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

[poctop]

Question on the P.S

I wanted to bypass the PCB for modulation.

Is this correct to link all together:

[[ XLR pin 3 > Chassis > Pin 7 > Pin 3 > PCB Gnd ]]

Reason I ask is because of switch on pin 3 to pin 7, default on schematic shows open position yet still goes to chassis regardless.

Cheers

could you explain the modulation thing ?


if you tie the cable shield from the cable to the mic body then pin 3 Sheild and pin 7 0V are at the same level , the SHLF jumper wich is open by default allows to lift the shield or not if your shield jumper is on or not , hence you can have a floating shield or not,  just permits 2 ways of doing things as somtimes it can help on RF wierd situation,  if you actually dont tie the pin 3 to pin 7 on the mic pcb or mic body you can have both functionnality operated with the jumper

but basically if it is now tied up to the mic body then ou are good to go ,

hope this helps,
Let me know .
Best,
DAn,

 

[JessJackson]

Great thanks dan,

I'm just anal over certain things, Like all the vintage power supplies, I just wanted to prevent modulation (audio + and -) from unnecessarily going through the PCB in an attempt to retain pure common mode rejection with a twisted pair direct to the XLR.

I have one more question, Inside the Gac-7 cable, do I attach the braided sleeve to pin 3 along with the (8th pin - housing shell) on both ends? My first time building a 7pin tube mic cable.

Cheers

J

 

[poctop]

Great thanks dan,

I'm just anal over certain things, Like all the vintage power supplies, I just wanted to prevent modulation (audio + and -) from unnecessarily going through the PCB in an attempt to retain pure common mode rejection with a twisted pair direct to the XLR.

There is no problem with that as the pad on the pcb are just a convienent option anywhay,

I have one more question, Inside the Gac-7 cable, do I attach the braided sleeve to pin 3 along with the (8th pin - housing shell) on both ends? My first time building a 7pin tube mic cable.

connect the cable sheild from pin 3 to psu and then run in to the cable, once inside the mic you can connect it to the pad for it on the mic pcb #3

then you connector should already be at ground level with the mic body even easier than on the connector as both will be at 0V

Best,
Dan,

Cheers

J

 

[JessJackson]

I'm at the end of my build, which one would you rock first?? hmm the choices… although that big 1841 won't fit

 

[JessJackson]

And heres a question…

When utilizing a dual backplate design such as erics capsules in a pure cardioid only circuit with rear capsule floating. Do you still tie both backplates together or do you use only the front backplate?

cheers

J

 

[poctop]

And heres a question…

When utilizing a dual backplate design such as erics capsules in a pure cardioid only circuit with rear capsule floating. Do you still tie both backplates together or do you use only the front backplate?

cheers

J

if you are in cardiod only then use only the front backplate connection,
Best,
Dan,

 

[JessJackson]

And heres a question…

When utilizing a dual backplate design such as erics capsules in a pure cardioid only circuit with rear capsule floating. Do you still tie both backplates together or do you use only the front backplate?

cheers

J

if you are in cardiod only then use only the front backplate connection,
Best,
Dan,

That makes sense to me in the u87 build but in designs which use a shared backplate such as the c12 unlike the elam, the backplates are tied together.

 

[pasarski]

And heres a question…

When utilizing a dual backplate design such as erics capsules in a pure cardioid only circuit with rear capsule floating. Do you still tie both backplates together or do you use only the front backplate?

cheers

J

if you are in cardiod only then use only the front backplate connection,
Best,
Dan,

That makes sense to me in the u87 build but in designs which use a shared backplate such as the c12 unlike the elam, the backplates are tied together.

For omni and fig8 yes. In cardioid mode the membrane "doesn't know" there's an other backplate, it only "sees" the one next to it

 

[poctop]

I'm at the end of my build, which one would you rock first?? hmm the choices… although that big 1841 won't fit

Miam miam , personnaly i would go for the ero the package is nice and it looks cool too, 
Best,
dAn,

 

[MikeFFG]

Hey guys -

I built this about 6 motnhs ago and got it fully working and sounding amazing! I've used it dozens or more times probably and was loving it. But all of a sudden it's been making some weird sounds and I'm very unhappy and sad  :-\

I haven't gotten in there with a scope or to see what's wrong just yet...I'm scared! Haha, but seriously, if anyone hears this and is like "oh that's definitely a the diaphragm, or the tube, or a capacitor" or whatever...That would be a HUGE help...

You can listen here: http://prettyuglyproductions.net/wp-content/uploads/2013/10/badu67.wav

Thanks fellas!

 

[micaddict]

Link doesn't work here, but the first thing I'd check would be the EF86.
Whimsical tube that (but so musical). Make sure you have a couple spares around.

 

[JessJackson]

so i finished my build, sounds great and just shot it out against vintage unmodified u67 here at paramount studios

Im using:

T67
Eric's 87 capsule with backplates tied together in cardioid
ero 1uf cap as seen above.
I'm at 208v b+ at full turn and 6.3 heater

Going back and forth on female singer my mic instantly is 5db hotter than the vintage u67
The top end is slightly more harsh/brittle and the bottom end is massive, too much lower mids in comparison to the u67 but was thinking it could be using the 1uf instead of a 0.5 over saturating the transformer possibly.

Other than that its very similar but I probably wouldn't use it until I can tune it to sound right without additional eq

I may throw a neumann k67 in there as i suspect thats the culprit for the slightly harsher tops.

cheers.

J

 

[poctop]

so i finished my build, sounds great and just shot it out against vintage unmodified u67 here at paramount studios

Im using:

T67
Eric's 87 capsule with backplates tied together in cardioid
ero 1uf cap as seen above.
I'm at 208v b+ at full turn and 6.3 heater

Going back and forth on female singer my mic instantly is 5db hotter than the vintage u67
The top end is slightly more harsh/brittle and the bottom end is massive, too much lower mids in comparison to the u67 but was thinking it could be using the 1uf instead of a 0.5 over saturating the transformer possibly.

Other than that its very similar but I probably wouldn't use it until I can tune it to sound right without additional eq

I may throw a neumann k67 in there as i suspect thats the culprit for the slightly harsher tops.

cheers.

J

did you jump the S2 internal switch this will affect the low end response  , what tube are you using for this one,  the end value of the bypass cap will also play a role into this i would stick to the original value to start with and go from there .  for sure trying it out with a real K67 would be nice to hear  your feedback from,  8)

Thanks for the post,
Keep us posted on how it goes,
Best,
dAN,

 

[poctop]

Hey guys -

I built this about 6 motnhs ago and got it fully working and sounding amazing! I've used it dozens or more times probably and was loving it. But all of a sudden it's been making some weird sounds and I'm very unhappy and sad  :-\

I haven't gotten in there with a scope or to see what's wrong just yet...I'm scared! Haha, but seriously, if anyone hears this and is like "oh that's definitely a the diaphragm, or the tube, or a capacitor" or whatever...That would be a HUGE help...

You can listen here: http://prettyuglyproductions.net/wp-content/uploads/2013/10/badu67.wav

Thanks fellas!

currently out of town but once i am back i will give it a listen and see if i can hear something that i feel i already heard before.
did you try another tube as a start and check all the reference voltage including ,bias, b+ ,and heater and if the plate voltage is swinging for no reason ,.
is the mic passing the breath test or not , checking cold solder or weak wire in the HZ section.
hope this helps,
DAn,

 

[JessJackson]

so i finished my build, sounds great and just shot it out against vintage unmodified u67 here at paramount studios

Im using:

T67
Eric's 87 capsule with backplates tied together in cardioid
ero 1uf cap as seen above.
I'm at 208v b+ at full turn and 6.3 heater

Going back and forth on female singer my mic instantly is 5db hotter than the vintage u67
The top end is slightly more harsh/brittle and the bottom end is massive, too much lower mids in comparison to the u67 but was thinking it could be using the 1uf instead of a 0.5 over saturating the transformer possibly.

Other than that its very similar but I probably wouldn't use it until I can tune it to sound right without additional eq

I may throw a neumann k67 in there as i suspect thats the culprit for the slightly harsher tops.

cheers.

J

did you jump the S2 internal switch this will affect the low end response  , what tube are you using for this one,  the end value of the bypass cap will also play a role into this i would stick to the original value to start with and go from there .  for sure trying it out with a real K67 would be nice to hear  your feedback from,  8)

Thanks for the post,
Keep us posted on how it goes,
Best,
dAN,

Whats up Dan, hope your well mate.

Yeah i have a jumper across S2 and I'm using a phillips mini watt tube. I just ordered two ero 0.47uf caps mkt1813 to keep it stock values for the moment.

cheers J

 

[poctop]

so i finished my build, sounds great and just shot it out against vintage unmodified u67 here at paramount studios

Im using:

T67
Eric's 87 capsule with backplates tied together in cardioid
ero 1uf cap as seen above.
I'm at 208v b+ at full turn and 6.3 heater

Going back and forth on female singer my mic instantly is 5db hotter than the vintage u67
The top end is slightly more harsh/brittle and the bottom end is massive, too much lower mids in comparison to the u67 but was thinking it could be using the 1uf instead of a 0.5 over saturating the transformer possibly.

Other than that its very similar but I probably wouldn't use it until I can tune it to sound right without additional eq

I may throw a neumann k67 in there as i suspect thats the culprit for the slightly harsher tops.

cheers.

J

did you jump the S2 internal switch this will affect the low end response  , what tube are you using for this one,  the end value of the bypass cap will also play a role into this i would stick to the original value to start with and go from there .  for sure trying it out with a real K67 would be nice to hear  your feedback from,  8)

Thanks for the post,
Keep us posted on how it goes,
Best,
dAN,

Whats up Dan, hope your well mate.

Yeah i have a jumper across S2 and I'm using a phillips mini watt tube. I just ordered two ero 0.47uf caps mkt1813 to keep it stock values for the moment.

cheers J

thanks Jesse,
Do you still plan on sticking a Neumann K67 in there to try out ?
Best,
daN,

 

[Melodeath00]

I'm looking forward to hear your new opinions with the stock values and k67. This project is definitely on my list of builds.

 

[JessJackson]

so i finished my build, sounds great and just shot it out against vintage unmodified u67 here at paramount studios

Im using:

T67
Eric's 87 capsule with backplates tied together in cardioid
ero 1uf cap as seen above.
I'm at 208v b+ at full turn and 6.3 heater

Going back and forth on female singer my mic instantly is 5db hotter than the vintage u67
The top end is slightly more harsh/brittle and the bottom end is massive, too much lower mids in comparison to the u67 but was thinking it could be using the 1uf instead of a 0.5 over saturating the transformer possibly.

Other than that its very similar but I probably wouldn't use it until I can tune it to sound right without additional eq

I may throw a neumann k67 in there as i suspect thats the culprit for the slightly harsher tops.

cheers.

J

did you jump the S2 internal switch this will affect the low end response  , what tube are you using for this one,  the end value of the bypass cap will also play a role into this i would stick to the original value to start with and go from there .  for sure trying it out with a real K67 would be nice to hear  your feedback from,  8)

Thanks for the post,
Keep us posted on how it goes,
Best,
dAN,

Whats up Dan, hope your well mate.

Yeah i have a jumper across S2 and I'm using a phillips mini watt tube. I just ordered two ero 0.47uf caps mkt1813 to keep it stock values for the moment.

cheers J

thanks Jesse,
Do you still plan on sticking a Neumann K67 in there to try out ?
Best,
daN,

yeah why not…

I'm gonna use the one from my u87ai and try it up against paramounts u67.

The sound is VERY close, its just an eq thing now at this point. It has to match for me, for times when songs that are half cut at one location and continued elsewhere.

I was actually close to just buying a u67 a few months ago and held off to see how this build would sound, its so close that i may as well get it perfect.

What was the original coupling cap used? anyone have one spare for me to try?

cheers

 

[MikeFFG]

Hey guys -

I built this about 6 motnhs ago and got it fully working and sounding amazing! I've used it dozens or more times probably and was loving it. But all of a sudden it's been making some weird sounds and I'm very unhappy and sad  :-\

I haven't gotten in there with a scope or to see what's wrong just yet...I'm scared! Haha, but seriously, if anyone hears this and is like "oh that's definitely a the diaphragm, or the tube, or a capacitor" or whatever...That would be a HUGE help...

You can listen here: http://prettyuglyproductions.net/wp-content/uploads/2013/10/badu67.wav

Thanks fellas!

currently out of town but once i am back i will give it a listen and see if i can hear something that i feel i already heard before.
did you try another tube as a start and check all the reference voltage including ,bias, b+ ,and heater and if the plate voltage is swinging for no reason ,.
is the mic passing the breath test or not , checking cold solder or weak wire in the HZ section.
hope this helps,
DAn,

Thanks for the ideas. I checked b+ and heater and they are fine...I think it passed the breath test, at least as far sa I understand it. It didn't do anything crazy at least.  I'm still figuring out how to check bias and the plate voltage...I'm searching through the thread. Part of the problem being that once I finished the build 6 months ago I kind of forgot half of what I learned while doing it!

Mike

 

[MikeFFG]

Hey guys -

I built this about 6 motnhs ago and got it fully working and sounding amazing! I've used it dozens or more times probably and was loving it. But all of a sudden it's been making some weird sounds and I'm very unhappy and sad  :-\

I haven't gotten in there with a scope or to see what's wrong just yet...I'm scared! Haha, but seriously, if anyone hears this and is like "oh that's definitely a the diaphragm, or the tube, or a capacitor" or whatever...That would be a HUGE help...

You can listen here: http://prettyuglyproductions.net/wp-content/uploads/2013/10/badu67.wav

Thanks fellas!

currently out of town but once i am back i will give it a listen and see if i can hear something that i feel i already heard before.
did you try another tube as a start and check all the reference voltage including ,bias, b+ ,and heater and if the plate voltage is swinging for no reason ,.
is the mic passing the breath test or not , checking cold solder or weak wire in the HZ section.
hope this helps,
DAn,

Thanks for the ideas. I checked b+ and heater and they are fine...I think it passed the breath test, at least as far sa I understand it. It didn't do anything crazy at least.  I'm still figuring out how to check bias and the plate voltage...I'm searching through the thread. Part of the problem being that once I finished the build 6 months ago I kind of forgot half of what I learned while doing it!

Mike

So this is weird, but I just tested it again after putting it back together (I took it apart for the troubleshooting and breath test, etc.) and now it sounds fine again!! I wonder if some wire or something was out of place or hitting the side or something? But anyways, it sounds fine for the moment...

Still a killer mike!