples.

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Definitely a difference in these before-and-after...

dmp said:

here is some sample before and after the complete fix. Thanks To Dan for the samples.

Click to expand...

Definitely a difference in these before-and-after...

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indeed ,
Dan,

Hey fellow builders,
I've been following the AMI errata since Dany sent me the email and I'm wanting to chime in. I have an AMI in my DU67 and I have A/B'd it against Tskguy's Du67 with ioaudio's trafo. We both have the same other components including HK-67 capsules. Our 2 mics are so close they could be a matched pair. We have both thought this since they were built in 2012.

That being said, I home etched my T67 adapter pcb as Dany's was not yet available at the time (this was very early on in development) I feel like when I look at photos of the fabricated pcb it's slightly different from my layout.

Any thoughts on this?

Dave

wave said:

Hey fellow builders,
I've been following the AMI errata since Dany sent me the email and I'm wanting to chime in. I have an AMI in my DU67 and I have A/B'd it against Tskguy's Du67 with ioaudio's trafo. We both have the same other components including HK-67 capsules. Our 2 mics are so close they could be a matched pair. We have both thought this since they were built in 2012.

That being said, I home etched my T67 adapter pcb as Dany's was not yet available at the time (this was very early on in development) I feel like when I look at photos of the fabricated pcb it's slightly different from my layout.

Any thoughts on this?





Dave

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The PCB kit for Max transformer has never changed since its apparition and it has been checked over and over for transfomer connection and it is 100% correct,
however the AMI adaptor board has been designed with all the connection mirrored as i tought this would null out but the feedback winding interaction with the rest of the transformer needs all the polarity to be corrected in order to have the feedback properly working as Dan sample show the true difference between the 2 in the previous post this way everything works as it should this is only valid for the AMI T67 the adaptor board deisgn is always been the same. could you explain the slight differences ?  That would not explain why the D-67 with Max traffo in your case is closer or airier than the D-67 with the AMI traffo.
DAn,

Best,
Dan,

Dany,
I was referring to my AMI Du67. Eric has the ioaudio version.
If you remember, I etched my own transformer adapter pcb and I'm wondering if because of how I made the file..if mine is right.
BTW mine does look kinda like a mirror of your fabricated pcbs.

Make sense?

Dave

Hi Wave,
I remember the samples you posted of your mic were fantastic - really great sounding.
Did you and tskguy every check the amplifier response for the proper rolloff?
Maybe there are capsule differences between the HK-67 and Beezneez.
Dan

Hey fellow builders,
I've been following the AMI errata since Dany sent me the email and I'm wanting to chime in. I have an AMI in my DU67 and I have A/B'd it against Tskguy's Du67 with ioaudio's trafo. We both have the same other components including HK-67 capsules. Our 2 mics are so close they could be a matched pair. We have both thought this since they were built in 2012.

That being said, I home etched my T67 adapter pcb as Dany's was not yet available at the time (this was very early on in development) I feel like when I look at photos of the fabricated pcb it's slightly different from my layout.

Any thoughts on this?

Dave

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Hi, I have inverted 5-12, sound very good like neumann, but not HF whit the -10pad..  :-[
I have try again the complete fix and no changes..
It is posible to modify for reduce HF??
Thanks!

kaguenpituak said:

Hi, I have inverted 5-12, sound very good like neumann, but not HF whit the -10pad..  :-[
I have try again the complete fix and no changes..
It is posible to modify for reduce HF??
Thanks!

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I have a hard time following here,
could you explain with a little more details what is your issue ,
Note that the correction is only for the AMI T67 wich i presume you have ,
the microphone shall be corrected in only one way wich is the 3 pair swap according to this ,

From transformer board to mic PCB

Pad 5 ----->  mic pcb pad T1212
Pad 12 -------> mic pcb pad T55
Pad 1 --------> mic pcb pad T44
Pad 4 --------> mic pcb pad T11
Pad 7 --------> mic pcb pad T1010
Pad 10 ------> mic pcb Pad T77

what is the issue you have with the pad,
Let me know, i will see if i can assist
Best,
DAN,

Yes I have the AMI t67. I have inverted the 3 pair and it is the same sound.. I have inverted only 5-12 and it sound very good, but if I put the -10 pad it sound very dark (no higth frecuencis..)
I consider (with the 3 pair swap) it is too bright..
What can I do to make it less bright?
;D

yeah somethings not right with this build.

What if we were to reverse all connections to the transformer but left the feedback connections like original the first revision.

I could be wrong but in my head the phase would be corrected and the feedback would work properly?

Has anyone thought about doing this?

Jesse

dmp said:

Hi Wave,
I remember the samples you posted of your mic were fantastic - really great sounding.
Did you and tskguy every check the amplifier response for the proper rolloff?
Maybe there are capsule differences between the HK-67 and Beezneez.
Dan

Hey fellow builders,
I've been following the AMI errata since Dany sent me the email and I'm wanting to chime in. I have an AMI in my DU67 and I have A/B'd it against Tskguy's Du67 with ioaudio's trafo. We both have the same other components including HK-67 capsules. Our 2 mics are so close they could be a matched pair. We have both thought this since they were built in 2012.

That being said, I home etched my T67 adapter pcb as Dany's was not yet available at the time (this was very early on in development) I feel like when I look at photos of the fabricated pcb it's slightly different from my layout.

Any thoughts on this?

Dave

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Click to expand...

Dan,
Do you mean the amplifier part of the mic circuit? No we didnt get that deep. We are both using the HK-67 capsules tho. Basically everything is the same between our two mics except the trafo. I etched my own AMI adapter PCB that I think may have been mirrored. I'm def not gonna change anything cuz that mic does sound amazing...I was just wondering.

Dave

wave said:

dmp said:

Hi Wave,
I remember the samples you posted of your mic were fantastic - really great sounding.
Did you and tskguy every check the amplifier response for the proper rolloff?
Maybe there are capsule differences between the HK-67 and Beezneez.
Dan

Hey fellow builders,
I've been following the AMI errata since Dany sent me the email and I'm wanting to chime in. I have an AMI in my DU67 and I have A/B'd it against Tskguy's Du67 with ioaudio's trafo. We both have the same other components including HK-67 capsules. Our 2 mics are so close they could be a matched pair. We have both thought this since they were built in 2012.

That being said, I home etched my T67 adapter pcb as Dany's was not yet available at the time (this was very early on in development) I feel like when I look at photos of the fabricated pcb it's slightly different from my layout.

Any thoughts on this?

Dave

Click to expand...

Click to expand...

Dan,
Do you mean the amplifier part of the mic circuit? No we didnt get that deep. We are both using the HK-67 capsules tho. Basically everything is the same between our two mics except the trafo. I etched my own AMI adapter PCB that I think may have been mirrored. I'm def not gonna change anything cuz that mic does sound amazing...I was just wondering.

Dave

Click to expand...

did you bridge the pins on the opposite side of the transformer as to what dany bridged?

Dan,
Do you mean the amplifier part of the mic circuit? No we didnt get that deep. We are both using the HK-67 capsules tho. Basically everything is the same between our two mics except the trafo. I etched my own AMI adapter PCB that I think may have been mirrored. I'm def not gonna change anything cuz that mic does sound amazing...I was just wondering.
Dave

Click to expand...

Yes, I was wondering if you checked if the response followed the spec (-10 dB at 15kHz).
Good to know that the mics sounded very similar with the two different transformers though.

Even if the transformer was mirrored, it is symmetrical. It shouldn't make a difference.

If someone has a function generator and a scope, the windings could be confirmed